.. \ ' mm Published by The Palaeontological Association • London Price £38-00 THE PALAEONTOLOGICAL ASSOCIATION (Registered Charity No. 276369) The Association was founded in 1957 to promote research in palaeontology and its allied sciences. COUNCIL 1997-1998 President : Professor D. Edwards F.R.S., Department of Earth Sciences, University of Wales College of Cardiff, Cardiff CF1 3YE Vice-Presidents'. Dr P. D. Lane, Department of Earth Sciences, University of Keele, Keele, Staffordshire ST5 5BG Dr P. Doyle, Department of Earth Sciences, University of Greenwich, Grenville Building, Pembroke, Chatham Maritime, Kent ME4 4AW Treasurer'. Dr T. J. Palmer, Institute of Earth Studies, University of Wales, Aberystwyth, Dyfed SY23 3DB Membership Treasurer : Dr M. J. Barker, Department of Geology, University of Portsmouth, Burnaby Road, Portsmouth POl 3QL Institutional Membership Treasurer '. Dr J. E. Francis, Department of Earth Sciences, The University, Leeds LS2 9JJ Secretary. Dr M. P. 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All members who join for 1998 will receive Palaeontology. Volume 41, Parts 1-6. Enquiries concerning back numbers should be directed to the Marketing Manager. Non-members may subscribe, and also obtain back issues up to five years old, at cover price through Blackwell Publishers Journals, P.O. Box 805, 108 Cowley Road, Oxford OX4 1FH, UK. For older issues contact the Marketing Manager. US Mailing: Periodicals postage paid at Rahway, New Jersey. Postmaster: send address corrections to Palaeontology, c/o Mercury Airfreight International Ltd, 2323 E-F Randolph Avenue, Avenel, NJ 07001, USA (US mailing agent). Cover: coalified terminal sporangia from the Lower Devonian of the Welsh Borderland containing permanent tetrads (far left) and dyads. Similar spores found dispersed in Ordovician rocks are considered the earliest evidence for embryophytic life on land (from left to right, NMW94.76G.1; NMW96.1 1G.6; NMW97.42G.4. All x 45). r MAR 1 0 1995 J NEUROPTERIS OBTUSA, A RARE BUT WIDESPREAD LATE CARBONIFEROUS PTERIDOSPERM by R. h. wagner and M. P. CASTRO Abstract. A rare but widespread neuropterid of Westphalian D and Stephanian age, Neuropteris obtusa (Brongniart) comb, nov., is redescribed from specimens from north-west Spain and Saarland, Germany. Its synonymy includes Neuropteris raymondii Zeiller, 1 Mixoneura ’ subraymondii Wagner, ‘ Callipteris' discreta Weiss, and Neuropteris thompsoniana Darrah. Pustules in the interveinal areas of the pinnules in some specimens are interpreted as the probable result of fungal attack by rusts, although that they are glands cannot be excluded. CoMPRESSiON/impression remains of neuropterid foliage from the Carboniferous (and early Permian?) have recently received detailed attention with reference to the type species of Neuropteris Brongniart (Laveine and Blanc 1996) and the general classification of the group (Cleal and Shute 1995). The genus Neuropteris has been restricted and several new genera distinguished on the basis of frond architecture and (where known) cuticle characters. Where such characters are absent, species can only be assigned to these genera by comparing their morphology with that of better known species. It is important to solve problems of synonymy in such pteridosperms if their stratigraphical and phytopalaeogeographical usefulness is to be maximized. In the present paper, a rare but apparently widespread species, Neuropteris obtusa (Brongniart) comb, nov., known under various different generic and specific names from the Westphalian D and Stephanian, is analysed on the basis of remains from north-west Spain and Saarland. Understanding this species is also important because its basionym ( Odontopteris obtusa Brongniart, 1831) has played a role in the definition of the genus Mixoneura Weiss. Some of the Spanish specimens have pinnules with ‘pustules’ in the interveinal areas, which we believe are probably evidence for fungal attack by rusts. MATERIALS AND METHODS The specimens described here from the Stephanian of north-west Spain, are penultimate and last order pinna fragments belonging to a single species of probable pteridosperm. All are preserved on silty and slightly silty mudrock. On weathered surfaces (localities 1176, 1181, 1184, 1301, 1821, 2706, 9584) they are impressions with little or no organic matter left. Specimens from a coal tip (loc. 931) and from boreholes (3689, 4563, 5366) are compressions preserving black organic material, but which is too highly carbonized to yield cuticles. All the figured specimens have been photographed with oblique lighting, partly with a Pentax SFX autofocus reflex camera equipped with a 100 mm macrolens in daylight, and partly (at higher magnifications) under a Zeiss preparation microscope with camera attachment with artificial lighting. Two specimens from Saarland, representing part and counterpart of the type of ‘ Callipteris ’ discreta Weiss, 1870, are an imprint on shale. These were photographed by Prof. M. Barthel with artificial lighting. [Palaeontology, Vol. 41, Part 1, 1998, pp. 1-22, 7 pls| © The Palaeontological Association PALAEONTOLOGY, VOLUME 41 LOCALITIES AND REPOSITORIES The Spanish localities are all on the southern flank of the Cantabrian Mountains, north-west Spain, where an almost complete succession of Stephanian strata is developed. These localities are identified by numbers. Where not stated otherwise, the repository is the Palaeobotanical Collections at Jardin Botanico de Cordoba (Spain). Catalogue numbers prefixed GT for Guardo-Tejerina and CM for Cinera-Matallana. Tejerina Syncline About 1000 m thickness of early Cantabrian strata is exposed in the valley and gorge north of the village of Tejerina, north of Prioro (Leon province, north-west Spain). A description of this section was originally published by Wagner et al. (1969); the environment of deposition has been discussed by Iwaniw (1985a). Of the more than 60 plant localities sampled from this section by Wagner (see Wagner and Winkler Prins 1985, p. 391), only three have yielded remains of Neuropteris obtusa. 1181-Ocejo Formation, Cerroso Member. North-eastern part of the Tejerina Syncline, in the quartzite conglomerate interval cropping out north of the main road to Prioro (Leon). Age: early Cantabrian. Catalogue numbers GT 00056-00067. 1184- Ocejo Formation, Cerroso Member. Intercalated shales in the top part of the conglomerate formation north of Tejerina, about 600 m north of the village. Age : early Cantabrian. Catalogue number GT 00046. 1821 - Prado Formation, 110 m above the base of the formation, north of Tejerina village (compare Wagner and Winkler Prins, 1985, p. 378, fig. 11). Age: early Cantabrian. Forty-two specimens: catalogue numbers GT 00001-00042 (including Pis 2-4). Specimens recorded as Mixoneura raymondii by Wagner in Wagner et al. (1969). Guardo Coalfield The extensively sampled Guardo Coalfield (Palencia and Leon provinces, north-west Spain), representing the same basin as Tejerina, has provided four additional localities. 2706 - Tarilonte Formation, Villaverde de la Pena (Palencia). Age: late Westphalian D. Catalogue numbers GT 00043-00044. 9584 - Tarilonte Formation, middle part of Las Heras section (Palencia). Age: late Westphalian D. Catalogue number GT 00068. 1176 -Prado Formation, road-wall locality about 500m west-north-west of Valderrueda (Leon). Age: early Cantabrian. Catalogue numbers GT 00047-00055 (GT 00047 recorded as Odontopteris cf. robusta by Wagner 1964a, pi. 1, figs 2, 2a). 5366 - Antracitas de Besande, Grupo Minero La Espina (Leon), borehole 18 bis. Age: early Cantabrian. Catalogue number GT 00045. Cinera-Matallana Coalfield The Stephanian B strata of the Cinera-Matallana Coalfield (Leon province, north-west Spain) have been described by Wagner (1971), who defined the various formations recognized within a total succession thickness of about 1500 m. The Stephanian B in the sense of the Carmaux succession of the Massif Central (France) is not the same as the Stephanian B sensu St Etienne, which is later in age. 931 - San Francisco Formation, tip of the San Francisco coal mine near the village of Correcillas. Age: Stephanian B. Three specimens (figured as Mixoneura subraymondii Wagner, 19646, pi. 10, figs WAGNER AND CASTRO: CARBONIFEROUS PTERIDOSPERM 3 21-23) are in the Museo Nacional de Ciencias Naturales, Madrid, catalogue numbers V-2576 and V-2821-V-2822. One specimen lodged in Madrid (Wagner, 19646, pi. 11, figs 24, 24a) has apparently been lost. Seven specimens (including counterparts of PI. 5, figs 4-6, and PL 6, figs 1-5) are in the Jardin Botanico de Cordoba, catalogue numbers CM 00001-00007. 1301 - Cascajo Formation, c. 3 m above the Leaia band at the base of the formation; roadside locality between Villalfeide and Correcillas. Age: Stephanian B. Specimen mentioned as Mixoneura subraymondii in Wagner (19646, p. 15). Catalogue number CM 00008. 3689 - Cascajo Formation, 18 m above the base of the formation, borehole S 26 (Sociedad Hullera Vasco-Leonesa) in the Vegacervera Syncline, near the synclinal core. Age: Stephanian B. One specimen (part and counterpart). Catalogue numbers CM 00009-00010 (PI. 5, fig. 3; PI. 6, fig. 6). 4563 - Pastora Formation, 60 m below the base of the Cascajo Formation, borehole S 41 (S. H. V. L.), at 698 m depth. Borehole in the southern flank of Matallana Syncline. Age: Stephanian B. Catalogue number CM 00011 (PI. 5, figs 1-2). Saarland ( Germany ) Amelung coal seam (Westphalian D), Von der Heydt colliery, near Saarbrucken. An imprint in shale recorded originally by Weiss (1870). Collection of the Museum fur Naturkunde, Palaontologisches Institut, Berlin, catalogue number 1212. SYSTEMATIC PALAEONTOLOGY Order trigonocarpales Seward, 1917 or medullosales Nemejc, 1950 Form-genus neuropteris Brongniart, 1822 Remarks. This genus, introduced by Brongniart (1822, p. 233) as the section Neuropteris of the general form-genus Filicites, has been restricted by Cleal et al. (1990) to only part of the wider grouping which is traditionally recorded under the name Neuropteris (cf. Cleal and Shute 1995). Neuropteris sensu stricto comprises dichotomous fronds with monopinnate pinnae of several orders with intercalated pinnae being present on the main rachis above the dichotomy ; lateral pinnules are attached by a single point or by part of the basal width ; generally anomocytic stomata, prominent intercellular flanges and trichomes on the abaxial pinnule surface, and a clear differentiation between costal and intercostal cells on the adaxial surface (Cleal et al. 1990). Brongniart (1828, 1831, p. 250) introduced the form-genus Odontopteris for bipinnate fronds with the pinnules adhering to the rachis by their entire basal width, and the veins ascending directly from the rachis without or almost without the intervention of a midrib. The type species is the well-known Stephanian element Odontopteris brardii Brongniart. Cleal et al. (1990) observed that the frond architecture as based on Odontopteris minor-zeilleri Potonie (a synonym of O. brardii, according to Wagner 19646) is similar to that of Neuropteris sensu stricto, and that the epidermal structure is also the same, with the exception of a more random orientation of the stomata in Odontopteris. Weiss (1869) distinguished Mixoneura as a subgenus of Odontopteris, with Odontopteris obtusa Brongniart as the type species. However, he interpreted this species in the sense of Brongniart’s (1831) plate 78, figure 3 which does not belong to the same taxon as Brongniart’s (1831) plate 78, figure 4, the holotype of Odontopteris obtusa. Brongniart’s plate 78, figure 3 and Weiss’s (1869) specimens are generally assigned to Odontopteris lingulata (Goppert) Schimper, which is a possible synonym of Odontopteris subcrenulata (Rost) Zeiller. It is noted that the species grouped around Mixoneura lingulata form a sufficiently characteristic complex to justify Mixoneura as a form-genus in its own right. However, Zeiller (1906) and, above all, Bertrand (1930) used Mixoneura for neuropterid species with partly odontopteroid pinnules, i.e. pinnules which are broadly attached to the rachis, in the upper parts of pinnae. This modification of Weiss’s (sub)genus has created a 4 PALAEONTOLOGY, VOLUME 41 certain amount of confusion, and this has caused most authors to abandon the term Mixoneura. Mixoneura, in Bertrand’s usage, refers to the group of Neuropteris ovata Hoffmann, which forms part of Neuropteris as restricted by Cleal et al. (1990). Bertrand’s different usage is to be regretted because Mixoneura Weiss, as originally described, refers to Mixoneura lingulata and similar species, which is a fairly closely circumscribed group that may well be retained as a separate genus. The members of this genus constitute a morphologically cohesive group of species, which correspond palaeoecologically to plants that seem to have lived in the better drained habitats, i.e. mesophile plants. Potonie (1893, p. 133) later introduced Neurodontopteris as a form-genus transitional between Neuropteris and Odontopteris. He compared it with Mixoneura Weiss, a genus which he rejected since he regarded it as being part of Odontopteris. Potonie (1893) based Neurodontopteris on the species Neuropteris auriculata Brongniart, a form which is quite different from the species grouped around Mixoneura lingulata. Zeiller (1906) considered Neurodontopteris to be synonymous with Mixoneura , which he interpreted as a morphogenus showing characters intermediate between Neuropteris and Odontopteris. He referred Neurocallipteris neuropteroides (Goppert) Sterzel to Mixoneura. Potonie (1907) assigned ‘ Mixoneura ’ neuropteroides to Neurodontopteris, and regarded Neurocallipteris Sterzel (1895) as a synonym. Nowadays, on considering the various type species of the genera Mixoneura, Neurodontopteris, and Neurocallipteris, it is apparent that these three form-genera may well be distinguished as separate entities. Cleal and Shute (1995), when discussing the various neuropterid genera, considered Neurodontopteris and Neurocallipteris, but did not comment on Mixoneura. *1831 non 1869-72 *1870 *1888 *1890 *1904 *1913 *1956 ?* 1961 1964 a *1964 b 1969 *1969 *1970 ?* 1971 Neuropteris obtusa (Brongniart) comb. nov. Plates 2-6 Odontopteris obtusa Brongniart pars, p. 255, pi. 78, fig. 4 ( non fig. 3 [= Odontopteris subcrenulata (Rost) Zeiller or Odontopteris lingulata (Goppert) Schimper], [Basionymj. Odontopteris obtusa Brongniart; Weiss, p. 36, pi. 3, figs 1-5 [ = Mixoneura lingulata (Goppert) comb, nov.]; pi. 6, fig. 12 [= Neurocallipteris neuropteroides (Goppert) Cleal, Shute and Zodrow?]. Callipteris discreta Weiss, p. 872, pi. 20, figs 1-2. Odontopteris obtusa Brongniart; Zeiller, in Renault and Zeiller, p. 224, pi. 23, figs 1, 1a, 2, 2a-b [fig. 2 = reillustration of holotype], Neuropteris raymondi Zeiller, p. 147, pi. 9A, fig. 4. Odontopteris obtusa Brongniart; Potonie, 11-23, 1 fig. Alethopteris discreta (Weiss) Franke (pars), 173, figs 1-2 ( non figs 3-4 [= Gondomaria grandeuryi (Zeiller) comb. nov.]). Neuropteris raymondi Zeiller; Doubinger, p. 114, pi. 12, fig. 3; pi. 13, fig. 1 [both photographic reproductions of the holotype]. Odontopteris glandulosa Remy und Remy, p. 1, pi. 1, figs 1-11. Odontopteris cf. robusta Zalessky; Wagner, pi. 1, figs 2, 2a. Mixoneura subraymondi Wagner, p. 10, pi. 10, figs 21-22; pi. 11, figs 23-24. Mixoneura raymondi (Zeiller) Wagner, in Wagner et al., p. 124, pi. 1, figs l-2a. Neuropteris thompsoniana Darrah, p. 99, pi. 54, fig. 2. Neuropteris raymondi Zeiller; Doubinger, p. 279, pi. 15, fig. 4 [holotype]. Odontopteris glandulosa Remy und Remy; Doubinger und Germer, p. 135, pi. 7, fig. 6 [reillustration of Remy and Remy 1961, pi. 1, figs 1-2, 5-6). EXPLANATION OF PLATE 1 Figs 1-2. Neuropteris obtusa (Brongniart) comb, nov; copy of Odontopteris obtusa as figured by Zeiller (1888, pi. 23); x 1 (except 1A, x 3). 1, 1A, Commentry (France). 2, Brongniart’s holotype; Terrasson near Brive (France). PLATE 1 WAGNER and CASTRO, Neuropteris 6 PALAEONTOLOGY, VOLUME 41 1981 Odontopteris alpina (Sternberg) Geinitz; Fritz and Boersma, p. 394, figs 7-8. 71985 Odontopteris obtusa Brongniart; Iwaniw, pi. 4, fig. 5. 1986 Odontopteris alpina (Sternberg) Geinitz; Fritz and Boersma, p. 255, fig. 20. Description. Pinnae of the penultimate order showing a flat rachis, up to 8 mm wide (PI. 1, fig. 1), and closely spaced pinnae of the last order (PI. 2, fig. 3). Thin rachis of the last order (0-3-0-5 mm wide), apparently rounded in cross section. Pinna terminals gradually tapering, with progressively more broadly adherent pinnule bases, and possessing a relatively small but well individualized apical pinnule, which tends to become rhombic (PI. 2, figs 3, 5). Pinnules variable in length/breadth ratio and also in the insertion, which ranges from adherence at a single point to, more commonly, a partial or even full adherence of the pinnule base to the rachis. Pinnule length 7-20 mm, at 3-7 mm width, with a length/breadth ratio of c. 2-2-2-5. Pinnules in the basal part of pinnae are attached by a strongly decurrent stalk, which is almost reclined on to the rachis, and thus simulates a partial adherence to the rachis; these pinnules are ovoid, with rounded (cordate) bases. However, higher up in the pinnae, the pinnule bases fuse with the rachis, with the decurrent midrib lying subparallel to the rachis, and the lateral veins arising from the partially and sometimes wholly fused decurrent midrib; this creates the impression of the lateral veins being derived from the rachis on the basiscopic side of pinnules that are rather asymmetrical. The pinnules in the higher parts of pinnae show a decurrent base on the basiscopic side, whilst the acroscopic side is still contracted to some extent. In the uppermost parts of pinnae, the pinnule bases slope downwards to such an extent as to form a narrow band of limb along the rachis. Veining pattern is characterized by a thin, decurrent midrib which dissolves into even thinner, although well- marked, lateral veins at about half-way to one-third up the pinnule length. Lateral veins arise from the midrib at a very narrow angle ; they are broadly arching and dichotomize at least twice, often even three times, before reaching the pinnule margin at angles of generally c. 60° (varying between 50° and 80°). Widely spaced lateral veins (16-37 veins/ 10 mm) reach the pinnule margin at fairly regular intervals (which become more irregular where vein splits occur near the pinnule margin). A rounded, rather large Cyclopteris pinnule (PI. 4, fig. 3), has been found in association. Comparisons. Neuropteris subauriculata Sterzel is another species with pinnules showing a decurrent midrib and, in the upper parts of pinnae, a tendency towards partial fusion of the pinnule bases with the rachis. The illustrations by Remy and Remy (1959) show a higher nervation density, and Neuropteris subauriculata, as figured by Daber (1955), shows rather massive terminals. The presence of large triangular pinnules and of pinnae with Cyclopteris pinnules suggests a comparison with Neuropteris ovata Hoffmann and similar species. However, epidermal characters support the attribution to Macroneuropteris, as proposed by Cleal et al. (1990) (see also Cleal and Shute, 1995, p. 23). The difference between this species and Neuropteris britannica Gutbier is not very clear. The latter species has also been referred to Macroneuropteris by Cleal et al. (1990). Odontopteris jeanpaulii Bertrand (= O. alpina sensu Geinitz, non Sternberg) (see Daber 1955, pi. 24, figs 1, la) is also quite similar, although this species possesses very large pinnules. Remy and Remy (1977, p. 294, fig. 167) apparently rejected Bertrand’s species, and referred its type specimen back to Odontopteris alpina (Sternberg) Geinitz. Doubinger and Grauvogel-Stamm (1980) also rejected the introduction of Odontopteris jeanpaulii, and admitted the correctness of Geinitz’s (1855) identification of his specimens with ‘ Neuropteris ’ alpina Sternberg. The illustrations provided by Daber (1955), Remy and Remy (1959, 1977) and Doubinger and Grauvogel-Stamm (1980) show pinnules which are broadly attached to the rachis. The veins are markedly bundled, showing up to EXPLANATION OF PLATE 2 Figs 1-6. Neuropteris obtusa (Brongniart) comb, nov; loc. 1821, near Tejerina (Leon, north-west Spain); Prado Formation (lower Cantabrian). 1-3, 5-6, GT 00001 ; two last order pinnae belonging to the pinna of the penultimate order (previously figured in Wagner et al. 1969, pi. 1, fig. 1, la) showing pinnules with decurrent basiscopic and constricted acroscopic sides ; pinna terminal and lateral pinnules enlarged to show details of venation ; carbonized dots between veins interpreted as masses of resting spores of rusts. 4, GT 00003; pinna fragment. 1-2, 5-6, x6; 3^4, x 3. PLATE 2 WAGNER and CASTRO, Neuropteris PALAEONTOLOGY, VOLUME 41 four successive dichotomies. They are very widely spaced, c. 14—15 veins/ 10 mm. The pinnule apices are less rounded than those of Neuropteris obtusa, and the veins are less arched, more repeatedly forked, and more widely spaced than in N. obtusa. Doubinger and Grauvogel-Stamm (1980, pi. 4) illustrated a dense array of spots in between veins, which they interpreted as hairs or glands. They did not consider the possibility of fungal attack (rusts). The specimens figured as Odontopteris alpina by Fritz and Boersma (1981, 1986) are here attributed to Neuropteris obtusa. Odontopteris robusta Zalessky, a similar species, was figured originally only with a diagrammatic drawing (Zalessky, 1934, p. 1113). A natural size photograph of a different specimen was added subsequently by Novik (1952, pi. 59, fig. 1). Both illustrations refer to material from the type area (Donbass in southern Russia and Ukraine). Although these illustrations are too poor to be judged adequately, the accompanying description by Zalessky (1934, p. 1112), mentions broadly attached pinnules with a decurrent basiscopic side and a slightly contracted acroscopic side, as well as a venation which is characterized by a well-defined midrib reaching two-thirds up the pinnule length, and repeatedly forked, arching lateral veins. Terminals to the pinnae of the last order are shown as rather massive, with a large, well-developed apical pinnule. A rather similar specimen from the Guardo Coalfield of north-west Spain has been figured photographically by Wagner (1983, pi. 7, fig. 2; pi. 8, fig. 1). It has only been identified tentatively in view of the poor illustration of the holotype, which is consequently difficult to use. Another specimen (Wagner 1964a, pi. 1, figs 2, 2a), from the same coalfield, is here included in the synonymy of Neuropteris obtusa. The possibility exists that ‘ Odontopteris ’ obtusa and ‘ Odontopteris ’ robusta are the same species. Not only are the pinnule shape and insertion fairly comparable, but the nervation is quite similar. Insofar as a vein count is feasible, Zalessky’s drawing shows c. 18 veins/ 10 mm, which is within the range recorded for Neuropteris obtusa. A similar vein density is recorded for the specimens figured by Wagner (1983) as Odontopteris cf. robusta. Zalessky (1934) provided only a description, not making any comparisons. Novik (1952) made comparison with Odontopteris kryshtofovichii Novik, but the latter seems to be a mariopterid; thus making the comparison irrelevant. The rounded apices and the tendency to show a contraction at the acroscopic side, make the pinnules of Neuropteris obtusa and Odontopteris robusta different from those of Odontopteris brardii Brongniart, which are characterized by a rather marked asymmetrical shape, and generally more acute apices. Remarks on synonymy. Odontopteris obtusa Brongniart was based on two specimens, which the author of the species already perceived as belonging to two different entities. Brongniart (1831, p. 255) designated his plate 78, figure 4 as the type. The other specimen (Brongniart, 1831, pi. 78, fig. 3) was attributed by Zeiller (in Renault and Zeiller 1888, p. 227) to Odontopteris lingulata (Goppert) Schimper, a species that had been illustrated by Weiss (1872, pis 2-3) as Odontopteris obtusa (note that the specimen figured on Weiss’s pi. 6, fig. 12 is different, i.e. possibly belonging to Neurocallipteris neuropteroides (Goppert) Cleal, Shute and Zodrow). Weiss (1869, p. 36) placed Neuropteris subcrenulata Rost, 1839 in synonymy, and the same suggestion was made by Zeiller (1888, p. 227). Weiss (1869, p. 36; 1870, p. 864) used his (incorrect) interpretation of Odontopteris EXPLANATION OF PLATE 3 Figs 1-3. Neuropteris obtusa (Brongniart) comb, nov; small carbonized dots irregularly distributed on the pinnule; loc. 1821 near Tejerina (Leon, north-west Spain); Prado Formation (lower Cantabrian). 1, GT 00009; single pinnule showing venation. 2, GT 00020; pinnules with a decurrent base on the basiscopic side, and a constriction on the acroscopic side, a midrib up to about half-way along the pinnule length, and broadly arching lateral veins ; note the apparent irregularity in scatter of small dots of carbonized organic material between veins. 3, GT 00004; fragment of penultimate pinna with relatively small, more-or-less ovoid pinnules with constricted bases, particularly in lower part of pinnae; pinnules higher up pinnae show progressive fusion of the basiscopic sides with the rachis, thus tending to become asymmetrical and decurrent; midrib thin; broadly arching, repeatedly forked lateral veins. All x 6. PLATE 3 WAGNER and CASTRO, Neuropteris 10 PALAEONTOLOGY, VOLUME 41 obtusa Brongniart as the type of the form-genus Mixoneura Weiss, which he introduced as a subgenus of Odontopteris. Since he based his concept on Odontopteris lingulata and not on the real Odontopteris obtusa, as represented by the holotype (as designated by Brongniart, 1831, p. 255, as Te veritable type’), the mention by Andrews (1970, p. 133) of Odontopteris obtusa as the type species of Mixoneura is formally correct but misleading in the absence of a reference to the misidentification involved. The synonymy of ‘ Odontopteris ’ lingulata and ‘ Odontopteris ’ subcrenulata used to be regarded as well-established, and this is why Mixoneura subcrenulata (Rost) is generally mentioned as the type of the form-genus Mixoneura (compare Wagner 19646, p. 8). However, Doubinger and Remy (1958) distinguished between ‘'Odontopteris lingulata ’ and ‘'Odontopteris'’ ( alias'. Neuropteris, Mixoneura ) subcrenulata , and regarded these species as different taxa. They further distinguished between three varieties of O. subcrenulata, viz. var. subcrenulata, var. gallica Doubinger and Remy, and var. elongata Doubinger and Vetter. The subtle differences between the three varieties of Mixoneura subcrenulata on the one hand and Mixoneura lingulata on the other require well- preserved material for a proper differentiation. If one accepts the criteria described by Doubinger and Remy (1958) as valid, the type species of Mixoneura Weiss is Mixoneura lingulata (Goppert) comb. nov. (basionym: Neuropteris lingulata Goppert, 1846, p. 104, pi. 8, figs 12-13). Since Doubinger and Remy (1958) reported Odontopteris lingulata as being restricted to the lower Rotliegend of the Saar-Nahe Basin and of Thuringia, this would apparently exclude Brongniart’s plate 78, figure 3, which was from Terrasson in the Brive region, south-central France. However, they may have simply overlooked Brongniart’s specimen, which is not discussed in their paper. Whatever the problems with the recognition of the different taxa in the Mixoneura subcrenulata- lingulata complex, it is clear that the specimen on Brongniart’s plate 78, figure 3 (originally attributed to Odontopteris obtusa Brongniart) belongs to the Mixoneura complex and must be excluded from Neuropteris obtusa (Brongniart) comb. nov. All authors are agreed on this point. Zeiller’s (1888) more accurate rendering of the true holotype of O. obtusa has allowed a proper assessment of the characters of the lateral pinnules of this species. Along with the holotype, Zeiller (1888) also figured a more substantial specimen of ’ Odontopteris’ obtusa from the upper Stephanian of the Commentry Coalfield in the Massif Central, France. Zeiller’s illustrations are reproduced here as Plate 1. This larger specimen is a fragment of a pinna of the penultimate order with subopposite last order pinnae, which taper gradually and end in a small, rhombic, apical pinnule. The lateral pinnules are attached by the entire base, as is shown by the single pinnule figured at x 3 enlargement (Zeiller 1888, pi. 23, fig. 1a), but there is a slight contraction on the acroscopic side. Zeiller’s illustration (PI. 1, fig. 1) also shows this. All pinnules are rather small (i.e. not longer than 10 mm, with a length/breadth ratio of about 2:1). The midrib is shown to be thin but well individualized to at least half-way up the pinnule, with arching lateral veins bundled into twice- forked units. The vein density is c. 24 veins/10 mm. Wagner (19646, p. 14) mentioned that ’ O.’ obtusa seemed to possess more broadly attached pinnules with a somewhat wider nervation than occurred in ‘ Mixoneura ’ subraymondii (which was put at 29-37 veins/ 10 mm). However, the subsequent inclusion of ‘ Mixoneura’ raymondii, with a lower vein density (16-25 veins/ 10 mm), and a more generous interpretation of the variation in pinnule morphology, apparently removes the objection to regarding all these remains as belonging to a single taxon. The large specimen of ‘O. ’ obtusa figured by Zeiller (1888, pi. 23, fig. 1) with length/breadth pinnule ratios of about 2:1, may well represent the higher part of a pinna of the penultimate order, whereas the holotype of Neuropteris raymondii Zeiller, 1890 represents the lower part of a penultimate pinna. The latter shows more elongate pinnules (length/breadth ratio c. 3:1), with more constricted bases, but it displays a venation which is totally comparable to that of Neuropteris obtusa. The pinnules in the upper part of the pinnae of the last order of N. raymondii display the wide insertion that is characteristic of N. obtusa. It is very likely that N. obtusa and N. raymondii represent examples of the same species, and that the differences observed are due merely to different positions in the frond. Indeed, specimens of transitional characteristics, albeit closer to N. raymondii, occur in the Stephanian of north-west Spain (Wagner 19646, under the name of Mixoneura subraymondii Wagner; Wagner, in Wagner et al. 1969, as Mixoneura raymondii (Zeiller) WAGNER AND CASTRO: CARBONIFEROUS PTERIDOSPERM 11 Wagner; specimen reproduced here partially as PI. 2, fig. 3). The thin midrib, the rather steep departure of the lateral veins from the midrib, their broadly arching course, and the repeated forking, are all characters shared between N. obtusa and N. raymondii (including Mixoneura subraymondii). The vein density of c. 25 veins/ 10 mm is also similar, as is the small rhombic terminal to the pinnae of the last order. The only apparent difference is in the pinnule insertion, but this can be explained with reference to the position in the frond. If the synonymy between these three taxa is admitted, as the present writers do, N. obtusa has priority. Another synonym is Callipteris discreta Weiss. This species was assigned to Gondomaria by Wagner and Lemos de Sousa (1982), but this is now perceived as having been in error. Callipteris discreta was introduced by Weiss (1870) on the basis of three specimens. The two figured specimens (compare the synonymy list), show a marked resemblance to Neuropteris obtusa in the shape and insertion of the pinnules as well as in the general pattern of the nervation (see PI. 7, figs 1-3, which is the counterpart of Weiss, 1870, pi. 20, fig. 1). Since Weiss used the species name obtusa for the Mixoneura lingulata - subcrenulata complex, it probably did not occur to him to compare his material with ‘ Odontopteris' obtusa Brongniart sensu stricto. Callipteris discreta Weiss was referred to Alethopteris by Franke (1913), who joined it with Alethopteris grand' euryi Zeiller. There is, indeed, a resemblance, particularly in the vein pattern, but the pinnules of Zeiller’ s species show more markedly decurrent bases and a length/breadth ratio of 3:5 to 4: 1. Wagner and Lemos de Sousa (1982) accepted the wide sense in which ‘ Alethopteris ' discreta had been interpreted by Franke, and synonymized it with Gondomaria alethifolia Teixeira, 1964. However, the two species synonymized by Franke (1913) are probably two different taxa. Teixeira’s G. alethifolia , from the upper Stephanian of Portugal, is apparently the same as Alethopteris grand' euryi as described by Zeiller (1888) from Commentry, and the correct combination should therefore be Gondomaria grand' euryi (Zeiller) comb. nov. (basionym: Alethopteris grand' euryi Zeiller, 1888). On the other hand, ‘ Alethopteris ' discreta Weiss is more properly assigned to Neuropteris obtusa. The specimens from the Westphalian of Portugal figured by Wagner and Lemos de Sousa (1982) as Gondomaria discreta (Weiss) are now believed to have been assigned incorrectly. Their proper identification is in abeyance, but it may be a fern and quite outside the group of fossils considered in the present paper, which are likely to be pteridosperms. The holotype of Neuropteris thompsoniana Darrah, 1969 may be included in Neuropteris obtusa. Darrah suggested a comparison with Neuropteris heterophylla, but this species is obviously very different. The type is from the upper Westphalian D of Illinois, USA. It is a matter of conjecture as to whether the small fragment figured and described by Remy and Remy (1961) as Odontopteris glandulosa may be assigned to Neuropteris obtusa. Not only is it a small fragment, but its venation is poorly preserved. However, it apparently shows the vein pattern known for N. obtusa. The justification for the recognition of this species as a special entity was the extensive covering by small dots, which Remy and Remy (1961) regarded a glands. They excluded the possibility that fungal attack was involved, but this is by no means clear to the present writers. Remy and Remy’s interpretation was accepted by Doubinger and Germer (1971), who refigured the holotype of O. glandulosa. The same kind of dots appear in a number of specimens figured as N. obtusa in the present paper. ‘ Odontopteris' obtusa Brongniart sensu stricto has rarely been reported in the literature, and some of the records must be regarded as doubtful. The small fragment figured by Zeiller (1890) from the Autunian may have been identified correctly, but it seems too fragmentary for confident identification. The same problem attaches to the small fragment figured by Iwaniw (19856). However, this fragment is from the same area in north-west Spain as most of the specimens figured herein. The specimen figured and described by Vetter (1968, p. 119, pi. 32, figs 1, 4) from the Stephanian of Decazeville, France, cannot be judged adequately from the illustrations, but does not conform to the species described here. The three fragments illustrated from Saarland as Odontopteris obtusa by Doubinger and Germer (1971, pi. 46, fig. 3a-c) are also excluded. Their vein density is too high. These specimens are also too small to be identified reliably. A North American (Dunkard) specimen figured by Darrah (1975, fig. 7) as Odontopteris cf. obtusa Naumann is 12 PALAEONTOLOGY, VOLUME 41 Odontopteris obtusiloba Naumann. Wagner and Lyons (1997) suggested that this specimen should be referred to Odontopteris brardii Brongniart. On the other hand, two specimens from the Stephanian of the Carnic Alps (Fritz and Boersma, 1981), recorded as Odontopteris alpina, clearly belong to Neuropteris obtusa. They show a marked resemblance to specimens recorded in the literature as Neuropteris (vel Mixoneura ) raymondii. Wagner (in Wagner et al. 1969, p. 125) compared ‘ Mixoneura ’ raymondii (Zeiller) with a specimen figured as Neuropteris sp. by Germer et al. (1966, pi. 5), which was later described as Neuropteris schaeferi by Doubinger and Germer (1975). The more adequate illustration of this specimen by Doubinger and Germer (1975) shows a higher nervation density (c. 45 veins/ 10 mm), and allows a comparison with Neuropteris ovata Hoffmann, as is suggested also by the investigation of its cuticle by Saltzwedel (1968), as quoted by Cleal and Shute (1995, p. 28). Remarks on generic assignment. The species dealt with in the present paper has been recorded variously as Odontopteris , Neuropteris, and Mixoneura, and it has been referred to various different species by the different authors. The distinctions apparently depended mainly on the position in the frond. The name Mixoneura is only applied properly to the species grouped around Mixoneura lingulata and Mixoneura subcrenulata, which are obviously quite different. The form-genera Neuropteris and Odontopteris were discussed most recently by Cleal et al. (1990), who pointed out the close similarities between these two genera, which are distinguished almost entirely on pinnule insertion and the virtual absence of a midrib in Odontopteris. Whereas this provides a reasonable distinction for the type species, Odontopteris brardii Brongniart, the presence of both neuropteroid and odontopteroid pinnules in the species dealt with in the present paper makes its attribution to either one or the other form-genus somewhat arbitrary. However, there may be merit in restricting Odontopteris to O. brardii and similar species (e.g. Odontopteris minor Brongniart and Odontopteris reichiana Gutbier), in which case the species described here is probably best regarded as Neuropteris obtusa (Brongniart) comb. nov. (basionym: Odontopteris obtusa Brongniart 1831 pars, as referenced in the synonymy list). Remarks on figured specimens. Plate 2, figure 3 is a partial reproduction of the pinna of the penultimate order depicted in Wagner et al. (1969, pi. 1, fig. 1, la) as Mixoneura raymondii (Zeiller). This specimen is directly comparable to the larger fragment of a pinna of the penultimate order figured from Commentry in France by Zeiller (1888, pi. 23, fig. 1; PI. 1), to which it could be attached to complete the upper part. This suggests a pinna up to c. 0-3 m long, with lateral pinnae (of the last order) 50-100 mm long. These two pinnae of the penultimate order show pinnules 6-10 mm long. The also very comparable remains figured by Weiss (1870) as Callipteris discreta (refigured as Alethopteris discreta by Franke 1913; PI. 7, figs 1-3) are penultimate pinna fragments with slightly longer pinnules (up to 13 mm), whereas the holotype of Neuropteris raymondi Zeiller, EXPLANATION OF PLATE 4 Figs 1-2, 4-5. Neuropteris obtusa (Brongniart) comb, nov; interveinal dots interpreted as carbonized remains of resting spore masses of rusts. 1-2, 5, loc. 1821, near Tejerina (Leon, north-west Spain); Prado Formation (lower Cantabrian). 1, GT 00015; terminal part of pinna showing characteristically small apical pinnule and relatively broad lateral pinnules with partially fused, decurrent bases; x 3. 2, GT 00016; presumably rather high part of a penultimate pinna with short, relatively broad pinnules showing partial fusion with the supporting rachis; x 6. 5, GT 00019; exceptionally long pinnules, corresponding most probably to the lower part of a major pinna ; pinnules constricted at both sides of the base ; venation pattern and interveinal dots difficult to see at this enlargement; x 3. 4, GT 00056; pinnules showing the venation and interveinal dots; loc. 1181, near Tejerina (Leon, north-west Spain); Ocejo Formation (lower Cantabrian); x6. Fig. 3. Cyclopteris assumed to belong to Neuropteris obtusa (Brongniart) comb, nov., with which it was found in association. It shows an equally wide venation, but no interveinal dots; GT 00041 ; same locality as figs 1-2, 5; x 1. PLATE 4 WAGNER and CASTRO, Neuropteris, Cyclopteris 14 PALAEONTOLOGY, VOLUME 41 1890 shows even longer pinnules (up to 16 mm). The shorter pinnules in the higher parts of pinnae are markedly odontopteroid, with a decurrent base on the basiscopic side, whereas the longer pinnules in the lower parts of pinnae show contracted bases on both the acroscopic and basiscopic sides, even though the basiscopic side is less heavily constricted. This type of pinnule is most obviously displayed by the holotype of N. raymondii, but it is also seen in the terminal part of a pinna of the last order figured by Wagner (in Wagner et al. 1969, pi. 1, fig. 2). These pinnule variations combined with the size variation of last order pinnae suggest that the frond was at least tripinnate, possibly about 0-7-0-8 m wide, with a total length in excess of 1 m. The variation in pinnule size, length/breadth ratio, and insertion (more or less decurrent basiscopic side which is contracted in the pinnules lower down the pinnae) is shown by the specimens depicted from a single locality (Tejerina, loc. 1821) on Plates 2—4. These include both short, rounded, broadly inserted pinnules (PI. 4, fig. 2) and rather elongate pinnules with constricted bases (PI. 4, fig. 5). Plate 7 of the present paper reproduces the counterpart of Weiss’s (1870, pi. 20, fig. 1) specimen of ‘ Callipteris' discreta Weiss, from the Westphalian D of Saarland. This shows pinnules that are wholly comparable to the examples figured on Plate 5, figure 4, and Plate 6, figure 6, from the Stephanian B of north-west Spain. Occurrence. Although Neuropteris obtusa is a rare species, the list of synonymy and the extensive illustration herein show it to have been widespread in Europe, with a stratigraphical range that embraces both Westphalian D (Saarland, Germany; Guardo Coalfield, north-west Spain) and the entire Stephanian (Massif Central, France; north-west Spain; Carnic Alps). The records by Brongniart (1831) and Zeiller (1888) are from the Stephanian C/lower Autunian in France, whilst Zeiller (1890) refers to the Stephanian B. The Spanish records are from lower down in the Stephanian, i.e. Cantabrian and Stephanian B ( sensu Carmaux, which is lower than the type Stephanian B of St Etienne, both in the French Massif Central). The Stephanian C and lower Autunian in France probably represent the same time interval in different (independent) basins. The records from the Carnic Alps are from the (high) Stephanian of Schulter and Rattendorfer Aim in Karnten, Austria (Fritz and Boersma 1981, 1986 -as Odontopteris alpina). If Neuropteris thompsoniana Darrah is accepted as a synonym, Neuropteris obtusa occurs also in the upper Westphalian D of the Mazon Creek horizon (Francis Shale overlying Colchester No. 2 Seam, Desmoinesian), Illinois, in North America. PROBABLE PARASITISM BY RUSTS The lower Cantabrian locality 1821 at Tejerina (Leon province), north-west Spain, has yielded 22 remains of Neuropteris obtusa (originally called Mixoneura raymondii by Wagner, in Wagner et al. 1969), all with a fairly dense scattering of round elevations on the pinnule lamina (Pis 2-4). Specimens from locality 1181, also in the lower Cantabrian of Tejerina, show these ‘pustules’ too (PI. 4, fig. 4). These rounded elevations occur invariably on the pinnule limb area in between veins and appear as carbonized dots even where the cuticle and other organic matter have disappeared as a result of oxidation by weathering. This suggests a dense array of organic matter in domed areas on the softer part of the pinnule lamina. There is no structure preserved and maceration (oxidation) would not have yielded any results in view of the fairly high rank of the coals in this area. Three possibilities come to mind: (1) rusts, (2) possible glands, and (3) sporangia (sori). The last is ruled out in view of the positioning in between veins; sporangia would require a vascular EXPLANATION OF PLATE 5 Figs 1-6. Neuropteris obtusa (Brongniart) comb, nov; Cinera-Matallana Coalfield (Leon, north-west Spain); Stephanian B. 1-2, CM 00011 ; loc. 4563; Pastora Formation. 3, 5-6, V-2821 (Museo Nacional de Ciencias Naturales, Madrid); pinnules previously figured as Mixoneura subraymondi Wagner (in Wagner 1964 b, pi. 10, fig. 22, 22a), without ‘pustules’; loc. 931 ; San Francisco Formation. 4, CM 00010; loc. 3689; Cascajo Formation. All x 6. PLATE 5 WAGNER and CASTRO, Neuropteris 16 PALAEONTOLOGY, VOLUME 41 connection. The second possibility is the one selected by Remy and Remy (1961) for their species Odontopteris glandulosa. This shows very similar structures to those found in the specimens figured in the present paper from locality 1821 (Pis 2^1). However, even though it cannot be rejected out of hand, this second possibility also seems unlikely to the present writers. The carbonized dots in between veins are irregularly distributed (see in particular PI. 3, fig. 2), whereas glands would show a more regular pattern. It is also noteworthy that the remains described as Mixoneura subraymondii by Wagner (19646), and assigned herein to Neuropteris obtusa, do not show rounded elevations in between veins. Assuming that the specimens from locality 931 in the Cinera-Matallana Coalfield (i.e. ‘ Mixoneura ’ subraymondii, as described by Wagner 19646), are correctly assigned to the same species as occurs at locality 1821 at Tejerina (Wagner et al. 1969; Wagner and Winkler Prins 1985, p. 378), then it is apparent that the rounded elevations found on the pinnules of the specimens from Tejerina (loc. 1821) are not invariably present in this species. The preservation is equally good in both localities. Although it is possible to contend that the presence of glands is ecologically controlled, thus allowing for their presence or absence in the different localities, it is easier to assume that one is dealing with an element foreign to the plant. A comparison with rusts thus becomes the more reasonable assumption. The same reasoning was applied by Goppert (1836, p. 262) when describing similar structures on Hymenophyllites zobelii Goppert (now Palmatopteris zobelii (Goppert) Potonie). He attributed these structures to ‘Blattpilze’ (rusts) and described these under the name of Excipulites neesii Goppert. The case was restated by Goppert (1841, pp. 55-56, pi. 5, figs 3-4), who refigured the same specimens. Goppert’s explanation has been generally accepted. Carpentier (1937) figured and described similar dots on Callipteris (now Autunia) conferta (Sternberg) Brongniart. He referred these to Excipulites and admitted the likelihood of fungal attack, but left open the possibility of glands. Potonie (1893) pointed out that an anatomical investigation of these rounded elevations would be required so as to be absolutely certain. This is undoubtedly true, but requires a very low degree of maturity of the organic matter to make this a viable proposition. In the absence of absolute proof, one has to rely on analogy for the assumption that these are rusts. Uredinales have a complicated life history, with five different stages, some of which are quite ephemeral. Some of these stages are characterized by fairly thick-walled spores occurring in sori which are apt to be preserved by carbonization, whereas others do not produce structures likely to be preserved in this manner. The resting stage, which is represented by teleutospores, is probably the one most likely to be preserved by carbonization. It lasts several months and the teleutospores possess relatively thick walls. Teleutospores are described as occurring either free or united laterally to form small groups, layers or columns (Alexopoulus et al. 1995). The teleutospore sori extend beyond the epidermis of the host (which they pierce), and are capable of forming small rounded elevations similar to the ones seen on the pinnules of Neuropteris obtusa from the lower Cantabrian of Tejerina (Iocs 1181 and 1821). However, aecia (with aeciospores) and uredia (with uredospores) also form masses which pierce the epidermis of the host forming a kind of pustule. The drawing presented by Goppert (1836, pi. 36, fig. 4) is suggestive of an aecial cup with a peridium surrounding the spore chains. This kind of structure is not present in the material from Tejerina, which shows small rounded elevations, without any suggestion of a central depression. It thus seems most likely that these represent masses of teleutospores, if they are accepted as being rusts. In the specimens from locality 1821 in the Tejerina section, these small elevations apparently EXPLANATION OF PLATE 6 Figs 1-6. Neuropteris obtusa (Brongniart) comb, nov; Cinera-Matallana Coalfield (Leon, north-west Spain); Stephanian B. 1-5, V-2821, V-2576 and V-2822 (Museo Nacional de Ciencias Naturales, Madrid); pinnules previously figured as Mixoneura subraymondi Wagner ( in Wagner 19646, pi. 10, figs 22, 22b; 21, 21a; and pi. 11, figs 23, 23a, respectively), without ‘pustules’; loc. 931 ; San Francisco Formation. 6, CM 00009; loc. 3689; Cascajo Formation. All x6. PLATE 6 WAGNER and CASTRO, Neuropteris PALAEONTOLOGY, VOLUME 41 cover the upper surface of the pinnules, where they occur in single rows of well-spaced dots in between the lateral veins. The spacing is irregular, even where the pinnule appears fully covered. Surface weathering has removed most of the organic matter, leaving the presumed resting spores of the rust as shiny dots of carbonized material on the convex surface of the pinnule. Where the carbonized elevations have been removed, a small rounded pit marks the position of each, thus showing that the probable spore mass partly protruded and partly occupied a position within the epidermis and the subepidermal area of the pinnules. The possibility of fungal attack by rusts was first mentioned from the Carboniferous of Spain by Wagner (19646) when describing material of Mixoneura matallanae Wagner. The presence of epiphytic fungi on Sphenopteris biturica Zeiller was mentioned by Doubinger and Alvarez-Ramis (1964), but the only specimen illustrated seems to show immature sporangia. Fernandez-Marron (1984) described fungal attack on certain plant fossils from the upper Westphalian of north-west Spain. She figured a specimen of Linopteris obliqua (Bunbury) Zeiller, which may indeed be assumed to have been infested by rusts. She also identified other cases of fungal attack, but these are rather less convincing. Fernandez-Marron (1984) suggested that certain specimens figured by Stockmans (1933), Laveine (1967) and Wagner (1965) would have suffered fungal attack, but this cannot be accepted since the specimens quoted show the adherence of Spirorbis pusillus Martin worm tubes. Iwaniw (19856, pi. 1, fig. 3) figured probable rusts on a specimen of Eusphenopteris neuropteroides (Boulay) Novik from the lower Cantabrian of north-west Spain. Probable rusts on foliage remains of Dicksonites and ‘ Mixoneura ’ wagnerii Lorenzo from the upper Stephanian of La Magdalena in north-west Spain were figured by Castro (1997), who discussed the phenomenon extensively. These examples are similar to the ones illustrated in the present paper. Fungal hyphae were demonstrated in connection with Carboniferous pteridosperm leaf remains by Barthel (1961), who concluded on an ectoparasitic relationship. Although this proves that fungal activity on Carboniferous pteridosperm leaves did occur, the nature of Barthel’s evidence is both different from and more convincing than ours. CONCLUSIONS The rare, but geographically widespread, Westphalian D and Stephanian species Odontopteris obtusa Brongniart is apparently the same as Neuropteris raymondii Zeiller, ‘ Mixoneura ’ subraymondii Wagner, ‘ Callipteris' discreta Weiss, and Neuropteris thompsoniana Darrah. This species is assigned to Neuropteris in the present paper. It is assumed that this species was prone to fungal attack leading to the fossilized (carbonized) remains of masses of resting spores (teleutospores?) of rusts found as small rounded elevations in the interveinal areas of pinnules. Whether these elevations merit separate taxonomic treatment as Excipulites Goppert remains an open question. It is admitted that the structures interpreted as possible evidence of fungal attack by rusts, may also be interpreted as glands, a point difficult to resolve without microscopic preparations which are not feasible due to the relatively high degree of carbonization. EXPLANATION OF PLATE 7 Figs 1-3. Neuropteris obtusa (Brongniart) comb. nov. MN1PB 1212; counterpart of type of ‘ Callipteris' discreta Weiss, 1870; Saarland; Amelung coal seam (Westphalian D). 1, two last order pinnae showing pinnules with decurrent basiscopic and constricted acroscopic sides; x2. 2-3, lateral pinnules enlarged to show details of the venation, which are wholly comparable with pi. 5, fig. 4, and pi. 6, fig. 6, from the Stephanian B of Cinera-Matallana ; x 5. PLATE 7 WAGNER and CASTRO, Neuropteris 20 PALAEONTOLOGY, VOLUME 41 Acknowledgements. Drs H. W. J. van Amerom and C. J. Cleal, and Professor H. J. F. Kerp are thanked for critical reading of the typescript, and the provision of literature. Dr Cleal also made some editorial changes, which are acknowledged as improvements. Dr. J. Ubera kindly instructed the authors on the biology of rusts. Photographic facilities in the Jardin Botanico de Cordoba and the Departamento de Paleontologia, Universidad Complutense, Madrid, are gratefully acknowledged. The authors are grateful to Professor M. Barthel (Berlin) for the provision of photographs of the type specimen (counterpart) of ‘ Callipteris' discreta Weiss, and permission to publish these. REFERENCES ALEXOPOULOS, c. J., mims, c. w. and BLACKWELL, M. 1995. Introductory mycology. 4th Edition. John Wiley and Sons, New York, 868 pp. Andrews, H. N. 1970. Index of generic names of fossil plants, 1820-1965. Bulletin of the United States Geological Survey , 1300, 1-354. barthel, m. 1961. Ein Pilzrest aus dem Saarkarbon. Geologie, 10, 856-857, pi. 1. bertrand, p. 1930. 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WAGNER Jardin Botanico de Cordoba Avenida de Linneo s/n 14004 Cordoba, Spain M. P. CASTRO c/ Guzman el Bueno, 84 28003 Madrid, Spain A NEW AREOLIGERACEAN DINOFLAGELLATE FROM THE MIOCENE OF OFFSHORE EASTERN CANADA AND ITS EVOLUTIONARY IMPLICATIONS by G. RAQUEL GUERSTEIN, ROBERT A. FENSOME and GRAHAM L. WILLIAMS Abstract. The dinoflagellate family Areoligeraceae, now extinct, was prominent from the Late Jurassic through to the Paleogene. Some areoligeracean species extend into the Neogene but, until now, no genus was known to originate in that interval. Thus, Ramidinium gen. nov., represented by Ramidinium tridens sp. nov. from the Lower to Middle Miocene of the Jeanne d’Arc Basin, offshore eastern Canada, becomes the last known areoligeracean genus to have appeared. In 1965, during an evaluation of the geology of the Grand Banks, offshore eastern Canada, Pan American Petroleum Corporation (now Amoco Production Company) and Imperial Oil Enterprises carried out a shallow corehole drilling programme (Amoco and Imperial 1973). Several of these coreholes penetrated Mesozoic and Cenozoic strata, including Corehole 16, which provided the material for the present study. Corehole 16 (46° 15' N; 49° 03' W ; Text-fig. 1a) was drilled in 66-8 m of water to a depth of 448 m. Subsequently, numerous hydrocarbon exploration wells were drilled, but the shallow coreholes remain a valuable source of information and stratigraphical control. Williams and Brideaux (1975) studied 15 samples from Corehole 16 (Text-fig. 1b), which they considered to be Mid Eocene to Mid? Miocene. In the present re-examination of this material, a new genus and species was found in the uppermost sample (33-36 m), which Williams and Brideaux dated as Mid? Miocene. The new taxon is clearly a gonyaulacalean dinoflagellate of the family Areoligeraceae: like other areoligeraceans it has an offset sulcal notch, a lenticular shape and an apical archaeopyle. However it bears commonly trifurcate sutural processes and thus superficially resembles the common gonyaulacacean species, Spiniferites ramosus (Ehrenberg, 1838) Mantell, 1854. The main purpose of this paper is to describe the new taxon, assess its phylogenetic relationships, and reassess the age of the uppermost sample of Corehole 16. MATERIALS AND METHODS The samples used for this study were originally processed in 1972, and the records from this work indicate that a two minute oxidation procedure (otherwise unspecified) was carried out. However, when the residues were re-examined in 1994, there appeared to be no evidence of this earlier oxidation. In order to make the original residues amenable to study, it was necessary to carry out a very mild oxidation treatment (10 per cent, nitric acid for 1-5 minutes) and base treatment (ammonia for 1 minute). These procedures were in addition to the standard hydrochloric and hydrofluoric acid treatments (carried out in 1972), heavy liquid separation of the organic component, differential centrifugation to remove fine particles, screening to divide the residue into fine (10-20 ^um) and coarse (20-180 /zm) fractions, and staining with Bismarck Brown (all in 1994). The reprocessed material was mounted in Elvacite and a cellosize substitute. [Palaeontology, Vol. 41, Part 1, 1998, pp. 23-34, 1 pi.) © The Palaeontological Association 24 PALAEONTOLOGY, VOLUME 41 text-fig. 1. a, location map, offshore eastern Canada (modified from McAlpine 1990). b, stratigraphical distribution of the palynological samples in Corehole 16 (after Williams and Brideaux 1975). GUERSTEIN ET AL. : AREOLIGERACEAN DINOFLAGELLATE 25 text-fig. 2. Ramidinium tridens gen. et sp. nov.; line sketches, a-b, GSC Atlantic slide no. P1433-10, coordinates 86-2 x 10 (EF K15/0), GSC specimen no. 116293. a, ventral surface, ventral view, b, dorsal surface, dorsal view (based on an inverted image), c, f, GSC Atlantic slide no. P1433-10, coordinates 93-3 x 8-3 (EF H23/3), GSC specimen no. 116304; c, ventral surface, ventral view; f, dorsal surface, dorsal view (based on an inverted image), d-e (holotype), GSC Atlantic slide no. P1433-10, coordinates 84-7 x2 (EF B 1 4/1), GSC specimen no. 116295; d, ventral surface, ventral view (based on an inverted image); e, dorsal surface, dorsal view, g-h, GSC Atlantic slide no. P1433-10, coordinates 97-5x5 (EF E27/0), GSC specimen no. 116297; G, ventral surface, ventral view (based on an inverted image); h, dorsal surface, dorsal view. I, GSC Atlantic slide no. P1433-10, coordinates 1 10-8 x 21 (EF V41 /3), GSC specimen no. 116298 ; operculum, apical view. (For line drawings of dinoflagellates, it is conventional to show an ‘external’ view; thus for those illustrations indicated to be based on an inverted view, the drawing here is a mirror image of the appearance of the specimen in the microscope.) Scale bar represents 30 /un. Light microscopy was undertaken using Zeiss photomicroscopes at the Geological Survey of Canada (Atlantic), Bedford Institute of Oceanography, Dartmouth, Nova Scotia. Coordinates quoted are from the Vernier Scale of Zeiss photomicroscope serial no. 4660390. The corresponding England Finder (EF) coordinates are given in the Plate and Text-figure explanations. Type and 26 PALAEONTOLOGY, VOLUME 41 figured specimens are lodged in the National Collection of Type Invertebrate and Plant Fossils, Geological Survey of Canada, Ottawa, Ontario, Canada. Some specimens were picked, mounted and coated with gold for scanning electron microscopy. An ElectroScan E3 environmental SEM at the Geological Survey of Canada (Atlantic) was used under a partial pressure of water vapour. STRATIGRAPHY Corehole 16 is located on the south-western margin of the Jeanne d’Arc Basin, which extends roughly north-south for about 220 km on the eastern periphery of the Grand Banks of Newfoundland. In areal extent the basin is about 15000 km2, with a maximum sedimentary thickness in excess of 22 km. It is a Mesozoic failed rift basin with some Tertiary fill (McAlpine 1990) and will be the most petroleum-productive basin in offshore eastern North America when the Hibernia field starts to produce oil in 1997. Shallow Corehole 16 is 18-2 km north-north-east of Amoco-Imperial Murre G-67 well, the first exploratory well drilled in the basin, and which attained a depth of 3337-3 m in 64-6 m of water. The youngest dated sediments in Murre G-67 are early Oligocene and are underlain sequentially by Eocene and Campanian strata (Barss et al. 1979). The total thickness of the Tertiary section is about 1000 m. All preparations studied from Corehole 16 are from clastic sediments; more detailed lithological information was not available to the present authors. Biostratigraphical control in Corehole 16, as in Murre G-67, is based on palynomorphs, primarily dinoflagellates. Williams and Brideaux (1975) considered the sample at 32-9-36-0 m (108-118'), from which the new taxon was recovered, to be no younger than mid Miocene. This was based on their recognition of the following species : Tanyosphaeridium sp. A (now Distatodinium paradoxum (Brosius, 1963) Eaton, 1976), Thalassiphora delicata Williams and Downie, 1966 (now identified as Imertocysta tabulata Edwards, 1984), Tuberculodinium rossignoliae Drugg, 1970 and Lingulodinium sp. B (now Sumatradinium druggii Lentin, Fensome and Williams, 1994). Williams (1975) outlined a palynostratigraphical zonation for the Mesozoic-Cenozoic rocks of offshore eastern Canada. The Apteodinium spiridoides Benedek, 1972 (as Apteodinium sp. B) Zone, of Early Miocene age, was defined on the Last Appearance Datum (LAD) of A. spiridoides. In the sample, A. spiridoides occurs together with Sumatradinium soucouyantiae and Thalassiphora sp. 1 of EXPLANATION OF PLATE 1 Figs 1-15. Ramidinium tridens gen. et sp. nov. 1-2, GSC Atlantic slide no. P1433-10, coordinates 86-2 x 10 (EF K15/0), GSC specimen no. 116293. 1, ventral surface, ventral view. 2, dorsal surface, ventral view. 3, GSC Atlantic slide no. P1433-10, coordinates 117-3 x 2 (EF B84/1), GSC specimen no. 1 16294; ventral surface, dorsal view of specimen with operculum. 4-5, holotype, GSC Atlantic slide no. P1433-10, coordinates 84-7 x2 (EF B14/1), GSC specimen no. 116295. 4, ventral surface, ventral view. 5, dorsal surface, ventral view. 6, GSC Atlantic slide no. P1433-10, coordinates 84-4 x 10 (EF K13/0), GSC specimen no. 116296; ventral surface, ventral view. 7-8, GSC Atlantic slide no. P1433-10, coordinates 97-5 x 5 (EF E27/0), GSC specimen no. 1 16297. 7, ventral surface, dorsal view. 8, dorsal surface, dorsal view. 9, GSC Atlantic slide no. P1433-10, coordinates 1108x21 (EF V41/3), GSC specimen no. 116298; operculum, antapical view; x 1470. 10, GSC Atlantic slide no. P1433-10, coordinates 91-4 x 18-8 (EF T20/2), GSC specimen no. 116299; ventral surface, ventral view. 11, GSC Atlantic slide no. P1433-10, coordinates 98-7 x 15-5 (EF P28/4), GSC specimen no. 116300; dorsal surface, dorsal view. 12, GSC Atlantic slide no. P1433-10, coordinates 108-4 x 3-8 (EF C39/4), GSC specimen no. 116301 ; dorsal surface, dorsal view. 13, GSC Atlantic slide no. P1433-10, coordinates 99 x 1 8-9 (EF T28/0), GSC specimen no. 116302; ventral surface, ventral view. 14-15, GSC Atlantic slide no. P1433-10, coordinates 113-7 x 10-7 (EF L44/1), GSC specimen no. 116303. 14, ventral surface, ventral view. 15, dorsal surface, ventral view. All x 490, except where indicated. PLATE 1 GUERSTEIN et al. , Ramidinium 28 PALAEONTOLOGY, VOLUME 41 Powell (1988). Powell (1992) placed the LAD of A. spiridoides in the early Burdigalian (Early Miocene); however, de Verteuil and Norris (1992) extended the LAD into the basal Serravallian. S. soucouyantiae de Verteuil and Norris 1992, originally described from the lower Middle Miocene of Maryland (de Verteuil and Norris 1992), is restricted to the Miocene. Thalassiphora sp. 1 of Powell (1988) has a stratigraphical range of Burdigalian-Langhian in surface sections from the eastern USA. The above association indicates a Burdigalian-Langhian (20-0-1 5-2 Ma; Early to early Mid Miocene) age for the sample. If Williams (1975) and Powell (1992) are correct in believing that Apteodinium spiridoides has its LAD in the Burdigalian, this would support a Burdigalian (late Early Miocene) age. SYSTEMATIC PALAEONTOLOGY Division dinoflagellata (Butschli, 1885) Fensome, Taylor, Norris, Sarjeant, Wharton and Williams, 1993 Class dinophyceae Pascher, 1914 Order gonyaulacales Taylor, 1980 Family areoligeraceae Evitt, 1963 Genus ramidinium gen. nov. Derivation of name. From the Latin ramus = branch, in reference to the branched processes, and the usual dinoflagellate suffix ‘ -dinium'. Type. Plate 1, figures 4-5; Text-figure 2d-e. Ramidinium tridens, gen. et sp. nov. Diagnosis. Areoligeracean proximochorate to usually chorate, acavate cysts, with processes that are primarily parasutural and typically irregularly branched. Comparisons. Among areoligeraceans, Ramidinium is distinct in having parasutural, branched processes. Chiropteridium Gocht, 1960 is also an areoligeracean with some isolated processes but differs from Ramidinium in having proximally membranous, confluent septa that occur principally in the marginal areas. Schindler (1992) described five Chiropteridium morphotypes, each exhibiting four lateral, crest-like structures on the dorsal and ventral surfaces, extending meridionally from the apical to the antapical region. These structures in Chiropteridium may be parasutural in part, although this is not clear from published descriptions. Ramidinium has a more uniform distribution of processes, and the crest-like structures of Chiropteridium are absent or may be represented by the low ridges joining adjacent processes (PI. 1, figs 1-2; Text-figs 2a, 3g). These low ridges may be relicts of the membranes observed in Chiropteridium. Areoligera Lejeune-Carpentier, 1938 is characterized by the presence of arcuate complexes and Glaphyrocysta Stover and Evitt, 1978 has processes that are predominantly marginate in position and typically nontabulate or intratabulate. Enneadocysta Stover and Williams, 1995 also has an apical archaeopyle and some dorsoventral compression, but differs from Ramidinium in having intratabular processes that, around the antapex, are apparently arranged in the partiform pattern. Cooksonidium Stover and Williams, 1995 differs from Ramidinium in having intratabular processes, which sometimes occur in penitabular complexes. Spiniferites Mantell, 1850 and Achomosphaera Evitt, 1963, which also have parasutural processes with furcate endings, are distinguished from Ramidinium by having a precingular archaeopyle. Ramidinium tridens sp. nov. Plate 1 ; Text-figures 2-3 Derivation of name. From the Latin tridens — trident, fork with three tines, in reference to the distal nature of the processes. The specific epithet is a noun in apposition. GUERSTEIN ET AL. . AREOLIGERACEAN DINOFLAGELL ATE 29 G H I text-fig. 3. Ramidinium tridens gen. et sp. nov., scanning electron photomicrographs; GSC Atlantic preparation P1433. a, stub no. 1433a, GSC specimen no. 116305, specimen lost; ventral view; x 526. b, stub no. 1433a, GSC specimen no. 116306 (specimen lost); ventral view?; x 847. c, stub no. 1433a, GSC specimen no. 116307 (specimen lost); x 581. d, stub no. 1433a, GSC specimen no. 116308 (specimen lost); x 555. e, stub no. 1433r, GSC specimen no. 116309; detail showing the wall structure and processes; x 1786. f-g, stub no. 1433r, GSC specimen no. 116310. f, ventral view; x 658. G, detail showing processes joined basally by low ridges; x 1538. h, stub no. 1433r, GSC specimen no. 116311; detail of trifurcate process; x 1389. i, stub no. 1433r, GSC specimen no. 116312; apical view; x 741. Holotype. Plate 1, figures 4—5; Text-figure 2d-e. GSC specimen no. 116295, National Collection of Type Invertebrate and Plant Fossils, Geological Survey of Canada, Ottawa, Ontario, Canada; GSC Atlantic slide No P1433-10, coordinates: 84.7x2 (EF B14/1). Type locality: 108-118 feet, Corehole 16, 46°15'N, 49° 03' W, Grand Banks, offshore eastern Canada. 30 PALAEONTOLOGY, VOLUME 41 text-fig. 4. Spindle plots showing the species diversity of individual genera of the family Areoligeraceae per unit time. The width of each bar represents number of species. See text for further details. Stages (Mesozoic) and epochs and subepochs (Tertiary) are indicated as follows, in ascending order: Jurassic stages: B = Bajocian, B = Bathonian, C = Callovian, O = Oxfordian, K = Kimmeridgian, unlabelled = Portlandian. Cretaceous stages : B = Berriasian, V = Valanginian, H = Hauterivian, B = Barremian, A = Aptian, A = GUERSTEIN ET AL. : AREOLIGER ACEAN DINOFLAGELLATE 3: Diagnosis. A species of Ramidinium with c. 20-26 primarily parasutural processes that have mostly irregular trifurcate endings. Description Shape. Cysts proximochorate to chorate, dorsoventrally compressed, central body lenticular. Antapical outline symmetrical or asymmetrical. Wall relationships. Autophragm only. Wall features. Autophragm finely ornamented, typically irregularly reticulate to rugulate (Text-fig. 3e). There are 20-26 processes, 1 1 or 12 on the epicyst, five to nine on the hypocyst, and four or five on the paracingulum. Processes usually gonal and intergonal (PI. 1, figs 7-8; Text-fig. 2d-h), possibly sometimes intratabular; they are usually cylindrical or rounded triangular in cross section, solid and generally ending in irregular trifurcations (Text-fig. 3d, h), but they may be distally bifurcate or asymmetrically expanded (Text-fig. 2b, h-i). Some processes may be hollow (Text-fig. 3e) and, occasionally, taeniate processes occur that give the impression of two stems joined by a membrane (PI. 1, figs 6, 10-12, 15; Text-fig. 3b, e-f, i). Adjacent processes are sometimes joined basally by low, possibly parasutural ridges (PI. 1, figs 1-2, 5, 10; Text-fig. 3g). Delicate trabeculae occasionally connect postcingular processes (PI. 1, fig. 13). Paratabulation. Areoligeracean paratabulation indicated on epicyst by archaeopyle sutures and location of parasutural processes. Elsewhere on central body, paratabulation indicated solely by primarily parasutural processes. Generally there is no process between paraplate 6” and the anterior sulcal paraplate (Text-figs 2a, d, g, 3a). Paracingulum. Indicated by four or five processes in gonal or intergonal positions. Parasulcus. Position indicated anteriorly by offset parasulcal notch (Text-fig. 2d, g). Rarely parasulcal notch medial or only slightly offset (PI. 1, fig. 14). Archaeopyle. Apical, type (tA); operculum tetratabular, simple, free and longer transversally than dorsoventrally (PI. 1, figs 3, 9; Text-fig. 2i). Size. Holotype: length of the central body (without operculum): 42 pm\ width of the central body: 53 pm; process length: 13-19 pm. Range of 20 specimens: length of the central body (including operculum): 47(55)63 pm; length of the central body (without operculum): 36(41)47 pm; width of the central body: 47(55)63 pm; process length: 9-23 pm. Comparisons Ramidinium tridens resembles the type material of Galea twistringiensis Maier, 1959, which has a smooth wall and distally widened and regularly divided processes. Sarjeant (1983) included G. twistringiensis in synonymy with Spiniferites ramosus var. multibrevis, implying that is has a precingular rather than an apical archaeopyle. Chiropteridium galea (Maier, 1959) Sarjeant, 1983 is the species of Chiropteridium most similar to R. tridens, having processes that may be furcate or Albian, C = Cenomanian, unlabelled = Turonian, unlabelled = Coniacian, S = Santonian, C = Campanian, M = Maastrichtian. Tertiary epochs: P = Paleocene, E = Eocene, O = Oligocene, M = Miocene, P = Pliocene. Teriary epochs are divided into Early (E) and Late (L) or Early (E), Mid (M) and Late (L) subepochs, except for the Pliocene, which is undivided in this study. The unlabelled interval at the top of the plot represents the Quaternary. The timescale used herein is based on that of Harland et al. (1990), except for our usage of Portlandian rather than Tithonian for the latest Jurassic stage. 32 PALAEONTOLOGY, VOLUME 41 branched. However, R. tridens differs from C. galea in having processes on the epicyst that are consistently parasutural in position, isolated or united by low ridges only. Processes on C. galea may be isolated, but tend to arise from four marginal meridional crests which usually are not obviously parasutural. Nevertheless, in some specimens of C. galea from the Grand Banks, meridional membranes are clearly in part parasutural, since they align with the accessory archaeopyle suture between precingular paraplates. Chiropteridium Morphotype E of Schindler (1992) also has four meridional membranes almost fully divided into hollow, distally closed and proximally interconnected processes ; towards the poles these processes are more slender and distally furcated. However, Morphotype E differs from R. tridens in lacking the processes on mid-ventral and mid- dorsal surfaces and in having a distinctly granulate wall. R. tridens has an irregularly reticulate to rugulate wall and, occasionally, low proximal ridges joining adjacent processes. Enneadocysta harrisii Stover and Williams, 1995 has similar process stems, but the processes are intratabular rather than parasutural and have licrate endings. Occurrence. Lower-lower Middle Miocene (Burdigalian-Langhian, as determined from palynology), Corehole 16, Grand Banks, offshore Eastern Canada. DISCUSSION AND CONCLUSIONS The family Areoligeraceae is an extinct dinoflagellate family that first occurred in the Late Jurassic and was common throughout the Cretaceous and Paleogene. The stratigraphical distribution and species richness of all areoligeracean genera are shown in Text-figure 4. In the Mesozoic, the family was represented by forms with no, or only low, spines (proximate and proximochorate cysts), whereas during the Paleogene, representatives tended to be spinose (chorate, e.g. Areoligera and Glaphyrocysta). In the later Paleogene, forms with marginal membranes or wall cavities (e.g. Membranophoridium Gerlach, 1961 and Chiropteridium) became common. Previously, no new genera were known to have evolved in the Neogene; Ramidinium, a possible derivative of Chiropteridium, is thus the only known areoligeracean genus to appear in the Neogene. Information for Text-figure 4 (except for the Ramidinium bar, which is based on the present work) was derived from PALYNODATA, a database compiled over the past quarter century by a consortium of several major oil companies and the Geological Survey of Canada. PALYNODATA stores biostratigraphical information from pre-Quaternary palynology publications: at present, PALYNODATA contains information from about 18000 such publications. In Text-figure 4, the number of species per genus per unit time are plotted. It was impractical to check the many hundreds of records that contributed to this plot, although a detailed search of anomalous records eliminated some that clearly represented reworking or contamination (for further elaboration of the techniques involved, see Fensome et al. 1996 and MacRae et al. 1996). Text-figure 4 emphasizes that Ramidinium is indeed the last evolving genus of a prominent and biostratigraphically important family of dinoflagellates. The later evolutionary pattern of the Areoligeraceae is reflected in our observations of the dinoflagellate assemblages from Corehole 16. The Early Oligocene assemblage (88-91 m) contains the areoligeraceans Membranophoridium aspinatum Gerlach, 1961 and Chiropteridium galea, with transitional forms between the two species. In the assemblage from the Upper Oligocene (116-5-1 19-5 m), C. galea was the only areoligeracean present and is a dominant element. Thus, there is an apparent trend from the membranous areoligeraceans to forms with divided membranes and isolated processes. This trend appears to culminate with Ramidinium tridens. Acknowledgements. The authors acknowledge the technical assistance of B. Crilley, W. C. MacMillan, N. Koziel, B. Medioli and A. S. Henry. For discussion and information we are grateful to J. Jansonius, R. A. MacRae, M. E. Quattrocchio and an unidentified reviewer. G. R. Guerstein’s participation was supported by Consejo National de Investigaciones Cientificas y Tecnicas, Argentina. We acknowledge the support of the PALYNODATA sponsors: Amoco Production Co., Exxon Production Research Co., Unocal Corporation, GUERSTEIN ET AL. : AREOLIGERACEAN DINOFLAGELLATE 33 Arco Oil and Gas Co., and the Geological Survey of Canada. This, is Geological Survey of Canada Contribution no. 1997017. REFERENCES amoco Canada petroleum company ltd and imperial oil ltd 1973. Regional geology of the Grand Banks. 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Bulletin of the British Museum ( Natural History), Geology Series, Supplement, 3, 1-248. G. RAQUEL GUERSTEIN Departamento de Geologia Universidad Nacional del Sur San Juan 670 8000 - Bahia Blanca, Argentina ROBERT A. FENSOME GRAHAM L. WILLIAMS Geological Survey of Canada (Atlantic) Typescript received 5 November 1996 P.O. Box 1006, Dartmouth Revised typescript received 24 April 1997 Nova Scotia B2Y 4A2, Canada NEW DRYOLESTOID MAMMALS FROM THE BASAL CRETACEOUS PURBECK LIMESTONE GROUP OF SOUTHERN ENGLAND by p. c. ensom and d. sigogneau-russell Abstract. The dryolestoid mammal Dorsetodon haysomi gen. et sp. nov. is described from the Purbeck Limestone Group (Lower Cretaceous) of southern England, on the basis of lower molars. Dorsetodon is assigned to the Paurodontidae, a family of Theria previously known only from North America. The distinction between Paurodontidae and Henkelotheriidae (from the Upper Jurassic of Portugal), although maintained for lack of solid contrary data, is argued to have been based on variable or subjective characters. A further small mammal. Chunnelodon alopekodes gen. et sp. nov., representing an undetermined cladotherian family, is also described from lower molar teeth. The non-procumbent paraconid on the lower molar places Chunnelodon as a sister-taxon to the Laurasian Dryolestoidea. The Purbeck Limestone Group has been known as a rich source of fossil vertebrates for approximately 150 years. An important new microvertebrate and dinosaur footprint site on the Isle of Purbeck at Sunnydown Farm near Langton Matravers continues to provide valuable new information on the coeval faunas within the Purbeck Limestone Group. New discoveries and increasing knowledge of the fauna, which includes fishes (Woodward 1916-19), amphibians (Ensom et al. 1994), reptiles (Benton and Spencer 1995) and mammals (Owen 1871 ; Simpson 1928; Kielan- Jaworowska and Ensom 1992, 1994; Sigogneau- Russell and Ensom 1994), in addition to vertebrate trace fossils (Ensom 1995a, 1995h) have led to the following statement by Howse and Milner (1995) : ‘the Purbeck fauna is becoming one of the richest mid-Mesozoic continental assemblages known’. The two new mammalian taxa described below further confirm this assessment. LOCALITY AND STRATIGRAPHY The new locality was first reported by Ensom (1987) and subsequently described in more detail by Kielan-Jaworowska and Ensom (1992). Two horizons were exploited. Both horizons lie within the Cherty Freshwater Member of the Purbeck Limestone Group (Clements 1993), which, along with much of the Purbeck Limestone Group, is increasingly considered to be of early Berriasian, Early Cretaceous, age (Allen and Wimbledon 1991) (this point has been discussed by Kielan-Jaworowska and Ensom 1994, and Sigogneau-Russell and Ensom 1994). The mammal teeth described below have been picked from residues derived from samples of clay collected from the higher of the two horizons at the Sunnydown Farm Quarry sauropod footprint site (NGR SY 9822 7880), 5 km west of Swanage, and from its equivalent in Durlston Bay NGR (SZ 035 780) just south of Swanage, both in Dorset, southern England. The upper horizon lies at the junction of a clay, locally termed the ‘Sly’, which immediately underlies the ‘Cap’ bed, 2-6 m below the base of the Cinder Member. This clay-limestone interface can be equated confidently with beds DB 102/103 in Durlston Bay (Clements 1993). The sedimentology and environmental setting of the upper horizon has been described by West (1988). Both horizons are thought to represent clays bordering shallow freshwater lakes. (Palaeontology, Vol. 41, Part 1, 1998, pp. 35-55] ©The Palaeontological Association 36 PALAEONTOLOGY, VOLUME 41 text-fig. 1. Dorsetodon haysomi gen. et sp. nov. ; holotype, DORCM GS 433, resin cast; lower right molar. a, lingual view; b, labial view; c, posterior view; D, anterior view; e, occlusal view. SEM stereophotographs; x 45. Kielan-Jaworowska and Ensom (1992, 1994) described a significant number of the multituber- culate mammals so far recovered from this horizon, and Sigogneau-Russell and Ensom (1994) recorded the only known example of a tribosphenic molar from the Purbeck Limestone Group, possibly the earliest so far recovered (this was from the lower horizon at Sunnydown Farm). Apart from the Multituberculata and Tribosphenida, all the main groups of mid Mesozoic mammals are represented amongst the teeth collected so far. These include Triconodonta, Docodonta, Symmetrodonta and Cladotheria. A general faunal list was prepared by Ensom et al. (1994). MATERIALS AND METHODS Sampling methods have been described in more detail in Kielan-Jaworowska and Ensom (1992). Approximately 3 tonnes of clay were collected from the site, in addition to smaller samples from ENSOM AND SIGOGNEAU-RUSSELL: CRETACEOUS MAMMALS 37 other locations. The clay samples have been sieved down to a mesh size of 0-3 mm. Residues are being picked down to and including the ratio retained by the 0-5 mm mesh. The teeth described in this paper come from the following samples: DORCM GS 376, 377 and 378 from sample 40; DORCM GS 433 from sample 34, DORCM GS 438 from sample 68, DORCM GS 747 from sample 83, DORCM GS 501 and 502 from sample 85 and DORCM GS 625 from sample 98. These samples were all from the excavation at Sunnydown Farm Quarry, Langton Matravers, within an area of 60 m2. The equivalent of the upper horizon at Durlston Bay yielded DORCM GS 313 and 315 (sample 01). Abbreviations. DORCM, Dorset County Museum; L, length; W, width. SYSTEMATIC PALAEONTOLOGY Order dryolestoidea Butler, 1939 Family paurodontidae Marsh, 1887 Genus dorsetodon gen. nov. Derivation of name. Allusion to the geographical origin of the genus. Type species. D. haysomi sp. nov. Differential diagnosis (based only on type). Protoconid moderately high, less so than in Paurodon or Archaeotrigon; lingual face concave and anteriorly oriented. Paraconid forming a distinct, but not tubular, cusp, inclined lingually as well as anteriorly, narrower than the metaconid, which distinguishes it from that of other paurodonts except Archaeotrigon and Tathiodon. Metaconid of moderate height. Posterior face of trigonid more strongly concave than in other paurodonts. Talonid relatively long, especially more so than in Paurodon and Araeodon-, sub-triangular as in Araeodon, low and medio-lingually situated without a well-defined cusp. Lower molars closest to Araeodon in labial ‘convexity’ (flatter in other genera, including Henkelotherium). Closest to Tathiodon for general proportions, but paraconid more inclined lingually and anteriorly ; metaconid less stout; trigonid flatter; talonid less sharply triangular. Differs from Henkelotherium by posterior trigonid face more concave, less compressed trigonid, para- and metaconid relatively more gracile, talonid less wide ; but to be noted is the variation of the talonid along the dental series in this genus (as well as in Foxraptor ) : short, wide and triangular in most molars, it becomes semicircular at the rear of the jaw. Dorsetodon haysomi sp. nov. Text-figures 1-6 Derivation of name. In honour of W. T. Haysom, a quarry owner on the Isle of Purbeck, who drew the attention of the senior author to the Sunnydown site. Holotype. DORCM GS 433, a right lower molar (Text-figs 1-2). L = 0-65 mm; W = 0-42 mm. Attributed material. DORCM GS 376, a right lower molar (L = 0-72 mm; W = 0-41 mm) (Text-figs 3^4); DORCM GS 502, a right lower molar (L = 0-70 mm; W = 0-38) (Text-fig. 5); DORCM GS 438, a left lower molar (L as preserved = 0-76 mm; W = 0-43 mm) (Text-fig. 6); DORCM GS 501, a left lower molar (L = 0-70 mm; W = 0-42 mm); DORCM GS 625, a left lower molar (L = 0 72 mm; W = 0-50 mm); DORCM GS 747, a right lower molar (L = 0-82 mm; W = 0-41 mm). PALAEONTOLOGY, VOLUME 41 text-fig. 2. Dorsetodon haysomi gen. et sp. nov. ; holotype DORCM GS 433 ; lower right molar, a, lingual view ; B, labial view ; c, posterior view ; D, anterior view ; E, occlusal view. Key : m, metaconid ; pa, paraconid ; pr, protoconid; p.w.f., posterior wear facet; ta, talonid. Hatching, wear; cross-hatching or crosses, broken areas or edges. Scale bar represents 0-5 mm. text-fig. 3. Dorsetodon haysomi gen. et sp. nov.; DORCM GS 376, resin cast; lower right molar. A, lingual view; b, labial view; c, posterior view; d, anterior view; e, occlusal view. SEM stereophotographs; x45. ENSOM AND SIGOGNEAU-RUSSELL: CRETACEOUS MAMMALS 39 text-fig. 4. Dorsetodon haysomi gen. et sp. nov.; DORCM GS 376.; lower right molar. a, lingual view; B, labial view; c, posterior view; d, anterior view; E, occlusal view. Key as for Text-figure 2. Scale bar represents 0-5 mm. Horizon and locality. Sunnydown Farm, Dorset, England; Cherty Freshwater Member, Lulworth Formation, Purbeck Limestone Group, basal Cretaceous (?Berriasian). Diagnosis. As for genus, this being the only species. Description of type. In addition to the diagnosis, some points should be stressed. In lingual view, para- and metaconid form a widely open V, the paraconid being strongly inclined towards the front. The metaconid is relatively high but distinctly shorter than the protoconid, the lingual face of which is deeply concave. The anterior crest of the protoconid is very finely denticulated. A faint bump is visible at the anterior labial base of the protoconid (also visible in the last preserved molar of Paurodori). In posterior view, the median crests of the meta- and protoconid delimit a wide and concave U, and each ends respectively on the labial and lingual border of the talonid. The latter is at present relatively small in occlusal surface, asymmetrically triangular with the apex being postero-lingual, aligned with the tip of the metaconid; the hypoconulid itself remains very low. The roots are not preserved : their bases are visible lingually, but labially a break occurred at the base of the protoconid. However, given the flattening of this face and of the cusps, as well as the position of the talonid, it can be safely concluded from what is left that the two roots were subequal, the posterior one following anterior and not being situated entirely lingual to it as in dryolestids. The tooth is in almost unworn condition, only the tips of the main cusps having been abraded. In contrast, the labial face of the talonid is strongly worn, even excavated, which may be partly responsible for its present triangular shape. This excavates an indentation at the base of the posterior trigonid crest, which is very characteristic. Another wear facet may be detectable at the anterior base of the protoconid. DORCM GS 376, 438, 501, 502, 625 and 747 are also interpreted as lower paurodontid teeth : their two roots were undoubtedly subequal and the open trigonid is as flat as or even flatter labially than that of the type. All teeth are slightly longer than the latter. As in DORCM GS 433, the posterior face of the trigonid of all these molars is hollowed between the same crests, and the lingual face of the protoconid is clearly concave and anteriorly oriented. A very slight elevation is again visible at the labial base of the protoconid, except in DORCM GS 625, where it may have been worn. However there are differences. On DORCM GS 376, the paraconid is even more shelf-like than that of the type but less inclined lingually (as in Archaeotrigon) and lower (even if we admit that the tip is missing) ; the lingual V between para- and protoconid is even more open, while the metaconid appears to have been relatively lower. Finally, the talonid appears to be significantly different from that of the type tooth, being relatively longer, situated at mid-width of the tooth, and having a quadrangular shape, the lingual angle being slightly displaced medially and another angle being present postero-labially. However, scrutiny of this distal border suggests that it may have been slightly abraded, which may be partly responsible for the difference in shape between the latter and that of the type. A wear facet is again visible on the labial face of the talonid, cutting into the posterior crest of the protoconid. Also, there may be an incipient triangular wear facet on the anterior base of the labial face of the protoconid. On DORCM GS 502, the paraconid is more inclined anteriorly than on the type ; the talonid lacks a chip of enamel posteriorly, but it is strongly worn labially, a wear that indents the posterior crest of the protoconid as on the preceding teeth ; wear has also touched the antero-labial face of the protoconid and the posterior edge of the paraconid. DORCM GS 501 has a lower paraconid, separated from the metaconid by a wide U-basin; 40 PALAEONTOLOGY, VOLUME 41 text-fig. 5. Dorsetodon haysomi gen. et sp. nov.; DORCM GS 502, resin cast; lower right molar. A, lingual view; b, labial view; c, posterior view; d, anterior view; E, occlusal view. SEM stereophotographs; x45. the talonid, which is clearly complete and unworn, is definitely triangular as on the type. On DORCM GS 625, again the paraconid is lower and more shelf-like, the talonid is triangular but shorter; wear is clearly visible on the anterior face of the protoconid, and on the occluso-labial face of the talonid, but the posterior crest remains untouched. Finally, on DORCM GS 747 and 438, the paraconid is quite extended anteriorly; on the former, the talonid is short and wide, worn labio-occlusally but again the posterior crest of the protoconid is not indented. The latter tooth is unworn but, unfortunately, the talonid is missing. These differences are likely to be attributable to a different position in the dental series. ENSOM AND SIGOGNEAU-RUSSELL: CRETACEOUS MAMMALS 41 A 8 C D E text-fig. 6. Dorsetodon haysomi gen. et sp. nov. ; DORCM GS 438; lower left molar, a, lingual view; B, labial view; c, posterior view; d, anterior view; E, occlusal view. Key as for Text-figure 2. Scale bar represents 0-5 mm. Legion cladotheria McKenna, 1975 Order incertae sedis Family incertae sedis Genus chunnelodon gen. nov. Derivation of name. To emphasize the French-British collaboration as demonstrated by this paper, and the Channel Tunnel inaugurated in the year of the discovery of the taxon. Type species. C. alopekodes sp. nov. Diagnosis. Lower molars with trigonid very flattened transversely. Cusps sharp. Protoconid moderately high; small paraconid not inclined anteriorly but recurved, and not shelf-like; metaconid high, slightly visible in labial view ; strong backwards inclination of the posterior wall of the trigonid. Talonid reduced to a sharp, lingual and relatively high cusp. Roots slightly unequal, with a pre-eminence of the anterior one; but labially, the two roots are nearly aligned antero- posteriorly. Chunnelodon alopekodes sp. nov. Text-figures 7-9 Derivation of name. From the Greek, dXojntjKo'jdrjq. sly as a fox: an allusion to the horizon in the Cherty Freshwater Member from which the material comes, which is called the ‘Sly’ by the quarrymen of the Isle of Purbeck. Holotype. DORCM GS 378, a left lower molar (Text-figs 7-8). L = 0-72 mm; W = 0-36 mm. Attributed material. DORCM GS 377 (Text-fig. 9), a right lower molar (probably from the same individual as the type, but the two molars did not occupy the same position in the dental series). L = 0-72 mm; W = 0-41 mm. Horizon and locality. Sunnydown Farm, Dorset; Cherty Freshwater Member, Lulworth Formation, Purbeck Limestone Group, basal Cretaceous (?Berriasian). Diagnosis. As for the genus, this being the only species. Description. DORCM GS 377 is the more complete of the two teeth in having the two roots partially preserved, but a small chip of enamel has come off between trigonid and talonid. These two teeth are very peculiar, with paraconid, metaconid and hypoconulid sharp and lingually aligned; the metaconid is notably longer and higher than the paraconid, itself slightly recurved. The protoconid is barely concave lingually. Another very distinctive feature is the backward and labial inclination of the posterior wall of the trigonid, a 42 PALAEONTOLOGY, VOLUME 41 text-fig. 7. Chunnelodon alopekodes gen. et sp. nov. ; holotype, DORCM GS 378, resin cast; lower left molar. a, lingual view; b, labial view; c, posterior view; d, anterior view; e, occlusal view. SEM stereophotographs; x 45. wall practically flat with no trace of any crest; in occlusal view, this inclination gives the impression of an expanded talonid, whereas the latter is in fact reduced to the hypoconulid, a high triangular cusp entirely lingual : such characteristics are found in no other Theria. The two specimens differ only slightly. The differences concern the paraconid, slightly more forwardly inclined on the holotype DORCM GS 378, and the metaconid, a little less visible. On DORCM GS 377, the presence of a minute bump at the labial base of the paraconid can be observed (rather like in Dorsetodon). These two teeth are unworn and show no clear wear facets, and, in particular, no paraconal sulcus. ENSOM AND SIGOGNEAU-RUSSELL: CRETACEOUS MAMMALS 43 text-fig. 8. Chunnelodon alopekodes gen. et sp. nov. ; holotype, DORCM GS 378; lower left molar. A, lingual view; b, labial view; c, posterior view; d, anterior view; e, occlusal view. Key as for Text-figure 2. Scale bar represents 0-5 mm. text-fig. 9. Chunnelodon alopekodes gen. et sp. nov.; DORCM GS 377; lower right molar, a, lingual view; b, labial view; c, posterior view; d, anterior view; e, occlusal view. Key as for Text-figure 2. Scale bar represents 0-5 mm. DISCUSSION History of paurodontid classification (Table 1) Butler (1939) created the suborder Dryolestoidea to separate, within the Pantotheria sensu Simpson, 1928, three families (Paurodontidae Marsh, 1887 (including Peramus ), Amphitheriidae Owen, 1846 and Dryolestidae Marsh, 1879) from the suborder Docodontoidea. This term Dryolestoidea has the same contents (as a sublegion) in Prothero (1981), with the exclusion of Peramus , since in this work, the term is used in opposition to the sublegion Zatheria McKenna, 1975 (Peramuridae plus Tribosphenida) within the legion Cladotheria McKenna, 1975. Sigogneau- Russell (1991) included her new family Donodontidae (from Morocco) in the Dryolestoidea (misspelled) on the basis of the upper molars; but the characteristics of the protoconid and of the roots of the attributed lower molars are not those of dryolestoids. Finally Krebs (1991) attributed his new family Henkelotheriidae to the order Eupantotheria Kermack and Mussett, 1958 (which is not equivalent to Pantotheria sensu Simpson, 1928, but which includes the same families as Dryolestoidea in Butler 1939 and Prothero 1981). One of us (DS-R) considers that Amphitheriidae is closer to Peramuridae and hence should be excluded from Dryolestoidea. Dryolestoidea would then include three families : Dryolestidae, Paurodontidae and Henkelotheriidae. However, Bonaparte (1992, 1994) has included four more monospecific South American families in the infraclass Dryolestida Prothero, 1981 (Dryolestoidea minus Amphitheriidae). We will not discuss these forms here, limiting our considerations to the Laurasian forms, but we would like to temper the proposals made by Bonaparte (1994) concerning the affinities between the North African and the Argentinian cladotheres. A relationship had indeed also been suggested by Sigogneau- Russell (1991) between Donodon Sigogneau-Russell, 1991 and Mesungulatum Bonaparte, 1986, on the basis of the upper molars; but the lower molars attributed to these taxa (Bonaparte 1986), 44 PALAEONTOLOGY, VOLUME 41 table 1 . History of the classification of the families mentioned in the text. Butler 1939: Order Pantotheria Simpson, 1928 Suborder Dryolestoidea Suborder Docodontoidea Prothero 1981: Legion Cladotheria Sublegion Dryolestoidea Sublegion Zatheria Krebs 1991 : Order Eupantotheria Sigogneau-Russell 1991: Suborder Dryolestoidea This paper: Legion Cladotheria Sublegion Dryolestoidea* Sublegion nov. Sublegion Zatheria Amphitheriidae Paurodontidae Dryolestidae Amphitheriidae Paurodontidae Dryolestidae Peramuridae Tribosphenida Amphitheriidae Paurodontidae Dryolestidae Henkelotheriidae Amphitheriidae Paurodontidae Dryolestidae Donodontidae Dryolestidae Paurodontidae Henkelotheriidae Donodontidae Chunnelodon Amphitheriidae Peramuridae Tribosphenida * South American families not considered here. devoid of talonid, do not support this relationship, and the rest of the mammalian fauna renders it even more tenuous. The Los Alamitos Campanian mammalian assemblage does seem to testify to a long isolation of that part of Argentina from the rest of the subcontinent and hence from the rest of Gondwana. Of the three Laurasian families in the suborder Dryolestoidea (Paurodontidae, Henkelotheriidae and Dryolestidae), only the last was known from the Purbeck Limestone Group (Simpson 1928; Lillegraven et al. 1979). However, the new discoveries of mammals made by one of us (PE) in the Lulworth Formation of the Purbeck Limestone Group (basal Cretaceous) in Dorset include, among lower teeth which are undoubtedly of a dryolestoid type (shelf-like and procumbent paraconid, asymmetrical trigonid, transverse paracrista-metacristid shear), a few elements that show a morphology incompatible with the definition of the Dryolestidae. The asymmetrical trigonid excludes the Gondwanan Donodontidae (insofar as the attribution of the lower teeth to the type upper molar of the only donodontid genus is correct); so their inclusion in Paurodontidae or Henkelotheriidae had to be envisaged (the four South American families, except Mesungulatidae, are known only from upper teeth). The family Paurodontidae itself was created for the genus Paurodon Marsh, 1887. It was united with Amphitheriidae by Gregory (1922), but Simpson (1927a) validated Marsh’s distinction of ENSOM AND SIGOGNEAU-RUSSELL: CRETACEOUS MAMMALS 45 text-fig. 10. Lower molars of, from top to bottom: Araeodon, Paurodon, Archaeotrigon brevimaxillus. A, lingual view; b, occlusal view; c, labial view. Scale bar represents 0-5 mm. Paurodon from Amphitherium. As indicated by the name, Marsh (1887) and later Simpson (1929) differentiated Paurodontidae from Dryolestidae by the reduced dental formula, as well as by the shape of the lower molars, not compressed transversely and supported by two subequal roots. Simpson’s diagnosis includes, moreover, the non-reduction of the unicuspid talonid (in fact, the paurodontid talonid is longer but not wider than that of the dryolestid, but as the tooth is flatter, hence longer, the talonid occupies a greater part of the total width), the smallness of the metaconid relative to the protoconid, and the shortness and stoutness of the lower jaw. Later, Prothero (1981) defined the family by what he considered to be a unique set of derived characters : ‘ broad shelf-like paraconid and talonid with reduced cusps, molars broaden antero-posteriorly, loss of anterior cusp on last lower premolar’. Krebs (1991) distinguished Paurodontidae from his Henkelotheriidae by its smaller dental formula, the greater reduction of the para- and metaconid (paraconid forming a ledge and metaconid very blunt), the situation of the semicircular talonid in the middle of the tooth 46 PALAEONTOLOGY, VOLUME 41 text-fig. 11. Lower molars of, from top to bottom: Tathiodon, Foxraptor, Henke lot herium. a, lingual view; b, occlusal view; c, labial view. Scale bar represents 0-5 mm. width and the shorter and stouter lower jaw; finally, Bakker and Carpenter (1990) emphasized the proportions of the jaw (more especially the symphysis) in defining Paurodontidae. Simpson (1927a) enlarged Paurodontidae with four new genera: Archaeotrigon, Tanaeodon (to become Tathiodon Simpson 19276), Peramus and Brancatherulum. He acknowledged, however, that this group was rather heterogenous ; indeed Peramus, isolated in the family Peramuridae by Kretzoi (1946), and later united with Amphitheriidae by Mills (1964), was reinstalled in a distinct family by Clemens and Mills (1971), a distinction accepted by Lillegraven et al. (1979) and Prothero (1981). ENSOM AND SIGOGNEAU-RUSSELL: CRETACEOUS MAMMALS 47 text-fig. 12. Profile of the lower jaw of various Dryolestoidea (dashed line), compared with that of Kepolestes (uninterrupted line, from Prothero 1981), with mandibular height below M/1 as a constant, a, Foxraptor (from Bakker and Carpenter 1990); b, Laolestes (from Prothero 1981); c, Henkelotherium (from Krebs 1991); D, Archaeotrigon (from Simpson 1929); e, Araeodon (from Simpson 1937); f, Tathiodon (from Simpson 1929); G, Paurodon (from Simpson 1929). H, Foxraptor (dashed line) compared with Paurodon (uninterrupted line). Tooth contour schematic. 48 PALAEONTOLOGY, VOLUME 41 table 2. Distribution of characters in the lower molars of the genera considered in this paper. Formula for incisors and canines not known. Dental formula pm + m Protoconid Paraconid Paurodon 2 + 4 High Median ridge lingually Convex labially Low Archaeotrigon brevimaxillus 2 + 3 to 4 High Median ridge lingually Slightly convex labially Very low and narrow Anteriorly directed Tathiodon 2 to 3 High Low + 3 to 4 Convex labially Anteriorly directed Araeodon 3 + 4 High? Median ridge lingually Convex labially Low Anteriorly directed? Foxraptor 3 + 5 High Median ridge lingually Flat labially Moderate Tubular Anteriorly directed Henkelotherium 4 + 6 to 7 Moderate? Median ridge lingually Slightly convex labially Low Slightly anteriorly directed Dorsetodon GS 433 Moderate height Concave lingually Slightly convex labially Short Moderately high Anteriorly directed Dorsetodon GS 376 Moderate Slightly concave lingually Slightly convex labially Short Low Anteriorly directed Dorsetodon GS 438 Moderate Slightly concave lingually Slightly convex labially Long Low Very anteriorly directed As for Brancatherulum, the edentulous lower jaw that constitutes the type and only specimen of the genus was reviewed by Heinrich (1991), who concluded that it was not possible to decide between a paurodont and a peramurid on the basis of the dental formula alone. To the three remaining genera of Paurodontidae, Araeodon was added by Simpson (1937). Finally, Bakker and Carpenter (1990) described a new therian genus, Foxraptor, which they attributed to the same family. These five genera are known only from lower teeth. However, Simpson (1929) had suspected that the dryolestid genus Pelicopsis Simpson 1927a, known from upper teeth, might in fact be a paurodont. This opinion was adopted by Prothero (1981). Later, Krebs (1991), citing what he considered to be similarities between the upper molars of Henkelotherium from the Kimmeridgian of Guimarota, Portugal and the Morrison genus Pelicopsis , as well as those between the lower molars of Henkelotherium and of another Morrison genus Tathiodon, included these two North American genera in his family Henkelotheriidae, thus leaving only four genera in Paurodontidae. All the paurodontid genera come from the Morrison Formation (late Jurassic, and, for Foxraptor, possibly basal Cretaceous). No contemporaneous or older locality has so far yielded paurodont remains (except for possibly Brancatherulum and Henkelotherium). ENSOM AND SIGOGNEAU-RUSSELL: CRETACEOUS MAMMALS 49 TABLE 2 (CONT). Metaconid Talonid Trigonid posterior face Wear Moderate Sloping Semicircular Shelf-like Wide and short 'No true cusp’ Narrow and flat More posterior than labial Moderate Semicircular Wide and long Cusp postero-lingual Flat Posterior and labial? Relatively high Triangular Wide and long Cusp postero-lingual Flat? ? Moderate Sub-triangular? Very small No cusp? Flat Posterior and labial? Low to moderate Semicircular Wide Cusp postero-lingual Slightly concave Posterior and labial? ‘Not reduced’ Triangular Wide and short Postero-lingual cusp Slightly concave Posterior and labial base Moderate Triangular? Relatively long No cusp Strongly concave Postero-labial base Moderate Triangular? Longer and wider No cusp Strongly concave Postero-labial base Relatively high Strongly concave Position of Dorsetodon By the subequality of the roots, the lack of compression of the crown, the relative extension of the talonid, these teeth are closer to those of paurodontids/henkelotheriids than to those of dryolestids. However, one possibility mentioned by Krebs (pers. comm. 1994) should be considered: could the teeth attributed to the new genus (especially DORCM GS 438) represent lower milk-molars of Dryolestidae? As far as we know, no such teeth have been described or mentioned. The slighter compression of the first molar in one or two dryolestid lower jaws would seem to give support to this interpretation. However, in no dryolestid specimen have we observed such a flattening, nor symmetry of the roots; the situation of the milk molars may of course have been different. But we consider that the type of wear is critical in determining the affinities : never, in dryolestids, is there an indentation at the base of the posterior crest of the protoconid ; in these forms, wear is perfectly transverse. On the contrary, talonid wear, with an indentation of the base of the posterior crest of the protoconid such as noted on DORCM GS 433 and others, can be observed in Henkelotherium, Araeodon, Foxraptor and possibly Archaeotrigon (cast damaged in this area) (Text-figs 10-11). Again the situation is different in typical dryolestids, where the labial cingulum may be affected by wear, but such a facet is completely independent from the talonid (unfortunately, wear cannot be 50 PALAEONTOLOGY, VOLUME 41 observed on our incomplete cast of the Purbeck dryolestid Peraspalax, which also has a slightly concave posterior trigonid surface). Wear is not recorded in Tathiodon and we remain uncertain of the shape of the posterior trigonid face, which, combined with the slight differences mentioned above, prevents us from attributing the Dorset specimens to a small species of this genus. The presence of at least one paurodontid-henkelotheriid in the Purbeck Limestone Group is thus well established. There remains the matter of the distinction between these two families and the establishment of to which one Dorsetodon should be attributed. One of the differentiating characters of henkelotheriids cited by Krebs (1991) concerns the relative slenderness of the lower jaw. Given the fragmentary state of most paurodont remains, it is difficult to express this objectively. We measured (from the published figures): (1) the height of the jaw under M/1 with respect to the height of this M/1: the results varied considerably according to the source used for the measurement, and from the value estimated for M/1 on imprecise drawings of partly worn teeth; (2) the height of the jaw under M / 1 with respect to the length of the alveolar border comprised between the anterior limit of the ultimate premolar and the posterior limit of M/3; the latter measurement excludes Tathiodon for which we have a figure of only the molar part of the preserved jaw (but said by Simpson (1929) to be more slender than in Paurodon and Archaeotrigon ). As shown in Text-figure 12, there does not seem to be a clear distinction between Paurodontidae and Dryolestidae as concerns the relative height of the jaw at that level, much less between Henkelotheriidae and the former. In fact, the difference lies mainly in the respective elongation of the molar series and of the anterior part. Unfortunately the shape and length of the symphysis, short in all paurodonts except Tathiodon, are unknown in the type specimen of Henkelotherium, the only specimen of this taxon described by Krebs. It also appears that the two other characters cited by Krebs as differentiating Paurodontidae and Henkelotheriidae are not familially diagnostic: the relative extension of the para- and metaconid and that of the talonid vary along the dental series in Henkelotherium itself, and also in paurodonts (for example, M/l-M/2 of Archaeotrigon brevimaxillus, or Foxraptor ). Even the shape of the talonid varies, since it is essentially triangular in most molars of Henkelotherium, but becomes semicircular in the last molar. In fact, the lingual view of the molars of Foxraptor (a genus not included in Krebs’ comparison) and Henkelotherium superpose nearly perfectly and the trigonids are very similar in details. The difference between Henkelotherium and Foxraptor lies mainly in the talonid, which is longer and more developed in Foxraptor, even though in this genus also there is some variation along the series. The dental formula of Foxraptor (3 or 4Pm/ + 5M/) is intermediate between that of other paurodontids and Henkelotherium (4 Pm/ + 6 or 7 M/). But, as already noted by Clemens (1970), and accepted by Lillegraven et al. (1979), the reduction of the dental formula may have occurred progressively within the family Paurodontidae. Finally, the type of wear in Henkelotherium is the same as that described in paurodonts and even more accentuated : the indentation at the base of the posterior protoconid crest is very characteristic. Therefore, with the data available, it is tempting to consider either Foxraptor as a member of Henkelotheriidae, or Henkelotheriidae as a junior synonym of Paurodontidae. The situation is not made any clearer by the inclusion of Tathiodon in Henkelotheriidae. The similarities invoked by Krebs (1991, pp. 95-96) are as follows: (1) non-shortened lower molars; (2) two subequal roots; (3) paraconid inclined anteriorly: these three characters are valid for all Paurodontidae (and the shortening of the molar is in fact greater in Tathiodon than in Henkelotherium and most paurodonts); (4) three trigonid cusps well developed: it is very difficult to evaluate this point ; besides being vague, it is rare to find paurodont teeth with their cusps intact ; they are in any case well developed in Foxraptor also; (5) triangular talonid with cusp lingually situated: however, this seems also to occur in Araeodon and is in any case more clearly indicated in Tathiodon than in Henkelotherium (see Simpson, 1929, fig. 22, p. 46; in Bakker and Carpenter (1990), the figures listed as Archaeotrigon and Tathiodon (fig. 7), clearly taken from Simpson 1929, have been inverted). Besides, in Krebs’ table 2 (p. 51), there remain only two characters shared by Henkelotherium and Tathiodon and separating the latter from the other paurodonts : (1) talonid cusp not reduced: but the hypoconulid is even better developed in Archaeotrigon and Foxraptor; (2) ENSOM AND SIGOGNEAU-RUSSELL: CRETACEOUS MAMMALS 5: paraconid and metaconid not much lower than the protoconid : the height of the metaconid relative to the protoconid may indeed be a good differential character. The trigonid angle may also be a good indicator. However, more significant is the type of wear at the level of the talonid: as mentioned above, that of Henkelotherium, with an excavation at the base of the posterior crest of the protoconid delimiting a slight concavity, is similar to the condition in Dorsetodon and Paurodon, only more accentuated. Again the mode of wear is unknown in Tathiodon. To sum up, the distinction of Henkelotheriidae and Paurodontidae founded on the lower molars needs to be confirmed by further comparative material and studies. Hence the conservative approach of this paper, in which we place Dorsetodon in Paurodontidae. The characteristics of Dorsetodon and the other paurodontid genera are listed in the table below (Table 2). We wish to stress once more that these evaluations are subject to variations (1) along the dental series; (2) according to state of preservation; and (3) which are subjective: an attempt at quantification is itself devalued by (1) and (2). Obviously we have envisaged the possible presence, in the new Purbeck collection, of upper molars corresponding to the lower molars of Dorsetodon. In the available sample, 36 upper molars could be attributed to Dryolestoidea. Without doubt 26 of them represent typical Dryolestidae, even if some do not perfectly correspond to any of the three taxa so far known in this fauna: Amblotherium nanum, A. pusillum and Kurtodon (some of the lower molars also indicate the presence of new dryolestid taxa). The teeth which cannot be identified as dryolestids make potential candidates as upper molars of Paurodontidae. As no paurodont genus is known from both upper and lower dentition, the peculiarities of the paurodont upper molars remain uncertain. Pelicopsis, as already mentioned, has been tentatively attributed to this family by Simpson (1929), mainly from the number of molars and the shape of the intermolar embrasures. Krebs (1991) went further by placing the genus in Henkelotheriidae. The common characters cited for the two genera (Krebs 1991, p. 50) are the non-compression of the trigon and the reduced stylocone. However, the latter is much more reduced in some Dryolestidae, e.g. Kurtodon. The only remaining character possibly linking the teeth of Henkelotherium and Pelicopsis is the proportions of the trigon ; but these should be expressed objectively, and measured along the dental series. In the absence of such data, we can only suggest that some teeth, such as DORCM GS 313 and 315 (Text-fig. 13), might represent upper molars of our new paurodontid. The establishment of this new taxon demands the search for the phylogenetic relationships of the various forms mentioned above. Prothero (1981) proposed a cladogram for the then known genera (Text-fig. 14). The knowledge acquired since 1981 exposes a few incongruities: Foxraptor, recognized as the most primitive paurodont by its authors, must indeed diverge before Tathiodon 52 PALAEONTOLOGY, VOLUME 41 text-fig. 14. Cladogram of paurodontids, after Pro- AY strongly procumbent paraconid, reduced to four j premolars. 2. reduction to two premolars, broad shelf-like paraconid and talonid, reduced paraconid and talonid cusps, metaconid slightly shorter than protoconid. 3. metaconid much shorter than proto- conid, jaw short and stout with short symphysis, last lower premolar loses anterior cingulum. 4. talonid semicircular in crown view. 5. anterior molar root much larger than posterior root, trigonid and talonid anteroposteriorly compressed, lingual alveolar border lower than labial border, angular process slender and dorsally deflected. 1 by the number of premolars; but it has already acquired the short symphysis of Araeodon and the semicircular talonid of Paurodon and Archaeotrigon, both characters considered, probably justly, as derived. Foxraptor also possesses a relatively high protoconid, again considered to be a shared derived character of the last three genera ; but this feature is apparently variable along the jaw. We must admit that, when we know too little to even ascertain the polarity of some characters, it becomes very ‘acrobatic’ to evaluate relationships between the relevant taxa. Finally, we note again that phylogenetic relationships cannot be as simplistic as our two-dimensional dichotomic cladograms would imply. These are necessarily based on very incomplete specimens as well as on the serendipitous discoveries of particularly small specimens ; such limitations are inescapable, but the value of such cladograms should not be overestimated, nor their presentation be dogmatic. Position of Chunnelodon The morphology of the crown and the proportions of the roots separate Chunnelodon from Dryolestidae, and the non-shelf-like paraconid ensures that these molars are not paurodont- henkelotheriid teeth. They might evoke Amphitheriidae, but the Dorset molars differ by the absence of a metacristid (the hypoconulid is not offset labially as in Amphitherium, hence there is no differentiation of a metacristid directed toward a labial hypoconulid); they also differ from Amphitheriidae by the wide U separating para- and metaconid, and by the lesser labial convexity of the trigonid ; by a much smaller talonid and the asymmetry of the para- and metaconid. The same asymmetry and the shape of the talonid distinguish the new genus from Donodontidae (Sigogneau- Russell 1991). Thus Chunnelodon, on the morphology of the lower molars, stands apart from the cladotherian (Dryolestoidea plus Zatheria in Prothero 1981) families so far known from lower teeth, while at the same time probably belonging to that group, on the basis of the presence of four derived characters: loss of lower molar lingual cingulum, trigonid angle less than 100°, talonid better defined than that of Symmetrodonta, transverse shear. However, such uncertainties as those concerning the angular region of the lower jaw, the structure of the premolars, not to mention the corresponding upper molars, leave some doubt as to this attribution. Within Cladotheria and as mentioned above, the non-procumbent paraconid would exclude Chunnelodon from Dryolestoidea sensu Prothero 1981 ; the same is true for Donodon. This character- state would justify either the position of these two latter taxa as a common sister-group to Dryolestoidea, or more likely, the isolation of both from that ‘sublegion’, according to the tentative scheme given below (Text-fig. 15). ENSOM AND SIGOGNEAU-RUSSELL: CRETACEOUS MAMMALS 53 Lower JURASSIC Middle JURASSIC Upper JURASSIC Lower CRETACEOUS Upper CRETACEOUS X* * / 1 ZATHZMAN L Wf SYMl 1ETRQD0NTA ' ?! II |l r M ^ J 1 *'vi 1 1 1 l ! 1 l V ■F* | ^ — * — « / 1 S— H 1 1 1 D0N0D0NTIC — CHUNNELODON — PAURODONTID ENKEL0THER1IDAE OF )AE AE ! IY0LEST1DAE O' text-fig. 15. Proposed relationships of the various cladotherian families considered in this paper, based on lower molars only. 1. loss of lingual cingulum on molars; trigonid angle < 100°; expanded talonid; transverse shear. 2. antero-posterior compression. 3. loss of symmetry; paraconid decreases; loss of anterior cuspule; slightly unequal roots. 4. shelf-like paraconid; procumbent paraconid. 5. decrease in number of molars; paraconid low relative to protoconid. 6. increase in number of molars; antero-posterior compression; strongly asymmetrical roots; talonid decreases. Poor though our knowledge is of these two new forms from the Purbeck, their discovery opens a small window on a much richer and more varied world of Mesozoic mammals than hitherto suspected. Acknowledgements. The authors acknowledge the help of the great many individuals and organizations previously thanked in the papers of Kielan-Jaworowska and Ensom (1992 and 1994). We are especially grateful to the Dorset Natural History and Archaeological Society, which owns and runs the Dorset County Museum, for permission to research and publish on material from Sunnydown Farm. Dr P. Robinson (Boulder, Colorado) is warmly thanked for the loan of the type specimen of Foxraptor. Dr P. M. Butler kindly read an earlier version of this work. SEM stereophotos are by Mme Weber-Chancogne, drawings by M. Lavina, both from URA 12 C.N.R.S., Paris. 54 PALAEONTOLOGY, VOLUME 41 REFERENCES allen, p. and wimbledon, w. A. 1991. Correlation of NW European Purbeck-Wealden (non-marine lower Cretaceous) as seen from the English type-areas. Cretaceous Research, 2, 511-526. barker, r. t. and carpenter, k. 1990. A new latest Jurassic vertebrate fauna, from the highest levels of the Morrison Formation at Como Bluff, Wyoming. Hunteria, 2, 1-19. benton, M. J. and spencer, p. s. 1995. Fossil reptiles of Great Britain. Geological Conservation Review, ser. 10. 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Proceedings of the Linnean Society of London, 175, 117-133. OWEN, R. 1846. A history of British fossil mammals and birds. John van Voorst, London, xlvi + 560 pp. — 1871. Fossil Mammalia of the Mesozoic formations. Monograph of the Palaeontographical Society, 33 (110), i-vi, 1-115, pis 1^1. ENSOM AND SIGOGNEAU-RUSSELL: CRETACEOUS MAMMALS 55 prothero, d. r. 1981. New Jurassic mammals from Como Bluff, Wyoming, and the interrelationships of non- tribosphenic Theria. Bulletin of the American Museum of Natural History, 167, 281-325. sigogneau-russell, D. 1991. Nouveaux mammiferes theriens du Cretace inferieur du Maroc. Comptes-Rendus de F Academic des Sciences , II, 313, 279-285. — and ensom, p. 1994. Decouverte, dans le groupe de Purbeck (Berriasien, Angleterre), du plus ancien temoignage de l’existence de mammiferes tribospheniques. Comptes Rendus de T Academie des Sciences, II, 319, 833-838. Simpson, G. G. 1927(3. Mesozoic Mammalia. VI. Genera of Morrison Pantotheres. American Journal of Science, 13, 411-416. — 19276. Correction. Tathiodon, new genus to replace Tanaeodon Simpson non Kirk. American Journal of Science , 14, 71. — 1928. A catalogue of the Mesozoic Mammalia in the Geological Department of the British Museum. British Museum (Natural History), London, x + 215 pp. — 1929. The American Mesozoic Mammalia. Memoirs of the Peabody Museum, Yale University, 3, 1-171, pis 1-32. — 1937. A new Jurassic mammal. American Museum Novitates , 943, 1-6. west, i. m. 1988. Notes on some Purbeck sediments associated with the dinosaur footprints at Sunnydown Farm, near Langton Matravers, Dorset. Proceedings of the Dorset Natural History and Archaeological Society , 109, 153-154. woodward, a. s. 1916-19. Fossil fishes from the English Wealden and Purbeck Formations. Monograph of the Palaeontographical Society, 69 (334), 1-48, pis 1-10 (1916); 70 (336), 49-104, pis 1 1-20 (1918); 71 (340), i-viii, 105-148, pis 21-26 (1919). p. c. ensom Yorkshire Museum Museum Gardens York, YOl 2DR, UK D. SIGOGNEAU-RUSSELL Institut de Paleontologie 8 rue Buffon Paris 75005, France Typescript received 16 January 1996 Revised typescript received 9 May 1997 SKELETAL ARCHITECTURE, HOMOLOGIES AND TAPHONOMY OF OZARKODINID CONODONTS by MARK A. PURNELL and PHILIP C. J. DONOGHUE Abstract. Conodonts are generally found as disarticulated skeletal elements, yet almost all aspects of conodont research rely on knowledge of the original arrangement of these elements in the apparatus. Analysis of rare, articulated ‘ natural assemblages ’ of taxa assigned to the order Ozarkodinida reveals that there was no significant variation in the skeletal architecture within this major group of extinct agnathans. The apparatus comprised 1 5 elements : a pair each of bilaterally opposed Pa and Pb elements ; an anterior, axial Sa element, flanked on each side by a group of four close-set, inward and forward inclined Sb and Sc elements ; and above and outside each S group, an inward and forward pointing M element. We identify the S positions in the ozarkodinid apparatus as Sa, Sb1; Sb2, Scj and Sc2. Architectural analysis sheds new light on the taphonomy of conodonts, indicating that the majority of natural assemblages represent ozarkodinid carcasses that did not lie parallel to the sea floor. Our new apparatus model also goes some way to removing some of the more significant architectural barriers that have hampered the recognition of homologies between conodont clades. There are many similarities between the apparatuses of ozarkodinids, prioniodinids, prioniodontids, and panderodontids ; it is possible that the Conodonta was rather more conservative architecturally than current hypotheses suggest. Over the last 15 years, our understanding of conodont anatomy, affinities and functional morphology has changed beyond recognition (see Aldridge and Purnell 1996 for review). Conodonts are now widely thought to be vertebrates or craniates, and have an important role to play in understanding the origins and early diversification of the clade (e.g. Sansom et al. 1992; Aldridge et al. 1993 ; Purnell 1995 ; Janvier 1996). Conodonts are among the first craniates to appear in the fossil record, and are far more diverse than any other group of jawless fish. Their fossil record is also more complete and better known than that of any other agnathan group. That is not to say that understanding and analysis of the conodont fossil record is without difficulties. With very few exceptions, conodonts are found as isolated skeletal elements, yet almost all aspects of conodont research, including taxonomy, palaeobiology, functional morphology, phylogenetic analysis and suprageneric classification, rely on knowledge of how these elements were arranged together in the conodont oropharyngeal apparatus. The last few years have seen publication of a number of three-dimensional reconstructions of conodont apparatuses (e.g. Aldridge et al. 1987 ; Smith et al. 1987 ; Dzik 1991 ; Aldridge et al. 1995), and recently we have produced a new, precise model of the ozarkodinid skeletal apparatus. This model has been widely illustrated (e.g. Palmer 1995, 1996; Purnell and Donoghue 1995; Purnell et al. 1995; Abrams 1996) and our aim here is to provide a discussion of our methodology and the wider significance of our model in understanding the taphonomy and homologies of the ozarkodinid apparatus. Aspects of apparatus function are dealt with elsewhere (Purnell and Donoghue 1997). Architecture and natural assemblages The development of ideas about conodont skeletal arrangement (see Text-fig. 1) has closely paralleled hypotheses of biological affinity and functional morphology (see Aldridge 1987 for a review). Rigorous analysis of functional morphology requires knowledge of apparatus architecture. [Palaeontology, Vol. 41, Part 1, 1998, pp. 57-102, 3 pis) The Palaeontological Association 58 PALAEONTOLOGY, VOLUME 41 text-fig. 1 . Hypotheses of element arrangement in ozarkodinid conodonts. Front, side and top views of the apparatus are projected onto the sides of each box; element morphology is diagrammatic, but based on Idiognathodus ; a also shows P, M, S element notation used in text, a, linear arrangement of Schmidt (1934); Pa elements anterior, b, linear arrangement of Rhodes (1952); neither anterior-posterior nor dorso-ventral axes were indicated by Rhodes, c, linear arrangement of Nicoll (1985, 1987, 1995, Nicoll and Rexroad 1987); M elements anterior, S element denticles directed ventrally, Sbj elements (his Sd) set back from other S elements. Nicoll did not reconstruct Idiognathodus, and it is not clear how he would orientate M elements of Idiognathodus morphology, d, vertical arrangement of Dzik (1991) (modified from Dzik 1976, 1986); M elements anterior, dorsally directed ends of elements are ‘posterior’ according to conventional designation, e, arrangement of Aldridge et al. (1987); S and M elements anterior. Text-figure modified from Purnell and Donoghue (1997). PURNELL AND DONOGHUE: OZARKODINID CONODONTS 59 but architecture cannot be based on hypotheses of function. Unfortunately, some studies have fallen into this trap (e.g. Schmidt 1934; Lindstrom 1964, 1973, 1974; Nicoll 1995) and have thereby contributed to the diversity of alternative and sometimes speculative models of skeletal architecture that have been proposed (see below). However, the lack of consensus regarding architecture also reflects a paucity of good fossil material and a consequent lack of morphological constraint. Because conodonts were primarily soft bodied organisms, the skeletal elements of their feeding apparatus became scattered in the sediment on the death and decay of the animals. Fortunately, however, there are fossils that preserve together different types of conodont elements, either associated on bedding-planes or as a cluster of elements fused together by diagenetic minerals. More than 1000 of these ‘bedding-plane assemblages’ and ‘fused clusters’ are now known, and although several conodont orders are represented in collections from around the world, the majority belong to taxa assigned to the order Ozarkodinida. These specimens represent a range of biostratinomic histories (see Appendix for a review), and some are undoubtedly accumulations of elements representing the faecal matter or stomach ejecta of animals that preyed upon conodonts. Such specimens may contain elements belonging to more than one individual and more than one taxon (e.g. Hinde 1879; Schmidt and Muller 1964, fig. 9) and generally they preserve very little of the original arrangement of the elements. Many clusters and bedding-plane assemblages represent the remains of a single dead conodont, but the amount of architectural information they preserve varies. At one end of the preservational spectrum the remains have become completely disarticulated and strewn over the bedding surface (e.g. Higgins 1981; Norby and Rexroad 1985) by current activity, scavenging, bioturbation, or other factors such as explosive release of gases from the decomposing conodont carcass. At the other, the only post-mortem process to have affected the apparatus is passive gravitational collapse as the soft tissues of the conodont body decayed (e.g. Pis 1-3; Text-figs 2-16). In such assemblages, post-mortem movement is limited to minor rotations of element long axes as they ultimately came to rest parallel to bedding. Only clusters and assemblages towards this end of the preservational spectrum are of use in reconstructing apparatus architecture. For convenience we will refer to them as natural assemblages. Diagenetic history apart, bedding-plane assemblages and fused clusters do not reflect different styles of preservation or record different information; the only significant difference between the two arises from the methods used to obtain the material. Bedding-plane assemblages are found on natural bedding-planes or bedding-parallel split-surfaces of black shales and occasionally other lithologies ; their elements may or may not be diagenetically bonded. Fused clusters, however, are recovered by acid dissolution of limestones and dolomites, and they can only preserve together those elements that were in physical contact at the time of formation of the diagenetic mineral that binds them. Adjacent elements that were not in contact, which would be preserved in a bedding- plane assemblage, are separated from the cluster along with the rock matrix. Fused clusters, therefore, tend to be less complete, but they do not record any information regarding original element arrangement that is not preserved in bedding-plane assemblages. Collections of fused clusters also tend to include a higher proportion of faecal associations, simply because the process of coprolite formation often brings elements into closer juxtaposition. Enhanced levels of phosphate in faecal material may also have increased the probability of elements becoming diagenetically fused. Compared with normal collections of disjunct conodont elements, natural assemblages are extremely rare, but despite this they are of paramount importance in conodont palaeontology. Conodonts have no close living relatives, and without homologous structures in extant organisms to aid interpretation, natural assemblages provide the only evidence for the original spatial arrangement of skeletal elements in the oropharyngeal feeding apparatus. Thereby, they serve as references in the development of conodont taxonomy and anatomical notation, and provide templates for reconstructing the apparatuses of the vast majority of taxa that are known only from dissociated remains. They are also fundamental in the recognition of homologies between taxa, in the interpretation of evolutionary pathways and relationships, and in the construction of meaningful suprageneric classification. 60 PALAEONTOLOGY, VOLUME 41 RECONSTRUCTION OF THE CONODONT APPARATUS Suprageneric classification of conodonts has yet to stabilize fully, but up to seven orders are currently recognized (Sweet 1988; Dzik 1991 ; Aldridge and Smith 1993). They all bore apparatuses composed of a number of different elements, with four orders characterized by morphologically simple elements. Of these, the architecture of some taxa assigned by Sweet (1988) to the Bellodellida and the Panderodontida has been reviewed recently by Sansom et al. (1994). Three orders (sensu Sweet 1988) bore an apparatus typically composed of more complex elements: Prioniodontida (see Aldridge et al. 1995 for a discussion of architecture), the Prioniodinida (architectural analysis in preparation (MAP)), and the Ozarkodinida {sensu Sweet 1988). Ozarkodinid taxa dominated conodont faunas through most of the Palaeozoic, in terms of both abundance and diversity. Most bedding-plane assemblages and clusters are ozarkodinids, and almost all attempts at reconstructing the conodont apparatus have dealt primarily with ozarkodinid taxa. Linear reconstructions A few studies have based architectural hypotheses on interpretations of function. Lindstrom’s (1964, 1973, 1974) reconstructions were based primarily on his functional interpretation of the conodont apparatus as a lophophore support, with spatial constraints imposed by the dimensions of the conodont eater Typhloesus. They are not considered further here. Similarly, the approach adopted by Nicoll (1995) is summarized in his statement (p. 247) ‘The conodont apparatus morphology has thus been placed in an amphioxus-like body . . . and this is used to explain and interpret the anatomical relationships of the elements’. However, almost all analyses of conodont apparatus arrangement have adopted one of two distinct approaches which rely on data from bedding-plane assemblages and clusters. Both recognize that the extremely rare natural assemblages that preserve bilaterally symmetrical arrangements of elements (e.g. Text-figs 2-3) record primary architectural information, but the approaches differ in the way they treat asymmetrical assemblages (e.g. Pis 1-3; Text-figs 4, 5a, 6a, 9, 10a, 11a, 12, 13a, 14a, 15, 16a). Most analyses have assumed that deviations from symmetry reflect post-mortem movement of the elements, and that recurrent asymmetrical patterns are produced by rotations and translations of elements into their final resting place by compression and decomposition or by systematic muscle relaxation-contraction effects. This approach dates back to the discovery of the first natural assemblages (Schmidt 1934; Scott 1934). Schmidt (1934) proposed that Gnathodus bore a linear arrangement of 14 elements with the long axes of the elements approximately parallel to one another (Text-fig. 1a). In this model, the M elements flank the S elements, the denticles of which are directed downwards, inwards and towards the P elements. Schmidt’s hypothesis of element arrangement was clearly based to a large extent on the specimen illustrated in Text-figures 7-8, but it was also influenced by his interpretation of the conodont apparatus as the mandibles, hyoid and gill arches of a placoderm fish. For this reason he oriented the apparatus with the Pa elements at the front. Apart from this error, however, and the omission of the Sa element, Schmidt’s reconstruction was ahead of its time and had no real rival until the work of Rhodes (1952) nearly 20 years later. The intervening period saw several publications documenting new conodont assemblages (see Appendix), but, with the exception of Scott (1942) and Schmidt (1950), these did not consider element arrangement in any detail. Scott (1942) drew his conclusions from a collection of around 180 assemblages, but only a very few appear to retain any trace of primary element arrangement, and there is very little evidence to support his hypothesis of the conodont apparatus. Schmidt (1950) augmented his 1934 reconstruction of Gnathodus with extra pairs of Pa elements and extra M elements, surmising that these elements had not been evident in the assemblages he described in 1934 because they lay in a different plane from the other elements of the apparatus. However, the additional elements resemble those of Lochriea and it seems very likely that his revised arrangement was based on an assemblage of two apparatuses. PURNELL AND DONOGHUE: OZARKODINID CONODONTS 61 Perhaps the most influential reconstruction of the conodont apparatus was that proposed by Rhodes (1952) for the apparatus of Idiognathodus (= Scottella , = Scottognathus) (Text-fig. 1b). Rhodes stated explicitly that this was intended to indicate the general form and number of the component elements and that the relative arrangement of the elements was diagrammatic, but the linear arrangement was clearly based on one of the natural assemblages of Du Bois (1943, pi. 25, fig. 14; Text-figs 2-3) and gave an impression of three-dimensionality. The reconstruction did not include an Sa element, nor did Rhodes recognize different morphologies of S element. His model was reillustrated in successive editions of the conodont Treatise (Moore 1962; Robison 1981) and provided a skeletal template for a number of subsequent reconstructions and hypotheses of conodont function. For example, Collinson et al. (1972), Avcin (1974) and Norby (1976) adopted Rhodes’s linear arrangement with only minor modifications, such as shifting the M elements away from the axis and grouping the S elements into two opposed pairs (Collinson et al. 1972), or suggesting a more cylindrical disposition of elements with cusps directed towards the midline of the apparatus, and with an axial Sa element present (Avcin 1974; Norby 1976). Schmidt and Muller (1964) considered their well-preserved bedding-plane assemblages (e.g. PI. 2; Text-figs 9-11) to be a better approximation of the original arrangement in the conodont animal than most previously described material. They recognized morphological differentiation within the S elements and advocated a linear apparatus pattern similar to that of Schmidt (1934), but with the P elements in opposition. A similar conclusion was reached by Jeppsson (1971), based on a review of the evidence from bedding-plane assemblages and clusters, and recently Walliser (1994) has also proposed a very similar linear model based on a re-examination of the material of Schmidt and Muller (1964). Nicoll (1977) also proposed a linear model, but arranged the elements as three groups. His later model (Text-fig. lc; 1985, 1987, 1995; Nicoll and Rexroad 1987; ‘Peraios’ style of Nicoll 1995) was also linear, but suggested a more posterior location for one pair of S elements in taxa which bore an Sa element with a posterior process. The emphasis placed on symmetrical assemblages, the interpretation of asymmetrical assemblages as ‘unnatural’, and the consequent need to invoke systematic post-mortem effects to explain recurrent asymmetrical patterns represent significant weaknesses in the approach to apparatus reconstruction adopted by many of these authors. Several authors, however, realized that different apparatus patterns reflected different orientations of collapse of the original three-dimensional structure. For example, based on their interpretation that their collections contained only a few more laterally than dorso-ventrally collapsed apparatuses, Schmidt and Muller (1964) concluded that the conodont animal was neither dorso-ventrally nor laterally flattened. Avcin (1974) recognized that different attitudes of repose of the conodont carcass would produce different assemblage configurations, but ruled out dorso-ventral collapse as impossible, given the extreme lateral flattening of what he mistakenly took to be the conodont animal (i.e. Typhloesus). Three-dimensional reconstructions Observations such as these led to the development of a more rigorous approach to apparatus reconstruction which, in contrast to the methodology outlined above, aimed to construct an hypothesis of apparatus architecture that could account for a variety of natural assemblage patterns without recourse to ad hoc post-mortem effects. Norby (1976, 1979), for example, suggested that a reconstruction with elements oriented side by side with their long axes vertical was more compatible with asymmetrical assemblage patterns than were linear models. Dzik (1976; later modified a little by Dzik 1986, 1991, 1994; Text-fig. Id) proposed a similar arrangement to account for the different patterns exhibited by the natural assemblages illustrated by Rhodes (1952, pi. 126, fig. 11; Text-figs 2-3) and Mashkova (1972, pi. 1; Text-figs 12-13). This approach was further developed (Aldridge et al. 1987) by incorporating techniques derived from Briggs and Williams (1981). The apparatus of the first-discovered conodont animal specimen (IGSE 13822) was taken as the primary data for a physical model of element arrangement (Text- fig. 1e) which was then tested by photographic simulation of a variety of recurrent patterns of 62 PALAEONTOLOGY, VOLUME 41 apparatus collapse (Aldridge et al. 1987). The resulting architectural model was utilized in several subsequent papers (e.g. Purnell and von Bitter 1992; Aldridge et al. 1993, 1994, 1995; Purnell 1993a, 1994), and similar methods have since been used to reconstruct the apparatus of the prioniodontid conodont Promissum pulchrum (Aldridge et al. 1995). Outstanding problems Rigorous architectural interpretation of bedding-plane assemblages and clusters is based on the recognition that, firstly, some associations of elements are faecal or disarticulated accumulations that preserve little or nothing of primary architecture, and secondly, that the remaining natural assemblages represent collapse of the original three-dimensional apparatus on to a two-dimensional bedding-plane. Different patterns of element arrangement in natural assemblages therefore represent different orientations of apparatus collapse, and the limited number of recurring patterns reflect the attitude of the dead conodont on the sea floor (cf. Dzik 1986). For example, symmetrical patterns (e.g. Text-figs 2-3) were produced by decomposition of a carcass lying on its belly (or belly- up). A carcass on its side produced one type of asymmetrical pattern (PI. 2; Text-fig. 11), and a carcass lying head down (or up) in the sediment produced another (e.g. Purnell and Donoghue 1997, figs 6-7). If one accepts that hypotheses that invoke ad hoc post-mortem movements of elements to explain element arrangements in symmetrical and asymmetrical natural assemblages are inferior to those that do not, then testing of reconstructions is simple. All linear models (e.g. Schmidt 1934; Rhodes 1952; Jeppsson 1971; Nicoll 1977, 1985, 1987, 1995; Walliser 1994; Text-fig. 1a-c herein) fail this test because they cannot account for the asymmetrical patterns observed in the majority of natural assemblages. The models proposed by Aldridge et al. (1987) and Dzik (1991) (Text-fig. 1d-e) are in much closer accord with observed patterns, and they have clarified important architectural features, such as the orientation of the P elements, and the anterior posterior spatial differentiation within the apparatus. But, there are still a number of discrepancies. Aldridge et al. (1987) were aware of a number of limitations of their model: the elements were more widely spaced than in nature, and details of the model, especially the relative positions of the ramiform elements (particularly the M elements) were in need of further refinement. Dzik (1991) also highlighted some of these difficulties with the orientation of S elements; in particular, it is difficult to account for the consistent inward inclination of S element denticles in collapse orientations approaching dorso-ventral (e.g. PI. 3; Text-figs 2, 3a, 7, 8a, 14a). Dzik’s own model (Text-fig. Id), however, is also a poor match for the arrangement of S elements in natural assemblages: the vertical orientation of the S elements is not seen in lateral or oblique lateral collapse patterns (e.g. Pis 1-2, Text-figs 4, 5a, 6a, 9, 10a, 11a, 12, 13a, 15, 16a), and his hypothesis that the elements of the symmetry transition series were arranged with their cusps in direct opposition across the axis, in a structure the shape of an anteriorly open V with a vertical closure, also places elements in positions that are not observed in natural assemblages. It is these difficulties, together with the acquisition of new material and re-examination of existing collections, that prompted us to produce our new model of ozarkodinid architecture. Furthermore, both Aldridge et al. (1987) and Dzik (1991) based their models on only a few taxa; we have attempted to test the degree to which our model can be applied to the ozarkodinids as a whole, and thereby to assess the architectural stability of the apparatus through time and across taxonomic distance. Materials and methods All published bedding-plane assemblage and cluster collections are listed in the Appendix along with notes on their preservation, completeness and collapse patterns. This list does not include prioniodontid or coniform taxa. As part of this study we have re-examined most collections of natural assemblages including those of Du Bois (1943), Rhodes (1952), Schmidt and Muller (1964), Rexroad and Nicoll (1964), Pollock (1969), Mashkova (1972), Avcin (1974), Norby (1976), Puchkov PURNELL AND DONOGHUE: OZARKODINID CONODONTS 63 et al. (1982), Briggs et al. (1983), Nicoll (1985), Aldridge and Briggs (1986), Aldridge et al. (1987), Nicoll and Rexroad (1987), Aldridge et al. (1993) and Purnell (1993a). We have also examined new or unpublished material from the Carboniferous of Bailey Falls and Wolf Covered Bridge in Illinois, USA, the Heath Shale Formation and its Bear Gulch Member, in Montana, USA (see Purnell 19936, 1994 for stratigraphical and locality details) and from the Devonian Cleveland Shale of Ohio, USA. Repository abbreviations are as follows: BM and PM, The Natural History Museum, London; BU, Lapworth Museum, University of Birmingham, UK; CGM, Central Geological Museum, VSEGEI, St Petersburg, Russia; CM, Carnegie Museum, Pittsburgh, USA; CPC, Commonwealth Palaeontological Collections, Canberra, Australia ; IGSE, British Geological Survey, Edinburgh ; IMGP Go, Institut und Museum fur Geologie und Palaontologie, University of Gottingen, Germany; ISGS, Illinois State Geological Survey, USA; IU-IGS, Indiana University -Indiana Geological Survey, USA; MPK, British Geological Survey, Keyworth; RMS, Royal Museum of Scotland; ROM Royal Ontario Museum, Canada; UI, Geology Department, University of Illinois, USA; UM, University of Montana, USA; UN, University of Nottingham; USNM, U.S. National Museum, Washington D.C., USA. Our architectural reconstruction is based primarily on ldiognathodus ( sensu Baeseman 1973; Grayson et al. 1991). Natural assemblages of ldiognathodus outnumber those of all other taxa, and in order to produce the most accurate reconstruction possible, we used regressions derived from measurements of bedding-plane assemblages (Purnell 1993a, 1994) to produce 1 : 50 scale models of all of the elements in an apparatus with Pa elements 2 mm long. These elements, made using epoxy putty modelling combined with moulding and casting techniques, were then used to produce our three dimensional reconstructions. The configuration of the elements in the model was determined by an iterative process analogous to the techniques of numerical forward modelling. An initial arrangement was produced and then compared visually with the arrangements of elements in the natural assemblages of ldiognathodus that formed the database of the analysis. This process revealed a number of discrepancies between the positions of elements in the preliminary model and those observed in the fossils; the positions of the elements in the model were adjusted accordingly, and the process of testing was repeated. This continued until the model converged on a solution which minimized the differences between the observed and modelled positions and orientations of the elements. Final testing was achieved by producing collapse patterns of element distribution from the model without any further adjustment. In nature, assemblages were produced as elements collapsed under the influence of gravity as the conodont carcass decayed. Rather than reproducing this physically, however, collapse of the model was simulated by photographing it from a variety of directions, each corresponding to a particular orientation of apparatus collapse. Modelling techniques similar to these have been used previously to great effect on conodonts (Aldridge et al. 1987, 1995), but they are not without minor drawbacks. The process of simulating collapse photographically does not reproduce the slight reorientations of elements that occur as they come to lie on a horizontal plane, and in some orientations the viewing angle causes elements to appear foreshortened. The discrepancies that arise as a result of these effects are generally very minor, but they are indicated below. The results of the final photographic testing of the model and a detailed description of the ldiognathodus apparatus are published elsewhere (Purnell and Donoghue 1997). Here, we provide three examples (PI. 1 ; Text-figs 2-6) in order to demonstrate the fidelity with which our model can reproduce the range of patterns of element arrangement seen in natural assemblages of ldiognathodus (for more examples, see Purnell and Donoghue 1997 and Appendix). During the course of this work, we have also developed a method for calculating the orientation of the principal axes of the conodont apparatus and the conodont head prior to collapse (x = rostro-caudal axis, y = dorso-ventral axis, z = medio-lateral axis; see Text-fig. 17). Photographs of the model simulate collapse of the apparatus, the focal plane of the camera simulating the bedding- plane of the fossil. The angular relationships between the model and the focal plane therefore reproduce the angular relationships between the conodont head and the sea floor at the time of apparatus collapse. In order to calculate the original orientation of the principal axes of the 64 PALAEONTOLOGY, VOLUME 41 conodont head, the model is arbitrarily fixed with the sagittal plane vertical and oriented north- south (i.e. with principal axes at x = 0°, y = 90°, z = 90°) ; the attitude of the focal plane of the camera is then measured while simulating collapse. Stereographic rotation of these data to restore ‘bedding’ (i.e. the focal plane) to horizontal thus yields the original orientation of the principal axes. Independent repetition of some measurements indicates that calculations of orientation using this technique are reproducible to within a few degrees. It is important to note that natural assemblage collections do not record the original way up of specimens, and part and counterpart (when both are known) are generally designated according to quality of preservation. Thus, it is generally impossible to determine whether it was the left or right side, or ventral or dorsal surface of the body which lay on the sea floor at the time of collapse. However, the orientations of the x and y axes indicate the pitch and roll of the head. The orientation of the z axis reflects the angle of yaw and has no effect on collapse patterns. Furthermore, because our method involves arbitrarily orienting the sagittal plane of the model north-south, the calculated angle of z (i.e. the yaw of the head) has no real meaning. APPARATUS ARCHITECTURE AND SIMULATIONS OF COLLAPSE PATTERNS A full description of our reconstruction is published elsewhere (Purnell and Donoghue 1997), but the various oblique and lateral views of our model shown here (Text-figs 3b, 5b, 6b, 8b, 10b, 11b, 13b, 14b, 16b) and the three-dimensional view (Text-fig. 18) provide sufficient detail for our purposes with this paper. The model differs from that proposed by Aldridge et al. (1987; Text-fig. 1e) primarily in the arrangement of the S and M elements, which they placed in parallel, with approximately equal forward inclination, with no vertical displacement from one element to the next, and with no inward inclination. It is also in the orientations of the S and M elements that our reconstruction differs from Dzik’s (1991) hypothesis (Text-fig. Id). He considered the S elements to be vertical, their long axes parallel, and their cusp directed inwards at 90°, with the M elements at the front of the apparatus. Collapse patterns Idiognathodus. The specimen in Text-figures 2 and 3a is the most widely illustrated natural assemblage (originally figured by Du Bois 1943, pi. 25, fig. 14; see Appendix for subsequent illustrations). Our simulation is of the apparatus as drawn in Text-figure 3a, with the counterpart on the bottom, replicating oblique collapse from above and behind with the principal axes of the apparatus oriented at x = 59°, y = 30°, z = 8° with respect to horizontal (Text-fig. 3b). The main visual differences between the simulation and the specimen arise from the foreshortening of elements caused by the oblique angle of photography ; in reality the long axes of elements came to lie parallel to bedding during collapse, but this cannot be simulated photographically. Du Bois (1943, pi. 25, fig. 4) figured another Idiognathodus assemblage exhibiting a similar pattern of element arrangement, but reflecting a slightly more posterior angle of collapse (x = 71°, y = 17°, z = 9°). The assemblage illustrated in Text-figures 4 and 5a is accurately simulated by photographing the model from behind and to the right, the principal axes of the apparatus oriented at x = 43°, y — 4°, z = 47° (Text-fig. 5b). The dextral Sb elements are not preserved on the specimen (which lacks a counterpart), but the correspondence between positions and orientations of the remainder of the elements in the fossil and the model is very close. The sinistral M element underlies all the S elements and its distal extremity can be seen protruding from behind, towards the Pb elements in both the assemblage and the model. The dextral M element, oriented at the time of collapse with its long axis at almost 90° to the sea floor, has broken part way down the process, the two parts coming to lie parallel to bedding in the orientations that one would predict from their orientations in the model. In the simulation, there is a space between the Pa and Pb elements, and another between the dextral Pb and the sinistral M element ; in reality these spaces were closed up as the elements came to lie on the sea floor. At this angle of collapse, all the S elements have their denticles directed anteriorly, PURNELL AND DONOGHUE: OZARKODINID CONODONTS 65 with the possible exception of the dextral Sbx element, the anterior process of which may have brought the element to lie with its denticles facing into the sea floor or posteriorly. Du Bois (1943) figured two other Idiognathodus assemblages with similar collapse patterns (pi. 25, figs 3, 11, x = 29°, y — 3°, z = 61°; fig. 12, x = 62°, y = 5°, z = 28°). A photograph of the model from front, left and below, with principal axes at x = 33°, y = 19°, z = 49° relative to sea floor at the time of collapse (Text-fig. 6b) simulates the pattern seen in Plate 1 and Text-figure 6a. The sinistral S and M elements lie above and behind their dextral counterparts, with the cusp region of the Sa element overlying the cusps of the dextral Sb2 and Sc elements. Identification of the Sb2, Sq and Sc2 elements on the dextral side of this assemblage is based on their stacking order, as breakage of the anterior processes renders morphologically based determination impossible. The sinistral Pb and Pa elements lie above and behind the dextral elements of the pair. The assemblage figured by Aldridge and Briggs (1986, fig. 5) exhibits a similar pattern of apparatus collapse (x = 36°, y = 8°, z = 53°). Other ozarkodinid taxa. Our primary aim with this paper is to evaluate the model as a general hypothesis of the skeletal architecture of ozarkodinid conodonts, and we have therefore attempted to simulate the collapse patterns observed in as many ozarkodinid taxa as possible (Pis 2-3 ; Text- figs 7-16; see also notes in Appendix). Schmidt (1934) was the first to illustrate complete natural assemblages of conodonts, and although the specimen illustrated in Text-figures 7 and 8a is lost, it is significant because of its strong influence on early models of apparatus arrangement. It is a specimen of Gnathodus (probably G. bilineatus), and although the pattern of element arrangement is very uncommon, a photograph of the model from front, left and above, with principal axes of the apparatus at x = 30°, y = 60°, z = 4° relative to the sea floor, accurately simulates the assemblage (Text-fig. 8b). Text-figures 9 and 10a also illustrate an assemblage of G. bilineatus, and this pattern of element arrangement, similar to that shown by the specimen of Idiognathodus in Plate 1 and Text-figure 6, is accurately reproduced by a photograph taken from front, left and below, simulating collapse with principal axes at x = 33°, y = 14°, z = 54°. Natural assemblages of Gnathodus have been illustrated by a number of authors, and these can also be simulated by photographs of the model. For example, the element arrangement in a specimen figured by Schmidt (1934, fig. 3, pi. 6 fig. 3) is similar to that simulated in Text-figure 16b (but from behind, so that the Pa elements have collapsed forwards; x = 27°, y — 59°, z = 14°). The arrangement of a specimen figured by Norby (1976, pi. 8, fig. 5) is similar to that in Text-figure 14b (x = 37°, y = 38°, z = 31°); another of his assemblages (Norby 1976, pi. 8, fig. 2; also figured by Sweet 1988, p. 2) is similar to that simulated in Text-figure 3b, but with a slight offset and a higher angle of collapse (x = 65°, y = 18°, z — 17°; approaching the orientation shown in Purnell and Donoghue 1997, fig. 7b). Two specimens (Norby 1976, pi. 8, figs 1, 7), although partially disrupted, are comparable to one of the arrangements simulated in Purnell and Donoghue (1997, figure 7b), as is a specimen figured by Varker (1994, pi. 1, fig. 7; x = 74°, y = 16°, z = 3°). Varker (1994, pi. 1, fig. 4) also figured a specimen with a collapse orientation between that of Text -figures 3b and 16b (x = 56°, y = 21°, z = 25°). Figure 6 of Schmidt and Muller (1964; x = 37°, y = 1°, z = 53°) is similar to the arrangement simulated in Text-figure 5b, and Purnell (1994, fig. 2b) figured one of Norby’s (1976) specimens, the arrangement of which is very close to that simulated in Text-figure 16b (see Appendix for further examples). From the accuracy with which the model can simulate these natural assemblages it is evident that the apparatus architecture of Gnathodus did not differ in any significant respect from that of Idiognathodus. This strong similarity lends support to the hypothesis that these taxa are close phylogenetic relatives (Grayson et al. 1991). Natural assemblages of Lochriea are less common than those of Idiognathodus or Gnathodus. Lochriea is a more distant relative of Idiognathodus, but the model can match collapse patterns observed in Lochriea assemblages. The specimen illustrated in Plate 2 and Text-figure 11a, for example, is reproduced by photographing the model from the side and very slightly in front, simulating collapse with principal axes at x = 10°, y = 3°, z = 80°. An interesting feature of this 66 PALAEONTOLOGY, VOLUME 41 text-fig. 2. Natural assemblage of Idiognathodus', UI X-1480; Pennsylvanian Modesto Formation, Bailey Falls, Illinois, USA; originally figured by Du Bois (1943; see Appendix for subsequent illustrations). All four P elements, the remains of at least six S elements, and one M element are preserved in the part; counterpart not illustrated; x 32. apparatus is that the S elements on the dextral side exhibit slight deviations from their primary positions, whereas those on the sinistral side do not, strongly suggesting that this apparatus collapsed onto its left side. Norby (1976) illustrated several assemblages of Lochriea, at least two of which are collapses without significant disruption. The arrangements of elements in these specimens (Norby 1976, pi. 14, figs 8-9) are very similar to the collapse patterns simulated in Text-figures 13b and 16b respectively (see Appendix). The ability of the model to simulate natural assemblages of Lochriea indicates that the apparatus architecture of Lochriea is very similar to that of Idiognathodus and Gnathodus. Some differences do exist, however, the most significant being the more posterior and slightly more ventral location of the M elements in Lochriea. The morphology of M elements in Lochriea is distinct from that of Idiognathodus, and the differences in shape and position suggest that the function of these elements in these taxa was different. The hypothesis that Ozarkodina represents the rootstock from which many members of the Ozarkodinida evolved (Sweet 1988) gives its architecture particular significance. A natural assemblage from the Lower Devonian of Tadjikistan (Text-figs 12-13) was originally figured by Mashkova (1972) but has subsequently been reillustrated many times (see Appendix). The importance of this specimen for understanding the architecture of ozarkodinid conodonts has long been recognized, and it has been reinterpreted by numerous authors (Dzik 1976, 1986, 1991 ; Carls 1977; Jeppsson 1979; Aldridge 1987; Nicoll and Rexroad 1987). Our identification of the elements in the assemblage (Text-fig. 13a) is based on a re-examination of the original material and differs in detail from all those previously suggested; we identify all the dextral S elements and the Sa element, with only the sinistral Sb elements missing from the assemblage (except for what is probably the posterior process of one of them). Although in terms of element morphology there are clear differences between Idiognathodus and Ozarkodina, the arrangement of elements is reproduced with good accuracy by photographing the model from the front and below (Text-fig. 13b), PURNELL AND DONOGHUE: OZARKODINID CONODONTS 67 A text-fig. 3. a, composite camera lucida drawing of specimen UI X-1480, counterpart and part (counterpart on bottom), b, photograph of model taken from above, behind and slightly to left to simulate collapse pattern of UI X-1480; small cube indicates orientation of principal axes of apparatus relative to sea floor at time of collapse, x = 59°, y = 30°, z = 8°. Note that as preserved on the specimen part (Text-fig. 2) the apparatus has collapsed obliquely, from below and in front towards top and behind, but without a transparent base to the model this orientation cannot be simulated photographically. Therefore, our simulation is of the whole apparatus as shown in the camera lucida drawing with the counterpart on the bottom. 68 PALAEONTOLOGY, VOLUME 41 text-fig. 4. Natural assemblage of Idiognathodus ; UI X-6377; Pennsylvanian Modesto Formation, Bailey Falls, Illinois, USA; originally figured by Du Bois (1943; see Appendix for subsequent illustrations). All four P elements, the remains of seven S elements, and both M elements are preserved on the part ; no counterpart ; x 35. simulating collapse with principal axes at x = 50°, y = 20°, z = 33° relative to the sea floor (an orientation similar to that shown in Text-fig. 6b). Clearly the architecture of the apparatus was extremely similar to that of Idiognathodus, although the orientation of the posterior processes of the M elements in the assemblage suggests that they may have been more parallel to the S elements than in Idiognathodus. Although incomplete, the natural assemblages of Ozarkodina from the Upper Silurian of Indiana (Pollock 1969; Nicoll and Rexroad 1987) also allow the similarities between Ozarkodina and other ozarkodinids to be assessed. These assemblages belong to a different species from that illustrated by Mashkova (1972), and have shorter Sb elements, of modified digyrate morphology, rather than the elongate bipennate Sb elements borne by all the taxa discussed so far. In assemblages reflecting lateral and oblique-lateral collapse (e.g. Pollock 1969, pi. Ill, figs 3-5, 16; Nicoll and Rexroad 1987, pi. 3.4, figs 1, 3, 5) these shorter Sb elements are aligned sub-parallel to the Sc elements, and their original orientation seems to have been similar to the bipennate elements of Idiognathodus, with their ‘inner lateral’ processes (conventional orientation) directed posteriorly and dorsally. The arrangement of elements in several of the assemblages illustrated by Pollock (1969, pi. Ill, figs 3-5) can be simulated closely by the model (Purnell and Donoghue 1997, fig. 7b); another of Pollock’s text-fig. 5. A, camera lucida drawing of specimen UI X-6377. B, photograph of model taken from behind, right to simulate collapse pattern of UI X-6377 ; small cube indicates orientation of principal axes of apparatus relative to sea floor at time of collapse, x = 43°, y = 4°, z = 47°. PURNELL AND DONOGHUE: OZARKODINID CONODONTS 69 text-fig. 5. For caption see opposite. 70 PALAEONTOLOGY, VOLUME 41 text-fig. 6. For caption see p. 72. PLATE 1 PURNELL and DONOGHUE, Idiognathodus (for explanation see p. 72) 72 PALAEONTOLOGY, VOLUME 4 text-fig. 7. Natural assemblage of Gnathodus from the lower Namurian, Hemer, Nordrhein-Westfalen, Germany; specimen lost during World War II, originally figured by Schmidt (1934; see Appendix for subsequent illustrations). Moulds of all 15 elements of the apparatus are preserved on the part; counterpart not illustrated. Photograph reproduced, with permission, from Schmidt 1934, pi. 6, fig. 1; x21. specimens (pi. 1 11, fig. 16) exhibits a similar pattern, but reflects collapse from behind-right rather than left. One of the specimens figured by Nicoll and Rexroad (1987, pi. 3.4, figs 1, 3, 5) reflects lateral collapse in an orientation very close to that simulated in Purnell and Donoghue (1997, figure 5b). The Appendix lists more assemblages of Ozarkodina with indications of collapse orientations determined from the model. Sweet (1988) suggested that many late Palaeozoic ozarkodinids were descended from Bispathodus. The apparatus of this genus is, therefore, of considerable interest, yet natural assemblages of Bispathodus have not previously been illustrated. The specimen figured (PI. 3; Text- fig. 14a) lies within, and was eaten by a shark ( Cladoselache ) but it is clearly a good natural assemblage with minimal post-mortem disruption of the apparatus. A photograph of the model from above and in front (Text-fig. 14b), simulating collapse with principal axes at x = 10°, y = 71°, z = 16° matches the assemblage closely. In true collapse, the long axes of the P elements would have come to lie parallel to the sea floor, bringing them into the positions seen in the specimen ; similarly, the apparent angle of inclination of the S elements would steepen. The greater disruption of S elements on the sinistral side of the apparatus suggests that collapse was on to the right side ; among text-fig. 6. a, composite camera lucida drawing of specimen PM X 2220, part and counterpart (part on bottom), b, photograph of model taken from front, left and below to simulate collapse pattern of PM X 2220; small cube indicates orientation of principal axes of apparatus relative to sea floor at time of collapse, x = 33°, y = 19°, z = 49°. EXPLANATION OF PLATE 1 Figs 1-2. Natural assemblage of Idiognathodus; PM X 2220; Pennsylvanian Modesto Formation, Bailey Falls, Illinois, USA. 1, part; 2, counterpart; x 40. PURNELL AND DONOGHUE: OZARKODINID CONODONTS 73 A text-fig. 8. a, tracing of Schmidt’s Gnathodus specimen, part, b, photograph of model taken from front, left and above to simulate collapse pattern of Schmidt’s specimen; small cube indicates orientation of principal axes of apparatus relative to sea floor at time of collapse, x = 30°, y = 60°, z = 4°. Note that sinistral and dextral in apparatus and model do not correspond; exact match would require photograph to be taken through base board of model. text-fig. 9. Natural assemblage of Gnathodus', IMGP Go 60CM4; lower Namurian, Hemer, Nordrhein- Westfalen, Germany; originally illustrated by Schmidt and Muller (1964; see Appendix for subsequent illustrations). Silicon rubber cast of part preserving moulds of all elements except dextral M; counterpart not illustrated. Cast coated with ammonium chloride; x23. the dextral S elements the only disruption evident has affected the Sbx element, the incurved anterior process of which has caused the element to rotate so that its denticles face those of the other dextral S elements. The vertical stacking of the sinistral S elements produced in this orientation of collapse (see Text-fig. 14b) is clearly unstable, and in the assemblage the Sb elements have been displaced outwards from the base of the pile. The accuracy and precision with which the pattern of collapse in this assemblage is simulated by the model provides strong evidence that the apparatus architecture of Bispathodus did not differ in any significant respect from that of Idiognathodus. An extremely similar pattern of apparatus collapse in Gnathodus has previously been illustrated by Norby (1976, pi. 8, fig. 5). Adetognathus has never been reported as a natural assemblage and the specimen illustrated here (Text-figs 15, 16a) has not been figured previously. There is some disruption of the apparatus, particularly affecting the P elements and the sinistral M element, but photographing the model from above and behind (Text-fig. 16b) simulating collapse with the principal axes at x = 40°, y — 20°, z = 43° relative to the sea floor accurately simulates the assemblage. There are, therefore, no significant differences in architecture between Adetognathus and Idiognathodus. Natural assemblages of a number of other ozarkodinid taxa have previously been figured by several authors, and, although we do not reillustrate them, their patterns of apparatus collapse can PALAEONTOLOGY, VOLUME 41 text-fig. 10. A, camera lucida drawing of Gnathodus specimen IMGP Go 600-44. B, photograph of model taken from front, left and below to simulate collapse pattern of IMGP Go 600-44; small cube indicates orientation of principal axes of apparatus relative to sea floor at time of collapse, x = 33°, y = 14°, z = 54°. PURNELL AND DONOGHUE: OZARKODINID CONODONTS 75 text-fig. 10. For caption see opposite. r "U 76 PALAEONTOLOGY, VOLUME 41 text-fig. 11. For caption see p. 78. PLATE 2 PURNELL and DONOGHUE, Lochriea (for explanation see p. 78) 78 PALAEONTOLOGY, VOLUME 41 text-fig. 12. Natural assemblage of Ozarkodina; CGM 1/10499; Lower Devonian, Turkparida Valley, Tadjikistan; originally figured by Mashkova (1972; see Appendix for subsequent illustrations). All P and M elements and seven S elements are preserved on the part; no counterpart; x27. be simulated by photographs of the model. A full listing appears in the Appendix, but we discuss a few examples here. The specimen of Hemilistrona illustrated by Habetin and Knobloch (1981, fig. 72) and Dzik (1991, fig. 1), although partially disrupted, exhibits a similar collapse pattern to that shown in Text-figure 16b, but reflects a higher and more posterior angle of collapse (x = 46°, y = 28°, z = 30°). Two of the assemblages of Polygnathus illustrated by Nicoll (1985, fig. 3a-b) are incomplete, but reflect a lateral collapse orientation similar to that simulated in Text-figure 1 1b. Of particular significance, because of their palaeobiological importance, are the apparatuses of the conodont animal specimens assigned to Clydagnathus Windsor ensis (Globensky). The apparatus in text-fig. 11. a, composite camera lucida drawing of Lochriea specimen IMGP Go 600-36, counterpart and part (counterpart on bottom), b, photograph of model taken from right side and slightly in front to simulate collapse pattern of IMGP Go 600-36 ; small cube indicates orientation of principal axes of apparatus relative to sea floor at time of collapse, x = 10°, y = 3°, z = 80°. EXPLANATION OF PLATE 2 Figs 1-2. Natural assemblage of Lochriea\ IMGP Go 600-36 from collection of Schmidt and Muller (1964); Namurian, Hemer, Nordrhein-Westfalen, Germany. 1, counterpart; 2, part; x 32. PURNELL AND DONOGHUE: OZARKODINID CONODONTS 79 text-fig. 13. For caption see p. 82. PALAEONTOLOGY, VOLUME 41 text-fig. 14. For caption see p. 82. PLATE 3 PURNELL and DONOGHUE, Bispathodus (for explanation see p. 82) PALAEONTOLOGY, VOLUME 41 text-fig. 15. Natural assemblage of Adetognathus ; ROM 49956; Namurian Bear Gulch Member, Heath Formation, Montana, USA. The assemblage preserves remains of all fifteen elements of the apparatus; it is one of five assemblages on a small slab, no counterpart; x 34. the first conodont animal, illustrated by Briggs et al. (1983, figs 1b, 2a-c, 3a-b; refigured many times - see Appendix), exhibits an oblique collapse pattern (x = 3°, y = 43°, z = 47°) similar to the simulation illustrated by Purnell and Donoghue (1997, fig. 9b). These data and the position of the apparatus relative to the eyes indicate that the head of this specimen collapsed neither laterally (i contra Aldridge et al. 1987) nor dorso-ventrally ( contra Bengtson 1983, and Aldridge et al. 1993) but obliquely, as suggested by Briggs et al. (1983). The cluster figured by Briggs et al. (1983, fig. 6) exhibits a lateral collapse pattern similar to that shown in Text-figure 1 1b. Aldridge et al. (1993, figs text-fig. 13. A, camera lucida drawing of Ozarkodina specimen CGM 1/10499. B, photograph of model taken from front, left and below to simulate collapse pattern of CGM 1/10499; small cube indicates orientation of principal axes of apparatus relative to sea floor at time of collapse, x = 50°, y = 20°, z = 33°. text-fig. 14. a, composite camera lucida drawing of Bispathodus specimen CMNH 9201, counterpart and part (counterpart on bottom), b, photograph of model taken from above, left, and front to simulate collapse pattern of CMNH 9201 ; small cube indicates orientation of principal axes of apparatus relative to sea floor at time of collapse, x = 10°, y = 71°, z = 16°. EXPLANATION OF PLATE 3 Figs 1-2. Natural assemblage of Bispathodus ; CMNH 9201; Upper Devonian, upper Cleveland Shale, Cleveland, Ohio, USA; 1, part; 2, counterpart; x 19. Specimen photographed under water. PURNELL AND DONOGHUE: OZARKODINID CONODONTS 83 text-fig. 16. For caption see p. 84. PALAEONTOLOGY, VOLUME 41 4, 6) illustrated an apparatus with a collapse pattern similar to that shown in Text-figure 6b, but slightly more lateral (x = 25°, y = 10°, z — 63°); they also illustrated (fig. 9) an apparatus with an oblique lateral collapse pattern similar to that of Text-figure 5b. There appear to be no significant architectural differences between the apparatuses of Clydagnathus windsorensis and Idiognathodus. A general model of ozarkodinid skeletal architecture Based on all the available natural assemblages, which represent at least five families (sensu Sweet 1988) of Silurian, Devonian and Carboniferous age, there is little evidence for significant variation in the apparatus architecture of ozarkodinid conodonts. Apart from subtle differences such as those noted above, the reconstruction based on Idiognathodus appears also to be a good model of the skeletal architecture of the apparatus borne by most or all ozarkodinids. The possibility exists that the apparatus of the earliest ozarkodinids was somewhat different from that described above, but there is no evidence to support this hypothesis at present, and the conservatism evident in known material argues against it. Similarly, the possibility that some Permian and Triassic ozarkodinids had apparatuses that differed significantly from that of Idiognathodus seems unlikely, but cannot be ruled out altogether. TAPHONOMY OF THE APPARATUS - ORIENTATIONS OF COLLAPSE With the possible exception of the panderodontid specimen from Wisconsin, USA (Mikulic et al. 1985; Smith et al. 1987) conodonts with fossilized trunk remains indicate that the body was elongate, eel-like and laterally compressed (Aldridge et al. 1993). One would expect, therefore, that most conodont carcasses would come to lie with their long axis parallel to the sea floor, with those lying on their side outnumbering other orientations (Aldridge et al. 1987, 1995 ; Nicoll and Rexroad 1987). Using our stereographic restoration technique we have calculated original collapse orientations of all the natural assemblages of ozarkodinids available to us either as fossils or as published illustrations. The results of this analysis (Text-fig. 17) provide some insights into the formation of natural assemblages. Only 8 per cent, of assemblages preserve collapse patterns recording orientations approaching dorso-ventral (i.e. y > 45°), which accords well with intuitive assessments of the likelihood of collapse orientations. But 68 per cent, of assemblages exhibit collapse patterns indicating long axis (i.e. x axis) angles in excess of 30° to the sea floor, with 50 per cent, indicating orientations of collapse in which x was 45° or more. This is not what one would predict from what is known of conodont body shape, and these counterintuitive results require some explanation. Thirteen of the natural assemblages in the > 45° sector of the graph (Text-fig. 17) are fused clusters of Ozarkodina. Preservation of fused clusters requires elements to be in contact after collapse, so orientations which produce element overlap are over-represented in cluster collections, whereas those that minimize overlap produce only very partial clusters. This may explain why only one cluster of Ozarkodina records collapse with x < 45° (and this cluster lacks P elements due to non-overlap). It is also worth noting here that the lack of elements (i.e. Nicoll’s Sd’s) in some of the clusters described by Nicoll (1985) reflects non-overlap resulting from lateral collapse (e.g. Text-figs 10-11, 16), not a more posterior position for the Sb1 elements ( contra Nicoll 1985, 1995 and Nicoll and Rexroad 1987). These taphonomic biases involved in cluster formation, however, are not enough to account for the overall distribution of collapse orientations in ozarkodinids because text-fig. 16. a, camera lucida drawing of Adetognathus specimen ROM 49956. Elements labelled X are not part of this apparatus, b, photograph of model taken from behind, left and above to simulate collapse pattern of ROM 49956; small cube indicates orientation of principal axes of apparatus relative to sea floor at time of collapse, x = 40°, y = 20°, z = 43°. PURNELL AND DONOGHUE: OZARKODINID CONODONTS 85 text-fig. 17. Collapse orientations of ozarkodinid apparatuses determined according to the methods outlined in the text; inset at right shows conodont head with principal axes indicated. The orientations of the x and y axes indicate the pitch and roll of the apparatus; the orientation of the z axis (not shown on graph), reflects the angle of yaw and has no effect on collapse patterns. Points with numeric labels are specimens shown in Text-figures. For details of collections from which data are derived see text and Appendix. N. B. The original way up of specimens is generally not known and it is therefore impossible to distinguish between dorsal and ventral, and between left and right. Idiognathodus data include unpublished material currently housed at the University of Leicester; Ozarkodina data are fused cluster material except for CGM 1/10499 (Text-fig. 13); the ‘other’ category includes Adetognathus (Text-fig. 16), Bispathodus (Text-fig. 14), Hemilistrona (see Dzik 1991), and three fused clusters of Polygnathus (Nicoll 1985). n = 79. the same pattern emerges from the collapse data for Idiognathodus, the most numerous of the assemblages. These data are derived from bedding-plane assemblages, not clusters, yet 71 per cent, of Idiognathodus assemblages reflect collapse angles in which x exceeded 30°, and in 51 per cent, x was more than 45°. There are a number of possible explanations for x angles in excess of 30° : it seems unlikely to be due to conodont head shape expanding anteriorly to the extent that it comes to rest at high angles to the sea floor, and the possibility that the long axis of the ozarkodinid apparatus did not coincide with the long axis of the animal is ruled out by the apparatuses in the preserved conodont animals. The most likely interpretation is that the sea floor at the time of death of the conodont animals was soft enough for the carcass to penetrate some way into the sediment, which allowed the head to come to rest in positions that would be gravitationally unstable on a solid surface. Such ‘soupy substrates ’ have been invoked to explain patterns of preservation of larger vertebrate skeletons in black shale environments (Martill 1993). In the case of the Idiognathodus collapse data, all the assemblages are from the black shales of the Modesto Formation at Bailey Falls. This unit lacks PALAEONTOLOGY, VOLUME 41 text-fig. 18. Stereo-pair of model viewed from above front. The long axes of the posterior, P elements are vertical; that of the axial, anterior Sa element is horizontal. a significant benthic fauna (Collinson et al. 1972), and although this may reflect conditions of reduced oxygen, it is also consistent with a soft substrate. The soft substrate hypothesis is also supported by the high abundance of conodont elements and assemblages in the shale ; this may have been produced by the concentration effects linked with the compaction of large volumes of low density sediment. It is possible that the commonness of relatively high angles of collapse in Idiognathodus is due to the weight of the mineralized conodont apparatus or the action of the tail causing dead conodonts to nosedive into the sediment. However, because we are currently unable to differentiate head-up from head-down collapse orientation, this hypothesis remains untested. An alternative hypothesis, that high angles of collapse result from death of conodonts within burrows, is contradicted by the lack of benthic fauna and bioturbation. Indeed, minimal bioturbation is one of the prerequisites for preserving articulated apparatuses. The hypothesis that substrate density exerted a significant control on carcass orientation in conodonts is supported to some extent by apparatus collapse patterns of Gnathodus and Clydagnathus (Text-fig. 17). We have only analysed 14 natural assemblages of Gnathodus, but nine of these (64 per cent.) are from early Namurian black shales from Hemer, Germany and they all exhibit collapse in which x is less than 45°, possibly because the sea floor at the time of deposition of these shales was not soft enough to allow conodont carcasses to penetrate. Only four Clydagnathus assemblages have been analysed, but these all come from the Granton Shrimp bed. This unit contains a benthic fauna, and was deposited in a mud-flat environment with possible algal binding of organic rich laminae and evidence of periodic exposure and desiccation (Cater 1987); the substrate was probably quite firm. All the assemblages exhibit collapse in which x axes were inclined at less than 30°, two having x axis inclinations close to zero. These angles are consistent with carcasses resting on the sea floor with little or no substrate penetration. PURNELL AND DONOGHUE: OZARKODINID CONODONTS 87 THE OZARKODINID SKELETAL PLAN, ELEMENT NOTATION, ORIENTATION, AND HOMOLOGIES Skeletal plan In contrast to hypotheses of architecture, the broad features of the general skeletal plan of ozarkodinid conodonts have been known for some time, and in recent years this plan (e.g. Aldridge et al. 1987, 1995; Smith 1990) or minor variants (e.g. Nicoll 1985, 1987, 1995; Nicoll and Rexroad 1987) has become fairly stabilized. Points of uncertainty and contention remain, however, and our architectural analysis goes some way to resolving these. From the taxonomic and stratigraphical range of the natural assemblages we have studied, it seems certain that the full complement of elements in the ozarkodinid apparatus was 15 elements (cf. Nicoll 1987), and we have encountered no evidence to suggest that elements were lost from this array in any of the taxa preserved as natural assemblages. Architectural analysis also reveals that the arrangement of these 15 elements was extremely similar in all taxa studied, from the Silurian to the Upper Carboniferous, and it is reasonable to extrapolate from this that the apparatuses of ozarkodinid conodonts remained essentially unchanged throughout their stratigraphical range. One point that is worth addressing specifically is that of the number, morphology and position of the S elements. In all the taxa we have analysed there are nine element positions in the symmetrical S array. On each side, the two outermost Sc positions are occupied by morphologically similar elements of bipennate morphology. Between the Sc’s and the axial Sa position, the two Sb positions are occupied by elements which are more similar to each other than to the Sc elements, although they are generally less similar to one another than are the Sc elements. The two Sb positions are occupied either by bipennate elements or modified digyrate elements; they are morphologically similar, and generally differ from one another only in the form and curvature of the process that in conventional terminology is considered anterior or outer lateral. Homologies and element notation Notation and homology. Element notation is another area in which our analysis of ozarkodinid architecture may help to resolve some outstanding difficulties. A stable and widely understood notation for conodont elements is crucial to communication of multielement taxonomic concepts and also expresses hypotheses of homology (e.g. Klapper and Philip 1971 ; Barnes et al. 1979; Sweet 1988; Dzik 1991). Despite its vital importance, notation of the elements in the ozarkodinid apparatus has yet to stabilize fully. With a few exceptions (e.g. Dzik 1991, 1994) the majority of work dealing with ozarkodinid conodonts uses Sweet’s P, M, S scheme for naming element positions (Sweet and Schonlaub 1975; Sweet 1981, 1988), but the notation is still applied inconsistently to some elements. For example, the notation ‘Sd’ has been applied by a number of authors (e.g. Aldridge et al. 1987 ; Nicoll 1985, 1987) to the element we consider to have occupied an Sb position, but according to Sweet (1981, 1988) ‘Sd’ refers to an axial position occupied by a quadriramate element and should not be applied to ozarkodinids (Sweet 1988; Over 1992). This problem has arisen because Sweet (1981) recognized only three major positions in the S series, the occupants of which were thought to form a transition series of increasing asymmetry away from the Sa. Sweet (1988, p. 25) realized that ‘there may be more than three morphologically distinct components of the S series and, to describe and locate them, it may be necessary to invent intermediate categories, such as Sa-b, or Sb-c’, but we now know that the ozarkodinid apparatus had four S positions on each side of the Sa, and that, based on morphological similarities, the occupants of these positions represent two pairs. We suggest that a solution more in keeping with the primarily locational nature of this notation is to identify these S positions as Sbx, Sb2, Scl5 and Sc2 as we have done throughout this paper (see also Aldridge et al. 1995, fig. 1). Over (1992) also suggested using the terms Sbx and Sb2, but we consider his Sbx element to be an Sb2 and vice versa, based on the location of the elements in our model. PALAEONTOLOGY, VOLUME 4 Application of element notation and hypotheses of homology are the foundations of biological taxonomy and evolutionary analysis of conodonts. Without hypotheses of homology, analysis of relationships among conodonts is reduced to mere speculation, but recognition of homology in conodonts relies on knowledge of element arrangement (Barnes et al. 1979; Purnell 19936). Except for the very few taxa known from clusters or bedding-plane assemblages, reconstruction of species from their disarticulated components relies on general skeletal blueprints or templates which allow the occupants of homologous element positions to be identified using morphological criteria. Over the last 1 5 years, most reconstructions of ozarkodinid taxa have relied on the template and criteria provided by Sweet (1981, 1988), but as we note above, this scheme only recognized three major positions in the S series of increasing asymmetry. It now seems clear that the apparatus of most, and possibly all ozarkodinid conodonts contained 15 elements which occupied two Pa positions, two Pb positions, two M positions and nine S positions (from left to right Sc2, Scl5 Sb2, Sb1? Sa, Sbl5 Sb2, Scj, Sc2). In none of the taxa preserved as natural assemblages are the S elements arranged as transition series of increasing asymmetry. Perhaps the time has now come to adopt the 1 5 element plan as the template for reconstructing ozarkodinid apparatuses. As pointed out by Dzik (1991) one corollary of accepting a standard number of element locations is that terms such as ‘ septimembrate’ or ‘ octomembrate ’ are redundant, or reduced to subjective assessments of the morphological thresholds taken as the boundaries between element types. If it is to have any biological meaning, application of P, M, S notation to the apparatuses of taxa assigned to other orders of conodonts should be based on the recognition of homologies with ozarkodinids. This notational scheme was first applied to Oulodus, a prioniodinid, but it was based on the recognition of principle categories of elements in natural assemblages (Sweet 1988), and given the material available at the time the scheme was developed, it must have been derived primarily from the arrangement of elements in ozarkodinid assemblages (Purnell 19936). The ozarkodinid apparatus, therefore, can be taken as the standard for the P, M, S scheme (cf. Dzik 1991). Homologies with prioniodinids. Natural assemblages of taxa assigned to the Prioniodinida and Prioniodontida ( sensu Sweet 1988), the other two orders with apparatuses composed of complex multidenticulate elements, are much scarcer than those of ozarkodinids. Prioniodinids, for example, are known from a single Hibbar della angulata (Hinde) from the Late Devonian Gogo Formation of Western Australia (Nicoll 1977), an incomplete Idioprioniodus from the lower Namurian of Germany (Schmidt and Muller 1964; Purnell and von Bitter 1996), a few Neogondolella from the Middle Triassic of Switzerland (Rieber 1980; Orchard and Rieber 1996), and a Kladognathus assemblage from the Mississippian of the USA (Purnell 19936). With such limited data, the three- dimensional architecture of prioniodinids cannot yet be determined, and hypotheses of element arrangement and homologies with ozarkodinids remain somewhat preliminary. However, Purnell (19936) interpreted the apparatuses of Hibbar della and Kladognathus to have been arranged according to the same basic skeletal plan, which did not differ significantly from that of ozarkodinids. Based on element locations, homologies were recognized with ozarkodinids, and the same element notation that we advocate for ozarkodinids can, therefore, be applied to prioniodinids. The morphology of the occupants of some of the 15 positions in the apparatus is, however, clearly different. This hypothesis of the prioniodinid apparatus stands in marked contrast to the architectural model of Idioprioniodus proposed by Stone and Geraghty (1994). This was based primarily on the concept of symmetry transition, which we consider a most unreliable indicator of element location in prioniodinids, and is contradicted by data from bedding plane assemblages (Purnell and von Bitter 1996). Homologies with prioniodontids. Natural assemblages of prioniodontids now number in excess of 100, but they are all the same species, Promissum pulchrum Kovacs-Endrody. Consequently, the architecture of the apparatus of Promissum is known with a high degree of confidence, and although it had more elements, similarities between Promissum and ozarkodinids reveal a number of homologies. These were recognized by Aldridge et al. (1995), but our improved understanding of PURNELL AND DONOGHUE: OZARKODINID CONODONTS 89 the architecture of the ozarkodinid apparatus makes these homologies more secure. The S arrays of both apparatuses contain the same number of elements and, morphology aside, they differ mainly in the position and orientation of the Sa element. This element is horizontal and the most anterior S element in ozarkodinids, but inclined and the most posterior of the S’s in Promissum. The remainder of the S elements in both apparatuses are inclined forwards with the angle of inclination increasing towards the axis from about 30° in the outermost Sc’s; the elements are inclined inwards with the angle increasing away from the axis; and element locations are increasingly dorsal and (except for the Sb2 element of Promissum ) anterior away from the axis. Despite the clear homologies between the S elements, Aldridge et al. (1995) labelled those of Promissum Sb15 Sd, Sb2, Sc rather than Sbj, Sb2, Sc15 Sc2. This was to avoid the terminological confusion of calling quadriramate elements Sb2, when they have been widely termed Sd in the literature. This solution reflects the difficulties of separating the locational from the morphological aspects of the P, M, S scheme, but does little to reduce confusion; the Sd element of Promissum is homologous with the Sb2 in ozarkodinids, and the Sb2 of Promissum is homologous with the ozarkodinid Scr Regarding the other elements of the apparatus, the location and orientation of the M elements in our revised model of ozarkodinid architecture also strengthens the homology proposed by Aldridge et al. (1995), but we can shed no new light on the homologies of Promissum's four pairs of P elements. The architecture of the Promissum apparatus is probably typical of the family Balognathidae (Aldridge et al. 1995), but the question remains as to the extent to which the skeletal plan of Promissum represents a standard for the prioniodontids. Several other bedding plane assemblages of prioniodontid taxa are now known (Nowlan 1993; Stewart 1995), and although these are probably faecal (Stewart 1995; pers. obs.), the number of elements present in these assemblages (Stewart, pers. comm. 1996; pers. obs.) provides some preliminary evidence to support the tentative suggestion of Aldridge et al. (1995) that some prioniodontid apparatuses may have been less complex than that of Promissum. It is possible that the architecture of these apparatuses may have been more similar to that of ozarkodinids. If this proves to be the case, then a 15 element apparatus may be a synapomorphy of ozarkodinids, prioniodinids and prioniodontids. But this speculative hypothesis remains just one possibility; alternatively, a 15 element apparatus may be a plesiomorphic character shared by all members of the Conodonta. Orientation of conodont elements. The similarities in element location and orientation that exist between ozarkodinids, prioniodontids ( Promissum ), and possibly prioniodinids, raise the question of the descriptive terminology conventionally applied to conodonts. It has been realized for decades that the terms of orientation applied to conodont elements are entirely arbitrary and may have no relation to their true orientation in the animal (e.g. Muller 1956), yet they have persisted. Conventional definitions of element orientations are complex (Sweet 1981, p. W7), but cusp curvature provides the best general guide, the concave side marking ‘posterior’, the tip ‘up’, and the upper margin of the base of the element or the posterior process ‘horizontal’. In no apparatuses for which the architecture is known do these conventional designations coincide fully or consistently with true biological orientations. This has been addressed recently by Dzik (1994), who proposed a new biologically based system of orientation, derived from his hypothesis of apparatus architecture. However, as we have discussed, there are significant differences between his hypothesis and the element orientations indicated by our analysis of natural assemblages, and we therefore consider some of his terminology to be incorrect. Descriptive terminology based on true orientations is indeed needed, but it must be based on a detailed consideration of the orientations of elements in as many different apparatuses as possible, not just ozarkodinids. The erection of new terminology, therefore, falls outside the scope of this paper. Homologies with pander odontids. Apart from the apparatuses of conodonts characterized by complex element morphology, the only other order for which an architectural reconstruction has been proposed is the Panderodontida (Sansom et al. 1994). This hypothesis is based primarily on two fused clusters and a bedding plane assemblage of Panderodus which are variable in their 90 PALAEONTOLOGY, VOLUME 41 completeness and degree of disarticulation. Sansom et al. (1994) introduced a locational notation for coniform conodonts, based on the spatial differentiation of the elements in their reconstructed apparatus. They recognized the value of identifying homologies between the panderodontid apparatus and the apparatuses of conodonts with more complex element morphology, but it was precisely because such homologies could not be recognized that they introduced a new notational scheme. There are some striking similarities between the spatial differentiation of the panderodontid apparatus and that of ozarkodinids, but the main obstacle to homologizing elements lay in the differences in orientation of the anterior elements (Smith 1990; Sansom et al. 1994). The orientation of these elements in panderodontids was compared with that in the ozarkodinid model of Aldridge et al. (1987) which had the S elements arranged with their cusps parallel to the sagittal plane, and with no anterior-posterior displacement. In panderodontids the anterior elements are opposed across the axis and are arranged in an anterior-posterior sequence (Smith et al. 1987; Smith 1990; Sansom et al. 1994). This is significantly different from the architecture proposed by Aldridge et al. (1987), but the S elements in our modified ozarkodinid model are oriented with their cusps inclined obliquely inwards towards the axis, and with significant vertical and horizontal displacement through the array. These changes in our understanding of the ozarkodinid apparatus in themselves significantly reduce the difference between the two apparatuses, but it is also possible that the panderodontid apparatus was more three-dimensional than is suggested by the illustrations of Sansom et al. (1994, fig. 6) and Smith et al. (1987, fig. 6.10). There are only three or four clusters and bedding plane assemblages from which to interpret 3D architecture, and although the Waukesha specimen is clearly the least distorted, no known assemblages are both complete and free of post-mortem disruption. With such a limited database, the possibility remains that with the discovery of more material, current architectural hypotheses will require some modification. It is interesting to speculate on the collapse pattern that would result from a slightly altered model of panderodontid architecture in which the elements occupied positions closer to those of our ozarkodinid model. Based on our experience of collapse patterns, it seems likely that this would produce an assemblage similar to the important Waukesha specimen if collapse was close to anterior-posterior, i.e. a high angle of x, but a low angle of y (see Text-fig. 17). This could also account for the posterior position of the axial ae element in the panderodontid model. The Waukesha specimen provides the only evidence that this element lay at the back of the apparatus (Sansom et al. 1994), but its posterior location in the fossil may reflect the orientation of collapse rather than its primary position. This is clearly a somewhat speculative hypothesis, but it is supported by the evidence that many natural assemblages which preserve bilateral symmetry reflect collapse orientations with high angles of x (e.g. Text-fig. 2-3, and see Text-fig. 17). Architectural conservatism in conodonts and a standardized notation. Understanding of apparatus architecture is a prerequisite for the recognition of homologies, an essential step in the interpretation of conodont evolution and in the development of a sound suprageneric classification. We agree with Sansom et al. (1994) that more architectural data are required before current problems can be resolved, and although it would be premature to apply standard P, M, S notation to the panderodontid apparatus, we are more optimistic than these authors that homologies between coniform apparatuses and those made up of more complex elements can be determined. Our model of the ozarkodinid apparatus goes some way to reducing some of the more significant architectural barriers between these apparatus types and suggests that application of a standard location-based notation to apparatuses belonging to conodont lineages with radically different element morphology may not be too far away. There are many similarities between the apparatuses of prioniodinids, prioniodontids, ozarkodinids and panderodontids; it is possible that the Conodonta was rather more conservative architecturally than current hypotheses suggest. Acknowledgements. For loans and access to material we thank Richard Aldridge, University of Leicester; Bob Nicoll, AGSO; Rod Norby, Illinois Geological Survey; Carl Rexroad and Alan Horowitz, Indiana Geological Survey and University of Indiana; Peter von Bitter, Royal Ontario Museum; Mike Williams, Cleveland PURNELL AND DONOGHUE: OZARKODINID CONODONTS 91 Museum of Natural History; and Otto Walliser and Dieter Meischner, University of Gottingen. Rod Norby, Peter von Bitter, and C. Pius Wiebel assisted in collecting assemblages from Bailey Falls. We thank Richard Aldridge for discussion and comments on the manuscript, and Howard Armstrong and Paul Smith for their detailed reviews. Photographic assistance was provided by Ian Paterson and Colin Brooks. 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The apparatus of Gondolella sublanceolata Gunnell (Conodontophorida, upper Pennsylvanian) and its relationship to Illinella typica Rhodes. Life Sciences Contributions of the Royal Ontario Museum, 109, 1—44. — and Merrill, G. k. 1990. The reconstruction of fossil organisms using cluster analysis. A case study from Late Paleozoic conodonts. Life Sciences Miscellaneous Publications of the Royal Ontario Museum, 1-23. walliser, o. H. 1994. Architecture of the polygnathid conodont apparatus. Courier Forschungsinstitut Senckenberg, 168, 31-36. weddige, k. 1989. Conodonten - problematische Fossilien. Natur und Museum, 119, 67-82. — and husken, t.-c. 1995. Reconstruction and architecture of Lower Devonian spathognathodontid apparatuses. 86. In brock, g. a. (ed.). First Australian conodont symposium (AUSCOS-1) and the Boucot symposium, Macquarie University, Sydney, July 1995, Abstracts and Programme. Special Publication of the Macquarie University Centre for Ecostratigraphy and Palaeobiology, 1, 1-108. zhang zhiming and zhang jinghua 1986. Discovery and functional analysis of a new conodont cluster. Geological Review, 32, 185-188. [In Chinese with English summary]. MARK A. PURNELL Department of Geology University of Leicester Leicester LEI 7RH, UK e-mail map2@le.ac.uk PHILIP C. J. DONOGHUE School of Earth Sciences University of Birmingham Manuscript received 5 December 1996 Birmingham B15 2TT, UK Revised manuscript received 12 March 1997 e-mail p.c.j.donoghue@bham.ac.uk APPENDIX: PUBLISHED BEDDING PLANE ASSEMBLAGES AND CLUSTERS We list here published bedding plane assemblages and clusters (not including prioniodontid and coniform taxa) in chronological order, with notes on preservation, completeness and collapse patterns. The term ‘ faecal ’ is applied to assemblages that may represent stomach ejecta or coprolitic 96 PALAEONTOLOGY, VOLUME 4 material. Notes on collapse indicate the orientation that would produce the observed pattern of element distribution relative to the axis of the apparatus (N.B. bedding plane assemblage and cluster collections do not record original way up of specimens, therefore ‘ oblique lateral collapse from side, above and behind’ for example, could also be ‘oblique lateral collapse from side, below and in front’). Hinde, 1879. Devonian, Genesee Shale, New York, USA; specimens BM A-4035, A-4036, actually part and counterpart (Aldridge 1987; pers. obs). Large faecal association, no primary architecture preserved, more than one individual, more than one species. Figured by Huddle (1972). Schmidt 1934. Lower Namurian, Hemer, Nordrhein-Westfalen, Germany; seven assemblages of Gnathodus illustrated: fig. 1 disarticulated, ?incomplete; fig. 2 disarticulated; fig. 3 and pi. 6, fig. 3, oblique collapse from above and behind (cf. PI. 3, Text-fig. 14, but more posterior, x = 27°, y = 59°, z = 14°); fig. 4, partial, articulated S and M array; fig. 5a-b and pi. 6, fig. 1, oblique axial collapse (see Text-figs 7-8; reillustrated by Aldridge et al. 1987, fig. 4.6a); fig. 6, disarticulated; fig. 7 and pi. 6, fig. 2, disarticulated, two individuals. All material lost in World War II. Scott 1934. Mississippian, Quadrant shales, Montana, USA; collection of 75 assemblages, 18 described and figured, including Lochriea, Gnathodus and Cavusgnathus. Most assemblages are incomplete, disarticulated and chaotic; a few retain some evidence of primary architecture (e.g. pi. 58, figs 1-3). Jones 1935. Pennsylvanian, Nowata Shale, Oklahoma, USA; unpublished thesis collection of > 50 assemblages, 17 described and illustrated, six of which are ozarkodinid. Plate 5, large faecal assemblage, more than one individual; remainder probably the remains of single individuals, but all incomplete and/or disrupted. Jones 1938. Pennsylvanian, Seminole Formation, Oklahoma, USA; unpublished thesis collection of 75 assemblages, 15 described and illustrated, including Gondolella (prioniodinid) and Neognathodus. These are probably the remains of single individuals, but are mostly incomplete and disarticulated; only a few retain traces of primary architecture. Assemblage 2 refigured by von Bitter (1976), assemblage 4 refigured by Merrill and von Bitter (1977). Burnley 1938. Pennsylvanian, Lexington Coal, Missouri, USA; unpublished thesis collection, assemblage 12 refigured by Merrill and von Bitter (1977, figs 2-5, 9a, c). Kraemer 1940. Namurian, Arnsberg, Germany; figured partial and/or scattered individual apparatuses and accumulations of more than one individual, little if any trace of primary architecture [Note : some of Schmidt’s material was found by Kraemer], Scott 1942. Mississippian, Heath Formation, Montana, USA; collection of c. 180 assemblages, 32 figured; most are incomplete, or disrupted and chaotic; some are remains of more than one individual (e.g. pi. 37, fig. 6), only a few retain traces of primary architecture (e.g. pi. 38, fig. 10). Plate 37, figure 4 reillustrated by Clark (1987, fig. 20.2a). Du Bois 1943. Pennsylvanian, McLeansboro Group, Bailey Falls, Illinois, USA; collection of > 75 assemblages, 19 figured (figs 3 and 11 are part and counterpart), mostly Idiognathodus, a few ldioprioniodus (prioniodinid). Plate 25, figures 1, 6, 8, 10, 15, 19-20, UI X-6361, X-6366, X-6368, X-6370, X-1494, X1493, X- 6376, partial remains, single individuals, little or no trace of primary architecture, several probably faecal (figs 6, 10, 15, 20); figs 2, 7, 18, UI X-6362, X-6367, X-6375, remains of more than one individual; figs 3 and 11, UI X-6363, lateral collapse from side and slightly posterior, x = 29°, y = 3°, z = 61° (cf. Text-figs 4—5; a little more posterior than Purnell and Donoghue 1997, figs 4-5); fig. 4, UI X-6364, collapse from behind and slightly above, x = 71°, y = 17°, z = 9° (angle a little lower than Text-figs 2-3); fig. 5 (specimen lost), oblique lateral collapse from side and behind, x = 67°, y — 10°, z = 21° (cf. Purnell and Donoghue 1997, figs 6-7, slightly more posterior collapse); fig. 9, UI X-6369, somewhat disarticulated, probably oblique axial collapse; fig. 12, UI X-6371, oblique lateral collapse from side and behind, x = 62°, y = 5°, z = 28° (cf. Text-figs 4-5, slightly more posterior collapse); fig. 13, UI X-6372, oblique lateral collapse from side and in front, x = 64°, y = 5°, z = 26° (cf. Purnell and Donoghue 1997, figs 6-7), but collapse from front and below, rather than rear and above) ; fig. 14, UI X-1480, oblique dorso-ventral collapse, x = 59°, y = 30°, z = 8° (see Text-figs 2-3 ; refigured by Rhodes 1952, pi. 126, fig. 11; Dzik 1976, fig. 10b; Sweet 1985, fig. 1; Aldridge 1987, fig. 1.6; Aldridge et al. 1987, fig. 4.12a; Clark 1987 fig. 20.2b; Sweet 1988, p. 2 (image reversed); Weddige 1989, fig. 5; von Bitter and Merrill 1990, fig. 1a; Purnell et al. 1995, fig. 6; Purnell and Donoghue 1997, figs 2-3); fig. 17, UI X-6374, lateral collapse from side and slightly behind, x = 32°, y = 12°, z = 55° (cf. Purnell and Donoghue 1997 figs 4-5); fig. 21, UI X-6377, lateral collapse from side and slightly behind, x = 43°, y = 4°, z = 47° (see Text-figs 4-5; refigured by Aldridge 1987, fig. 1.2, Aldridge et al. 1987, fig. 4.2a; Weddige 1989, fig. 6; Aldridge 1990, fig. 1 ; Purnell et al. 1995, fig. 5). Du Bois’ collection restudied as part of this investigation. PURNELL AND DONOGHUE: OZARKODINID CONODONTS 97 Cooper 1945. Lower Carboniferous, Kentucky, USA; partial apparatus, unfigured. Schmidt 1950. Namurian, Arnsberg, Germany; sketch figures, several reconstructed assemblages illustrated; fig. 7a, disarticulated remains of two individuals. Rhodes 1952. Pennsylvanian, Illinois and Kentucky, USA; studied >100 bedding plane assemblages of Idiognathodus , Gondolella (prioniodinid), and Idioprioniodus (prioniodinid), including material of Du Bois (1943); pi. 126, figs 1, 5-6, 8 and 10, partial remains, 1, 5 and 6 retaining some primary architecture; fig. 9, UI X-1489, complete apparatus, oblique collapse, probably from side, above and behind, but partly disarticulated, x = 36°, y = 10°, z = 52° (cf. Text-figs 15-16; refigured by Avcin 1974, pi. 1, fig. 10); fig. 11, refigured UI X-1480 (Du Bois 1943, pi. 25, fig. 14). The remains of Idioprioniodus and Gondolella (pis 128-129) are partial and/or disarticulated, many probably faecal (e.g. pi. 129, fig. 13, UI X-1505, includes elements of Gondolella and Neognathodus). Rhodes’ collection of assemblages of Idiognathodus restudied as part of this investigation. Schmidt and Muller 1964. Lower Namurian, Hemer, Nordrhein-Westfalen, Germany; > 50 bedding plane assemblages, seven prepared by acid dissolution of elements followed by rubber casting, and illustrated by line drawings ; figured specimens are remains of single Gnathodus apparatuses except : fig. 9, IMGP Go 600-1 7, disarticulated, faecal, elements from one or two Gnathodus apparatuses and an Idioprioniodus (prioniodinid), fig. 10, IMGP Go 600-16, partial apparatus of Idioprioniodus. Fig. 1, IMGP Go 600-12, lateral collapse from side and slightly below, some disruption of P element articulation, x = 19°, y = 6°, z = 70° (reillustrated by Huddle 1972, fig. 2; Muller 1978, fig. 12); fig. 3, IMGP Go 600-22, disrupted, probably faecal; fig. 5, IMGP Go 600-3, oblique dorso-ventral collapse from above, behind and slightly to left, x = 17°, y = 64°, z = 20° (angle of collapse forwards has rotated Sbj elements backwards); fig. 6, IMGP Go 600-23, lateral collapse, x = 37°, y = 1°, z = 53° (cf. Text-figs 4-5; reillustrated by Rietschel 1973, fig. 7); fig. 7, IMGP Go 600-44, oblique lateral collapse from front left and slightly below, x = 33°, y = 14°, z = 54° (see Text-figs 9-10; refigured by Lane and Ziegler 1984, pi. 1). Schmidt and Muller’s collection restudied as part of this investigation. Rexroad and Nicoll 1964. Silurian, northern Indiana, USA; two partial fused clusters of Ozarkodina, one Pa element pair, one Pb pair. Lange 1968. Upper Devonian, Rheinisches Schiefergebirge, Germany; collection of c. 70 clusters, five figured; fig. 1, partial prioniodinid cluster; fig. 2, partial ozarkodinid cluster; pi. 1, complete apparatus of Palmatolepis, faecal, but retaining some original juxtaposition of elements (reillustrated by Weddige 1989, fig. 7); pis 3^4, cluster of two ozarkodinid apparatuses, faecal, but preserving some aspects of primary architecture; pi. 5, cluster of Belodella (belodellid). Austin and Rhodes 1969. Single fused cluster, very incomplete apparatus of Synclydagnathus, no primary architecture preserved. Pollock 1969. Silurian, northern Indiana, USA; collection of 54 fused clusters of Ozarkodina and Pander odus (panderodontid), 25 ozarkodinid clusters figured ; most clusters very incomplete remains of single individuals (pi. 110, figs 1-9, 14-17, pi. Ill, figs 1-2, 6-13, pi. 112, figs 7-8, 11-16); pi. Ill, fig. 3, IU-IGS 11815, partial apparatus, oblique lateral collapse from the posterior, x = 61°, y = 22°, z = 19° (cf. Purnell and Donoghue 1997, figs 6-7, more lateral and from right); pi. 1 11, figs 4-5, IU-IGS 11843, partial apparatus, oblique lateral collapse, x = 15°, y = 1°, z = 15° (cf. Purnell and Donoghue 1997, figs 6-7); pi. Ill, figs 14-15, IU-IGS 11803, partial apparatus, S elements only, lateral collapse; pi. Ill, fig. 16, IU-IGS 11817, partial apparatus, oblique lateral collapse from behind and slightly below, x = 69°, y = 0°, z = 21° (cf. Purnell and Donoghue 1997, figs 6-7, but from right); pi. 112, figs 1-2, IU-IGS 11818, almost complete apparatus, axial collapse from below, x = 73°, y = 17°, z = 3°; pi. 112, fig. 3, IU-IGS 11820, partial apparatus, no primary architecture, ?faecal; pi. 112, fig. 4, IU-IGS 11814, partial apparatus, S elements only, axial collapse from below; pi. 112, figs 5-6, IU- IGS 11807, partial apparatus, S elements only, lateral collapse; pi. 112, figs 9-10, IU-IGS 11819, partial apparatus, S elements only, oblique lateral collapse, slightly behind and below. Scott 1969. Mississippian, Heath Formation, Montana, USA; illustrated nine bedding plane assemblages as sketches, most appear to be Lochriea, all probably faecal, no primary architecture (cf. opinion of Scott). Collinson et al. 1972. Figured single disarticulated apparatus of Idiognathodus, ISGS 57P-1, from the Avcin thesis collection. Huddle 1972. Figured Hinde’s (1879) large faecal assemblage, and reillustrated IMGP Go 600-12 (Schmidt and Muller 1964, fig. 1). Mashkova 1972. Lower Devonian, Tadjikistan; fig. 2, pi. 1, CGM 1/10499, single specimen of Ozarkodina, oblique lateral collapse from side and below, x = 50°, y = 20°, z = 33° (see Text-figs 12-13; reillustrated by Dzik 1976, fig. 10c; Barskov and Alekseev 1986, p. 68; Weddige 1989, fig. 5; Dzik 1991, fig. 3a; Dzik 1992, fig. 9.16). PALAEONTOLOGY, VOLUME 41 Rietschel 1973. Fig. 7, reillustrates IMGP Go 600-23 (Schmidt and Muller 1964, fig. 6). Scott 1973. Mississippian, Bear Gulch Limestone Member, Montana, USA; pi. 1, figs 1-2, pi. 2, figs 1-2, USNM 183567, 183568, disarticulated faecal assemblage of Cavusgnathus (reillustrated by von Bitter and Merrill 1990, fig. 1a, d); pi. 3, fig. 2, UM 6028, Kladognathus (prioniodinid) within a Typhloesus (reillustrated by Melton and Scott 1973, fig. 17; Conway Morris 1985, pi. 1, fig. 7; 1989, fig. 1.6; 1990, figs 25-26; Purnell 19936, fig. 4). Melton and Scott 1973. Mississippian, Bear Gulch Limestone Member, Montana, USA; gut contents of Typhloesus, fig. 13, UM 6027, disarticulated apparatus of Kladognathus ; fig. 17, refigured UM 6028 (Scott 1973, pi. 3, fig. 2); fig. 19, UM 6030, sketch of apparatuses of more than one Adetognathus, one retaining some primary architecture (also figured by Conway Morris 1985, pi. 2, fig. 2, 1990, figs 16, 18). Avcin 1974. Pennsylvanian, Illinois, USA; unpublished thesis, re-examined Du Bois (1943) and Rhodes (1952) collections, plus c. 300 new assemblages from Bailey Falls locality, c. 200 from other localities, c. 40 assemblages figured, many partial and/or disarticulated, but several collapsed apparatuses of Idiognathodus. PI. 1, fig. 4, ISGS 57P-180, oblique lateral collapse from side, behind and slightly above, x = 59°, y= 12°, z = 29° (refigured by Aldridge et al. 1987, fig. 4.9a); pi. 1, fig. 8, pi. 2, fig. 1, ISGS 57P-72I, oblique lateral collapse from side and below, x = 1°, y = 40°, z = 50° (cf. Purnell and Donoghue 1997, figs 8-9; refigured by Aldridge et al. 1987, fig. 4.8a); pi. 1, fig. 10, reillustrated UI X-1489 (Rhodes 1952, pi. 126, fig. 9); pi. 2, fig. 12, ISGS 57P- 129(A) I, half apparatus, lateral collapse (cf. Purnell and Donoghue 1997, figs 4-5); pi. 2, fig. 19, ISGS 57P- 38(A) I, collapse from behind and slightly to side, x = 71°, y = 9°, z = 17° (cf. Purnell and Donoghue 1997, figs 6-7; refigured by Aldridge et al. 1987, fig. 4.4). Avcin’s collection of Idiognathodus assemblages restudied as part of this investigation. Behnken 1975. Permian, Minnekahta Member, Goose Egg Formation, South Dakota, USA; three partial clusters of Ellisonia excavata, pi. 1, fig. 9, two Sc elements, fig. 10, two ?Pb elements, fig. 14, Sa, Sc and M element. Higgins 1975. Westphalian, Staffordshire, UK; pi. 6, figs 13, 15-16, two partial clusters of two elements; pi. 14, fig. 14, (SAD 663 K5) incomplete fused cluster, Pa, S and M elements, ?faecal, but retains some evidence of element juxtaposition. Dzik 1976. Fig. 10b, reillustrated UI X-1480 (Du Bois 1943, pi. 25, fig. 14), fig. 10c, reillustrated CGM 1/10499 (Mashkova 1972, fig. 2, pi. 1). von Bitter 1976. Figured several assemblages of Gondolella (prioniodinid) and a partial Idioprioniodus (prioniodinid); all appear to be faecal, partial, or disrupted, with little if any primary architecture preserved. Figs 1 3a-b, 14a-b, 15a-b, reillustrated UI X-1505, UI X-1506, UI X-1507, UI X-1508, UI X-1503, UI X-1504 (Rhodes 1952, pi. 129, figs 8-13); fig. 16, reillustration of Assemblages 2 of Jones (1938). Norby 1976. Mississippian, Heath and Tyler formations, Montana, USA; unpublished thesis collection of c. 400 assemblages, 29 assemblages figured. PI. 4, fig. 1, ISGS 62P-1A, Gnathodus bilineatus, partial, probably faecal; pi. 4, fig. 2, ISGS 62P-401A, Cavusgnathus altus , disrupted, incomplete (reillustrated by von Bitter and Merrill 1990, fig. 1b); pi. 8, fig. 1, ISGS 62P-21A, G. bilineatus, oblique collapse from behind, to one side and below, some disarticulation, x = 56°, y = 30°, z = 16° (cf. Purnell and Donoghue 1997, figs 6-7); pi. 8, fig. 2, ISGS 62P-2A, G. bilineatus, collapse from behind, slightly to right, and very slightly above, x = 65°, y = 18°, z = 17° (cf. Text-figs 2-3, angle of collapse more axial; refigured by Sweet 1988, p. 2); pi. 8, fig. 3, ISGS 62P- 6A-1, G. bilineatus, partial, no primary architecture; pi. 8, fig. 4, ISGS 62P-17A, G. bilineatus, possibly disrupted axial collapse, or faecal; pi. 8, fig. 5, ISGS 62P-19A, G. bilineatus, oblique collapse from above, front left, slight post-mortem disruption, x = 37°, y = 38°, z = 31° (cf. PI. 3, Text-fig. 14); pi. 8. fig. 6, pi. 10, fig. 5, ISGS 62P-16A, disarticulated probable faecal assemblage of a G. bilineatus and an Idioprioniodus (prioniodinid) (refigured by Norby and Avcin 1987, pi. 9.1, fig. 7); pi. 8, fig. 7, ISGS 62P-12A, G. bilineatus, possible oblique lateral collapse from side and behind (cf. Purnell and Donoghue 1997, figs 6-7); pi. 8. fig. 8, ISGS 62P-3A, G. bilineatus, incomplete, disrupted, no primary architecture; pi. 8, fig. 9, ISGS 62P-20A, G. bilineatus, disarticulated, no primary architecture; pi. 8, fig. 10, ISGS 62P-13A, G. bilineatus, disarticulated, remnants of S element juxtaposition ; pi. 10, fig. 2, ISGS 62P-604, Idioprioniodus (prioniodinid), incomplete, no primary architecture (refigured by Norby and Avcin 1987, pi. 9.1, fig. 3); pi. 10, fig. 4, ISGS 62P-605, Idioprioniodus (prioniodinid), incomplete, no primary architecture (refigured by Norby and Avcin 1987, pi. 9.1, fig. 2); pi. 13, fig. 1, CM 33965, Lochriea commutata, disrupted, little if any primary architecture; pi. 13, fig. 2, pi. 14, fig, 6, ISGS 62P-217A, L. commutata, disrupted oblique lateral collapse; pi. 13, fig. 3, ISGS 62P-213A, L. commutata, faecal, no primary architecture; pi. 14, fig. 1, ISGS 62P-208, L. commutata, faecal, no primary architecture; pi. 14, fig. 2, ISGS 62P-601A, faecal assemblage of G. bilineatus and Idioprioniodus (prioniodinid); pi. 14, fig. 3, ISGS 62P-204A, three or four apparatuses of L. commutata, possibly faecal, but some apparatuses retain architectural information (e.g. uppermost apparatus, oblique lateral collapse, only slightly disarticulated, x = PURNELL AND DONOGHUE: OZARKODINID CONODONTS 99 32°, y = 10°, z = 57°); pi. 14, fig. 4, ISGS 62P-205A, L. commutata, faecal, no primary architecture; pi. 14, fig. 5, ISGS 62P-206A, L. commutata, faecal, two apparatuses, no primary architecture; pi. 14, fig. 7, ISGS 62P- 207A, L. commutata, lateral collapse, post-mortem separation of P and S elements; pi. 14, fig. 8, ISGS 62P- 216A, L. commutata, oblique lateral collapse from the side, slightly in front and slightly below, x = 29°, y = 6°, z = 60° (cf. Text-figs 12-13); pi. 14, fig. 9, ISGS 62P-210, L. commutata , oblique collapse from behind, above and to one side (cf. Text-figs 15-16); pi. 19, fig. 1, ISGS 62P-701A, Vogelgnathus campbelli, disarticulated, no primary architecture, ?incomplete (less than nine S elements; refigured by Norby and Rexroad 1985, fig. 4, pi. 1, figs 1-2); pi. 19, fig. 2, ISGS 62P-602A, B, faecal assemblage of Idioprioniodus (prioniodinid) and G. bilineatus, partial, no primary architecture; pi. 19, fig. 3, pi. 10, fig, 1, ISGS 62P-603, Idioprioniodus (prioniodinid), disarticulated, no primary architecture (refigured by Norby and Avcin 1987, pi. 9.1, fig. 1); pi. 19, fig. 4, pi. 10, fig. 3, ISGS 62P-751, Kladognathus (prioniodinid), partial (refigured by Norby and Avcin 1987, pi. 9.1, fig. 4). Most ozarkodinid assemblages in Norby’s collection restudied as part of this investigation. Merrill and von Bitter 1977. Pennsylvanian, USA; Neognathodus assemblages; figs 2-5, 9a, c, refigured assemblage 12 of Burnley (1938), incomplete, disrupted, no primary architecture; figs 6-8, refigured assemblage 4 of Jones (1938), faecal, very little primary architecture; fig. 1, refigured specimen UI X-1505 (Rhodes 1952, pi. 129, fig. 13), faecal, contains elements from a Gondolella and a Neognathodus apparatus, no primary architecture. Nicoll 1977. Upper Devonian, Gogo Formation, Western Australia; articulated apparatus of Hibbardella angulata (prioniodinid). Ramovs 1977. Middle Triassic, central Slovenia; four incomplete fused clusters of Pseudo furnishius (prioniodinid), one preserving primary architectural information (several refigured by Ramovs 1978). Muller 1978. Fig. 12, reillustrated IMGP Go 600-12 (Schmidt and Muller 1964, fig. 1). Ramovs 1978. Middle Triassic, central Slovenia ; 92 incomplete fused clusters of Pseudo furnishius (prioniodinid), several preserving primary architectural information (some refigured from Ramovs 1977). Rieber 1980. Middle Triassic, Grenzbitumenzone, Ticino, Switzerland; bedding plane assemblage preserving a complete articulated apparatus of Neogondolella (prioniodinid). Habetih and Knobloch 1981. Figure 72, Hemilistrona, Zikmundova specimen, some post-mortem dis- articulation, but reflects oblique collapse from above, left, and behind, x = 46°, y = 28°, z = 30° (higher and more posterior than Text-figs 15-16); refigured by Dzik 1991. Higgins 1981. Westphalian, Staffordshire, UK; Idiognathoides, ten disarticulated, probably faecal assemblages, variable completeness, no primary architecture in figured specimen. Metcalfe 1981. Upper Visean, North Yorkshire, UK; three partial fused clusters of Gnathodus S elements preserving some evidence of element juxtaposition. Mietto 1982. Triassic, Trento, north-eastern Italy; partial fused cluster (Pa pair), Budurovignathus (prioniodinid). Puchkov et al. 1982. Upper Devonian, northern Urals, Russia; two bedding plane assemblages each preserving an incomplete, disarticulated apparatus of Palmatolepis. Briggs et al. 1983. Lower Carboniferous, Granton Shrimp bed, Edinburgh, UK; figs 1b, 2a-c, 3a-b, IGSE 13821 and 13822, apparatus of Clydagnathus windsorensis in head of conodont animal, preservation of apparatus (particularly position of Sb, probably Sb2 elements, between Sc elements of sinistral and dextral sides, and position of M element) indicates oblique lateral collapse at c. 45° from axial plane of apparatus, x = 3°, y = 43°, z = 47° (cf. Purnell and Donoghue 1997, figs 8-9). Apparatus refigured by Higgins 1983, p. 107; Briggs 1984, p. 17; Aldridge and Briggs 1986, fig. 8b; Aldridge 1987, fig. 1.9b; Aldridge et al. 1987, fig. 4.2b; Clark 1987, fig. 20.5b, C; Sweet 1988, fig. 3.1b-c; Weddige 1989, fig. 9; Briggs and Crowther 1990, p. 415; Conway Morris 1989, fig. 4; Lane 1992, 10.18; Aldridge et al. 1993, fig. 2. fig. 6, IGSE 13823, fused cluster of Clydagnathus windsorensis, missing P elements, lateral collapse, x = 2°, y = 2°, z = 87° (cf. PI. 2, Text-fig. 11; refigured by Aldridge 1987, fig. 1.4). Higgins 1983. P. 107, refigured IGSE 13822 (Briggs et al. 1983, figs 2b, 3b). Briggs 1984. P. 17, refigured IGSE 13822 (Briggs et al. 1983, figs 2b, 3b). Lane and Ziegler 1984. Figured IMGP Go 600-44, fig. 7 of Schmidt and Muller (1964). Conway Morris 1985. Mississippian, Bear Gulch Limestone Member, Montana, USA; pi. 1, fig. 4, UM 6027, Kladognathus (prioniodinid) in Typhloesus, no primary architecture (refigured by Conway Morris 1989, fig. 1.5, Conway Morris 1990, fig. 11); pi. 1, fig. 7, refigured UM 6028 (Scott 1973, pi. 3, fig. 2); pi. 1, fig. 9, UM 6029, Gnathodus bilineatus in Typhloesus, no primary architecture (refigured by Conway Morris 1990, figs 28-29); pi. 2, fig. 2, UM 6030, assemblage of two apparatuses of Adetognathus in Typhloesus, one retains some primary architecture (oblique posterior collapse with some post-mortem disarticulation; refigured by Conway Morris 100 PALAEONTOLOGY, VOLUME 41 1990, fig. 18); pi. 2, fig. 7, UM 6100, bituminous mass of broken conodonts (refigured by Conway Morris 1990, fig. 47). Norby and Rexroad 1985. Fig. 4, pi. 1, figs 1-2, refigured ISGS 62P-701A, Vogelgnathus campbelli, (Norby 1976 pi. 19, fig. 1). Nicoll 1985. Upper Devonian, Western Australia; collection of > 200 fused clusters of Polygnathus xylus and Ozarkodina brevis. Figs 3c-f, CPC25167-CPC25170, partial clusters of two or three S and M elements; figs 4a-i, 9b, CPC25171-CPC25179, CPC25202, are partial clusters of two or three P elements; Fig. 3a, CPC25165, S and M array, lateral collapse from side and very slightly above, x = 15°, y = 21°, z = 64° (cf. PI. 2, Text-fig. 1 1 ; P and Sbx elements not in contact with other elements and therefore not preserved as part of cluster); fig. 3b, CPC25166, oblique lateral collapse from side and above, x = 3°, y = 23°, z = 67° (cf. PI. 2, Text-fig. 1 1 ; slightly higher collapse angle); fig. 4J, CPC25180, ?complete apparatus, oblique axial collapse from slightly above, x = 66°, y = 24°, z = 1°; fig. 5a, CPC25181, partial apparatus, S and M elements only, disrupted lateral collapse (dextral M on sinistral side); fig. 5b, CPC25182, partial apparatus, S and M elements only, disrupted lateral; figs 8a, 9c, CPC25199, disrupted ?axial collapse, x = 84°, y = 4°, z = 5°; figs. 8b, 9d, CPC25200, partial apparatus, oblique lateral collapse from posterior, x = 69°, y = 12°, z= 17°; fig. 9a, CPC25201, partial apparatus, no primary architecture. Much of this collection is lost. Rhodes and Austin 1985. Carboniferous, UK; figured and described 41 bedding plane assemblages, but all are partial, disrupted, faecal or the remains of more than one individual ; none preserves significant architectural information. Collection deposited with British Geological Survey has been re-examined, but much material is missing. Sweet 1985. Fig. 1, refigured UI X-1480 (Du Bois 1943, pi. 25, fig. 14) Swift and Aldridge 1985. PI. 7.1, fig. 12, partial cluster (fused Pa pair), Mesogondolella. Aldridge and Briggs 1986. Fig. 5, UN 5545/015 new specimen of Idiognathodus from Pennsylvanian, Illinois, USA, oblique lateral collapse from side, above and behind, x = 36°, y = 8°, z = 53° (cf. Text-figs 15-16; refigured by Aldridge et al. 1987, fig. 4.3; Smith 1987, fig. 8.1-8.2; Black 1988, fig. 170; Aldridge et al. 1994, fig. 2); fig. 6, IU-IGS 15169 (specimen missing), cluster of Ozarkodina from Silurian of Indiana, USA, x = 71°, y = 4°, z = 19°; fig. 8b, refigured IGSE 13822 (Briggs et al. 1983, figs 2b, 3b). Aldridge et al. 1986. Lower Carboniferous, Granton Shrimp bed, Edinburgh, UK; figured apparatuses in head of conodont animals: figs 1a, 3, RMS GY 1986.17.1, gen. indet., probable oblique lateral collapse; figs 6, 8, BM X1065, Clydagnathus windsorensis, probable oblique lateral collapse. Barskov and Alekseev 1986. p. 68, reillustrated CGM 1/10499 (Mashkova 1972, fig. 2, pi. 1). Zhang and Zhang 1986. Upper Permian, central Fujian Province, China ; partial cluster of ‘ neohindeodelliform ’ S elements. Aldridge 1987. Fig. 1.2, refigured UI X-6377 (Du Bois 1943, pi. 25, fig. 21); fig. 1.4, IGSE 13823 (Briggs et al. 1983, fig. 6); fig. 1.6, X-1480 (Du Bois 1943, pi. 25, fig. 14); fig. 1.9b, IGSE 13822 (Briggs et al. 1983, figs 2b, 3b). Aldridge et al. 1987. Figs 4.5, 4.10, ISGS 57P-170 II (from Avcin 1974, thesis collection), oblique collapse from above and behind, x = 47°, y = 30°, z = 28°(a little more posterior than Text-figs 15-16). Refigured: fig. 4.2a, UI X-6377 (Du Bois 1943, pi. 25, fig. 21); fig. 4.2b, IGSE 13822 (Briggs et al. 1983, figs 2b, 3b); fig. 4.3, UN 5545/015 (although numbered UN 5830/016 in caption) (Aldridge and Briggs 1986, fig. 5); fig. 4.4, ISGS 57P- 38 (Avcin 1974, pi. 2, fig. 19); fig. 4.6a, (Schmidt 1934, fig. 5a-b and pi. 6, fig. 1); fig. 4.6b, 4.12a, UI X-1480 (Du Bois 1943, pi. 25, fig. 14); fig. 4.8a, ISGS 57P-72(A) (Avcin 1974, pi. 2, fig. 1); fig. 4.9a, ISGS 57P-180, (Avcin 1974, pi. 1, fig. 4). Clark 1987. Fig. 20.a, reillustrated Lochriea assemblage (Scott 1942, pi. 37, fig. 4); fig. 20.2b, reillustrated UI X-1480 (Du Bois 1943, pi. 25, fig. 14); fig. 20.5, reillustrated IGSE 13821 and 13822 (Briggs et al. 1983, figs 1b, 2a-c, 3a-b). Nicoll 1987. Figured partial clusters (fused Pa pairs) of Ozarkodina brevis, O. eosteinhornensis, Icriodus expansus. Polygnathus xylus. Nicoll and Rexroad 1987. Silurian, northern Indiana, USA; collection of > 700 fused clusters of Ozarkodina, 14 clusters figured; pi. 3.1, figs 7-9, IU-IGS 16827-16829, clusters of Pa element pairs only; pi. 3.1, fig. 10, IU- IGS 16830, partial cluster, three S elements; pi. 3.2, fig. 1, IU-IGS 16831, almost complete apparatus, oblique axial collapse from above and slightly to the right, x = IT, y = 12°, z = 5°; pi. 3.2, figs 2, 5, IU-IGS 16832, almost complete apparatus, collapse from below and slightly anterior; pi. 3.2, figs 3-4, IU-IGS 16833, almost complete apparatus, oblique-lateral collapse from the posterior and slightly below, x = 68°, y = 10°, z = 20°; pi. 3.2, figs 6-7, IU-IGS 16834, partial apparatus, S and M elements only, oblique-lateral collapse from the posterior and slightly below, x = 52°, y = 4°, z = 38°; pi. 3.3, figs 1-2, IU-IGS 16835, almost complete apparatus, oblique dorso-ventral collapse from above, front and slightly right, x = 56°, y = 30°, z = 16°; pi. PURNELL AND DONOGHUE: OZARKODINID CONODONTS 101 3.3, figs 3-4, IU-IGS 16836, ?complete apparatus, oblique dorso-ventral collapse from front and below, x = 75°, y = 15°, z = 3°; pi. 3.4, figs 1, 3, 5, IU-IGS 16837, partial apparatus, lateral collapse (cf. Purnell and Donoghue 1997, figs 4-5); pi. 3.4, figs 2, 4, IU-IGS 16838, partial apparatus, S and M elements only, oblique- lateral collapse from anterior and slightly below, x = 38°, y = 9°, z = 51°; pi. 3.5, figs 1, 3, IU-IGS 16829, complete apparatus, oblique axial collapse, from below, slightly to right, x = 68°, y = 18°, z = 12°; pi. 3.5, fig. 2, IU-IGS 16840, partial apparatus, no primary architecture. Norby and Avcin 1987. PI. 9.1, figs 1^1, 7, refigured ISGS 62P-603, 62P-605, 62P604, 62P715, 62P16A (Norby 1976, pi. 10, figs 1-5); pi. 9.1, fig. 5, ISGS 62P-313, Lochriea commutatal, disrupted, ?oblique collapse from behind, below and to one side; pi. 9.1 fig. 6, ISGS 57P-500, Idiognathodusl , ?oblique collapse from behind and to one side. Smith 1987. Fig. 8. 1-8.2, refigured UN 5545/015 (Aldridge and Briggs 1986, fig. 5). Black 1988. Fig. 170, refigured UN 5545/015 (Aldridge and Briggs 1986, fig. 5). Sweet 1988. P. 2, refigured UI X-1480 (Du Bois 1943, pi. 25, fig. 14, reversed); ISGS 62P-2a (Norby 1976, pi. 8, fig. 2); fig. 3.1b-c reillustrated IGSE 13821 and 13822 (Briggs et al. 1983, figs 1b, 2a-c, 3a-b). Weddige 1989. Refigured: fig. 5, UI X-1480 (Du Bois 1943, pi. 25, fig. 14), CGM 1/10499 (Mashkova 1972, fig. 2, pi. 1); fig. 6, UI X-6377 (Du Bois 1943, pi. 25, fig. 21); fig. 7, Palmatolepis cluster (Lange 1968, pi. 1); fig. 9, IGSE 13821 and 13822 (Briggs et al. 1983, figs 1b, 2a-c, 3a-b). Aldridge 1990. Fig. 1, refigured UI X-6377 (Du Bois 1943, pi. 25, fig. 21). Briggs and Crowther 1990. p. 415, refigured IGSE 13822 (Briggs et al. 1983, figs 2b, 3b). Conway Morris 1989. Fig. 1.5 refigured UM 6027 (Conway Morris, 1985, pi. 1, fig. 4), fig. 1.6 refigured UM 6028 (Scott 1973, pi. 3, fig. 2), fig. 4, refigured IGSE 13822 (Briggs et al. 1983, figs 2b, 3b). Conway Morris 1990. Mississippian, Bear Gulch Limestone Member, Montana, USA; fig. 11, refigured UM 6027 (Conway Morris 1985, pi. 1, fig. 4); figs 16, 18, refigured UM 6030 (Conway Morris 1985, pi. 2, fig. 2); figs 25-26, refigured UM 6028 (Scott 1973, pi. 3, fig. 2); figs 28-29, refigured UM 6029 (Conway Morris 1985, pi. 1, fig. 9); fig. 47, refigured UM 6100 (Conway Morris 1985, pi. 2, fig. 7); fig. 64, CM 35527, disarticulated elements in Typhloesus\ fig. 68, CM 6031, scattered Kladognathus (prioniodinid) elements in Typhloesus\ fig. 71, UM 5878, Cavusgnathus apparatus in coprolite, some post-mortem disruption, but may reflect oblique collapse from above and behind, parallel to long axes of S elements. von Bitter and Merrill 1990. Fig. 1a, refigured UI X-1480 (Du Bois 1943, pi. 25, fig. 14); fig. 1b, ISGS 62P-401a (Norby 1976, pi. 4, fig. 2); fig. lc-D, USNM 183567-183568 (Scott 1973, pi. 1, figs 1-2, pi. 2, figs 1-2). Dzik 1991. Fig. 1, refigured Hemilistrona, Zikmundova specimen (Habetin and Knobloch 1981, fig. 72; fig. 3a, reillustrated CGM 1/10499 (Mashkova 1972, fig. 2, pi. 1). Ritter and Baesemann 1991. Lower Permian, Wolfcamp Shale, Texas, USA; collection of nine bedding plane assemblages; four, identified as Sweetognathus, illustrated. None preserves significant primary architecture. Dzik 1992. Fig. 9.16, refigured CGM 1/10499 (Mashkova 1972, fig. 2, pi. 1). Lane 1992. Fig. 10.18, refigured IGSE 13822 (Briggs et al. 1983, figs 2b, 3b). Aldridge et al. 1993. Lower Carboniferous, Granton Shrimp bed, Edinburgh, UK; figured apparatuses of Clydagnathus windsorensis in head of conodont animals: fig. 2, refigured IGSE 13822 (Briggs et al. 1983, figs 2b, 3b); figs 4, 6, RMS GY 1992.41.1, incomplete, oblique lateral collapse from side and below, x = 25°, y = 10°, z = 63° (cf. PI. 1, Text-fig. 6, but not as far forward; refigured by Aldridge et al. 1994, fig. 4; Long 1995, p. 35); fig. 9, RMS GY 1992.41.2, incomplete, x = 29°, y = 3°, z = 61° (Pa, Pb, and dextral Sb15 Sc, Sc), lateral collapse from side and slightly behind (cf. Text-figs 4-5). Purnell 1993a. Fig. 2, BU 2183, bedding plane assemblage of Idiognathodus from Pennsylvanian, McLeansboro Group, Bailey Falls, Illinois, USA; oblique lateral collapse from side, behind and above (cf. Text-figs 15-16, but slightly more posterior collapse; refigured by Purnell 1994, fig. 2a). Purnell 1993b. Mississippian, Bear Gulch Limestone Member, Montana, USA; figs 2-3, ROM 48915, articulated apparatus of Kladognathus (prioniodinid) in guts of Typhloesus (specimen also contains small apparatus of Lochriea)-, fig. 4, reillustrated UM 6028 (Scott 1973, pi. 3, fig. 2). Varker 1994. Namurian, North Yorkshire, UK; collection of >60 fused clusters, figured 11 incomplete apparatus clusters of Gnathodus bilineatus and Lochriea. PI. 1, fig. 1, MPK 9774, S elements only, ?faecal, preserves some element juxtaposition ; pi. 1, fig. 2, MPK 9775, very incomplete , no primary architecture; pi. 1, fig. 3, MPK 9776, S elements, probably faecal, little or no primary architecture; pi. 1, fig. 4, MPK 9777, S array and Pb element, oblique collapse from behind left, x = 56°, y = 21°, z = 25° (orientation between Text- figs 2-3 and Text-figs 15-16; pi. 1, fig. 5, MPK 9778, S and M elements, no primary architecture; pi. 1, fig. 6, MPK 9779, S and M elements, possibly preserving some primary element juxtaposition; pi. 1, fig. 7, MPK 9780, S and M elements and Pa element, axial collapse from behind, x = 74°, y = 16°, z = 3° (cf. Purnell and Donoghue 1997, figs 6-7, but lower and more posterior); pi. 2, fig. 1, MPK 9781, S elements and Pb, probably 102 PALAEONTOLOGY, VOLUME 41 faecal, possibly preserving some primary S element juxtaposition ; pi. 2, fig. 2, MPK 9782, Pa and S fragments, faecal, no primary architecture; pi. 2, fig. 3, MPK 9783, Pa and Sbx, no primary architecture ; pi. 2, fig. 6, MPK 9786, S elements and Pa, probably faecal, possibly preserving some primary S element juxtaposition. Aldridge et al. 1994. Fig. 2, refigured UN 5545/015 (Aldridge and Briggs 1986, fig. 5), RMS GY 1992.41.1 (Aldridge et al. 1993, figs 4, 6). Purnell 1994. Fig. 2a, refigured BU 2183 (Purnell 1993a, fig. 2); fig. 2b, Gnathodus bilineatus (from Norby 1976, thesis collection), some post-mortem disruption, oblique lateral collapse from side, above and behind (cf. Text- figs 15-16). Stone and Geraghty 1994. Pennsylvanian, Carbondale Formation, Illinois, USA; figs 1-2 (ISGS 100P-19B) partial apparatus of Idioprioniodus (prioniodinid), disarticulated, no primary architecture. Long 1995. p. 35, refigured RMS GY 1992.41.1 (Aldridge et al. 1993, figs 4, 6). Merrill and von Bitter 1995. Described new assemblage of Neognathodus, almost complete apparatus, one individual, elements parallel ; possibly reflects axial collapse, but disruption of P elements, orientation of M element, and juxtaposition of S elements indicates that faecal origin likely, with little primary architecture preserved (cf. Merrill and von Bitter 1995; photographs kindly provided by G. K. Merrill and P. H. von Bitter). Nicoll 1995. Text-fig. 5, four incomplete fused clusters, P elements only. Purnell et al. 1995. Figs 5-6, refigured IU X-6377 (Du Bois 1943, pi. 25, fig. 21), and IU X-1480 (Du Bois 1943, pi. 25, fig. 14). Weddige and Hiisken 1995. Lower Devonian, Germany; collection of > 250 bedding plane assemblages, c. 30 thought by authors to preserve primary architecture, none figured, but collapse patterns probably consistent with our model (pers. obs. ; cf. Weddige and Hiisken). Orchard 1996 : Upper Devonian, British Columbia, Canada; fig. 7.4, partial cluster (fused Pa pair) of Palmatolepis, partial cluster (fused Pb pair) of ? Polygnathus, partial cluster of indeterminate S elements. Purnell and Donoghue 1997. Pennsylvanian, McLeansboro Group, Bailey Falls, Illinois, USA; Natural assemblages of Idiognathodus: figs 2, 3a, reillustrated UI X-1480 (Du Bois 1943, pi. 25, fig. 14); figs 4, 5a, PM X 2217, lateral collapse from side and slightly below (x = 0°, y = 8°, z = 82°); figs 6, 7a, PM X 2218, collapse from behind, left and slightly below (x = 67°, y = 14°, z = 18°); figs 8, 9a, PM X 2219, collapse from above, right, and slightly behind (x = 12°, y = 43°, z = 44°). MID DEVONIAN PHYLLOCARID CRUSTACEA FROM BOLIVIA by PATRICK R. R ACHEBOEUF Abstract. The Givetian Dipleura dekayi Zone of the Bolivian Altiplano, and adjacent stratigraphical levels, yield representatives of the phyllocarid genera Echinocaris and Dithyrocaris. The peculiar morphology and well-preserved original features of the exoskeleton allow erection of a new species, Echinocaris spiniger sp. nov. Discovery of a carapace with abdominal somites still connected allows identification of the corresponding tail piece and description of the complete exoskeleton of Dithyrocaris oculeus sp. nov., probably one of the earliest representatives of the genus. Palaeobiological and taphonomic data regarding these species are discussed. Two other forms, represented by only few specimens from other isolated localities, are provisionally left in open nomenclature: Echinocaris sp. and Dithyrocaris sp. Numerous papers have been devoted to the description of phyllocarid taxa or to more general topics such as their evolution and palaeobiogeography. Despite this abundant literature, phyllocarid crustaceans remain poorly known and are probably much more diverse than previously established. Besides the general rarity of these fossils, our relatively poor knowledge is due partly to the fact that most taxa have been described only from isolated parts of the exoskeleton, mainly the tail piece, and little is know about their ontogeny. Species described from complete exoskeletons are few, and little data on intraspecific variability are available. As a consequence, the taxonomic value of many morphological characters is still uncertain. For such reasons any description of complete exoskeletons or of numerous isolated elements may prove to be significant for diversity, taxonomic, palaeoecological, evolutionary and palaeobiogeographical studies. This is the case for the Mid Devonian Bolivian phyllocarids described here. Occurrence. Fossiliferous siliciclastic concretions occur at several lithostratigraphical levels within the Devonian sequence of Bolivia; these concretions are well known throughout the world for their well-preserved fossils. Many examples of trilobites, brachiopods, bivalves, conulariids and vertebrate remains are described in the literature. This is also true for rarer fossils, such as phyllocarids, which have only recently been described by Hannibal et al. (1994). These authors described and illustrated Echinocaris cf. punctata (Hall, 1863), Dithyrocaris cf. insignis Jones and Woodward, 1898, undetermined rhinocaridid abdomens and telsons, as well as mandibles. Due to their poor preservation or fragmentary condition, specimens were left in open nomenclature. Most of these materials were collected many years ago by L. Branisa and are now housed in various institutions: the United States National Museum (USNM), the American Museum of Natural History (AMNH), the Hunterian Museum of the University of Glasgow (GLAHM), and the Museum of Comparative Zoology, Harvard University. In 1993 three concretions yielding phyllocarid remains were collected in situ in the Belen section, 25 m above the top of the Cruz Loma Sandstone, i.e. in the lower part of the Sica Sica Formation. These beds belong to the Dipleura dekayi Zone (Text-fig. 1b). The first concretion yielded a well- preserved right valve of Dithyrocaris, with three abdominal somites still connected. The second yielded the ventral external mould of an almost complete tail piece of the same genus. The third concretion yielded both articulated valves, although incomplete, of a specimen of Echinocaris. Lengthy preparation using hydrochloric acid, needles, and an engraver-pen revealed that the right valve of Dithyrocaris exhibits several details that do not fit with the description of specimens [Palaeontology, Vol. 41, Part 1, 1998, pp. 103-124, 3 pls| © The Palaeontological Association 104 PALAEONTOLOGY, VOLUME 41 text-fig. 1 . a, location map of the Belen section in the Bolivian Altiplano. b, corresponding lithostratigraphical column, with location of concretion levels and Dipleura dekayi Zone. previously studied by Hannibal et al. (1994). Hence it was necessary to compare the newly discovered specimen with those which had been previously collected and described, after the latter had been prepared using the same method. It was clear that features and morphological details observed on the newly found carapace of Dithyrocaris were likewise evident on each of the other previously collected carapaces. All the material belongs to the same species and allows a complete description of the exoskeleton of Dithyrocaris oculeus sp. nov., including the abdomen and tail piece; but no appendages, except for the mandible are known. In the same way, after preparation, the material of Echinocaris allows the description of a new species, Echinocaris spiniger sp. nov., co- occurring with Dithyrocaris oculeus in at least one level. Among the undetermined specimens illustrated by Hannibal et al. (1994, fig. 4.6) is a large tail piece of a rhinocaridid, probably of the genus Dithyrocaris, from the locality Achumani Alto (south of La Paz), the stratigraphical position of which remains uncertain. As indicated by the authors, this specimen (GLAHM A2793) is from a larger individual than those from the Dipleura dekayi Zone. It is re-illustrated for comparison, and described herein as Dithyrocaris sp. Another less complete specimen, similar in size and every aspect of its morphology (GLAHM 101283), comes from the locality Aiquile (Department Cochabamba), also of uncertain stratigraphical position. Both specimens undoubtedly belong to a rhinocaridid species distinct from Dithyrocaris from the Dipleura dekayi Zone and they are possibly from a different stratigraphical level. To ensure accuracy, only specimens which definitely or presumably come from the uppermost Belen Formation, and from the lower part of the Sica Sica Formation (Cruz Loma Sandstone and overlying siltstones, Givetian Dipleura dekayi Zone), are described herein. Measurements and terminology follow those used by Rolfe (1962, 1969, 1981) and by Hannibal et al. (1994). New specimens are deposited in the YPFB collection, under numbers ‘YPFB Pal’, RACHEBOEUF: DEVONIAN PH YLLOCARID CRUSTACEA 105 Centro de Tecnologi'a Petrolera, Santa Cruz de la Sierra, Bolivia. Other studied specimens are housed in the American Museum of Natural History (AMNH) and in the Hunterian Museum of the University of Glasgow (GLAHM = HMGU in Hannibal et al. 1994). Stratigraphical background. Almost all known Devonian Bolivian phyllocarid occurrences are from the Belen and Sica Sica formations of the Altiplano region, assigned to the Emsian, although the upper part of the Sica Sica Formation may be Eifelian (Isaacson 1977). Such a stratigraphical assignment led Rolfe and Edwards (1979) to consider that representatives of the genus Dithyrocaris from the Sica Sica Formation had ‘an earlier’, unsuspected biostratigraphical occurrence...’ than previously known. More recently Isaacson and Sablock (1988) assigned an Eifelian age to the uppermost Belen Formation, whilst the whole of the Sica Sica Formation was considered to be Eifelian. Hannibal et al. (1994, pp. 62-63) concluded that Bolivian representatives of the genera Echinocaris and Dithyrocaris are among the earliest in the world. The age of the Devonian sequence of Bolivia has been discussed recently, and a new vertical range proposed (Racheboeuf et al. 1993, 1994; Blieck et al. 1996). As a consequence of new palynological data and proposed lithostratigraphical correlations, an Eifelian age was assigned to the upper member of the Belen Formation and a Givetian age to the Sica Sica Formation, the Eifelian- Givetian boundary being placed provisionally just below or within the Cruz Loma Sandstone. Such results are in better agreement with the Givetian age of the Dipleura fauna in North America, and imply that representatives of both Echinocaris and Dithyrocaris are of about the same age as those in North America. Most available Devonian phyllocarid specimens from Bolivia come from Branisa’s zones of the Belen section of the Altiplano, about 120 km south of La Paz (Text-fig 1a): Belen 7-0, 7-7, 8-1, 8-3, Cl 5. These zones are not easy to place precisely within the stratigraphical column, but according to Branisa (1965) and his personal communications to various authors, some of them can be clearly defined (see Babcock et al. 1987). The stratigraphical position of locality 7-0 remains uncertain and belongs to either the Belen or the Sica Sica Formation. 7-7 belongs to beds with Taonurus candegalli of the Metacryphaeus venustus Zone, lower part of the Cruz Loma Sandstone, lowermost beds of the Sica Sica Formation. Locality 8-3 corresponds to the Cierro Cieloloma section of the Belen section, and belongs to the Givetian Dipleura dekayi Zone of the Sica Sica Formation, above the Cruz Loma Sandstone. Locality 8-1 of the Belen section could not be precisely located; the only available information from Branisa is ‘Middle Devonian’. Among a collection of 37 concretions from these localities, the distribution of phyllocarid remains (mandibles excluded) is as follows: concretions with Echinocaris from localities 7-0 and 8-1 respectively yielded one and five specimens; those with Dithyrocaris from localities 7-7, 8-1, and Cl 5, respectively yielded one, 15, 14 and one specimen. Although there is no stratigraphical order inferred from the increasing locality numbers, it appears clearly that the distribution of phyllocarid remains is not random: (1) phyllocarids are more abundant at localities 8-1 and 8-3; (2) representatives of Dithyrocaris are commoner than representatives of Echinocaris ', (3) each genus is represented by a single species; (4) the distribution of phyllocarid remains per locality is strongly suggestive of a longer vertical range for Dithyrocaris oculeus than for Echinocaris spiniger. SYSTEMATIC PALAEONTOLOGY Suborder ceratiocarina Clarke, in Zittel, 1900 Family echinocarididae Clarke, in Zittel, 1900 Genus echinocaris Whitfield, 1880 Type species. Echinocaris sublevis Whitfield, 1880, by original designation, from the Upper Devonian of Ohio. 106 PALAEONTOLOGY, VOLUME 41 Echinocaris spiniger sp. nov. Plate 1, figures 1-10; Text-figure 2 1994 Echinocaris cf. E. punctata (Hall, 1863); Hannibal et al. p. 60, figs 2. 1-2.6. Holotype. Tail piece and abdominal somites GLAHM A2790. Derivation of name. From the Latin ‘ spina ’ (spine) and ‘gero' (to bear): an allusion to the strong lateral spinules on the telson. Locality and horizon. In the Belen section, just above the Cruz Loma Quartzite, in the Dipleura dekayi Zone (Branisa’s zone 8-3), lowermost Sica Sica Formation, the same locality and level as most of the material studied by Hannibal et al. (1994). Material. The anterior part of the two valves of an articulated carapace (YPFB Pal 9290) ; both moulds of an almost complete tail piece with the two last abdominal somites displaced (GLAHM A2790); both moulds of an almost complete, articulated exoskeleton (AMNH 43516A-B), and an incomplete, crushed carapace (AMNH 43515A-B). Diagnosis. Echinocaridid without tubercles on the dorsal and posterodorsal lobes of the carapace. Telson with stout, spaced latero-dorsally inserted spinules, and two shallow longitudinal ventral furrows. Furcal rami with dorsal, ventral and inner furrows, the latter with a row of minute pits for insertion of setae. Description Carapace. The carapace of the almost complete exoskeleton (AMNH 43516) is poorly preserved, except for its anterior region (PI. 1, fig 5), and is about 35 mm long for an overall length of the exoskeleton about 85 mm. The only new available specimen (YPFB Pal 9290) exhibits about two-thirds of the left valve, and the corresponding dorsal region of the right valve, still articulated. The maximum preserved length is 40 mm and its estimated total length is about 50 mm. The external mould exhibits the anterior margin of the carapace which is very slightly convex forward, almost straight, truncated, and roughly perpendicular to the dorsal line. A narrow border is well developed. Antero-dorsally the border is a rounded rim which tapers progressively antero-ventrally, becoming narrower, and more flattened. The border is markedly geniculated inwards, at 90° from the plane of the valve, developing a flattened proximal wall, and bounded by a thin, narrow, ridge. The distal shelf could not be observed. The wall is very finely ornamented by very thin, almost imperceptible, longitudinal ridges. The surface of the valves is similar to that described by Hannibal et al. (1994), in the distribution and morphology of the lobes, as well as in their ornamentation, which is better developed in the posterior half of the valves, and composed of very small, low tubercles. However, the anterior slope of the anterodorsal lobe exhibits shallow, rounded, variably anastomosing canals which end in the furrow delineating the rounded border. The anterior half of the carapace is almost smooth and lobes are devoid of tubercles (Text- EXPLANATION OF PLATE 1 Figs 1-10. Echinocaris spiniger sp. nov.; Givetian Dipleura dekayi Zone, Lower Sica Sica Formation, Belen section, Bolivian Altiplano. 1-4, YPFB Pal 9290; latex replica; incomplete articulated carapace. 1, general view; x 1-5. 2, enlarged view of the postero-dorsal node; x 10. 3-4, enlarged view of the anterior margin of the left valve, respectively exterior and interior; x4. 5-7, AMNH 43516; latex replica; almost complete, articulated exoskeleton. 5, general view of the dorsal side; x 1-5. 6, dorsal side of the 5th to 7th abdominal somites and telson head; x 3. 7, ventral side of 4th to 6th abdominal somites; note the ventral platform with two posterior spines and limb insertions on the 4th somite; x 3. 8-10, GLAHM A2790; latex replica; well preserved tail piece, respectively in dorsal, dorso-lateral, and ventral views (with the 7th abdominal somite superimposed); note the large and spaced spinule bases on the telson, the shallow dorsal and ventral longitudinal furrows, and the articulatory dorsal and ventral condyles on the furcal rami; x2. Fig. 11. Echinocaris, sp. from Branisa’s zone 7-0, Belen section, GLAHM 101282; latex replica; abdominal somites 4 and 5 in ventral view; note the three spines on the ventral tubercle of the 4th somites; x 3. PLATE 1 RACHEBOEUF, Echinocaris 108 PALAEONTOLOGY, VOLUME 41 fig. 2d; PI. 1, figs 1, 5). The carapace is covered posteriorly by minute and dense granulations. Along the dorsal side of the left valve a small, rounded well-differentiated tubercle is developed. The ventral region of the carapace, as well as its posterior part, were not observed. The corresponding internal mould of the left valve of specimen YPFB Pal 9290 is smooth, without any kind of ornament. The ridges, corresponding to the furrows separating the lobes on the external surface, are better developed. The most interesting feature is the development of two blade-like vertical expansions (PI. 1 , fig 4) text-fig. 2. Echinocaris spiniger sp. nov. ; Givetian Dipleura dekayi Zone, Lower Sica Sica Formation, Belen section, Bolivian Altiplano. a-c, reconstruction of the tail piece. Camera lucida drawings from specimen GLAHM A 2790. Broken lines refer to non-observed, hypothetical outlines, a, reconstruction of the tail piece in dorsal view; a, cross section of the left furcal ramus, b, anterior region of the tail piece in lateral view, c, anterior region of the tail piece in ventral view, d, tentative reconstruction of the outline of the left valve of the carapace. Camera lucida drawings from specimens YPFB Pal 9290, AMNH 43515, and AMNH 43516. Dotted line indicates the outline of the observed parts of the carapace. Broken line corresponds to a hypothetical outline of the carapace. Note the lack of tubercles on the lobes, the lack of granulation in the anterior region of the carapace, and the postero-dorsal node. Scale bars represent 10 mm. RACHEBOEUF: DEVONIAN PHYLLOCARID CRUSTACEA 109 in the antero-dorsal angle of the valves, close to the dorsal line and expanded from the rounded ridge corresponding to the external furrow separating the border from the valve surface. These lamellar processes are here interpreted as apodemes, insertion areas for muscles of the carapace. Abdominal somites. The two moulds of the almost complete exoskeleton, AMNH 43516, were prepared carefully so that the ventral and dorsal sides of abdominal somites could be examined. The posterior edge of each somite is characterized by two strong postero-ventral lateral spines, and two main dorsal spines (PI. 1, fig. 6). The latter are 2-6-2-9 mm apart and two smaller spines are inserted between them on each side of the plane of symmetry. On their ventral side, somites 6 and 7 exhibit a well differentiated, transversely elongated, convex anterior tubercle. Abdominal somites are finely ornamented dorsally with numerous small granulations, and they are almost smooth ventrally. The 4th abdominal somite is 3-6 mm long and 9-36 mm wide. Its ventral side exhibits a relatively small, prominent ventral tubercle with two postero-lateral spines and no antero-medial spine. Limb insertions are markedly oval, and obliquely displayed. Their maximum width is 3-27 mm, almost pependicular to the longitudinal axis, while their length is 2-02 mm. Somites 5, 6 and 7 are, respectively, 4-2 mm, 5-6 mm and 9-5 mm long. Somites 6 and 7 are, respectively, 6-24 mm and 4-48 mm wide. Telson and furcal rami. The head of the telson of specimen AMNH 43516 is 6-24 mm wide. The telson of specimen GLAHM A 2790 is 32 mm long. At its anterior margin, the head is 6 mm wide. It widens posteriorly up to 9 mm before it narrows to 2 mm, at the site of insertion of the furcal rami. Telson head convex, globose, with two lateral and two posterolateral shallow furrows. Dorsal side of the telson with two rows of small circular or elongated depressions. The anterior row is weakly arched, convex posteriorly, while the posterior row is strongly arched, posteriorly concave, horseshoe-shaped (Text-fig. 2A).Telson axis sub-cylindrical in cross section, with straight lateral margins and two shallow longitudinal ventral furrows, getting progressively narrower up to its spinose posterior extremity. Stout spinules are inserted latero-dorsally on each side of the telson. Spinules are widely spaced and they are not inserted in a longitudinal furrow. They number seven on the left side of the telson with intermediate spaces varying from 2-5 mm to 1-8 mm; spacing decreases backwards. Spines are not symmetrically inserted, but alternate either side of the telson, except for the last posterior two spinules which are almost opposed. Ventral platform not observed. The ventral side of the telson is weakly convex in cross section and smooth. The maximum preserved length of the furcal rami is 28 mm. Their head is sub-cylindrical to oval in cross section and 3 mm wide, with well differentiated dorsal and ventral articulatory condyles (Text-fig. 2b-c). Lateral margins of furcal rami are straight and narrow posteriorly. At 5 mm posterior from their anterior extremity they are 2 mm wide, and at 23 mm, 1 mm wide. Furcal rami are rod-like, sub-circular in cross section, with three shallow longitudinal furrows producing a clover-leaf-like cross section. The outer lateral margin is rounded and larger than the other two lobes defined by the longitudinal furrows. The inner furrow, which faces the telson, bears small pits which are spinule or setal insertions. They number 5 per mm and their diameter is about one-quarter the diameter of the pits observed on the telson. If we consider that the furcal rami are regular in shape and that their width regularly decreases up to their extremity, their total length could reach 50 mm, i.e. about one-and-one-half times the corresponding telson length. Remarks. The generic assignment of the carapace was established by Hannibal et al. (1994), and there is no doubt about the conspecificity of the newly described specimen which comes from the same level and locality, the Dipleura dekayi Zone of the Belen section. Hannibal et al. (1994) tentatively assigned his material to E. punctata (Hall, 1863), based on a strong overall resemblance in shape, ornamentation and relative proportions of carapace lobes and abdominal somites. However, the authors noted differences in the morphology of the dorsal and posterodorsal lobes of the carapace, as well as on the third last abdominal segment. The development of strong, latero- dorsal spines on the telson is undoubtedly one of the most original features of the Bolivian form. Such a peculiar features is very different from that illustrated by Hall (1863, pi. 1, fig. 2) in ‘ Ceratiocaris armatus’’ and has not been described in other representatives of Echinocaris. This character, added to the differences emphasized by Hannibal et al. (1994, p. 62), makes the Bolivian form a new species, distinct from E. punctata. 110 PALAEONTOLOGY, VOLUME 41 Echinocaris sp. Plate 1, figure 11 Material. The external mould of the ventral side of three incomplete abdominal somites (GLAHM 101282), locality 7-0 of Branisa, Belen section; unknown stratigraphical position. Comparison. This specimen is left in open nomenclature due to its fragmentary nature. Moreover, the ventral tubercle of the (?)4th abdominal somite exhibits three stout posteriorly directed spines, one antero-medial and two postero-lateral. This character distinguishes this form from Echinocaris spiniger which lacks the antero- medial spine on the ventral tubercle of 4th somite. However, the taxonomic significance of this character remains poorly known, and it could be related to dimorphism. Suborder rhinocarina Clarke, in Zittel, 1900 Family rhinocarididae Hall and Clarke, 1888 Genus dithyrocaris Scouler, in Portlock, 1843 Type species. Argas testudineus Scouler, 1835, from the Lower Carboniferous of Scotland. Dithyrocaris oculeus sp. nov. Plates 2-3 ; Text-figures 3-5 1994 Dithyrocaris cf. D. insignis Jones and Woodward, 1898; Hannibal et al., p. 63, figs 4.1, 4.3-4.4. Holotype. Both external and internal moulds of the left valve of a probably complete, articulated carapace, AMNH 44692. Locality and Horizon. Lower part of the Sica Sica Formation within the lowest 30 m above the Cruz Loma Sandstone, in the Belen section of the Bolivian Altiplano, c. 120 km south-east of La Paz; Givetian Dipleura dekayi Zone. Derivation of name. From the Latin oculeus, ‘which has eyes’; alluding to the presence of the ocular tubercle. Material. A total of 35 concretions has been studied; 12 of them yielded more or less complete isolated or articulated valves ; eight abdominal segments, alone or in connection with the carapace or with the tail piece ; 1 1 tail pieces, and nine mandibles, whilst five other concretions yielded valve fragments only. Diagnosis. Dithyrocaris with a single, very weakly curved, mesolateral carina and well-developed posteroventral spine. Ventral margin regularly rounded, with a wide, smooth, and flat border. Ocular tubercle well differentiated. Median dorsal plate almost smooth, with well differentiated posterodorsal node. Doublure shelf very narrow. Carapace ornamentation very discrete, mainly made of curved, obliquely, postero-ventrally oriented lines, without any granulation. Abdominal somites with very thin ornamentation of anastomosed, anterodorsally-posteroventrally directed oblique lines. Limb site on 5th somite. 6th somite with lateroventral carina and ventral explanation of plate 2 Figs 1-8. Dithyrocaris oculeus sp. nov.; Givetian Dipleura dekayi Zone, Lower Sica Sica Formation, Belen section, Bolivian Altiplano. 1, 3-5, YPFN Pal 8432; latex replica; right valve of a large specimen with abdominal somites 5-7 still connected. 1, general view; x 2. 3, enlarged view of the ‘ocular’ tubercle; x 10. 4, enlarged view of the anterior part of the mesolateral carina showing the ornament and the smooth nature of the carina; x 10. 5, enlarged lateral view of abdominal somites 6 and 7; x3. 2, AMNH 44693; latex replica; detail of the posterior margin of a left valve; x3. 6-8, AMNH 44692; latex replica; left valve. 6, detail of the postero-ventral doublure ; x 4. 7, external mould ; note the location of the postero-dorsal node; x2. 8, internal mould; x2. PLATE 2 RACHEBOEUF, Dithyrocaris 112 PALAEONTOLOGY, VOLUME 41 table 1. Dithyrocaris oculeus sp. nov. ; Givetian Dipleura dekayi Zone, Lower Sica Sica Formation, Belen section, Bolivian Altiplano. Outline of the left valve of the carapace showing the position and orientation of measurements (above), in millimetres. Asterisks in table refer to estimated measurements. YPFB 8432 AMNH 44692 AMNH 44693 AMNH 44694 GLAHM A2791 GLAHM 101261 GLAHM 101263 GLAHM 101272 GLAHM 101278 L 47* 37 38 43* 35 27* 35* 27-5 Hm 25 18-5 20-8 21 23* 16* 13 18 13* H(L : 2) 23-4 19-9 20-5 21* — — 131 — — Hmdp 2-3 1-8 2-1 1-6* 1-9 1-8 1-3 1-6 — He 10 9-5 8-8 9-3 9-6 — 5-2 7-0 — Hv 8-5 6-6 7-5 8-0 8-7 — 4-7 60 — Hb 2-8 2-0 2-1 21 — — 1-9 — 60 Lmdp 35 27 — — 33-5 — 21-3 29-3 — Lrp — 8-0 — — — — — 8-5 5 Wrp 2-2 1-7 — — — — — 1-7 — D 4? 3-0 — — — — 2-3 2-6 2-2 Lvs — 3-6 5-2 41 — 3-5 3-2 — — Hpm 9-2 8-0 8-2 90 91 7-0 5-8 7-5 — Lot 7* 6-5 7-5 — — — — — — Hot 5-4 3-8 4-0 — — — — 3-6 - ornamentation. 7th somite sub-cylindrical, smooth ventrally. Telson long and narrow with acute extremity, two dorso-lateral shallow longitudinal furrows, and two rows of small spinules. Furcal rami typical for the genus, one-and-one-half times longer than the telson. Description Carapace. The smallest observed carapace is 27 mm long and c. 1 3 mm (estimated) high, whilst the largest is c. 50 mm long, including posteroventral spine, for a corresponding height of c. 25 mm, measured from midline to ventral border, including the lateral side of the median dorsal plate. Approximate length/height ratio of 2-0, varying between 1 -8 and 2- 1 . Maximum height of the valve located at about three-fifths the valve length from the anterior border. Anterior margin regularly convex, bounded by a narrow rounded border, becoming sub- perpendicular to midline dorsally. Ventral margin weakly, regularly convex, with well differentiated, flattened, ventral border widening posteriorly, up to 4 mm high, posteriorly merging into a large, triangular, flattened, up to 4-5 mm long posteroventral spine. Dorsal margin of the spine in the prolongation of the mesolateral RACHEBOEUF: DEVONIAN PHYLLOCARID CRUSTACEA 13 text-fig. 3. Dithyrocaris oculeus sp. nov. ; Givetian Dipleura dekayi Zone, Lower Sica Sica Formation, Belen section, Bolivian Altiplano. a, schematic reconstruction of the carapace. Rectangles with letters indicate the location of enlarged details b to f. b-f, Camera lucida drawings showing details of the morphology and ornamentation; arrows indicate the front of the carapace, b, AMNH 44692, rostral plate in dorsal and lateral views (the ornamentation could not be observed along the longitudinal axis, left blank), c, YPFB Pal 8432, ‘ocular tubercle’ of right valve, d, YPFB Pal 8432, ornamentation of the right mesolateral carina. e, AMNH 44693, posterior part of left valve. F, GLAHM 101272, posterior part of the right side of median dorsal plate, showing curved ornament, posterodorsal projections of the dorsal carina, and the posterior node. Scale bars represent 2 mm. 114 PALAEONTOLOGY, VOLUME 41 text-fig. 4. Dithyrocaris oculeus sp. nov. ; Givetian Dipleura dekayi Zone, Lower Sica Sica Formation, Belen section, Bolivian Altiplano. Reconstruction of the inner side of right valve of carapace, showing the doublure. Doublure shelf stippled, separated from the doublure wall by the corrugated groove. Scale bar represents 5 mm. carina. Posterior margin of the valve at about 100° with midline, with a fairly well developed rounded border, up to 2 mm wide, very weakly concave dorsally, then weakly sinuous or almost straight towards posteroventral spine. Measurements are given in Table 1. The rostral plate was observed on four specimens. It is completely preserved on specimens AMNH 44692 and GLAHM 101272, whilst only its posterior half is preserved on specimens GLAHM 101262 and YPFB Pal 8432. The plate is weakly arched in cross section in its posterior part which is about two-thirds its total length. The anterior part of the plate is elevated, markedly triangular in cross section, ending anteriorly in a stout head, just extending beyond the anterior margin of the valve (Text-fig. 3b). Interval of 2-6 mm between the rostral plate and the median dorsal plate. Median dorsal plate well developed, long and relatively narrow, weakly arched in its anterior 3 mm, then becoming triangular, roof-shaped, in cross section with a well differentiated median dorsal carina, and posterior pointed termination. The maximum height of the plate is 2-3 mm. The dorsal longitudinal carina is crossed by oblique, weakly developed, chevron-like lines, the strongest of which develop short spine-like, posteriorly directed, expansions of the carapace (Text-fig. 3f). These very small projections number 3 to 4 per mm. At a distance between 4T mm and 5-8 mm from its posterior spinose extremity, the median dorsal plate exhibits a small node developed on both sides of the carina (Text-fig. 3f). This structure, described below, could not be observed on the internal moulds. Only one well differentiated, weakly curved, narrow, rounded, mesolateral carina inclined at about 5-10° to the dorsal margin, originating anteriorly below the ‘ ocular ’ tubercle, or just anterior of it, and terminating posteriorly in the prolongation of the posteroventral spine. Length of the carina about 39 mm. At three-fifths the valve length from anterior margin, the carina is located at 53 per cent, the total valve height from dorsal midline. A relatively small, slight, yet well differentiated, and perforated ‘ocular’ tubercle could be observed on six valves. It is located 6-5-7 mm from the anterior margin of the valve, usually straight below the posterior extremity of the rostral plate, or slightly behind this point, and at a distance between 3-6 mm and 5-4 mm from the midline, i.e. at about one-third the valve height measured (Text-fig. 3a). The hole in the centre of the tubercle is also present on the internal mould, indicating a perforation through the exoskeleton (Text-fig. 3c). However, the ‘ocular’ nature of the tubercle remains unclear, and even unlikely if we refer to the body plan of most crustaceans in which eyes always occupy an anterior location. Five internal moulds display the doublure of the carapace. The doublure is well differentiated but relatively narrow, and elaborated into a proximal wall and a distal shelf separated by a narrow corrugated groove (Text- fig. 4). The doublure wall is similar to the external ventral border in size and morphology. The doublure shelf is relatively narrow, not exceeding 1-5 mm wide, i.e. c. one-third the maximum width of the wall. The width of the doublure shelf is constant and regular ventrally and posteriorly ; it gets narrower anteroventrally and anteriorly, to 0-4 mm. Both wall and shelf are fiat, smooth, devoid of any ornamentation. The groove is very narrow, c. 0-25 mm wide, mainly developed in the ventral part of the carapace, and bounded by two well differentiated ridges. The ventral ridge terminates at the extremity of the posteroventral spine, while the dorsal ridge curves dorsally to connect the posterior edge of the valve. The corrugated groove is not developed in the anterior part of the valve where the doublure is narrow and rounded. Abdominal somites. Six concretions yielded abdominal segments, isolated or still connected with either the carapace or the tail. They correspond to somites 5, 6 and 7. Fragments of somite 4 have been observed but they are so poorly preserved that they cannot be used for description or reconstruction. Two specimens of somite 5 have lengths of 3 mm (GLAHM 101250) and 31 mm (GLAHM 101255). Ornamentation of somite 5 exhibits typical sinuous lines perpendicular to the longitudinal axis dorsally, bending backwards postero-ventrally. Ventral side of the somite almost smooth, with a markedly convex ventro-central tubercle, with sub-elliptical limb insertions similar to those described by Rolfe (1981). Centroventral tubercle surrounded by a narrow furrow. Median part of ventral side not preserved (GLAHM 101255, Text-fig. 5i; PI. 3, figs 2-3). Somite 6 is RACHEBOEUF: DEVONIAN PHYLLOCARID CRUSTACEA 15 4-5-8 mm long and 6 mm high, sub-cylindrical and shows a well differentiated, narrow, weakly pronounced, and sigmoid ventrolateral carina. This ridge originates anteriorly, posterior to the anterior lateral socket. Ornamentation dorsally chevron-like along the longitudinal axis. On the anterior part of the somite, lines are almost perpendicular to the somite axis whilst they become progressively oblique postero-ventrally. In the anterior part of the somite, sinuous dorso-lateral lines are deflected strongly backwards near the carina, which they do not cross. Ventrally, the ornamentation comprises thin, weakly pronounced lines, chevron-like anteriorly. The curvature along the midline become progressively reversed backwards whilst the ornamentation disappears progressively posteriorly, along the longitudinal axis (Text-fig. 5g-h). Somite 7 is 4-8-18 mm long, with a corresponding mean height of 2-4-6-8 mm (see Table 2). Somite 7 is anteriorly almost cylindrical in cross section, becoming sub-triangular, rounded posteriorly, devoid of lateral carina. The anterior lateral socket is relatively small, circular and smooth. Ventrally, the posterior part of the somite is depressed where it articulates with the head of the telson. The two antero-ventral condyles are prominent and rounded. Ornamentation of somite 7 is chevron-like dorsally, and postero-ventrally oblique on the flanks, whilst the ventral side is smooth, devoid of any sinuous lines (Text-fig. 5e-f). The length ratio between somite 7 and somite 6 of the same specimens lies between 0-56 and 0-59 (three measurements), while between somite 6 and somite 5 it is 0-6 (two measurements). Tail piece. Eleven variably preserved specimens were available for description. The telson head is relatively wide, rounded, sub-semicircular in cross section, with weakly convex lateral margins. The telson becomes progressively narrower posteriorly; while the lateral margins become concave and the section becomes triangular. A longitudinal median carina, then two longitudinal lateral, shallow, rounded, furrows, differentiate progressively from the head, and extend posteriorly up to its acute extremity. Lateral margins are straight, very low-angled (about 5° to each other), and bear a very narrow groove in which very small spinules are inserted (Text-fig. 5b). A complete small telson (GLAHM 101250) is 14-5 mm long for a head which is 3 mm wide. Lateral spinules number 6 per mm. Spinules preserved on specimen GLAHM 101271 are 0-2-0-3 mm long. Ventral side of telson concave in its posterior part with a shallow median longitudinal groove, becoming flat to weakly convex posteriorly. Ventral platform sub-triangular, longitudinally depressed, with straight lateral margins and a rounded posterior free margin. Anterior part of the ventral platform with a relatively wide, V-shaped groove (Text-fig. 5c). Head of the telson ornamented by oblique, chevron-like lines which curve dorsally in the plane of symmetry (Text-fig. 5b). Furcal rami very long and narrow, but only specimen YPFB Pal 8433 shows an almost completely preserved furca. The head of the telson is broken, and its total length is more than 21-5 mm. Furcal rami are c. 30 mm long (estimated). In specimen GLAHM 101250 furcal rami head is 1-5 mm wide and its reconstruction suggests that furcal rami are at least one-and-one-half times longer than the telson, i.e. c. 21-75 mm for a telson length of 14-5 mm. The length: width ratio of the telson is c. 4-5; that of the furcal rami is c. 14-5. Furcal rami flattened in cross section, with a rounded outer lateral edge. Dorsal side of the furcal rami with a deep, narrow, smooth, longitudinal groove, very close and parallel to the inner margin (Text-fig. 5b). Inner margin with a very narrow and deep groove in which spinules are inserted, as one the lateral margins of the telson. Anterior part of furcal rami ornamented by oblique lines on both ventral and dorsal sides. Specimen YPFB Pal 8433, found in the Dipleura dekayi Zone of the Belen scetion, lacks the ornamentation on the anterior ventral region of the furca, and furca are slightly bent outwards in their distal region. These two characters may possibly be related to sexual dimorphism rather than indicating a distinct species. Comparable differences related to sexual dimorphism are know in the recent leptostracan Nebalia bipes. Males have longer setae and paddles than females (Vannier et al. 1997). Mandibles. Concretion GLAHM 101255 yields three abdominal segments, the tail piece and the two mandibles, undoubtedly belonging to Dithyrocaris. Palp foramen relatively large with respect to the size of the grinding surface, and anteriorly placed. Grinding surface not easy to observe because acicular minerals are often developed on tubercles. Gnathal lobe regularly arcuate, with five well differentiated denticles and (?)one large, posterior, molar denticle. Incisor process high, well developed, followed by one simple, less elevated, conical denticle. Third and fourth denticles with two cusps. Molar denticle transversely ridged. Ornamentation. The ornamentation of Dithyrocaris oculeus sp. nov. is very discrete, delicate, and varies from one part of the exoskeleton to another. It differs strongly between carapace and abdomen. Details are given in Text-figures 3 and 5. Two main types of microsculptures have been recognized on the carapace. The first type, located in the anterodorsal part of the carapace, above the mesolateral carina, and around the ‘ ocular ’ tubercle, is made of very small circular or sub-circular ridges, which open progressively towards the mesolateral 116 PALAEONTOLOGY, VOLUME 41 carina, producing volutes (curled ridges), which increase progressively in length (Text-fig. 3c-d). These volutes are always variably oblique to the dorsal margin. They have initially a dorso-anterior direction, then they turn progressively dorso-posteriorly, their ventral extremity progressively becomes unrolled, and they tend to become parallel to the carina which they never cross (Text-fig. 3d). These curved ridges occur radially on the flanks of the ‘ocular’ tubercle. Small, rounded, similar microsculptures appear again just below the mesolateral carina, which is always smooth. They increase in length progressively while their ventral extremity uncoils, and extend to the ventral border. The second type of ornamentation is developed mainly on the anterior and anteroventral rounded rims as well as on the posterior margin. In the anterior part of the carapace, it is composed of sinuous, terrace-line- like ridges, initially parallel to the anterior margin of the carapace, then progressively curving backwards ventrally, and orientated at c. 45° to dorsal margin, crossing the anteroventral rounded rim, then extending with the same orientation on the ventral flat border, where the ridges are less prominent. The same kind of ornamentation is developed on the posteroventral spine as well as on the posterior margin to which they are more or less parallel (Text-fig. 3e). The abdominal region (pleomeres 5-7) exhibits a different, typical, better developed ornamented pattern, which is common to many phyllocarid Archaeostraca and comparable to the ornamentation of many burrowing organisms. This ornament consists of a pattern of linear, sinuous, terrace-line-like ridges, roughly parallel to each other, and at 45° to the axis of each abdominal segment. These ridges are variable in length; some increase by intercalation (Text-fig. 5). They are not as developed as in Dithyrocaris quinni Copeland, 1967 where they form true cuestas, interpreted herein as possible features to prevent the animal from back slippage during the burrowing phase (Vannier et al. 1997). In the new species, the function of these structures was probably similar, although no other evidence for burrowing habits is available from preserved soft parts or carapace design. In D. oculeus sp. nov., as in other fossil phyllocarid crustaceans, the integumental microstructures are likely to have minimized fluid turbulence both in the water column or in soft, water- permeated sediments. This interpretation finds some support in the fact that the preferential depositional environment of Bolivian phyllocarids is fine, organic-rich, muddy sediment. Suprageneric and generic assignment. At the family level, the Bolivian material differs from the Treatise diagnosis in that the median dorsal plate is typically narrow, folded longitudinally and roof-shaped in cross section, rather than ‘...slightly bent along dorsal median carina.’ (Rolfe 1969, p. R321). But it is clear that most Devonian species are poorly known, and this species is one of the earliest certain, completely described representatives of the genus (Rolfe and Edwards 1979). The distinction between genera of the family Rhinocarididae remains difficult, especially between Rhinocaris, Tropidocaris and Dithyrocaris (Morzadec and Rolfe 1968; Rolfe 1969; Feldmann et al. 1986; Hannibal et al. 1994; Racheboeuf 1995). Assignment of the Bolivian form to the genus Dithyrocaris follows the interpretation of Hannibal et al. : a single mesolateral carina on each valve and a well developed posteroventral spine. The main question remains the significance of the carapace ornamentation which is very different between the type species of Dithyrocaris (Argas testudineus) and the Bolivian species. One of the most interesting features of the carapace of D. oculeus is the node developed on the posterior part of the median dorsal plate. EXPLANATION OF PLATE 3 Figs 1-6. Dithyrocaris oculeus sp. nov. ; Givetian Dipleura dekayi Zone, Lower Sica Sica Formation, Belen section, Bolivian Altiplano. 1, GLAHM 101272; latex replica; enlarged view of the postero-dorsal region of the right valve, showing the dorsal node on the median dorsal plate, the posterior spine-like projections of the dorsal carina, and the ornament of the carapace; x 10. 2-3, GLAHM 101255; latex replica; respectively right and left sides of abdominal somites 5 to 7 and tail piece ; note the limb insertion on the 5th somite, and the lateral carina on the 6th somite; x 5. 4-6, GLAHM 101250; latex replica; abdominal somites 5 to 7, and tail piece. 4, enlarged view of the telson showing the ornamentation and the lateral rows of setae insertions; x 8. 5-6, abdominal somites and tail piece, respectively in dorsal and ventral views; x4. Fig. 7. Dithyrocaris sp. from Achumani Alto, south of La Paz ; GLAHM A2793 ; latex replica ; external mould of the ventral side of a tail piece ; x 2. PLATE 3 RACHEBOEUF, Dithyrocaris PALAEONTOLOGY, VOLUME 41 text-fig. 5. Dithyrocaris oculeus sp. nov. ; Givetian Dipleura dekayi Zone, Lower Sica Sica Formation, Belen section, Bolivian Altiplano. Arrows indicate anterior. Broken lines refer to non-observed, hypothetical outlines, a, reconstruction of the entire exoskeleton, b, reconstruction of the tail piece in dorsal view, mainly from specimens GLAHM 101250 and 101271. c, reconstruction of the ventral side of telson head, from specimen GLAHM 101250. d-f, 7th abdominal somite in dorsal (d), ventral (e), and lateral (f) views, g-h, 6th abdominal somite in lateral (g), and ventral (h) views, i, 5th abdominal somite in lateral view, showing site of left limb insertion. Scale bars represent 5 mm. RACHEBOEUF: DEVONIAN PHYLLOCARID CRUSTACEA 119 table 2. Dithyrocaris oculeus sp. nov.; Givetian Dipleura dekayi Zone, Lower Sica Sica Formation, Belen section, Bolivian Altiplano. Measurements of the abdominal somites, in millimetres. L: length; W: width; H: height; L6:L7: length of the 6th somite versus length of the 7th somite. YPFB 8432 AMNH 44696 GLAHM A2792 GLAHM 101250 GLAHM 101253 GLAHM 101254 GLAHM 101255 5th L — — 3 — — 31 W — — — — — — — 6th L 7-6 — — 4-9 — — 4-5 W — — — — — — — H 60 — — — — : — 7th L 13-1 18 11-5 8-2 11 4-9 8-0 W 4-2 — — — — — — H 4-8 6-8 5-4 4-6 5* 2-4 — L6:L7 0-58 — — 0-59 — — 0-56 Remarks. Valves, abdominal somites, tail pieces and mandibles are assigned to the same species, allowing one of the most complete descriptions of a representative of the genus Dithyrocaris. Such an assignment was made possible owing to the preservation, in a concretion, of a carapace with abdominal somites still connected. These somites are identical in morphology, size, and ornamentation to those which are connected with tail pieces in other concretions. The new available concretion, as well as specimens collected by Branisa, are from the same locality (Belen section), and level (lowermost Sica Sica Formation) as most of the specimens described by Hannibal et al. (1994). This fact, added to the description by these authors, as well as our own observations, precludes any doubt about the conspecificity of our specimens and hence about their assignment to the genus Dithyrocaris. Hannibal et al. (p. 63) compared the Bolivian species with four Carboniferous species: D. quinni Copeland, 1967, D. glabra Woodward and Etheridge, 1873, D. granulata Woodward and Etheridge, 1873, and D. insignis Jones and Woodward, 1898, and only one Devonian species : D. neptuni (Hall, 1863). These authors stated that the Bolivian specimens ‘...lack... a distinct “ocular” tubercle (= anterior tubercle)...’, although ‘Three specimens ... seem to exhibit a weakly developed anterior tubercle or tubercles.’ Although they questioned the taphonomic or authentic anatomical nature of these tubercles, they considered that the Bolivian species lacks a distinct ocular tubercle, and that this character distinguishes this form from both D. quinni and D. neptuni. Hence the Bolivian form was assigned to Dithyrocaris cf. D. insignis due to its produced median dorsal plate and similar size. The good preservation of the ‘ocular’ tubercle on specimen YPFB Pal 8432, as well as on specimens AMNH 44692, 44693; GLAHM 101261, 101272, raises again the question of comparison at the specific level. The new species differs strongly from the type species, D. testudinea from the Lower Carboniferous of Scotland, by the carapace ornamentation, devoid of strong, oblique, sinous ridges, by its more elliptical outline, and by the relative length of furcal rami, which are much longer than the telson, whilst they are about the same length in the type species. Among other species compared by Hannibal et al., Dithyrocaris oculeus sp. nov. differs from D. quinni Copeland, 1967, from the upper Mississippian of Arkansas, in its almost straight (instead of regularly curved) mesolateral carina originating anteriorly in a posterior position with respect to the ‘ocular’ tubercle. In Copeland’s species the mesolateral carina originates at mid-length between the anterior margin and the ‘ocular’ tubercle (see Copeland 1967, pi. 162, figs 10-12) and the ornamentation is better developed, denser and more prominent on the valve as well as on the abdominal pleonites (pi. 162, figs 6, 12). In D. quinni, the denticles point backwards, in contrast to 120 PALAEONTOLOGY, VOLUME 41 those of D. oculeus. They are replaced by irregular curved structures whose anterior edge bounds a depressed posterior area. Hannibal et al. (1994) assigned (with a query) the Bolivian form to the Carboniferous species Dithyrocaris insignis Jones and Woodward, 1898 due to its ‘less pronounced carapace ornamentation’ (p. 63). In fact, D. insignis exhibits a carapace surface with both strong linear and reticulate ornaments which are absent in the Bolivian form. According to Jones and Woodward, the ‘ . . . mesolateral ridge... [is like]... that of D. tricornis ’ (p. 159) which is said to be ‘rugose or tuberculate’ (p. 171); in the Bolivian form the mesolateral ridge is entirely smooth. Moreover, the Bolivian form differs from D. tricornis Jones and Woodward, 1898, in the lack of any punctae, from D. granulata Woodward and Etheridge, 1873 in the lack of granulation, and from D. glabra Woodward and Etheridge, 1873 in the development of the mesolateral carina as well as by the lack of granulation (see Jones and Woodward 1898). All specimens described and illustrated by Jones and Woodward (1898, 1899) exhibit another peculiar feature: the dorsal side of the posteroventral spine is curved dorsally, whilst in the Bolivian form it is parallel to the carapace midline, in perfect prolongation of the mesolateral carina. Most interesting is the comparison with Devonian species. Dithyrocaris neptuni (Hall, 1863) is a poorly known species, initially described from a tail piece and a fragment of a lateral caudal spine. The illustration of the type specimen (Hall and Clarke 1888, pi. 33, fig. 1) indicates that D. neptuni is a very much larger species, but that the relative length of the telson and furcal rami are similar to those of D. oculeus sp. nov. Stumm and Chilman (1969, p. 60) described Dithyrocaris sp. cf. D. neptuni (Hall) from the early Givetian Silica Shale of Ohio and indicated that the total length of the species was about 300 mm. Ornamentation (Stumm and Chilman 1969, pi. 5, fig 4) resembles that of the Bolivian species. Such a peculiar ornamentation has not been illustrated elsewhere, except for another species from the Silica Shale, Hebertocaris wideneri, described in the same paper by Stumm and Chilman (1969, p. 63, pi. 6, fig. 4). Although reconstructions exhibit strong morphological differences between Dithyrocaris sp. cf. D. neptuni and Hebertocaris wideneri (compare Text-figs 2 and 3), such a similar ornamentation in two forms, only known by fragments, and from the same stratigraphical level, may be due to an erroneous assignment of carapace fragments. However, D. oculeus sp. nov. can be distinguished from both forms of the Silica Shale by its smaller size, less developed carapace ornamentation, without spines on the rostral plate as well as on the median dorsal plate, and especially by its smooth as opposed to rugose or cordate mesolateral carina, crossed by the ornamentation. Dithyrocaris oceani (Hall and Clarke, 1888) from the Portage Group differs from the Bolivian species in its larger size, relatively shorter and curved furcal rami, in the development of coarse granulation in the anterodorsal part of the carapace above the ocular tubercle, and in the straighter lateral carina and ornamentation (Hall and Clarke 1888, pis 32-34). Dithyrocaris sp. Plate 3, figure 7 Material. The ventral external mould of a tail piece (GLAHM A2793) from Achumani Alto, south of La Paz, and the anterior part of a tail piece (GLAHM 101283) from Aiquile in the centre of Cochabamba department. Both are of uncertain formation and age. Comparison. Both specimens assigned provisionally to Dithyrocaris sp. differ primarily from Dithyrocaris oculeus in their much larger size and less elongated telson and furcal rami. The width of the telson head is c. 12-5 mm, and its estimated length is c. 45 mm, i.e. a length: width ratio of c. 3-6. The anterior margin of the ventral platform is 1 1 mm from the anterior side of the telson. The telson is less elongated than in D. oculeus where the length: width ratio reaches c. 4-5. The furcal rami head is 7-5 mm wide. The furcal rami width versus telson head width ratio is about 0-6. For D. oculeus the same ratio is 0-5. A tentative reconstruction from specimen GLAHM A2793 gives an estimated length of about 75 mm for the furcal rami, i.e. a length:width ratio of 10. For D. oculeus. RACHEBOEUF: DEVONIAN PHYLLOCARID CRUSTACEA the length: width ratio of the furcal rami is c. 14-5. The ventral side of the telson is more flattened, except for a better differentiated, rounded, narrower longitudinal ridge, than in D. oculeus. The ornamentation of the telson head, as well as that of furcal rami head, is twice as dense in D. oculeus as in Dithyrocaris sp. Moreover, the flanks of the telson head of Dithyrocaris sp. exhibit curved, scale-like lines which have not been observed in D. oculeus , where the ornament is made of sinuous, oblique lines only. Size and relative proportions of the elements of the tail piece, as well as ornamentation, indicate that this rhinocaridid is a species distinct from D. oculeus. PALAEO BIOLOGY AND TAPHONOMY The postero-dorsal node. Despite its small size and weak relief, this peculiar feature, restricted to the dorsal side of the posterior part of the median dorsal plate, is always well differentiated along the dorsal longitudinal carina, especially in specimen GLAHM A2791 . Its location is marked by a weak flexure of the carina in front of the node, and by a stronger flexure behind the node (Text-fig. 3f). The node is symmetrical on both sides of the carina. It is weakly convex and usually slightly pronounced dorsally. Its length does not exceed 1-2 mm, for corresponding height and thickness of 0-8 mm and 0-3 mm respectively. In lateral view, the node is drop-shaped, widening backwards, and smooth in its anterior part. Each side of the node bears minute sub-circular to polygonal punctae which fan out to form a delicate reticulate net which does not cross over the dorsal line. On the internal mould of the carapace, the location of the node is indicated only by a very weak relief without any kind of ornamentation. This fact suggests strongly that the node is not perforated, and that punctae are thinnings of the carapace. The node can be interpreted probably as a sensory organ, possibly for hydrodynamic flow. Dorsal nodes have been described previously in fossil phyllocarids. Rolfe (1962, p. 916) described three hinge nodes (anterior, median and posterior) on the carapace of Ceratiocaris and summarized these observations. The nodes are asymmetrical features developed only on the right valve of ceratiocarines, i.e. phyllocarids whose carapace is devoid of a median dorsal plate. These nodes are smooth ‘...free of ornament and the carapace striae are distorted or bowed-out in the immediate vicinity of the nodes’ (Rolfe 1962, p. 917), although the posterior node shows a circular hole in its centre in both Ceratiocaris acuminata Hall and C. papilio. Features described in Mesothyra oceani by Hall and Clarke (1888, p. 189, pi. 32, fig. 6), and in Rhinocaris by Clarke (1893, p. 794), are not homologous in either their morphology or location, to the posterodorsal node of Dithyrocaris oculeus sp. nov. On the other hand a node exhibiting a similar shape and postero-dorsal location, was also observed on the single left valve specimen of Kerfornecaris roscanvelensis Racheboeuf and Rolfe, 1990 of the family Echinocarididae, but as the right valve of this species is unknown the symmetry of the feature cannot be established, and its possible ornamentation could not be described, due to the grain-size of the sediment. Rolfe (1962, p. 917) considered that the three dorsal hinge nodes on the right valve of Ceratiocaris may have acted as hinge clasps, but he wrote that the presence of a circular hole on the posterior node of some species ‘...may represent some original structure of unknown function.’ Although I could not find any similar structures in the literature, it is to be noted that it is situated along the posterodorsal side of the carapace, i.e. opposite to the anteroventral side of the organism, where most sensory organs are located (antennae, eyes, palps, etc.). Moreover, the small sub-circular to polygonal depressions mainly developed backwards, on the posterolateral part of the node, correspond most probably to thinnings of the carapace, although thin sections through the carapace could not be produced. These considerations led the author to interpret the posterodorsal node as a sensor of the surrounding hydrodynamic flow. If the homologous structure and function of the single node described in Kerfornecaris could be established, each valve of this genus would have developed a node. This would indicate some kind of parallel tendencies between ceratiocarines and rhinocarines. Further investigations are needed of well preserved phyllocarid material to find similar structures. 122 PALAEONTOLOGY, VOLUME 41 Taphonomy. Carapaces of Echinocaris spiniger sp. nov. are mostly incomplete. Moreover, they are often broken, exhibiting clean breaks, except for their anterior part which was probably more resistant, due to the development of stout, convex, lobes. Clean breaks, instead of folds or distortion as in Dithyrocaris oculeus sp. nov. which occurs in the same level, strongly suggest that the carapace was more thickened and mineralized, and hence more brittle. Clean breaks, even in complete exoskeletons of E. spiniger sp. nov. (AMNH 43516), are a consequence of diagenetic processes. The exterior of the left valve of E. spiniger specimen YPFB Pal 9290 exhibits sinuous, anastomosing, sub-cylindrical tubes of epizoans. The same specimen shows two very small, juvenile shells of an ambocoelid brachiopod which were possibly attached to the carapace close to the anterior part of the mesolateral carina (PI. 1, fig. 1). These shells probably belong to the same ambocoelid species as the shell described by Hannibal et al. (1994, pp. 60-61), presumably attached to the 7th abdominal somite of specimen AMNH 43516 and re-illustrated herein (PI. 1, fig. 5). The post-mortem settlement of these epizoans strongly suggests that the carapace of these echinocaridid specimens was not rapidly buried. If the epizoans settled during the life of the organism, this would reflect a nekto-benthic mode of life. Carapaces of D. oculeus sp. nov. are found either with both valves still articulated, or as isolated valves. For three of the available articulated carapaces the angle between the two valves varies between 90° and 100°. This is probably not random, and this angular value may correspond to the maximum ‘normal’ opening of the carapace when the animal was alive. A somewhat similar condition was illustrated for an undetermined late Emsian rhinocaridid from the Massif Armoricain (Racheboeuf 1995, pi. 5, fig. 7). Several other Bolivian specimens, apparently represented by isolated valves, are in fact also articulated carapaces. This is the case for specimens AMNH 44692, GLAHM 101262 and YPFB Pal 8432 which have been prepared to observe the rostral plate. The fact that many concretions appear strongly asymmetrical after breaking, with a ‘ thin ’ part yielding the external mould of a valve, and a much thicker part with the corresponding internal mould, strongly suggests that this kind of concretion yields articulated carapaces, and that they break along only one of the two valve planes. In this respect, careful preparation of newly collected concretions would probably allow the collection better data about the taphonomy of the lowermost beds of the Sica Sica Formation. However, the relatively high percentage of articulated carapaces, added to the discovery of connected abdominal somites and tail pieces, and the occurrence of mandibles associated with carapace remains, indicate a quiet environment. Such preservation strongly suggests that the D. oculeus remains were buried rapidly. It has to be noted that the carapace of D. oculeus never shows epizoan tubes, whilst they are commonly developed on the carapace of E. spiniger. This may be related to a different mode of life, Dithyrocaris being a better swimmer than Echinocaris which lived on the sea bottom. Moreover, if carapace and abdominal somite remains show evidence of weak post-mortem distortion, this is directly related to the thin cuticle. Specimens are well preserved, not flattened like most phyllocarids of the Silurian black graptolitic shales, for example. This implies the very early development of the concretions. Such considerations could not be drawn from associated faunal elements such as brachiopods, vertebrate remains, and even complete trilobite exoskeletons occurring in the same level, which are much more heavily mineralized than the phyllocarids. CONCLUSIONS Echinocaris spiniger and Dithyrocaris oculeus can now be listed among the few well-known phyllocarid taxa. The chemical preparation of the moulds of the carapace revealed details of the ornamentation and peculiar, minute features, such as the dorsal node. The latter, which probably represents a sensory organ, developed symmetrically on both sides of the median dorsal plate of the rhinocarine D. oculeus, and may have homologues in the ceratiocarine genera Kerfornecaris and Echinocaris, for which symmetrical development remains questionable. Both Bolivian species described herein are Givetian. That means that the two genera Echinocaris and Dithyrocaris do not appear in Bolivia earlier than their respective representatives in North RACHEBOEUF: DEVONIAN PHYLLOCARID CRUSTACEA 123 America. From a palaeobiogeographical point of view, the occurrence of representatives of the genera Echinocaris and Dithyrocaris in the cooler climate of the Malvinokaffric realm is somewhat surprising, because both genera, especially the former, have up to now only been recorded as having tropical to subtropical distribution. The Bolivian representatives of the two genera may have preferred different environmental conditions, i.e. cooler temperatures. In this respect, the overall size of Bolivian specimens from the Dipleura dekayi Zone may be of some interest. The largest carapace of Echinocaris spiniger is estimated to have been about 50 mm long, whilst that of the North American species E. punctata is 90 mm long. The carapace of Dithyrocaris oculeus apparently does not exceed a length of 50 mm, whilst in North America D. oceani may be as large as 140 mm long. Very small representatives of both genera may co-occur in the same beds as these ‘giant’ North American species (some of them could possibly be juvenile forms). Recent crustaceans generally reach smaller sizes in cool waters than under tropical or subtropical conditions. The relatively smaller size of Bolivian phyllocarid carapaces, compared with North American representatives of the same genera, may possibly be the expression of the impact of cooler water temperature on the growth of these crustaceans. Acknowledgements. I am grateful to Drs E. N. K. Clarkson (University of Edinburgh), D. A. T. Harper (University College Galway), and an anonymous referee for comments which improved the manuscript. The author is greatly indebted to Mrs Jenna McKnight and Mr John Maret (Collection managers, American Museum of Natural History, New York), for the loan of specimens and for permission to further prepare them. Dr Neil Clark (Hunterian Museum, University of Glasgow) kindly loaned all specimens housed in this collection. Dra Alejandra Dalenz (CTP of YPFB, Santa Cruz, Bolivia) is acknowledged for her help during field trips and for providing collection numbers for the specimens in her charge. Prof. D. E. G. Briggs (University of Bristol) and Drs J.-L. Henry (Universite Rennes I), W. D. I. Rolfe (Edinburgh) and J. Vannier (Universite Claude-Bernard-Lyon I) are gratefully acknowledged for helpful comments on the manuscript. Photographs were taken by Noel Podevigne, UMR 5565, Lyon. The field work was a part of the ‘Siluro- Devonien malvinocafre ’ program of the IFEA (Institut Frangais d’Etudes Andines). This institution and its Director, Christian de Muizon, are greatly acknowledged for their help and financial support. REFERENCES babcock, l., feldmann, R. m., wilson, m. T. and SUAREZ-RIGLOS, m. 1987. Devonian conulariids of Bolivia. National Geographic Research, 3, 210-231. BLIECK, A., GAGNIER, P.-Y., BIGEY, F. P., EDGECOMBE, G. D., JANVIER, P., LOBOZIAK, S., RACHEBOEUF, P. R., SEMPERE, T. and steemans, P. 1996. New Devonian fossil localities in Bolivia. Journal of South American Earth Sciences, 9, 295-308. branisa, L. 1965. Los Fosiles guias de Bolivia. I. Paleozoico. Boletin of the Servicio Geologico de Bolivia, 6, 1-282. clarke, j. m. 1893. On the structure of the carapace in the Devonian Crustacea Rhinocaris, and the relation of the genus Mesothyra and the phyllocarids. The American Naturalist, 27, 473-801. copeland, m. j. 1967. A new species of Dithyrocaris (Phyllocarida) from the Imo Formation, Upper Mississipian, of Arkansas. Journal of Paleontology, 41, 1195-1196. FELDMANN, R. M., boswell, R. M. and kammer, T. w. 1986. Tropidocaris salsiusculus, a new rhinocaridid (Crustacea: Phyllocarida) from the Upper Devonian Hampshire Formation of West Virginia. Journal of Paleontology, 60, 379-383. hall, J. 1863. On the occurrence of crustacean remains of the genera Ceratiocaris and Dithyrocaris, with a notice on some new species from the Hamilton Group and Genesee Slate. 16 th Report of the New York State Cabinet of Natural History, Appendix D, 71-75. — and clarke, j. m. 1888. Trilobites and other Crustacea of the Oriskany, Upper Helderberg, Hamilton, Portage, Chemung and Catskill Groups. Geological Survey of the State of New York , Palaeontology, 7, 1-236. hannibal, j. t., feldmann, r. m. and rolfe, w. d. i. 1994. Phyllocarid crustaceans from the Devonian of Bolivia. In suarez-soruco, r. (ed.). Fosiles y facies de Bolivia, vol. II Invertebrados y Paleobotanica. Revista Tecnica Yacimientos Petroleros y Fiscales de Bolivia, 13-14, 59-69. 124 PALAEONTOLOGY, VOLUME 41 isaacson, p. e. 1977. Devonian stratigraphy and brachiopod paleontology of Bolivia. Part A, Orthida and Strophomenida. Palaeontographica, Abteilung A, 155, 133-192. — and sablock, p. e. 1988. Devonian system in Bolivia, Peru and northern Chile, 719-728. In McMillan, n. J., embry, A. F. and glass, D. J. (eds). Devonian of the World. Volume I, regional syntheses. Canadian Society of Petroleum Geologists, 795 pp. jones, t. r. and woodward, h. 1898. A monograph of the British Palaeozoic Phyllopoda (Phyllocarida, Packard). Part 3. Monograph of the Palaeontographical Society, 52(243), 125-176, pis 18-25. — 1899. A monograph of the British Palaeozoic Phyllopoda (Phyllocarida, Packard). Part 4. Monograph of the Palaeontographical Society, 53 (248), 177-211, pis 26-31. morzadec, p. and rolfe, w. d. i. 1968. Decouverte d’un nouveau Phyllocaride (Crustaces) dans le Devonien superieur du Massif armoricain. Comptes Rendus sommaires de la Societe Geologique de France, 6, 189—190. racheboeuf, p. r. 1995. Silurian and Devonian phyllocarid crustaceans from the Massif Armoricain, NW France. Revue de Paleobiologie, 13, 281-305. LE HERISSE, a., PARIS, F., BABIN, C., GUILLOCHEAU, F., TRUYOLS-MASSONI, M. and SUAREZ-SORUCO, R. 1993. Le Devonien de Bolivie : biostratigraphie et chronostratigraphie. Comptes Rendus de PAcademie des Sciences, Paris, 317, Serie 2, 795-802. — 1994. El Devonico de Bolivia: bio y chronoestratigrafia. Bulletin de Plnstitut Frangais ct Etudes Andines, 22, 645-655. — and rolfe, w. d. i. 1990. Kerfornecaris roscanvelensis n. g. n. sp. : a new Paleozoic phyllocarid crustacean from the Massif Armoricain. Neues Jahrbuch fur Geologie und Palaontolgie, Monatshefte, 12, 735-740. rolfe, w. d. i. 1962. Grosser morphology of the Scottish Silurian phyllocarid crustacean, Ceratiocaris papilio Salter in Murchison. Journal of Paleontology, 36, 912-932. — 1969. Phyllocarida. R296-R331. In moore, r. c. (ed.). Treatise on invertebrate paleontology. Part R. Arthropoda 4. Geological Society of America and University of Kansas Press, Boulder, Colorado and Lawrence, Kansas, 398 pp. — 1981. Phyllocarida and the origin of the Malacostraca. Geobios, 114, 17-27. — and edwards, v. a. 1979. Devonian Arthropoda (Trilobita and Ostracoda excluded). 325-329. In house, m. R., scrutton, c. T. and bassett, M. G. (eds). The Devonian System. Special Papers in Palaeontology, 23, 1-353. stumm, e. c. and chilman, r. b. 1969. Phyllocarid crustaceans from the Middle Devonian Silica Shale of northwestern Ohio and southern Michigan. Contributions from the Museum of Paleontology, University of Michigan, 23, 53-71. vannier, j., boissy, p. and racheboeuf, p. r. 1997. Locomotion in Nebalia bipes : a possible model for Palaeozoic phyllocarid crustaceans. Lethaia, 30, 89-104. Whitfield, r. p. 1880. Notice of new forms of fossil crustaceans from the Upper Devonian rocks of Ohio, with descriptions of new genera and species. American Journal of Science, Third Series, 19, 33 — 42. zittel, k. a. 1990. Text-book of Palaeontology. Vol. 1. Eastman, c. r. (ed.). Macmillan and Co., New York, 706 pp. PATRICK R. RACHEBOEUF U.M.R. 5565 du C.N.R.S. Universite Claude-Bernard - Lyon I U.F.R. Sciences de la Terre Typescript received 19 December 1996 43, Bd du 11 Novembre 1918 Revised typescript received 25 March 1997 69622 Villeurbanne, France MORPHOLOGY AND PALAEOECOLOGY OF A PRIMITIVE MOUND-FORMING TUBICOLOUS POLYCHAETE FROM THE ORDOVICIAN OF THE OTTAWA VALLEY, CANADA by H. MIRIAM STEELE-PETROVICH and THOMAS E. BOLTON Abstract. Build-ups of the calcareous tube, Tymbochoos (gen. nov.) sinclairi (Okulitch), occur in mid Ordovician limestones of the Ottawa Valley; the oldest previously known build-ups of calcareous tubes are Devonian. The Tymbochoos build-ups occurred as elongate dune-shaped structures in tidal channels on intertidal flats, and as small isolated pillow-shaped structures on near-shore subtidal shoals. Clustered tubes radiated horizontally from small attachment areas and then grew vertically. Individual tubes widened quickly to a diameter of about 1 mm and then grew cylindrically ; irregularly spaced concentric constrictions of the tube wall developed in places into thin anteriorly directed internal collars. Growth forms include (1) a framework of concentrated clumps of densely packed, long vertical tubes, found only in the dune-shaped structures, (2) a sparser concentration of clumps with more loosely packed shorter vertical tubes in the pillow-shaped structures, and (3) scattered tube aggregates. T. sinclairi was probably a primitive suspension-feeding polychaete that fed with short tentacles and was supported by its setae-bearing parapodia against the irregularities of the inner tube surface. Few other species were associated with these Ordovician tube build-ups ; exploitation of the intertube environment probably began at the end of the Cretaceous. Build-ups with frameworks dominated by calcareous tubes are rare in the fossil record. The oldest previously reported tube-supported framework is Devonian (Beus 1980), but its taxonomic affinity is uncertain (ten Hove and van den Hurk 1993). Several Carboniferous reefs have tubicolous frameworks, considered to be of vermetid origin (Leeder 1973; Burchette and Riding 1977; Wright and Wright 1981; Weedon 1990). Although build-ups supported by serpulid tubes have been documented from rocks at the Triassic- Jurassic boundary, they remain fairly uncommon through the Tertiary (ten Hove and van den Hurk 1993). With the discovery of well-defined build-ups in the Ottawa Valley, Canada, the geological range of confirmed build-ups that are supported by calcareous tubes has been moved back to the early mid Ordovician. These Ordovician build-ups and the environments they occupied are similar in many ways to those of Recent serpulids and vermetids; the similarities imply both considerable evolutionary and ecological convergence and conservatism of calcareous tube-dwelling organisms over the past 450 million years. The build-ups of this study occur as dune-shaped structures, both in the wall and on the top surface of a quarry at L’Orignal, as a field of well exposed small pillow-shaped structures at Braeside, and as poorly exposed mounds on a crumbly exposure face at Dunrobin (Text-fig. 1); small scattered clumps of tubes are relatively rare. Detailed knowledge of the environments of deposition (Steele-Petrovich 1984, 1986, 1989, 1990) and the exceptional preservation of numerous tubes have enabled the detailed studies of taxonomy, morphology and palaeoecology, presented here, of this Ordovician tube-building organism. This species, until now classified as a rugose coral, Fletcheria sinclairi (Okulitch 1937; Wilson 1948), is here reassigned to Tymbochoos , a new genus, which is inferred to be a primitive polychaete. IPalaeontology, Vol. 41, Part 1, 1998, pp. 125-145] © The Palaeontological Association 126 PALAEONTOLOGY, VOLUME 41 STRATIGRAPHY AND GEOLOGICAL SETTING The tubicolous build-ups of this study occur in limestones of Blackriveran age, assigned traditionally to the Pamelia and Lowville formations (e.g. Wilson 1946), and more recently (e.g. Williams and Telford 1986) to the Shadow Lake and Gull River formations of Liberty (1964), and to the B, C and /? lithostratigraphical units of Steele-Petrovich (1986, 1989; Text-fig. 2). The sediments at Braeside and Dunrobin accumulated in a shallow quiet tropical lagoon behind a lime-mud bank (Steele-Petrovich 1984, 1989); there is evidence that the bank and lagoon developed within a narrow gulf, and migrated with the transgressing sea up a pre-existing rift valley that preceded the present Ottawa-Bonnechere Graben. In contrast, the sediments at L’Orignal were deposited on a normal level bottom within the Ottawa Basin (Steele-Petrovich 1989). ARCHITECTURE OF THE BUILD-UPS Dune-shaped mounds Dune-shaped mounds of Tymbochoos occur at two stratigraphical horizons in a small quarry near L’Orignal (Text-fig. 3). The upper horizon is exposed both in the quarry wall and on the table rock at the top of the quarry (Text-fig. 4a). Forty-eight mounds, somewhat reminiscent of Andrews’ (1964) subfossil serpulid reef fields from Baffin Bay, Texas, occur at the top of the south side of the quarry, in an area of about 20 x 150 m; their lengths are generally L 5-3-0 m but up to 5 0 m, length- to-width ratios are 1 -5-2-5. Actual mound heights are generally 0-45-0-50 m; heights above the contemporary intermound sediment vary from about OTO-O-35 m, and are comparable to those of many Recent and fossil serpulid build-ups (e.g. Andrews 1964; Braga and Lopez-Lopez 1989; ten Hove and van den Hurk 1993). The mounds trend north-north-east, most within azimuths 20-35° (Text-fig. 5). They are asymmetrical in cross section, with the west-north-west side generally sloping STEELE-PETROVICH AND BOLTON: ORDOVICIAN POLYCHAETE 127 Steele-Petrovich Proposed Units Traditional Williams and Ottawa- Bonnechere Graben (1986) Ottawa Basin (1989) ( Classification e.g. Wilson 1946) Telford (1986) (after Liberty 1964) c o F 6 c c Y cc .x: O CTJ Lowville Gull River B P CD Pamelia Shadow Lake A a Rockcliffe Rockcliffe r. O text-fig. 2. Middle Ordovician stratigraphy of the Ottawa Valley. between 30° and 60° and the opposite side sloping at less than 20° (Text-fig. 4a); smaller disconnected mound patches commonly occur along the periphery of the more gently sloping side. The mound surfaces are commonly knobby or ridged, with shallow relief. The lower mound horizon can be seen only on a small weathered portion of the quarry wall and on a few square metres of horizontal shelf; these exposed mounds are rounded and appear to be almost symmetrical dune- shaped structures (Text-fig. 6a-b), about 0-7 m across, 0-4 m high with height about 50 mm above the contemporary sediment surface. Tymbochoos sinclairi was a suspension feeder, as implied by the current-controlled dune-shaped mounds. Orientation of the asymmetrical mounds can be interpreted by analogy with Recent serpulid build-ups, studied by Behrens (1968), that encrust the insides of rectangular water-intake tunnels of an electric power plant in Corpus Christi, Texas. This Recent encrusting growth develops shapes and orientations similar to those of ripple marks formed in non-cohesive sediment: the structures are perpendicular to the current, with gentle and slightly rounded up-current slopes and steep down-current slopes. Although both of these forms have the same asymmetrical shape, the Recent structures, with wavelengths of 0T0-0T5m, heights of 10-20 mm, and crest lengths of 0T 0-0-20 m, are considerably smaller than the asymmetrical mounds of this study. The similarity in form suggests that the asymmetrical Tymbochoos mounds developed where the dominant tidal current (probably the incoming current) flowed west-north-westwards; the symmetrical mounds probably formed where incoming and outgoing current strengths were similar. 128 PALAEONTOLOGY, VOLUME 41 BRAESIDE (road cut) BRAESIDE (horizontal exposure) LEGEND vertical scale in metres Tymbochoos buildups PoWoj fossiliferous ooidal intraclastic b°o°o°o°l packstone-grainstone 1 h j 1 1 1 1 1| fossiliferous mudstone- i' id wackestone-packstone E3S33 stromatolites/ microbial deposits dolomite □ siliciclastics text-fig. 3. Stratigraphical sections as measured at each locality, showing Steele-Petrovich locality numbers for the Tymbochoos occurrences. Pillow-shaped structures Limestone ‘pillows’ are concentrated on what appears to be a single bedding plane that crops out at several locations near Braeside (Text-fig. 1). The structures are sub-circular to elliptical in plan, usually OT 0-0-2 5 m across and up to 0-4 m long, flat on the bottom and flat to slightly domed on top, with sharply defined rounded to angular edges (Text-fig. 7); their thickness is generally about 100 mm, with 30-50 mm exposed above the bedding plane (Text-fig. 7d). In rare cases the upper surfaces of the ‘pillows’ are pitted and appear to have been bored (Text-fig. 7c). Although a bulldozer had disturbed the exposures, 14 ‘pillows’ were in place in an undisturbed area measuring about 3 x 2 m, and were generally spaced no more than 0-3-0-5 m apart; some were almost touching each other and in several cases two or three had grown together. . Other mounds Clusters of mounds are poorly exposed and/or poorly preserved at several horizons in a road-cut and associated narrow ditch near Dunrobin (Text-fig. 1); those in the ditch have been sheared off horizontally, and those in the road-cut occur in a crumbly part of the section and are poorly defined. These build-ups vary considerably, from small buttons to poorly defined masses nearly one metre across, from regular saucer or mound shapes to build-ups with irregular projections, and from isolated mounds to those that grew together, both laterally and vertically. Because of poor STEELE-PETROVICH AND BOLTON: ORDOVICIAN POLYCHAETE 129 text-fig. 4. Macrostructures of asymmetrical, dune-shaped mounds from near L’Orignal (see Text-figure 3 for identification of S-P locality numbers). A, view down the crest of an individual mound at top of south end of quarry. Slope of right (i.e. east-south-east) flank about 20°; slope of left (west-north-west) flank about 50°. Surface irregular due to shallow channels. Small disconnected patches of mound along periphery of gently sloping flank. Inferred current direction from right. Length of tape case 65 mm. b, GSC hypotype No. 115517; hand specimen showing horizon of densely packed, long vertical tubes between horizons of densely packed horizontal tubes; x 1. c, GSC hypotype No. 115518; hand specimen from scree at south end of quarry (S-P Locality No. 146), showing relatively densely packed tubes with concentric crenulations and, in some cases, longitudinal ridges; x 6. d, top surface of a mound showing scattered clumps of radiating, mainly horizontal tubes. Scale in inches. Photographs a-b and d taken at S-P Locality No. 146-4D (GSC No. 0-104069). 30 PALAEONTOLOGY, VOLUME 41 10 m I 1 • position of mound y/ long axis of mound text-fig. 5. Map showing relative positions and alignment of asymmetrical, dune-shaped mounds at top of south side of quarry, near L’Orignal. text-fig. 6. Macrostructures of symmetrical, dune-shaped mounds formed by Tymbochoos, located near L’Orignal (see Text-figure 3 for identification of S-P locality numbers), a, section through lower mound horizon in west-facing quarry wall, showing individual growth horizons of tubes. Arrow marks position of left side of B. Scale in inches. S-P Locality No. 146-3A (GSC No. 0-104065). b, enlargement of part of a, to right of arrow ; relatively dense, subvertical tubes in radiating clumps that are emphasized by differential weathering, between horizons of densely packed, horizontal tubes that have not been emphasized by weathering. preservation and exposure, these mounds are of interest primarily for the environment that they occupied. Isolated tube aggregates Isolated small clumps of Tymbochoos tubes occur in living position, often close to build-ups. STEELE-PETROVICH AND BOLTON: ORDOVICIAN POLYCHAETE 131 text-fig. 7. Macrostructures of pillow-shaped mounds from Braeside (see Text-figure 3 for identification of S-P locality numbers), a-b, on disturbed (a) and undisturbed (b) bedding planes, showing sub-circular and elliptical shapes in plan view. Length of hammer 0-35 m (only partially visible in b); S-P. Locality No. 75-1A (GSC No. 0-106469) (lateral equivalent of 10-1A). c, enlargement of far side of large ‘pillow’ in figure a showing pitted surface; scale in inches, d, vertical section through small ‘pillow’ (about 40 mm thick) showing its flat bottom, slightly domed top and sharply defined, angular edges; S-P. Locality No. 74-5C (GSC No. 0-105755). FORM AND GROWTH OF THE TUBES The tubes of T. sinclairi (Text-figs 8, 9a-b, 10-11) are circular in cross section and expand very quickly from c. 0T2mm at the base to a mature size of generally 0-95-1 -30 mm (maximum 132 PALAEONTOLOGY, VOLUME 41 text-fig. 8. Photomicrographs of symmetrical, dune-shaped mounds from near L’Orignal; S-P Locality No. 146-3A (GSC No. 0-104065) (see Text-figure 3 for identification of S-P locality numbers), a, GSC hypotype No. 115519; vertical section showing long tubes and dense, subparallel vertical growth of framework-type structure. Horizontal radiating growth at base appears to be from three closely packed tube aggregates; vertical tubes show fine tube walls with concentric constrictions; x 5. b, GSC hypotype No. 115520; horizontal section through framework-type structure showing dense packing and sub-circular cross section of mature tubes ; x 10. 1-50 mm); subsequent growth produced straight to slightly sinuous, cylindrical tubes. The circular cross section is seldom distorted significantly by contact with other tubes (Text-fig. 8b). Unlike some Recent serpulid species, which share walls in the area of contact (Hartmann-Schroder 1967), contiguous individuals of T. sinclairi each appear to have produced a complete tube; apparent sharing of walls, where it occurs, appears to result from selective dissolution of a part of one tube. Tube-wall thicknesses vary greatly (0-02-0T2 mm) in a manner that is unrelated to tube diameter (compare Text-figs 8-9, 11) and is probably due to diagenesis. In rare cases, longitudinal ridges occur on the weathered exteriors of T. sinclairi tubes (Text-fig. 4c). In thin section these ridges have been seen only on specimens with unusually thin, apparently unaltered, walls (Text-fig. 1 1b); about 20 fine ridges can be spaced somewhat unevenly around a tube, or several can occur on only a part of the surface, suggesting that certain ridges were obliterated by diagenesis. However, as considerable variation in tube morphology of another group of polychaetes, the Recent serpulids, can be associated with different growth stages (Hartmann-Schroder 1967) and environmental changes (ten Hove and van den Hurk 1993), one cannot dismiss the possibility that variation in ridging in the T. sinclairi tubes is primary. Most of the studied tubes are constricted concentrically at semi-regular intervals (Text-figs 8a, 9b, 1 1a, c), which results in unevenly corrugated inner and outer surfaces. In places these constrictions have developed into thin, anteriorly directed, internal collars (Text-fig. 11c) that result from the inward growth of the leading edge of the tube. These collars do not occur in all tubes ; when present, they can encircle the whole tube and be relatively regularly spaced at about 0-4 to 0-6 mm intervals, or they can be well defined on only a part of the STEELE-PETROVICH AND BOLTON: ORDOVICIAN POLYCHAETE 133 text-fig. 9. Photomicrographs of asymmetrical, dune-shaped mounds from near L’Orignal (see Text -figure 3 for identification of S-P locality numbers). A, GSC hypotype No. 115522; S-P Locality No. 146-4D (GSC No. 0-104069); vertical view of small scattered radiating Tymbochoos clumps growing on and overgrown by stromatolitic laminae; x 4-95. b, enlargement of centre left of a showing attachment of small isolated radiating clump of tubes to firm stromatolitic surface; x 13-85. c, GSC hypotype No. 115521 ; S-P Locality No. 146-4B (GSC No. 0-104067) (lateral equivalent of 146-4D); vertical section showing small Tymbochoos clump in early stage of tube growth with filamentous microbial overgrowths; x 32-65. d, GSC hypotype No. 115523; vertical section showing Tymbochoos tubes in burrowed microbial deposits; x 13-85; S-P Locality No. 146-4D (GSC No. 0-104069). :34 PALAEONTOLOGY, VOLUME 41 text-fig. 10. GSC hypotype No. 115524; polished vertical surface from the upper part of an asymmetrical, dune-shaped mound showing a few radiating clumps of Tymbochoos tubes near the base, and toward the top an increase in abundance of isolated horizontal tubes and wavy and mounded microbial growths ; x 0-99 ; S-P Locality No. 146-4D (GSC No. 0-104069) (see Text-figure 3 for identification of S-P locality numbers). tube and pass into simple constrictions on the opposite side. The degree to which these differences are primary or an artefact of preservation is difficult to determine. After a collar had formed, tube growth resumed on the outside of the tube below the collar and then enclosed the collar region. Unlike the tubes of most Recent species of serpulids and vermetids (ten Hove and van den Hurk 1993), the tubes of T. sinclairi, with intermittent periods of tube constriction at the anterior ends, could not have been closed by an operculum ; even a flexible fleshy operculum would probably have caught on the constrictions as it was withdrawn into the tube (H. A. ten Hove, pers. comm. 1996). Tubes typically grew in clumps, which have the same pattern of growth in the different kinds of build-ups. Most clusters were probably anchored to a firm base, such as a shell fragment, ooid, intraclast, stromatolitic hardbed, or upper tip of a clump of previously abandoned tubes (Text-figs 9a-b, 1 1a, c). Many Recent serpulids attach themselves to fallen tube fragments of their own species STEELE-PETROVICH AND BOLTON: ORDOVICIAN POLYCHAETE 135 (Bosence 1979; ten Hove and van den Hurk 1993), but broken fragments of T. sinclairi are rare. This scarcity can be attributed to several factors: to negligible bioerosion during the Ordovician, compared with the Recent (cf. Bosence 1979; ten Hove and van den Hurk 1993), to the support given to the tubes by penecontemporaneous sediment filling the intertube space (cf. Straughan 1972; ten Hove and van den Hurk 1993), and to microbial overgrowth of the tubes shortly after the animal’s death (discussed later). Attachment areas of the clumps are invariably small, almost certainly because of both the gregarious settling of the larvae and the scarcity of suitable substrate, as analogies with Recent serpulids suggest (cf. Bosence 1979; ten Hove 1979; ten Hove and van den Hurk 1993); available hard particles, other than the worm tubes, were very small and relatively scarce in Tymbochoos- inhabited environments, and only the initial settlers in a clump appear to have been attached to a firm external base. Succeeding spat settled at the base of the established tubes ; tubes within a clump grew sub-horizontally and radially out from the initial attachment area, and after a sufficient base had been established, they turned upward and grew vertically (Text-figs 8a, 1 1a, c). There is no evidence of spat having settled on the vertical walls of growing tubes, as with some Recent serpulids (cf. Hartmann-Schroder 1967; ten Hove and van den Hurk 1993), possibly because periodic larval production more-or-less coincided with the death of the previous generation, as in some Recent serpulid communities (cf. Behrens 1968; Straughan 1972) (discussed below), and/or because conditions that were suitable for larval settlement lasted for only a short time after initial settlement. INTERNAL STRUCTURES OF BUILD-UPS Internal structures of the different kinds of T. sinclairi build-ups differ considerably in maximum density of clumps of tubes, tube density within the clumps, maximum tube length, and concentration of associated microbial growth/ binding. Clumps that form the ‘pillow’ structures are usually relatively widely spaced and small, consisting of a comparatively few short tubes (Text-fig. 1 1a, c-d), which rarely reach more than 4—8 mm above the base. In contrast, a dense framework structure of tubes dominates the dune-shaped mounds (Text-figs 4b-c, 6, 8), except near the tops of at least the asymmetrical mounds, where stromatolitic growths dominate (Text-fig. 10). Tube density The framework structure consists of relatively long horizontal and vertical (or sub-vertical) tubes, commonly in well-differentiated rows (Text-figs 4b, 6, 8a). At densest packing, the vertical tubes are several tens of millimetres long, occupy at least two-thirds of any horizontal cross sectional area, and appear to be more-or-less subparallel throughout and in contact with one or more other tubes along much of their lengths (Text-figs 4b, 8). The strength provided by tube contact in these Ordovician structures must have outweighed the competitive disadvantage of not having had a regular separation of feeding apparatuses. In contrast, many Recent serpulids have both equal spaces between tube apertures (Bosence 1979; ten Hove and van den Hurk 1993) and lengthwise contact with other tubes (ten Hove, pers. comm. 1996), thereby combining strength with feeding effectiveness. A somewhat flaring upward growth in the Recent serpulids results in intertube space that is subsequently colonized by younger tubes, producing a closely packed tube structure posterior to the evenly spaced apertures (compare text-figs in Bosence 1973, 1979 and those in ten Hove and van den Hurk 1993). As tube growth in Recent serpulids accounts for most of their expended energy (Dixon 1980), maximum tube growth must occur under optimum environmental conditions (cf. Hartmann- Schroder 1967). High larval survival rates, which also depend on favourable conditions (cf. Straughan 1972), are necessary for the growth of densely packed tubes (cf. Hartmann-Schroder 1967). By analogy, the framework structure of T. sinclairi , with its long densely packed tubes, must have developed when conditions were particularly favourable, and the more sparsely distributed clusters with short tubes grew in poorer conditions. The increase in microbial growths with decrease 136 PALAEONTOLOGY, VOLUME 41 in tube density (discussed below) supports the argument that sparse tube growth formed under poorer conditions. Death and replacement Intermittent mass death and subsequent replacement by another generation of tubes occurred in both dense and sparse populations of T. sinclairi : clumps of tubes originated at a single horizon and grew to approximately the same height (Text-figs 4b, 6, 1 1a), indicating that the clumps developed from the same spatfall, grew at about the same rate, and died en masse. Where clumps and tubes are relatively widely spaced, new growth commonly occurred on a thin sediment layer that covered the death horizon. In contrast, the dense framework structure has alternating horizontal and vertical growth in contiguous layers, commonly several tens of millimetres thick (Text-figs 6b, 8a). A similar growth pattern of dense tubes is found in the sub-Recent serpulid patch reefs of Baffin Bay (cf. Andrews 1964) and in the fouling structures within the water-intake tunnels in Corpus Christi (cf. Behrens 1968); in the latter, each couplet represents an annual cycle of growth. Laboratory studies indicate that growth rates of the serpulid tubes in the first two to four weeks after settlement of the spat are ten to twenty times greater than in later life, leading Behrens (1968) to suggest that the newly settled worms crowd out and kill the previous generation. However, a more likely interpretation is that the adult worms die each year immediately after reproducing. A similar growth pattern in the framework structure of T. sinclairi suggests a comparable type of replacement. Intertube burrowing A penecontemporaneous carbonate mud, commonly with scattered peloids and ooids, occurs between the tubes in T. sinclairi build-ups (Text-figs 8-9, 11). Horizontal, vertical and oblique burrows (diameters 0-8-1 -2 mm) are common in association with microbial growths amongst the sparsely distributed clusters of tubes in the asymmetrical dune-shaped mounds (Text-fig. 9d). Well defined horizontal burrows (about 0-5 mm diameter) and poorly defined swirls occur more rarely and in the absence of microbial growths within the compact framework structure. In most cases, poorly defined, almost ethereal swirls are the only evidence of burrowing within the ‘pillows’. Microbial growths Stromatolitic growths, as well as non-stromatolitic microbial growths with filamentous, vermiform, and clotted textures, occur only with sparsely distributed tube clumps (Text-figs 9-10, 11c). There is no evidence of microbial development associated with the dense framework structure that dominates the dune-shaped mounds (Text-fig. 8), although abundant stromatolitic growth occurs text-fig. 11. Photomicrographs of pillow-shaped mounds from Braeside (see Text-figure 3 for identification of S-P locality numbers), a, GSC hypotype No. 115525; S-P Locality No. 10-X (GSC No. 0-105757) (lateral equivalent of 10-1 A); vertical view showing (1) relatively widely-spaced tube aggregates with radiating, sub- horizontal basal tube growth and relatively short vertical tube growth; (2) several tube aggregates growing from a single horizon to approximately the same height and being replaced subsequently by another aggregate that grew directly on the abandoned tubes ; (3) tube aggregate (lower right) growing on a trepostome bryozoan fragment; x 5. b, GSC hypotype No. 115525; same locality as a; horizontal section through two Tymbochoos tubes showing thin shells with radial projections (representing longitudinal ridges) on the outer surfaces; x 40. c, GSC hypotype No. 115526; S-P Locality No. 10-1A (GSC No. 90071); vertical views of tube aggregate with radiating, sub-horizontal basal tubes and relatively short vertical tubes; vertical tubes with fine tube walls, concentric constrictions, and well defined inward-projecting collars; tops of tubes overgrown by microbial growths; scattered ooids and peloids in micrite of matrix and tube infillings; x 10. d, GSC hypotype No. 115528; S-P Locality No. 10-X (GSC No. 0-105757) (lateral equivalent of 10-1A); horizontal section of mature relatively scattered tubes with sub-circular cross section; x 14. STEELE-PETROVICH AND BOLTON: ORDOVICIAN POLYCHAETE 137 text-fig. 11. For caption see opposite. 138 PALAEONTOLOGY, VOLUME 41 with scattered tubes toward the tops of these mounds (Text-figs 4d, 10). Microbial remains within the ‘pillow’ structures are discrete to nebulous; they occur as thin overgrowths on clumps of Tymbochoos or on a thin layer of sediment that covers the clumps (Text-fig. 11c), as patches between tube clumps and between tubes within the same clump and, more rarely, as faint growths within the tubes. The fact that microbial growths are associated only with relatively poor tube development indicates that the conditions that caused the demise of Tymbochoos were advantageous for microbial growth. In some cases, the spread of microbes may have sped up the demise of Tymbochoos or even finished them off. However, the fact that most tubes in both environments have some sediment fill and show little evidence of microbial growths, either within the cavity or across the aperture, implies that the microbes generally grew over the tubes after the worms had died and sediment had filtered into the tubes. Stromatolitic growth, which flourished when Tymbochoos declined (Text-figs 9a-c, 10), gave structural strength in the absence of a framework structure to both the upper part of the dune-shaped mounds and to the ‘pillows’. Penecontemporaneous cementation, which could have been a direct result of high salinity (see below) (e.g. Brantley et al. 1984), may have helped to stabilize some of the Braeside ‘pillows’, as implied by rare surface borings (Text-fig. 7c). HABITATS Near-shore settings The Tymbochoos build-ups all developed in near-shore settings. Most of the mounds at both L’Orignal and Dunrobin occur on a packstone-grainstone of ooids, intraclasts and ostracod fragments (Text-fig. 3); these sediments were laid down in tidal channels within tidal flats that were colonized, at least in part, by stromatolites (Steele-Petrovich 1984). In some cases T. sinclairi tubes grew on firm stromatolite mounds, some of which were overturned and had probably been undermined by the meandering channel and fallen into it. In other cases dispersed clumps, that developed repeatedly on the hard laminar surfaces of stromatolites, were overgrown by stromatolitic laminae after only a few millimetres of vertical tube growth (Text-fig. 9a); these stromatolites, which occurred at the edge of the environment necessary for Tymbochoos survival, probably developed on levee backslopes and in subtidal ponds within the tidal flats. The Tymbochoos ‘pillow’ structures at Braeside developed in a slightly deeper environment, also on an oolite; they are preserved in a packstone-grainstone of ooids, intraclasts, peloids and fossil fragments, which formed discontinuous shoals where relatively gentle waves made contact with the bottom (Steele-Petrovich 1984). The tidal channels and the near-shore shoals where Tymbochoos lived were comparatively high-energy settings for this study area, although the oolites, at least in the western part of the valley, formed in muddy environments close to the low-energy limit of ooid formation. Mounds from the lowest stratigraphical occurrence at Dunrobin (Text-fig. 3) are anomalous in not having developed in association with an oolite ; they formed in a peritidal environment, probably close the low-tide mark and are preserved in a unit that is sandwiched between intertidal stromatolites. Most Recent serpulid build-ups also occur in near-shore environments, commonly in association with oolites (e.g. Andrews 1964; ten Hove 1979; Bone and Wass 1990; ten Hove and van den Hurk 1993). Environmental conditions Mass deaths of young adults after only a short period of tube growth imply fluctuating conditions that for short periods of time were tolerable for both the larvae and young adults and then quickly deteriorated to a state that killed the adults. Only those worms that formed dense frameworks appear to have lived a full life. The dispersed clumps of short tubes throughout the ‘pillows’ suggest that the ‘pillows’ were subjected to more marginal, although more uniform, conditions throughout their development than the dune-shaped mounds. The development of dune-shaped mounds at L’Orignal and ‘pillows’ at Braeside is in keeping with stronger currents in the tidal channels at L’Orignal compared with a quiet and more restricted shallow subtidal setting at Braeside. There is no evidence that deteriorating conditions toward the tops of the dune-shaped mounds STEELE-PETROVICH AND BOLTON: ORDOVICIAN POLYCHAETE 139 resulted from changes in either sedimentation rate or current regimes, and the close association of T. sinclairi with oolites, which form in shallow agitated conditions, is evidence against suboxia. An alternative explanation is fluctuating salinity: abundant linked evidence on the faunas and the lithofacies within the graben, west of Ottawa, shows that salinity of the near-shore environments fluctuated from hypersaline much of the time, with gypsum forming occasionally, to normal marine more rarely. In comparison, Recent serpulids with the highest salinity tolerance cannot survive salinities above about 55%0 (ten Hove and van den Hurk 1993), while gypsum forms at salinities of at least 125%0 (Brantley et al. 1984). Studies of the Ottawa basin in the eastern part of the valley are not sufficiently advanced to determine if hypersalinity was common there also ; more sustained and denser tube growth, a lack of gypsum, and more open-marine conditions are in keeping with a lower salinity than in the graben, although the scarcity of near-shore epifaunas in the east may reflect some hypersalinity. The common disruption of microbial textures by burrowing (Text-fig. 9d) indicates that the conditions that adversely affected Tymbochoos within the dune-shaped mounds and encouraged microbial growth also sustained burro wers. As burrowers and cyanobacteria can tolerate higher salinities than most epifauna (e.g. Fogg 1973; Savrda et al. 1984), their survival in the eastern part of the valley when T. sinclairi died fits the explanation that a salinity increase terminated the growth of the dune-shaped mounds. Smaller and sparser clumps of Tymbochoos tubes with large microbial growths (Text-figs 4d, 10) are somewhat reminiscent of build-ups in Baffin Bay, Texas, in which mats of green algae have overgrown serpulid reefs that have died since the turn of the century, apparently in response to high salinity (cf. Andrews 1964). ASSOCIATED FAUNA/FLORA A diverse and abundant fauna lives in association with tube build-ups today (Woodin 1978). In contrast, only a few species are preserved with the Tymbochoos build-ups. Intertube forms were limited to burrowers and to microbial overgrowths that spread as environmental conditions deteriorated and Tymbochoos died. A semi-infaunal byssally attached bivalve, Cyrtodonta breviuscula / subcarinata (C. breviuscula is the juvenile form of C. subcarinata), and a low-spired gastropod, Raphistomina distincta, were common to abundant in the tidal channels amongst the asymmetrical dune-shaped mounds; small michelinocerid cephalopods were rare. Ostracods probably lived in tidal pools but not in the channels. C. breviuscula/ subcarinata also lived commonly amongst the T. sinclairi ‘ pillows ’ ; the absence of gastropods from amongst the ‘ pillows ’ may be related to weaker microbial growth in that setting. There is little fossil evidence of possible competition and predation that could have restricted Tymbochoos sinclairi to the nearshore region. Because of the morphological and ecological similarities between T. sinclairi and Recent serpulids, the two groups would be likely to share the same competitors and predators. Most competitors (barnacles, brown algae) and, except for gastropods, most predators (echinoids, starfish, crabs, fish) of Recent serpulids (Straughan 1969, 1972; Bosence 1973, 1979; O’Donnell 1984) have poor fossilization potentials, and within these groups, only the starfish and gastropods were significant predators during the mid Ordovician. Although there is no evidence for external digestion in Ordovician starfish (Spencer and Wright 1966), the chance of such evidence being preserved is slight, and it is impossible to ascertain the ability of Ordovician starfish to feed on tubicolous forms that could withdraw into tubes. The absence of boreholes in T. sinclairi tubes indicates a lack of gastropod predation. Therefore, the effects of competition and predation on the distribution of T. sinclairi during the Ordovician appear to have been minor compared with similar effects on serpulids today. FUNCTIONAL MORPHOLOGY AND SYSTEMATIC AFFINITY Tymbochoos was neither a serpulid worm (H. A. ten Hove, pers. comm. 1996) nor a vermetid gastropod, each of which belongs to a common Recent group that produces build-ups of calcareous tubes. T. sinclairi, with episodic constrictions of the aperture and irregularly spaced constrictions 140 PALAEONTOLOGY, VOLUME 41 with anteriorly directed inner collars on the inner tube surface, could not have withdrawn quickly in the face of danger (ten Hove, pers. comm.); in contrast, Recent serpulids, with smooth inner surfaces and constant tube diameters, pull in rapidly. Also, fast expansion to mature diameter of the T. sinclairi tube is unlike the gradual and continuing tube expansion of Recent serpulids (H. A. ten Hove, pers. comm.). T. sinclairi lacks the coiled protoconch and the complete septa of vermetid gastropods; the inner rings of T. sinclairi, although superficially resembling incomplete septa of the vermetids, formed when the whole leading edge of the tube turned inwards, in contrast to the development of vermetid septa from the inner shell layer (cf. Burchette and Riding 1977). T. sinclairi was a suspension feeder, as indicated by its current-controlled structures, the feeding positions of its tubes, and the living habits of morphologically similar Recent forms. Of tube builders, only the polychaetes have the repetitious segmentation that the semi-regular constrictions and collars on the inner tube wall could reflect. A primitive polychaete, with parapodia and setae on each segment (cf. Fauchald 1975), could have maintained itself at a desired level within the tube by bracing its setae against the irregularities of the inner tube wall. Internal collars may have developed where there was a need for a firmer grip. The inability to withdraw quickly probably reflects the low predation pressures of the Ordovician (see above) ; as these pressures increased in intensity later in the Phanerozoic (cf. Vermeij 1977), tubicolous animals evolved characteristics that permitted more efficient escape. Analogies with Recent tubicolous suspension-feeding polychaetes indicate that T. sinclairi had either a tentacular feeding crown or a system of relatively independent tentacles. Although a feeding crown in the Ordovician would probably have been smaller and not as efficient or as well co-ordinated as in Recent worms, it would have had greater difficulty moving in and out past the anteriorly projecting collars than would independent tentacles. Also, the lack of regular spacing between the long, parallel tubes (see above) argues against feeding crowns. Therefore, T. sinclairi probably resided within its tube and fed with a series of short independent tentacles that projected into the water column. The closest living analogues of Tymbochoos appear to be cirratulids. One of these, Dodecaceria fewkesi, forms reefs 0-5-1-0 m across, has smooth calcareous tubes without constrictions or inner collars, and each worm feeds with 1 1 pairs of independent tentacular cirri that project from the tube opening (Meinkoth 1981, p. 433; ten Hove and van den Hurk 1993). A closely related species, D. cor alii (illustrated by Meinkoth 1981, p. 433), has a generalized polychaete body with setae on each segment and with eight pairs of tentacular cirri near the anterior end. These analogies reflect characteristics of a primitive polychaete and do not necessarily imply a close genetic relationship between the two groups. Preliminary microscopic examination of the tubes (magnification 250 x ) consistently shows a single tube layer with a fine radial calcite structure. Studies of the microstructure, which are beyond the scope of this paper and planned for the future, are needed before the systematics of Tymbochoos sinclairi can be worked out. COMMUNITY STRUCTURES OF THE TUBE-SUPPORTING BUILD-UPS DURING THE PHANEROZOIC Large and consistent differences occur between the community structures of the build-ups of Recent serpulids or vermetids and T. sinclairi. Recent tubicolous build-ups serve as refuges for other organisms (Woodin 1978); abundances and diversities of associated organisms are considerably greater within the build-up than away from it. Epifauna associated with Recent serpulid build-ups include stromatolites and other microbial deposits, encrusting bryozoans, byssate bivalves, grazing gastropods and, less commonly, boring sponges and endolithic algae, as well as predatory echinoids, starfish, crabs and fish (cf. Mastrangelo and Passed 1975; Bosence 1979; Haines and Mauer 1980a, 19806; Kirkwood and Burton 1988; Rasmussen et al. 1993; ten Hove and van den Hurk 1993). Of the 54 infaunal invertebrate species living amongst the serpulid tubes in Delaware Bay, the most abundant are soft-bodied suspension feeders and deposit feeders that burrow into the intertube sediment, build their own tubes and/or inhabit empty serpulid tubes (Haines and Mauer 19806). STEELE-PETROVICH AND BOLTON: ORDOVICIAN POLYCHAETE 141 There is little information on the community structures of tubicolous worm build-ups in either the Cenozoic or the Mesozoic. Diversity was high in both a serpulid build-up and a vermetid-algal reef of Miocene age (Pisera 1985; Friebe 1994). Low diversities in the only known Jurassic serpulid structures that are in situ (Johnson and McKerrow 1995) could reflect either the evolved complexity of tube communities of that age or the high-stress environmental conditions under which they had developed. However, a low-diversity epifauna, mainly of brachiopods, that was associated with serpulid build-ups that formed below storm-wave base in sediments near the Triassic-Jurassic boundary (Braga and Lopez-Lopez 1989) must represent the true development of intertube diversity associated with build-ups of calcareous tubes at that time. Faunal diversities and abundances associated with the Ordovician build-ups of Tymbochoos Sinclair i are very low. Although these build-ups developed in environments that were affected by adverse conditions, there is no difference between the flora/fauna associated with the long, densely packed tubes representing optimal growth and those associated with poorer growth. The presence of gastropods and byssally attached bivalves in the surrounding sediments indicates that conditions were satisfactory, at least at times, for other fauna. Therefore, this low-diversity fossil community probably represents the true complexity of mid Ordovician communities that are associated with calcareous tube-building organisms, and indicates that tubicolous build-ups had scarcely been exploited as a refuge during the mid Ordovician. In particular, relatively constant burrow diameters suggest that the diversity of intertube burrowers was low ; there was no encrusting growth on the worm tubes, in spite of the presence of encrusting bryozoans in other mid Ordovician settings ; no organisms had bored into the tubes, although the boring of shells occurred elsewhere at this time ; byssate bivalves, although associated with the build-ups, did not live amongst the tubes, as they do amongst Recent tubes. Other Palaeozoic tube-dominated build-ups, such as the Cambrian Scolithus build-ups (Goodwin and Anderson 1974) and the Carboniferous vermetid build-ups (cf. Burchette and Riding 1977; Wright and Wright 1981), show the same pattern of associated low-diversity communities. Because build-ups that were formed by different kinds of tube-forming organisms throughout the Phanerozoic occupied many of the same environments, the exploitation of intertube space probably intensified in the different kinds of structures at about the same time. The scanty fossil record suggests that a significant increase in faunal diversities and abundances associated with tube build- ups occurred between the Jurassic and the Miocene. Considering the enormous overall increase in invertebrate diversity at the end of the Cretaceous (e.g. Sepkoski et al. 1981), it is reasonable to suggest that the extensive exploitation of intertube space began at that time. SUMMARY 1 . Build-ups of calcareous tubes, previously unknown in rocks older than Devonian, occur in mid Ordovician carbonates of the Ottawa Valley, Canada. 2. The tubes of Tymbochoos sinclairi (Okulitch) are circular in cross section and expand quickly to adult diameter (0-95—1-30 mm); irregularly spaced concentric constrictions develop in places into thin anteriorly directed internal collars ; growth succeeding the collars began outside and below the collars and subsequently enclosed the collar region. 3. Clumps of tubes formed when the tubes grew sub-horizontally and radially out from small firm attachment areas and then turned and grew vertically. 4. T. sinclairi produced dune-shaped structures and smaller isolated pillow-shaped structures. 5. Deteriorating environmental conditions resulted in microbial growths and weak tube development. 6. The build-ups generally formed on oolites, either in intertidal channels or on shallow subtidal shoals. 7. T. sinclairi was probably a primitive polychaete that braced itself against the constrictions and collars of the inner tube surface with the setae-bearing parapodia of each segment, and fed with a series of short tentacles that protruded through the tube opening. 142 PALAEONTOLOGY, VOLUME 41 8. Predation and competition pressures on T. sinclairi were low. 9. Only a few other species lived in association with T. sinclairi build-ups, in contrast with the high- diversity communities of refuge-seeking species that live amongst the tubes in Recent calcareous- tube build-ups. The large increase in intertube diversity probably occurred at the end of the Cretaceous. SYSTEMATIC PALAEONTOLOGY The figured material is housed in the National Type Collection of Invertebrate and Plant Fossils at the Geological Survey of Canada (GSC), Ottawa. Genus tymbochoos gen. nov. Derivation of name. From the Greek tymbokd’ds (= mound builder). Type species. Tymbochoos sinclairi (Okulitch, 1937). Diagnosis. Small calcareous tubes, circular in cross section, expanding quickly from the base to a mature diameter just greater than one millimetre, then growing as straight to slightly sinuous cylinders. Tubes with concentric constrictions, semi-regularly spaced, resulting in corrugated walls. Constrictions extending in places into narrow, anteriorly directed internal collars. Tube growth beyond the collar beginning below the collar on the outside of the tube, and enclosing the collar region. Exterior surface marked rarely by fine longitudinal ridges. Tubes occurring singly or, more typically, in clumps with tubes radiating sub-horizontally from small attachment areas and then growing vertically. Tymbochoos sinclairi (Okulitch, 1937) Text-figures 4, 6-1 1 1937 Fletcheria sinclairi Okulitch p. 315, pi. 1, figs 5-7, Text-fig. la-c. 1948 Fletcheria sinclairi Okulitch; Wilson, p. 43, pi. 21, figs 4-5. Types. Holotype, Royal Ontario Museum, Toronto, P6871; paratype, ROM P6870; hypotypes, Geological Survey of Canada 115517-115528 Description. Clustered tubes radiating sub-horizontally from small attachment areas and then projecting vertically (Text-figs 4b, 8a, 9a-b, 1 1a, c). Tubes circular in cross section (Text-figs 8b, 1 1b, d) with diameters increasing quickly from about 0T2 mm to a maximum of 1-50 mm (usually 0-95-T30 mm); subsequent tube growth as straight to slightly sinuous cylinders (Text-figs 4b-c, 8a, 9a-b, 11a, c). Wall thickness varying greatly, probably due to diagenesis. Semi-regularly spaced concentric constrictions common and resulting in corrugated inner and outer walls (Text-figs 4c, 8a, 9a-b, 1 1a, c). In places these constrictions developing into thin, anteriorly directed, internal collars that result from inward growth of the leading edge of the shell; succeeding growth beginning on the outside of the tube below the collar and subsequently enclosing the collar region (Text-fig. 1 lc). Exterior sculpturing varying: most tubes unridged, but about 20 fine longitudinal ridges occurring on others (Text-figs 4c, 11b). Growth forms including (1) dense concentrations of clumps with densely packed vertical to sub-vertical tubes (up to 0-4 m long) (Text-figs 4b, 8a), occurring only in dune- shaped structures (Text-fig. 4a, 6) ; (2) sparser concentrations of clumps with loosely packed vertical to sub- vertical tubes (a few mm long) (Text-figs 9a-b, 10-11), occurring in isolated pillow-shaped structures (Text- fig. 7); (3) isolated tube clumps on certain bedding planes. Remarks. Okulitch (1937) related this species to the Chazyan tabulate coral Fletcheria [Eofletcheria] incerta (Billings) from the mid Ordovician (Chazyan) Mingan Formation of the Mingan Islands, Quebec, and assigned it to a new species, Fletcheria sinclairi , on the basis of different tube growth, smaller tube diameter, lack of septa and tabulae, a markedly rugose exterior, and rejuvenescence (i.e. a new start after growth of a collar). Bassler (1950, p. 266) noted similar STEELE-PETROVICH AND BOLTON: ORDOVICIAN POLYCHAETE 143 corrugated walls in the tubicolous annelids Conchiolites and Cornulites. The present study confirms that this species is not a coral, but a calcareous tube, probably of a primitive polychaete. It is here assigned to a new genus Tymbochoos. Occurrence. G. W. Sinclair (pers. comm. 1970) collected the type specimens from the Pembroke Quarry (Text-fig. 1) (see Goudge 1938, p. 162). Kay (1942) reported 4-3 m of Lowville Beds in this quarry. According to C. R. Barnes (pers. comm. 1995), the quarry in 1966 contained 2 0 m of Pamelia Beds overlain by 4-2 m of Lowville beds. In 1970, B. A. Liberty and T. E. Bolton noted this species in the upper exposed Lowville beds of the quarry. Previous publications report F. Sinclair i from probable late Chazyan rocks in the vicinity of Pembroke (Okulitch 1937 ; Bassler 1950, p. 266), the Pamelia Beds near Ottawa (Okulitch 1937) and the Pamelia Beds on Highway 17 about 10 km south of Pembroke (Wilson 1948). Specimens studied here are from the Pamelia Beds near L’Orignal and Dunrobin and Lowville Beds at Braeside (Text-fig. 2). Acknowledgements. We thank H. A. ten Hove for helpful comments on a previous version of the manuscript, R. Petrovich for various kinds of assistance, G. Martin (Geological Survey of Canada, Ottawa) for thin section preparation, R. J. 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MIRIAM STEELE-PETROVICH Department of Geosciences University of Tulsa Tulsa, Oklahoma, USA 74104 THOMAS E. BOLTON Typescript received 4 June 1996 Revised typescript received 9 April 1997 Geological Survey of Canada 601 Booth St Ottawa, Ontario, Canada K1A 0E8 THE EARLIEST KNOWN PIG FROM THE UPPER EOCENE OF THAILAND by S. DUCROCQ, Y. CHAIM ANEE, V. SUTEETHORN and J.-J. JAEGER Abstract. Several dental remains of a new suid, Siamochoerus banmarkensis gen. et sp. nov., have been collected in the Late Eocene Krabi basin in southern Thailand. This species is morphologically close to but more primitive than Dubiotherium waterhousi (formerly Palaeochoerus waterhousi ), and represents one of the oldest known suids. The date of origination of suids can therefore be placed back to the Late Eocene or even earlier, and the early evolution and diversification of the family might have occurred largely in the Oligocene of Asia. Pigs are artiodactyls belonging to the family Suidae, characterized by their ubiquity and ability to radiate rapidly in new territories. For these reasons, suids are considered to be useful for intercontinental as well as local and regional biostratigraphy. The palaeontological history of the family Suidae is well documented in the Miocene and afterwards (Pickford 1988, 1993), but the fossil record and the evolutionary history of suids and their close relatives the tayassuids is almost unknown during the Paleogene of the Old and New worlds. According to the recent work of Pickford (1993), only two tayassuids (the peccaries Palaeochoerus and Doliochoerus) and one suid (. Hyotherium ) occur in Paleogene deposits of the Old World. The earliest known true suid is Hyotherium from the Upper Oligocene of Europe (Pickford 1993). Hyotherium belongs to the subfamily Hyotheriinae which is considered to be the ancestral group that gave rise to further subfamilies of pigs. However, the major evolution and diversification of suids occurred during the Neogene in the Old World, with over 30 genera recognized. Suidae evolved in a rather different way than Tayassuidae and are distinguished by limb structure (four toes on both front and hind limbs and unfused third and fourth metatarsals) and dentition (for example, suids possess outwardly and upwardly curved upper canines; see for example Nowak and Paradiso 1984). The Late Eocene Krabi Basin in southern Thailand (Text-fig. 1) has yielded a rich and diverse mammalian fauna including a dermopteran, a megabat, primates, carnivores, rodents, a tayassuid, anthracotheres, ruminants, a tapir and a rhino (Ducrocq et al. 1995, 1996; Chaimanee et al. 1997). Holroyd and Ciochon (1994) have dated the Krabi basin as late Mid Eocene, and of similar age to the locality of Pondaung, Burma, because of similarities between the anthracothere associations at both sites. However, they based their work on information from Ducrocq et al. (1992) that has since been updated. The anthracotheres from Krabi are somewhat more derived than those from Pondaung, and morphologically closer to forms described from the basal Oligocene of Europe (Monteviale, Italy) and China (Ducrocq 1993, 1994a). In addition, the recently described anthropoid primate Siamopithecus eocaenus Chaimanee, Jaeger, Suteethorn and Ducrocq, 1997, displays strong similarities to Pondaungia cotteri from Pondaung, but shows somewhat more derived dental features compared to those of the Burmese species. We therefore conclude that the Krabi fauna is more probably Late Eocene in age rather than older. Dental remains of a small artiodactyl have been collected from the Late Eocene Bang Mark pit at the Krabi mine in southern Thailand. The morphology and structure of these fossils allow them to be attributed to a suid and they are placed in a new genus and species. This new form from Thailand further illustrates the early differentiation of Suidae in South-east Asia. [Palaeontology, Vol. 41, Part 1, 1998, pp. 147-1561 © The Palaeontological Association 148 PALAEONTOLOGY, VOLUME 41 text-fig. 1. Map of Thailand showing location of the Krabi Basin fossil site. The mine that yielded the specimens of S. banmarkensis reported here, is represented by the letter F. SYSTEMATIC PALAEONTOLOGY Order artiodactyla Owen, 1848 Family suidae Gray, 1821 Genus siamochoerus gen. nov. Derivation of name. From Siam (former name of Thailand), and from ‘ choerus' , the Greek for pig. Type species. Siamochoerus banmarkensis sp. nov. Diagnosis. As for species. Siamochoerus banmarkensis gen. et sp. nov. Text-figures 2-4 Derivation of name. From Bang Ban Mark, the type locality. Holotype. A left lower jaw with P4-M3; Specimen No. TF 2905 (Text-figs 2-3), Collections of the Department of Mineral Resources, Bangkok. Additional material. All from Bang Ban Mark: isolated left P3 (TF 2963; Text-fig. 4a-b); isolated left M3 (TF 2906); and fragmentary left maxillary with damaged MJ-M3 (TF 2907; Text-fig. 4c). Type locality. Lignite mine. Bang Ban Mark pit, Krabi basin, southern Thailand (latitude : between 7° 54' 49" N and 8° 12' 16" N; longitude; between 98° 11' 35" E and 99° 8' 35" E). Horizon. Upper level of the main lignite seam of Bang Ban Mark pit (Formation B2, see Bristow 1991). The mammalian fauna associated with the suid remains is identical to that from Wai Lek pit (which yielded most of the taxa known in Krabi) and Bang Mark pit, and faunal evidence indicates a Late Eocene age (see above and Ducrocq et al. 1995). DUCROCQ ET AL.\ EOCENE PIG 149 Table 1. Dental dimensions of Siamochoerus banmarkensis gen. et sp. nov. (in mm). Length Width (trig.) Width (tal.) TF 2963 Left P3 10-3 5-3 TF 2905 Left P4 9-4 6-4 — Left M1 10-9 7-9 7-6 Left M2 13-8 10-2 9-4 Left M3 18-7 10-5 8-4 TF 2907 Left M3 18-6 9-8 8-3 TF 2907 Left M2 12-5 — Left M3 13-7 14-6 text-fig. 2. Siamochoerus banmarkensis gen. et sp. nov. ; TF 2905; left lower jaw preserving P4-M3; Bang Ban Mark, south Thailand, a, labial, and b, lingual views. Scale bar represents 10 mm. Diagnosis. Primitive suid, close to Propalaeochoerus pusillus in size. P3 simple lacking a metaconid, P4 with small metaconid and hypoconid and lacking a paraconid. Lower molars show a marked increase in size from front to back, with the mesial lobe wider than distal lobe, a small hypoconulid and extremely weak accessory cusps. M3 elongated with two-cusped hypoconulid. Upper molars 150 PALAEONTOLOGY, VOLUME 41 C text-fig. 3. Siamochoerus banmarkensis gen. et sp. nov.; holotype, TF 2905; left lower dental row (P4-M3) ; Bang Ban Mark, south Thailand; Late Eocene a, labial, b, occlusal, and c, lingual views. Scale bars represent 1 mm. simple, lacking accessory cusps. M3 without distally salient talon. Enamel very finely wrinkled. Measurements given in Table 1. Description. The lower jaw is laterally crushed, so that it is not possible to know with certainty if the horizontal ramus was wide, as is generally the case in suids. However, the base of the mandible is broken and it can be supposed that it was relatively deep (Text-fig. 2). Three dental foramina occur on the mandible : one under the posterior root of P2, one under the posterior root of P3 and a third, which is also the smallest, under the anterior root of M4. On the lingual face of the mandible, the posterior end of the symphysis reaches P2. The isolated P3 and the fragmentary lower jaw very probably belong to the same individual on the basis of their state of preservation. P3 displays a sharp triangular shape, and is more distally curved than P4. There is no accessory cusp, and only a small depression runs lingually from the apex of the cusp to the base of the crown. The talonid is made of a weak elongation of the distal part of the tooth. A weak crest is present on the mesial and distal edges of the tooth (Text-fig. 4a-b). The morphology of P4 is typical of the ancestral condition in suids. It is triangular, somewhat posteriorly curved. It displays a main cusp (protoconid) and a very small lingual cusp (metaconid or ‘InnenhugeT according to Stehlin [1899, 1900]) situated on the distolingual edge of the main cusp, but slightly lower than it. The apices of these two cusps are joined by a very weak crest. A talonid is well developed and consists of a single labial cusp (hypoconid) connected with the apex of the protoconid by a straight crest. A very slight cingular spur of enamel occurs on the mesial side of the crown and might be interpreted as an incipient paraconid. A very weak crest runs up the mesial face of the premolar. The enamel is smooth and there is no cingulid (Text-fig. 3). DUCROCQ ET AL.\ EOCENE PIG text-fig. 4. Siamochoerus banmarkensis gen. et sp. nov. a-b, TF 2963; isolated left P3. a, labial and b, lingual views, c, TF 2907; left maxilla with crushed M1-3, occlusal view. Scale bars represent 1 mm. The Mj is an elongated tooth with four main cusps (protoconid, metaconid, hypoconid and entoconid), the mesial cusps being slightly higher than the distal ones. A small hypoconulid occurs on the distal side in a median position, and there are slight swellings of the enamel in the transverse valley and in the trigonid basin that might correspond to incipient accessory cusps. Weak transverse crests join the metaconid to the protoconid and the entoconid to the hypoconid. The middle of the lingual and labial faces of the molar is waisted, so that the anterior and posterior lobes are clearly distinct. A tiny cingulid only occurs on the mesial edge of Ml5 and the anterior lobe is slightly wider than the posterior lobe. M2 is similar to except in its larger size (Text-fig. 3). M3 displays the same structure as Mx and M2, but its width decreases from front to rear. This tooth also possesses a hypoconulid consisting of a large posterolabial cusp associated with a smaller lingual one. The third lobe is joined to the middle of the second lobe by a very low longitudinal crest. The two cusps that form the hypoconulid are separated by a shallow groove. The isolated left M3 does not differ from the M3 of the holotype. On all molars the trigonid is somewhat higher than the talonid part, and the system of grooves or ‘Furchenplan’ of von Hunermann (1968) is well expressed. The enamel of all the molars is very finely wrinkled, especially on the apices of cusps and on M3 (Text-fig. 3). Although they are badly crushed, the upper molars display a rather simple structure with four main cusps (paracone, metacone, protocone and hypocone) and no well-defined accessory cusps. The ‘Furchenplan’ is poorly expressed. The crests that join the different cusps are weak and low, and a cingulum occurs on the mesial and distal faces and between the paracone and the metacone on the labial face. The enamel is finely wrinkled and the roots of the molars are unfused (Text-fig. 4c). COMPARISONS Dental and mandibular features of suids include the transversely thick horizontal ramus of the mandible; a dental row that crosses over the body of the mandible from anterolabial to posterolingual ; a tendency for the lower canine to splay out laterally; lingual and labial flaring of 152 PALAEONTOLOGY, VOLUME 41 the molars; molars with four main cusps and anterior, median and posterior accessory cusps; scoring of the main cusps of the molars by three distinct grooves (= ‘Furchenplan’ of von Hunermann (1968); anterior and posterior cingula on the upper molars; strong elongation of M3 with a complex and polybunous talonid; and unfused molar roots. Other cranial features that characterize suids, although lacking in the Thai fossil material, are a basicranium in which the convex glenoid cavity is higher than the level of the occlusal plane of the cheek teeth, but lacking a postglenoid ‘stop’ and thus allowing lateral movement of the jaws (Pickford 1993). Several dental features allow us to suggest that Siamochoerus belongs not in Tayassuidae but in Suidae. Siamochoerus displays the association of laterally flared lower and upper molars, with incipient accessory cusps and a distinct ‘Furchenplan’, an elongated M3, with a complicated talonid part, and unfused molar roots. Moreover, although it displays a protoconid and a tiny metaconid the P4 trigonid of the Thai specimen is not fully developed and the two trigonid cusps are dissimilar in size. In addition, the P3 is about the same size as the P4 (whereas it is generally smaller in Tayassuidae), and is the simpler of the two, indicating that the anterior lower premolars (P4 and P2) were probably even less molarized. It is not possible to know whether the horizontal ramus of the mandible was thick laterally, because the bone was crushed during fossilization ; however, the unfused molar roots together with the lateral flare of the molars suggest that the mandible was thick. A major difficulty in the familial attribution of this specimen is that the classification of Suoidea differs from one author to another. Pickford (1988, 1993), for example, considered the genus Palaeochoerus to belong in Suidae, whilst Hellmund (1992) attributed it to Tayassuidae. Moreover, several taxa formerly referred to Tayassuidae have, after revisions, been shifted into Suidae. This is the case, for example, for Palaeochoerus waterhousii, now considered by Hellmund (1992) as a suid ( = Dubiotherium waterhousii) and for Odoichoerus uniconus from the Lower Oligocene of China (Tong and Zhao 1986) which Ducrocq (19946) referred to Suidae. As these points of view are not shared by different authors, we think it is better to begin by comparing Siamochoerus with different early suoid taxa, including members of Tayassuidae and Suidae. Tayassuidae As the basic topological morphology of the molars is rather constant throughout the family Suidae (Pickford 1988), the lower premolars of Siamochoerus are a valuable element that allow the Thai species to be compared with other known suoid taxa. The fourth premolar of Siamochoerus differs markedly from that of members of the Doliochoerinae (a tayassuid subfamily), described by Ginsburg (1974, p. 60), in its distolingually situated with respect to the main cusp (protoconid), accessory cusp or ‘Innenhugel’ (metaconid), its labially displaced and unique posterior cusp (hypoconid), its much less developed paraconid, and in its lower crest connecting the hypoconid and the protoconid. Also, the P3 of Siamochoerus displays a posterior crest running from the protoconid down to the distal base of the crown which, unlike the condition in tayassuids, is not divided into small cusplets. The oldest known European suoids are the genera Propalaeochoerus and Doliochoerus from the Lower Oligocene of Europe (Ginsburg 1974; Hellmund 1992). Both these genera differ from Siamochoerus in that P3 has a higher and better developed distal crest, P4 is much more molarized and the upper and lower molars have better developed accessory cusps and crests. Doliochoerus quercyi differs from Siamochoerus further in its shorter and more massive M3, better developed cingula on the upper molars and stronger talon on M3. Palaeochoerus (a tayassuid known from the beginning of the Oligocene, according to Ginsburg (1974) and Pickford (1993), but considered as a suid by Hellmund (1992)) also differs from the Thai species in its distolingually to mesiolingually elongated upper molars, its much stronger cingula, its better developed preprotocrista, and its less bulbous lower molars and more molarized P4. Odoichoerus uniconus was described as a tayassuid from the Lower Oligocene of China by Tong and Zhao (1986). Recently, Ducrocq (19946), suggested that, on the basis of its dental morphology, DUCROCQ ET AL.\ EOCENE PIG 153 this Chinese species probably belongs to Suidae rather than to Tayassuidae. Therefore, it seems that Odoichoerus might be one of the earliest known representatives of the family Suidae. This genus differs from Siamochoerus in its smaller size, its shallower mandibular ramus, a much smaller hypoconulid on M3 and sharper and simpler P4 without accessory cusps, but with a higher distal crest. Tong and Zhao (1986) further compared Odoichoerus to the tayassuids Taucanamo and Albanohyus (the latter being considered a synonym of Taucanamo by Pickford (1993)) in which P4 is simpler than in other tayassuid taxa. Taucanamo is known from the Miocene of Europe (Thenius 1956) and Turkey (Pickford 1979, 1993). The P4 of Siamochoerus is similar to that figured by Pickford (1979, fig. 6) and attributed to cf. Taucanamo from Turkey. However, the Turkish premolar differs from that of the Thai species in its larger size, the greater lingual development of the metaconid, which is more mesially situated, and in its better developed mesial and distal cingulids. In addition, the lower molars associated with cf. Taucanamo are less elongated, less waisted labially and more massive than those of Siamochoerus. The latter is about the size of T. sansaniense, but differs from it in its more elongated M3, its smaller hypoconulid and in its weaker accessory cusps. Siamochoerus is also distinguished from T. pygmaeum by its shorter P3 without cingulid, M4 is much smaller than M2, the system of grooves (‘Furchenplan’) is poorly expressed and the upper molars are squared, not elongate, and have very weak accessory cusps. The tayassuid Egatochoerus jaegeri from the Krabi Basin, south Thailand (Ducrocq 19946) is very different from Siamochoerus. Both taxa differ in their size and in their upper and lower premolar and molar structure and morphology. Given their distinct tooth morphology, Tayassuidae and Suidae seem therefore to have diverged before the Late Eocene. Suidae In his revision of the Oligocene suoids from western Europe, Hellmund (1992) erected the new genus Dubiotherium for the Late Oligocene Palaeochoerus waterhousi, and placed it in Suidae. Dubiotherium and Siamochoerus are similar in overall morphology, but can be distinguished by several features : Siamochoerus is somewhat smaller ; the mesial face of its P3 is convex ; its P4 exhibits a more reduced metaconid and a shallower and weaker crest connecting the protoconid and the hypoconid ; the lower molars lack the enamel cuspules on their distal cingulid, and the M3 is more slender distally. According to Pickford (1993, p. 242), it is not clear whether early suid-like fossils from Asia attributed to the genus Propalaeochoerus are suids or tayassuids. Pickford (1993) further argued that the European forms of this genus, considered to belong in Hyotheriinae, might be the ancestral group for other subfamilies of pigs. The only hyotheriid known in the Paleogene (Upper Oligocene in Europe and the Indian subcontinent) is Hyotherium. However, Siamochoerus differs markedly from Hyotherium in its narrower P3_4 with much less developed trigonid and talonid, without mesial and distal cingulid, its slender lower molars that lack well developed accessory cusps and labial cingulid, its shorter upper molars with a stronger increase in size from front to back, the absence of mesial and medial distinct accessory cusps, and the absence of a distal expansion of the M3 talon. Other Eurasian suid genera (e.g. the Miocene Aureliachoerus and Listriodon ) are too specialized to be related, at least from a morphological point of view, to the Thai species. They differ from Siamochoerus in the same features that distinguish Hyotherium , and Listriodon also exhibits lophodont cheek teeth. Among other primitive artiodactyls, the genus Cebochoerus from the Middle-Upper Eocene of western Europe has previously been suggested as a possible ancestor to the Suidae (Pearson 1927). This hypothesis is now abandoned (Hellmund 1992). The lower molars of the European genus display few similarities to those of Siamochoerus (bunodont cusps, bulbous labial tooth walls, and faint mesial cingulid). However, Cebochoerus differs from Siamochoerus in its more elongated and massive lower premolars with better developed mesial and distal cusps, its shorter, lower M3 with more simple third lobe, and in details of the upper molars which have external cusps joined by a crest and more selenodont internal cusps. 154 PALAEONTOLOGY, VOLUME 41 DISCUSSION In its overall morphology, the dental material of Siamochoerus banmarkensis is more similar to that of Dubiotherium than to other European species, although the Thai species is obviously more primitive. The structurally simple lower molars and the elongated M3 with relatively simple hypoconulid are found in both European and Thai genera. Indeed, the lower molars of the suid Dubiotherium waterhousi (from the MP 26 European level ( = late Early Oligocene)) are similar to those of Siamochoerus in the relative height of the mesial and distal cusps, the lack of well defined accessory cuspules, the salient distal hypoconulid on M4_2 (called the enamel knob or ‘ Schmelzknospe ’ by Hellmund (1992, p. 25)), and the absence of an accessory cusp between the second and third lobe on M3, which also has a two-cusped hyopoconulid lobe. In addition, P4 in Dubiotherium and Siamochoerus has a crest that connects the apex of the protoconid and the mesiolingual corner of the tooth, and lacks a distinct paraconid and entoconid. P3 is also very simple in both genera, with a very short talonid and lacks the incipient metaconid. No upper molars are attributed to Dubiotherium ; thus a comparison of these teeth is not possible. However, the posterior lower premolars are more derived in Dubiotherium, reflecting the separation of Tayassuidae and Suidae before these families invaded Europe. The Thai species might be related to the previously described Odoichoerus uniconus from the Lower Oligocene of China (Tong and Zhao 1986). Indeed, the Early Oligocene age attributed to the Chinese species does not contradict such an hypothesis since it has recently been suggested that most Chinese fossiliferous localities might be older than currently considered (Ducrocq 1993). In addition, the sparse mammal fauna associated with Odoichoerus (cf. Anthracokeryx sp., Heothema sp., cf. Indomeryx sp., and Guixial sp.) seems to indicate a Late Eocene rather than an Early Oligocene age (it should also be noted that the genus Heothema is synonymized with Anthracotherium by Ducrocq 1992, in press). Odoichoerus displays lower molars with four main cusps and slight swellings of the enamel in the transverse valleys which might be regarded as incipient accessory cusps. These structures are better developed in Siamochoerus and Dubiotherium, and fully developed in Hyotherium. In addition, the M3 hypoconulid lobe of Odoichoerus is very small, but exhibits three distinct cusplets that might foreshadow further complexity of this structure, as seen in Siamochoerus and Dubiotherium. The labial flare of the lower molars observed in Siamochoerus also occurs in Odoichoerus, and M1 is markedly smaller than M2 (Mx is 20-26 per cent, shorter than M2) in both these taxa and Dubiotherium. In addition, the P4 of Odoichoerus does not display the lingual cusp (metaconid) as in Siamochoerus, but exhibits a sharp and high crest that runs from the apex of the protoconid down to the distal end of the crown. The distal half of the crest shows two weak cusplets reminiscent of the P4 of Hyotherium rather than that of Siamochoerus. Nevertheless, Odoichoerus might represent an ancestor to Siamochoerus because of its smaller size and the more primitive morphology of P4 and the lower molars. These observations and the known fossil record suggest that suids had appeared by the Late Eocene in Asia and then colonized Europe in the Early Oligocene. This is contrary to the opinion of Pickford (1993) who suggested that the earliest known suids are from the Upper Oligocene of Europe. Moreover, if suids originated from Tayassuidae, as Pickford suggested (1993, p. 242), the splitting probably occurred during the Late Eocene or even earlier, because the oldest known tayassuid ( Egatochoerus jaegeri ) so far described was found in the Upper Eocene of Thailand (Ducrocq 1994). This species already displays characteristic tayassuid features, such as the vertical lower canine without labial symphyseal splaying, the strongly developed trigonid of P4 and the poorly expressed ‘ Furchenplan ’ on the molars, and thus suggests that the tayassuid pattern was achieved by the early or mid Late Eocene. The difficulty of distinguishing between early tayassuid and suid dental morphologies, together with the poorly documented fossil record of Asian Oligocene mammal localities, has long obscured our knowledge of the earliest representatives of suoids. In addition, our incomplete understanding of suoid systematics renders their use for biostratigraphical purposes and stratigraphical inferences somewhat doubtful. These apparent deficiencies in the fossil record and related biostratigraphy clearly demand further investigation of the Paleogene mammal localities of Asia. DUCROCQ ET AL.: EOCENE PIG 155 CONCLUSIONS At present, the Krabi mammal fauna contains the most primitive known Eurasian tayassuid {Egatochoerus jaegeri Ducrocq, 1994), but, it must be stressed that, because of the well-differentiated structure of its teeth, this form cannot represent the stem-taxon of both tayassuids and suids. In the same way, Siamochoerus banmarkensis gen. et sp. nov. from the Upper Eocene of Thailand is a true suid that displays affinities with European Dubiotherium and the Chinese Odoichoerus. These new finds suggest that the origin of suoids might have occurred earlier than previously thought : obviously by the Late Eocene and perhaps even earlier. The as yet unknown common ancestor of Suidae and TTayassuidae probably emerged in southern Asia, and should be searched for in deposits older than those that yielded Egatochoerus and Siamochoerus. Acknowledgements. Work in Thailand was supported by the Mission Paleontologique Franchise en Thailande (Ministere des Affaires Etrangeres). This study was conducted in part during an Alexander von Humboldt Fellowship (S. Ducrocq) at the Staatliches Museum fur Naturkunde, Stuttgart, Germany. Drawings are by L. Meslin (Montpellier). This is publication ISEM 97-083, CNRS. REFERENCES bristow, c. s. 1991. Sedimentology of the Tertiary Krabi basin, Thailand. Seventh Regional Conference on Geology, Mineral and Energy Resources of Southeast Asia ( GEOSEA VII), Bangkok, 5-8 November 1991, 22-23. chaimanee, y., jaeger, J.-J., suteethorn, v. and ducrocq, s. 1997. A new Late Eocene anthropoid primate from Thailand. Nature , 385, 429^43 1 . ducrocq, s. 1992. Etude biochronologique des bassins continentaux tertiaires du Sud-Est asiatique: contribution des faunes de mammiferes. Unpublished Ph.D. thesis, University of Montpellier II, France. — 1993. 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Journal of Southeast Asian Earth Sciences, 12, 65-78. — 1996. An unusual anthracotheriid artiodactyl from the Late Eocene of Thailand. Neues Jahrbuch fur Geologie und Palaontologie, Monatshefte, 7, 389-398. ginsburg, L. 1974. Les Tayassuidae des Phosphorites du Quercy. Palaeovertebrata, 6, 55-85. gray, j. e. 1821. On the natural arrangement of vertebrate animals. London Medical Repository, 15, 296-310. hellmund, m. 1992. Schweineartige (Suina, Artiodactyla, Mammalia) aus oligomiozanen Fundstellen Deutschlands, der Schweiz und Frankreichs. II. Revision von Palaeochoerus Pomel 1847 und Propalaeo- choerus Stehlin 1899 (Tayassuidae). Stuttgarter Beitrage zur Naturkunde, Reihe B, 189, 1-75. holroyd, p. a. and ciochon, r. l. 1994. Relative ages of Eocene primate-bearing deposits of Asia. 123-141. In fleagle, j. G. and kay, R. F. (eds). Anthropoid origins. Plenum Press, New York, 698 pp. hunermann, k. a. von 1968. Die Suidae (Mammalia, Artiodactyla) aus den Dinotheriensanden (Unterpliozan = Pons) Rheinhessens (Siidwestdeutschland). Schweizerische Palaontologische Abhandlungen, 86, 1-96. nowak, r. m. and paradiso, J. L. 1984. Walker's mammals of the world. 4th Edition. The Johns Hopkins University Press, Baltimore, 1362 pp. owen, r. 1848. Description of teeth and portions of jaws of two extinct anthracotherioid quadrupeds ( Hyopotamus vectianus and Ho. bovinus) discovered by the Marchioness of Hastings in the Eocene deposits on the N. W. coast of the Isle of Wight: with an attempt to develop Cuvier’s idea of the classification of pachyderms by the number of their toes. Quarterly Journal of the Geological Society, London, 4, 103-141. 156 PALAEONTOLOGY, VOLUME 41 pearson, h. s. 1927. On the skulls of early Tertiary Suidae, together with an account of the otic region in some other primitive Artiodactyla. Philosophical Transactions of the Royal Society of London, Series B, 215, 389-460. pickford, M. 1979. Suidae and Tayassuidae from Turkey. Bulletin of the Geological Society of Turkey, 22, 141-154. — 1988. Revision of the Miocene Suidae of the Indian Subcontinent. Miinchner Geowissenschaftliche Abhandlungen, Geologie und Palaontologie, Reihe A, 12, 1-91. — 1993. Old World suoid systematics, phylogeny, biogeography and biostratigraphy. Paleontologia i Evolucio, 26-27, 237-269. stehlin, H. G. 1899. Uber die Geschichte des Suidengebisses. Erster Theil. Abhandlungen der Schweizerischen palaontologischen Gesellschaft, 26, 1-336. — 1990. Uber die Geschichte des Suidengebisses. Zweiter Theil. Abhandlungen der Schweizerischen palaontologischen Gesellschaft, 27, 337—527. thenius, E. 1956. Die Suiden und Tayassuiden des steirischen Tertiars. Sitzungsberichten der Akademie der Wissenschaften ( Mathematik-Naturwissenschaft Abteilung I), 4-5, 337-382. tong yongsheng and zhao zhongru 1986. Odoichoerus, a new suoid (Artiodactyla, Mammalia) from the early Tertiary of Guangxi. Vertebrata PalAsiatica, 24, 136-138. stephane ducrocq JEAN- JACQUES JAEGER ISEM, UMR 5554, C.N.R.S. Case 064, Universite Montpellier II Place E. Bataillon, F-34095 Montpellier cedex 5, France e-mail ducrocq@isem.univ-montp2.fr e-mail jaeger@isem.univ-montp2.fr YAOWALAK CHAIMANEE VARAVUDH SUTEETHORN Paleontological Section Geological Survey Department of Mineral Resources Typescript received 29 April 1996 Rama VI Road, Bangkok 10400 Revised typescript received 5 April 1997 Thailand EARLY SILURIAN SINACANTHS (CHONDRICHTHYES) FROM CHINA by ZHU MIN Abstract. Histological study of new specimens of sinacanth fin spines from the Lower Silurian of the north- western margin of the Tarim Basin (Xinjiang, China) shows that they have the same histology as the fin spines of chondrichthyans. On this basis it is argued that sinacanths are one of the oldest known chondrichthyans, rather than acanthodians, and their spines are the oldest known shark fin spines. Previous studies on sinacanths are critically reviewed. The family Sinacanthidae is erected to include Sinacanthus and its relatives with more than 15 fin spine ridges per side. It is suggested that Sinacanthus fancunensis is synonymous with S. wuchangensis. A new sinacanth genus and species, Tarimacanthus bachuensis , from the Lower Silurian of Tarim and South China, is erected. The sinacanths are a middle Palaeozoic fish group, exemplified by Sinacanthus wuchangensis which was erected by P’an (1959, 1964) for isolated fin spines from the Guodingshan Formation (Silurian: Wenlock) of Wuhan, China (Text-fig. 1), and referred originally to Acanthodidae. Liu (1973) reported Sinacanthus in Ningguo, Anhui, China (Text-fig. 1). Since then, large numbers of sinacanth specimens, all of Silurian age, have been found in eight provinces of South China (P’an et al. 1975; Li 1980; Pan 1986a, 19866; Zeng 1988; Text-fig. 1). They are a key element of the endemic Silurian vertebrate fauna of South China, and have also been significant in regional stratigraphical correlation (Pan 19866). Turner (1986) assigned to ‘cf. Sinacanthus' some fin spines from the Lower Devonian of Australia, previously reported by Chapman (1917) and Talent and Spencer-Jones (1963). She indicated some doubt as to their acanthodian affinity, and suggested that they may have belonged to a shark akin to Antarctilamna Young, 1982. At the same time, fin spines from the Upper Silurian-Middle Devonian of Bolivia were considered to resemble Sinacanthus (Janvier and Suarez- Riglos 1986; Gagnier et al. 1988), and Gagnier et al. (1988) erected Sinacanthus boliviensis. Gagnier et al. (1988) placed Sinacanthus in Acanthodii (order and family undetermined), but suggested that Sinacanthus might be a chondrichthyan rather than an acanthodian. Because all of the fin spines were disarticulated and preserved mainly as external or internal moulds, there was no sound evidence to distinguish them from either chondrichthyans or acanthodians, and the systematic position of Sinacanthus and related forms remained unclear. In a recent study, Liu (1995, footnote on p. 94) doubted the presence of Sinacanthus in Australia and Bolivia, and returned to the traditional classification of sinacanths as acanthodians. I have had the opportunity to examine the Bolivian fin spines, currently housed in Paris (Museum National d’Histoire Naturelle), and am able to confirm that both sinacanths and acanthodians are present in Bolivia. As to sinacanths in Australia, I follow Turner’s (1986) proposal, based on the material illustrated by Talent and Spencer-Jones (1963) which shows similarities to the Chinese sinacanths. The sinacanth material reported in this study was collected from the Silurian of the north-western margin of the Tarim Basin in 1992 by the author and his colleagues (Wang Junqing and Liu Shifan; Text-fig. 1, localities 11 and 12). Abundant fin spines, some galeaspids and large numbers of vertebrate microremains including dermal scale-units of galeaspids and scales of chondrichthyans indicate a diverse vertebrate fauna similar to the Llandovery-Wenlock vertebrate fauna of South China. This fauna was first reported from Tarim by Wang et al. (1988), and further investigated by [Palaeontology, Vol. 41, Part 1, 1998, pp. 157-171, 1 pi.) © The Palaeontological Association 158 PALAEONTOLOGY, VOLUME 41 text-fig. 1. Sincanth localities in China. Dotted lines represent province boundaries. 1, Nanjing and Wuxi, Jiangsu; 2, Ningguo, Anhui, and Changxing, Zhejiang; 3, Chaoxian, Anhui; 4, Jingshan, Hubei; 5, Wuhan, Hubei; 6, Ruichang, Jiangxi; 7, Lixian, Hunan; 8, Dayong, Hunan; 9, Xiushan, Sichuan; 10, Kaili, Guizhou; 11, Kalpin, Xinjiang; 12, Bachu, Xinjiang. Liu (1995) and Wang et al. (1996). The discovery of sinacanths in Tarim supports other evidence for biogeographical affinity between the South China and Tarim blocks in the Silurian (Liu 1993, 1995 ; Wang et al. 1996). The new sinacanth spines can be used to determine the systematic position of this group because, although disarticulated, like those from South China, they are composed of well preserved hard tissues and are suitable for histological research. Resolution of the debatable systematic position of sinacanths, using histological details, will also help to classify the various fin spine species. In South China, five species (P’an 1959, 1964; Liu 1973; P’an et al. 1975), as well as several unnamed forms (Zeng 1988), have been referred to sinacanths. However, different types of fin spine found in the same bed, such as Sinacanthus wuchangensis and S. triangulatus, might represent different taxa if they are chondrichthyans, or may be better regarded as from the same fish if they are acanthodians. For this reason, the systematic revision of the sinacanths given below follows the discussion of the systematic affinity of sinacanths. Institutional abbreviations. GM.V (Geological Museum of China, Beijing); HV (Regional Geological Surveying Team, Bureau of Geology and Mineral Resources of Hunan Province, Xiangtan); IVPP.V (Institute of Vertebrate Paleontology and Paleoanthropology, Beijing) ; VF (Institute of Geology, Chinese Academy of Geological Sciences, Beijing). ZHU: EARLY SILURIAN SINACANTHS 159 HISTORICAL REVIEW OF STUDIES OF SINACANTH Sinacanthus was erected by P’an (1959), with one species (. ’ magnus group are here assigned to Neodiplograptus , whilst those of the 1 D. ’ modestus group are tentatively assigned to ‘ Neodiplograptus ’ as discussed below. Riva (1988, in Riva and Ketner 1989) considered Climacograptus tubuliferus and some allied species to belong to Normalograptus. Several partial relief specimens illustrated by Williams and Bruton (1983, fig. 15a, n), however, clearly show that thl2 has an initial downward direction in its growth, a feature not seen in Pattern H taxa. The specimen illustrated by Riva (1988, fig. 2j) shows a particularly wide descending protheca l1. This morphology is typical of Pattern D species of Climacograptus ( sensu Mitchell 1987), especially C. caudatus, a species designated as the type species of Ensigraptus by Riva (in Riva and Ketner 1989). From these illustrations, and from material acquired by Mitchell (pers. comm., 1992) it seems most likely that C. tubuliferus and its allies such as C. putillus (Hall, 1865) and C. nevadensis Carter, 1972 are not species of Normalograptus , but rather species of Climacograptus (e.g. Mitchell 1987) or Ensigraptus. All of the above species show a more rounded profile in the proximal end and less exposure of the sicula below thl1 than is typical of Normalograptus. Genus pseudoglyptograptus Bulman and Rickards, 1968, emend. Type species. Glyptograptus ( Pseudoglyptograptus ) vas Bulman and Rickards, 1968. Emended diagnosis. Pattern H species similar to Normalograptus but with gently sigmoidal thecae, apertural margins commonly undulate. Species included. Pseudoglyptograptus vas Bulman and Rickards, 1968, P. cf. vas (Melchin 1989), P. barriei Zalasiewicz and Tunnicliff, 1994 (= P. n. sp. Melchin 1989; P. spp. 1, 2 Rickards 1972; and P. sp. Bjerreskov 1981) (PI. 1, figs 10-14) and possibly P. rigidus Chen and Lin, 1978. Remarks. Examination of the Canadian Arctic material has added several insights to the understanding of this genus. First, the fact that it possesses a Pattern H rather than Pattern I astogeny (Koren’ and Rickards 1996) allies it with Normalograptus rather than Glyptograptus, the latter being a Pattern I genus. Second, the strong affinities of this genus with Normalograptus are seen in the immature specimens of Pseudoglyptograptus barriei, which show almost climacograptid thecae (PI. 1, figs 10, 12). With increasing maturity of the rhabdosome the degree of sinuosity of the thecal profile and degree of development of the apertural lip increases, giving a more typical pseudoglyptograptid profile (PI. 1, figs 13-14). This range of variation in the thecal form, also illustrated by Zalasiewicz and Tunnicliff (1994), as well as the wide range of dimensions seen in Pseudoglyptograptus barriei, indicates that Pseudoglyptograptus spp. 1, 2 of Rickards (1972) and P. sp. of Bjerreskov (1981) are all within the range of variation of this single species. Third, two species previously assigned to Pseudoglyptograptus, P. rhayaderensis Rickards and Koren’, 1974 and possibly P. tabukensis Rickards and Koren’, 1974 are here assigned to Comograptus based on the presence of numerous spines on the sicular rim, as well as an extensively exposed sicula and the complete lack of a median septum, both indicating a Pattern I astogeny (see discussion of the genus Comograptus below). Genus metaclimacograptus Bulman and Rickards, 1968, emend. Type species. Diplograptus hughesi Nicholson, 1869. MELCHIN: SILURIAN ‘ DIPLOGR APTID ’ GRAPTOLITES 291 Emended diagnosis. Biserial rhabdosome, circular to ovate in cross section. Thecae strongly geniculate with convex to straight supragenicular walls, introverted to straight apertures and deep, short excavations. Geniculum marked by a hood or, less commonly, a thickening which may partly obscure the thecal apertures. Median septum complete, beginning between the second pair of thecae and showing distinct, rounded or angular undulations. Pattern H proximal development type. Proximal end profile is rounded with sicula exposed only slightly below th 1 2 and for about half its length on the obverse side. Proximal ornamentation, other than a short virgella, is lacking. Species included. Among the species included are Metaclimacograptus hughesi (Nicholson, 1869) (e.g. Bulman and Rickards 1968), M.fidus Koren’ and Mikhailova, in Koren’ et al., 1980, M. minimus (Paskevicius, 1976) (PI. 2, figs 3-5, 9-10), M. orientalis (Obut and Sobolevskaya, 1966) (PI. 2, figs 1-2, 7; Text-fig. 4a), M. pictus Koren’ and Mikhailova, in Koren’ et al., 1980, M. sculptus (Chen and Lin, 1978) (PI. 2, fig. 8) and M. undulatus (Kurck, 1882) (PI. 2, figs 13-14). Remarks. The characteristic sinuous median septum and convex supragenicular walls are features shared by both the Ordovician and Silurian ‘ pseudoclimacograptids ’ and have long been considered evidence for their close relationship. The proximal development types, however, are distinctly different. The early growth stages of Metaclimacograptus very closely resemble those of other Silurian normalograptids and are much simpler than those of Pseudoclimacograptus scharenbergi (Lapworth, 18766) as illustrated by Bulman (1947) and Mitchell (1987). As a result, the Silurian forms are considered as a separate genus, having arisen from a separate stock, probably among the earliest Silurian normalograptids such as N. angustus or N. mirnyensis (Obut and Sobolevskaya, 1967). Metaclimacograptus orientalis was assigned by Rickards et al. (1977) to P. ( Pseudoclimacograptus ) since it lacks genicular hoods. However, their illustration (fig. 36) shows a slight thickening of the genicular rim and this can be clearly seen in the present material (PI. 2, figs 2, 7). In addition, the present specimens clearly show that the proximal development is of the same type as the more typical M. undulatus. Based on the above considerations, Metaclimacograptus is raised to the genus level as suggested by Paskevicius (1976), Mitchell (1987), Loydell (1991) and Koren’ and Rickards (1996). In compressed material, the Silurian species can be reasonably distinguished from their Ordovician counterparts in that the former lack any proximal ornamentation other than a virgella and the sicula is always at least slightly exposed below thl2. Based on this, several new species of ‘ Pseudoclimacograptus ’ described by Chen and Lin (1978), including P. sculptus , can be reassigned to Metaclimacograptus. The present collections have also yielded an abundance of ‘ Lithuanograptus' minimus Paskevicius, 1976 and a detailed comparison can be made between this species and the uncompressed specimens of the similar Metaclimacograptus undulatus. The only appreciable differences occur in the development of the genicular hood. In M. undulatus the hood of theca x is first formed only as the flat infragenicular wall of theca x 4- 1 , with a thickened rim, which grows well in advance of the fusellae of the lateral walls of theca x + 1 (PI. 2, fig. 14). The overhanging hood is later grown by the accretion of material onto the thickened rim. In ‘ L. ’ minimus the infragenicular wall of theca x + 1 grows at once as a concave upward surface, its edges overhanging the aperture of theca x (PI. 2, figs 4-5). It also grows in advance of the fusellae of the lateral walls, apparently by about the same amount as in M. undulatus. The hood is later unconformably overgrown by the lateral thecal walls (PI. 2, fig. 3) but it appeared as an overhanging structure from its inception. The main distinction between these ‘ genera ’ then is only a matter of timing and degree of hood development, but the basic hood-forming structure (the infragenicular wall) and the timing of its development are the same. From a practical point of view, the distinction of these genera relies on knowledge of the details of hood development, information rarely available in compressed specimens and often not even discernible from uncompressed material. It is doubtful that these two genera could be distinguished in any but the most well-preserved, uncompressed specimens unless the specimens 292 PALAEONTOLOGY, VOLUME 41 could first be assigned to a species known to belong to one or the other genus. I consider that these criteria do not merit distinction of a separate genus, and that Lithuanograptus is a junior synonym of Metaclimacograptus, a conclusion drawn also by Loydell (1992, p. 55). Talacastograptus Cuerda, Rickards and Cingolani, 1988 may represent an extreme development of the metaclimacograptid thecal form, with rounded supragenicular walls, introverted thecae, and very pronounced genicular hoods, that impart a hooked appearance to the thecae when fully developed. The gently undulose median septum also points to metaclimacograptid affinities. Genus neodicellograptus Mu and Wang, 1977, emend. Type species. Neodicellograptus dicranograptoides Mu and Wang, 1977. Emended diagnosis. Pattern H species with distally diverging stipes. Thecae ‘ pseudoclimacograptid ’ with introverted apertures and undulose dorsal stipe walls. Species included. Neodicellograptus dicranograptoides Mu and Wang, 1977 (e.g. Chen and Lin 1978), N. siluricus Mu, Li, Ge, Chen, Ni, Lin and Mu, 1974 (PI. 2, figs 6, 1 1-12, 15) and N. superstes Chen and Lin, 1978. Remarks. This genus, placed in Dicranograptidae by Mu and Wang (1977) and Chen and Lin (1978), was considered by Melchin and Mitchell (1991) to possess a Pattern H astogeny, based on well-preserved, flattened specimens (Melchin and Mitchell 1991, fig. 7a-c). Uncompressed specimens (PI. 2, figs 6, 11-12, 15) clearly show that N. siluricus does, indeed, possess a Pattern H astogeny rather then the Pattern A' seen among the Dicranograptidae (Mitchell 1987). This genus appears to have arisen by secondary distal stipe divergence of a Pattern H diplograptid. Metaclimacograptus is the most likely ancestor based on the similarities in both astogenetic pattern and thecal form. The apex of the sicula is exposed in some specimens, but is enveloped within the first thecal series in most specimens (PI. 2, fig. 12), rarely the second in others. The nema is usually free but short. A case could be made for the inclusion of Neodicellograptus species in Metaclimacograptus since the thecal form is the same. Rare examples of some otherwise normal biserial species show distal stipe divergence (e.g. Normalograptus normalis, Williams 1983, text-fig. 3b; Normalograptus cf. ojsuensis (Koren’ and Mikhailova) (Text-fig. 6i). In these cases, however, the virgula divides and follows the dorsal walls of both stipes. Neodicellograptus differs from Metaclimacograptus not only in that both stipes grow out of contact with the virgula, but also in that the dorsal walls of the stipes are undulose across their width rather than being straight in the centre where they contact the virgula and undulose along the lateral margins. Of the four species previously assigned to this genus, three ( N . dicranograptoides, N. siluricus and N. superstes) appear to differ only slightly in thecal form, dimensions and in the timing and angle of stipe divergence. The present collections of compressed and uncompressed specimens, however, show a considerable range of variation in timing and angle of stipe divergence. In some specimens the stipes diverge at the base of the second thecal pair (PI. 2, figs 12, 15; Melchin and Mitchell 1991, fig. 7a) whereas in others this takes place at the third (PI. 2, fig. 6; Melchin and Mitchell 1991, fig. 7c) or fourth thecal pair (Melchin and Mitchell 1991, fig. 7b). This evidence suggests that these three species may be synonymous. The other species, Neodicellograptus sp. (Chen and Lin 1978), possesses a much more blunt proximal end with mesial spines on all of the thecae. It is Ordovician in age and appears to be a true dicranograptid. Genus neodiplograptus Legrand, 1987, emend. Type species. Diplograptus magnus H. Lapworth, 1900. MELCHIN: SILURIAN 1 DIPLOGRAPTID ’ GRAPTOLITES 293 Emended diagnosis. Modified Pattern H species, most with only two primordial thecae, a delayed th.21, and weakly to strongly biform thecae. Proximal thecae normally climacograptid, less commonly glyptograptid or possibly pseudoclimacograptid, with an abrupt geniculum, parallel supragenicular walls and relatively close spacing. Proximal end relatively narrow and widens rather abruptly as thecae become more gently sigmoidal to almost straight distally. Partial median septum in the proximal end becomes complete at or slightly beyond the point of thecal change, between the fourth and ninth thecal pair, except in a few possible ‘ ancestral ’ forms where the median septum is complete from the second thecal pair. Species included. Neodiplograptus magnus (H. Lapworth, 1900) (see e.g. Rickards et al. 1977), Neodiplograptus tcherskyi tcherskyi (Obut and Sobolevskaya, 1967) (PI. 3, figs 1-3, 10, 12), Neodiplograptus tcherskyi subsp. nov. (PI. 3, fig. 1 1) and Neodiplograptus sinuatus sinuatus (Nicholson, 1869) (PI. 3, figs 4—9) have been observed in the present material to share the attributes noted above. The following taxa appear to have similar thecal and rhabdosomal characteristics and are, therefore, included in this group : Neodiplograptus tcherskyi sectilis (Chen and Lin, 1978); TV. tcherskyi variatus (Chen, 1984); TV. thuringiacus (Kirste, 1919) (see e.g. Bjerreskov 1975); TV. mucroterminatus (Churkin and Carter, 1970); and Neodiplograptus sinuatus crateriformis (Rickards, 1970). Neodiplograptus ? elongatus (Churkin and Carter, 1970) (Text-fig. 6k), TV.? cf. elongatus (Melchin 1989; Text-fig. 6j, n) and TV.? sp. nov. (Melchin 1989; Text-fig. 6p, r-s) may also be assigned to this group. Remarks. Among Pattern H graptolites, there are at least two distinct groups of species with biform to polyform thecae (Storch 19836). There are those with a robust, rapidly widening proximal end and generally ‘ amplexograptid ’ thecae proximally, which will hereafter be referred to as 1 Neodiplograptus ’ (e.g. ‘ Neodiplograptus ’ modestus and its allies). The second group defined by Storch possesses a more tapering proximal end with ‘climacograptid’ thecae, including ‘ D . ’ elongatus and ‘ZX’ thuringiacus, here assigned to Neodiplograptus. Storch considered that ‘ D. ’ tcherskyi and possibly ‘ZX’ magnus belong to the ‘TV.’ modestus group, although examination of the illustrations of ‘ZX’ magnus of Elies and Wood (1907) and Rickards et al. (1977) and those of ‘ZX’ tcherskyi in Obut and Sobolevskaya (1967) and in the present collections suggests that these two taxa are much more similar to TV. thuringiacus than to ‘TV. ’ modestus. Storch showed that these two species groups represented two different, independent lineages and, as discussed below, they may have arisen from two or more separate Normalograptus ancestors. Two of the taxa assigned to Neodiplograptus that have been found in uncompressed form here are TV. tcherskyi tcherskyi and TV. tcherskyi subsp. nov. These differ from normal Pattern H species in that theca 21 is derived from near the aperture of thl2 in a manner like that of all subsequent thecae and is, therefore, not a primordial theca as defined by Mitchell (1987). In addition, the fusellae of thl2 are differentiated rather late from thl1, although thl2 still emerges from the foramen in protheca l1 as in all other Pattern H species. The result is a very slender first thecal pair. Other characteristic features of these two taxa that are shared with other TV. tcherskyi subspecies, TV. thuringiacus, TV. mucroterminatus and TV. magnus are the relatively strongly tapered proximal end, the fact that the change in thecal form is abrupt and coincides with a change in rate of widening and with the insertion of the complete median septum (the septum is partial in the proximal end). Whether or not these other named species share the delayed thi1 is not known. This suite of features is not shared with other Pattern H ‘ Neodiplograptus ’ species such as ‘TV.’ modestus. ‘ Glyptograptus' sinuatus sinuatus has also been found in uncompressed form in the present collections and shares all of the above noted features, including the delayed differentiation of th2\ The only way in which this species differs from TV. tcherskyi is that the proximal thecae are not sharply geniculate but change from strongly sigmoidal to very weakly sigmoidal (see also Hutt 1974, pi. 4, figs 1^1, 10; Loydell 1991, pi. 1, fig. 2). This species, therefore, is included in Neodiplograptus. A problem arises when attempting to assess the relationship between Neodiplograptus and Normalograptus, and the systematic position of Neodiplograptus ? elongatus , which does not exhibit all of the above features. It does not show an abrupt change in either thecal form or rate of widening. It does, however, show a rather slender, tapering proximal end and climacograptid proximal thecae (Text-fig. 6k). Several compressed specimens assigned to Neodiplograptus ? cf. 294 PALAEONTOLOGY, VOLUME 41 elongatus were found in the present collections that appear to be transitional between N.l elongatus and N. thuringiacus in that there are fewer climacograptid thecae, the thecae change more abruptly and the rhabdosome widens more rapidly (Text-fig. 6j, n). It is possible, that N.l elongatus and N.l cf. elongatus represent the transition from Normalograptus to Neodiplograptus. The first step in this transition would be distal introduction of weakly sigmoidal thecae on to a long, gently tapering rhabdosome with climacograptid thecae, such as that of Normalograptus rectangularis or N. normalis. The next step would be accelerating and increasing the abruptness of the thecal change and the rate of widening. Delaying the insertion of the median septum allows the proximal end to become more slender relative to the distal regions. The delay of the origin of th2x allows the first thecal pair to be even more compact. A third species closely related to N.l elongatus found in the Canadian Arctic is Neodiplograptus ? sp. nov. (Text-fig. 6p, r-s). This new species is similar to N.l elongatus in rhabdosomal form and dimensions, but the first five thecae are pseudoclimacograptid with convex supragenicular walls, slightly introverted apertures and a wavy median septum. The following five thecae are climacograptid and thereafter they change gradually through glyptograptid to fully orthograptid distally. This species appears to be unique in that four different thecal morphologies are represented in a single rhabdosome and it illustrates the intergradational and transitional nature of these various thecal styles. Whereas Neodiplograptus ? elongatus represents one line along which Neodiplograptus may have arisen directly from Normalograptus, another possible ancestral line is the ‘ Glyptograptus' persculptus-sinuatus transient forms described by Chen and Lin (1978) (Text-fig. 6v). If these forms are indeed transitional between these two taxa as suggested by Chen and Lin, and if ‘ G. ’ sinuatus does indeed belong in Neodiplograptus as suggested here, then this may represent the line of origin for this species group. In fact, some of the specimen assigned by Chen and Lin to N. sinuatus are preserved in partial relief and appear to show an early origin for th2J (Text-fig. 6q, t), so there may be some variability in this feature within this species. Neodiplograptus sinuatus appears to be the earliest reported member of this genus. A third possibility is that some or all of the Neodiplograptus species arose directly from species such as ‘ N. ’ modestus, by aquiring a narrower, more tapering proximal end and delaying the origin of th2h Only further work on well-preserved Early Llandovery material will allow resolution of these problems. Genus ‘neodiplograptus’ Legrand, 1987 Diagnosis. Pattern H species with biform thecae that widen rapidly from a relatively blunt proximal end. Proximal thecae normally amplexograptid, less commonly climacograptid, becoming glyptograptid to orthograptid distally. Median septum complete, normally inserting at or slightly beyond the second thecal pair. Rhabdosome usually broad, sometimes foliate in profile. Species included. Among the species included are ‘ Neodiplograptus ’ modestus (Lapworth, 1876ft) (Text-fig. 6d-e), ‘TV.’ africanus (Legrand, 1970), lN. ’ diminutus (Elies and Wood, 1907), ‘ N ’ fezzanensis (Desio, 1940) (see e.g. Storch 1983ft), ‘ N. ’ lanceolatus Storch and Serpagli, 1993, ‘ N. ’ parajanus (Storch, 1983ft), and possibly ‘ N .' merzlyaslovi (Obut and Sobolevskaya, 1968) and ‘ N .' orientalis (Ye, 1978). Remarks. Species of ‘ Neodiplograptus ’ tend to have a proximal end that is relatively blunt in comparison with other normalograptids, although the sicula is still exposed below thl2. Usually, the maximum width is achieved rapidly, the proximal thecae are amplexograptid rather than climacograptid (i.e. with inclined supragenicular walls), and the change in thecal form is gradual, in some species almost imperceptible, to gently sigmoidal or straight distally, and does not coincide with a change in rate of widening as it does in Neodiplograptus. The complete median septum is commonly evident, even in completely flattened specimens, and appears to arise at or near the second thecal pair in species where it can be seen. MELCHIN: SILURIAN ‘ DIPLOGR APTID ’ GRAPTOLITES 295 The proximal end appears to possess a normal Pattern H development, thl1 originates at the base of thl2 (Text-fig. 6d) as in Normalograptus species, as opposed to the delayed origin of th2x seen in many species of Neodiplograptus. All these features taken together suggest that this group may, indeed, be distinct at the generic level from Neodiplograptus, although the range of variation within each group and the lines of distinction between them are still unclear. The origin of ‘ Neodiplograptus ’ was clearly from a Normalograptus ancestor, such as N. normalis, within the latest Ashgill. Genus cystograptus Hundt, 1942 Type species, Diplograptus vesiculosus Nicholson, 1868. Species included. Cystograptus vesiculosus (Nicholson) (Text-fig. 6l-m, o), C. penna (Hopkinson, 1869) (see Jones and Rickards 1967) and possibly C.? ancestralis Storch, 1985. Remarks. This genus has yet to be found in Arctic Canada but well-preserved, compressed specimens of C. vesiculosus from Ireland examined by the author (Text-fig. 6l-m, o) show that, despite the very long sicula and downward-growing portion of thl1, the latter still terminates in two foramina, and thl2 grows across the reverse side of the sicular and upward as in all other Pattern H species. Storch (1985) has suggested a likely origin for Cystograptus. The oldest species, C.? ancestralis, from the ascensus and acuminatus biozones, possesses a relatively short sicular (2-5-3 0 mm long) and less strongly sinuous thecae than C. vesiculosus or C. penna, and most arose from a Persculptograptus or Neodiplograptus species with sinuous thecae (e.g. Persculptograptus persculptus or ‘ Neodiplograptus ’ ex gr. ‘NT modestus). Family petalolithidae Bulman, 1955, emend. Emended diagnosis. Biserial graptolites with Pattern I primordial astogeny and continuous thecal periderm. Thecae commonly glyptograptid to petalolithid, less commonly climacograptid or (possibly) pseudoglyptograptid. Proximal end commonly acicular or slender and rounded. Rhabdosome aseptate or with a partial median septum (obverse side); no dicalycal theca is present. Ancora may be present but is not integrated with the proximal thecal framework. Genera included. Petalolithus Suess, 1851, Agetograptus Obut and Sobolevskaya, 1968, Cephalograptus Hopkinson, 1869, Comograptus Obut and Sobolevskaya, 1968, Dimorphograptoides Koren’ and Rickards, 1996, Dischidograptus Ni, 1978, Dittograptus Obut and Sobolevskaya, 1968, Glyptograptus Lapworth, 1873, Parapetalolithus Koren’ and Rickards, 1996, Pseudorthograptus Legrand, 1987, Rivagraptus Koren’ and Rickards, 1996, Sudburigraptus Koren’ and Rickards, 1996 and possibly Paraclimacograptus Pribyl, 1947, Victorograptus Koren’ and Rickards, 1996 and Corbograptus Koren’ and Rickards, 1996. Remarks. Description of the Pattern I development type and comparisons with other subfamilies are discussed in preceding sections. Some unique modifications of the petalograptine rhabdosome, however, should be pointed out here. Unlike most of the Silurian Diplograptoidea, which possess an unornamented proximal end (apart from the virgella and its modifications), Comograptus is characterized by spines on the sicular rim. These spines are not considered homologous with the antivirgellar spines of the Pattern F and G forms (within the Orthograptidae ; see Mitchell 1987) but are secondarily derived within this group. Another apparent anomaly within this subfamily is Dischidograptus Ni, 1978 (type species, D. mirabilis (Mu, Li, Ge, Chen, Ni, Lin and Mu, 1974)) in which the stipes give the appearance of 296 PALAEONTOLOGY, VOLUME 41 diverging at the distal end. Close examination of the type specimens of D. mirabilis, however (Text- fig. 6u), shows that stipe divergence does not take place, but that the distalmost thecae arose alternately, but are long and slender and no periderm is preserved between the last two thecae. The virgula appears to split in two and then distally ramify into numerous fine strands. Ni (1978) considered that Petalolithus ovatus scopaecularis Schauer, 1971 (a junior synonym of P. regius (Hundt, 1957); see Loydell 1992, pp. 51-52) also belongs in this genus as it shows a similar distal ‘divergence’ of stipes and virgula. Koren’ and Rickards (1996) described an array of styles of virgellar and thecal apertural modification seen in petalolithid genera. They also erected a number of new genera within this group, based on groups of taxa that share these features. One aspect of the rhabdosomal structure that has received very little attention from the point of view of its possible phylogenetic significance in Silurian diplograptoideans is the position of the virgula and presence or absence of a partial or complete median septum. This aspect of the internal structure can often be deduced from well-preserved, flattened and pyritized specimens. As noted previously, all the Pattern H species studied to date are fully septate distally, and therefore possess a dicalycal theca that divides the rhabdosome into two, separately growing series of thecae, whereas all the Pattern I species are either aseptate or partly septate and the thecae orginate by alternate budding of a single growth series throughout the rhabdosome. However, within the Pattern I forms the position and mode (or lack) of attachment of the virgula is variable and these features may have significance at the specific and generic level. The possible inclusion of Paraclimacograptus in this family is discussed in the remarks for the Normalograptidae, above. The possible astogenetic development patterns for the genera Victorograptus and Corbograptus are discussed by Koren’ and Rickards (1996). Genus petalolithtus Suess, 1851 Type species. Prionotus folium Hisinger, 1837. Diagnosis (after Koren’ and Rickards 1996). Pattern I species with ventrally concave proximal thecae and concave to straight distal thecae, disposed at moderate to high angles to the rhabdosome producing a foliate profile. Apertures usually everted. Rhabdosome ovate to tabular in cross section. Proximal end bears an ancora. Species included. Among the species included are Petalolithus folium (Hisinger, 1837) (see e.g. Lenz 1982), P. ankyratus Mu, Li, Ge, Chen, Ni, Lin and Mu, 1974 (PI. 4, figs 1-2, 5), P. intermedius (Boucek and Pribyl, 1941a) (e.g. Lenz 1982), P. minor (Elies, 1897), P. ovatus (Barrande, 1850) (see e.g. Boucek and Pribyl 19416). Remarks. Loydell (1992) established that the name Petalolithus has priority over Petalograptus. The definition of this genus was expanded by Mitchell to include Silurian species of Orthograptus (assigned by Legrand 1987 to Pseudorthograptus ) with the Pattern I proximal end. The line of distinction between the Silurian ‘ orthograptids ’ and ‘ petalograptids ’ had been rather ill-defined in the past, with some Petalolithus species (e.g. P. tenuis (Barrande, 1850)) having straight thecae and a rhabdosome which is not particularly foliate and some Orthograptus species (e.g. O. mutabilis) with a relatively protracted proximal end and strongly upward-growing early thecae. In addition, Loydell (1992) noted that the presence or absence of an ancora may be of phylogenetic significance among these species. Koren’ and Rickards (1996) restricted the definition of this genus to include only those species with ventrally curved thecae (at least proximally) and an ancora. Their analysis of the evolutionary relationships among these species indicates that they do, indeed, represent a monophyletic group. The limited data available suggest that these taxa also share a partial median septum (PI. 4, fig. 2). MELCHIN: SILURIAN ‘ DIPLOGRAPTID ’ GRAPTOLITES 297 Genus parapet alolithus Koren’ and Rickards, 1996 Type species. Parapetalolithus dignus Koren’ and Rickards, 1996. Diagnosis (after Koren’ and Rickards 1996). Pattern I species with straight (‘orthograptid’) thecae, with everted, unornamented apertures. Proximal thecae are protracted and strongly upward- growing. Proximal end bears only a simple, undivided virgella. Species included. Typical species include Parapetalolithus dignus Koren’ and Rickards, 1996, P. kurcki (Rickards, 1970), P. palmeus (Barrande, 1850) and P. sp. (PI. 4, figs 3, 9-10). Remarks. Koren’ and Rickards (1996) erected this genus to include those taxa previously included in Petalolithus that lack an ancora, and typically possess straight rather than conspicuously ventrally curved proximal thecae and a less foliate rhabdosome. They also suggested a distinct evolutionary origin for these taxa, from Sudburigraptus Koren’ and Rickards, 1996, rather than Pseudorthograptus. The differences between Sudburigraptus and Parapetalolithus are subtle, the former possessing a less protracted proximal end, and species of the latter being generally larger and more robust (Koren’ and Rickards 1996). P. sp. is aseptate with a free, central virgula (PI. 4, fig. 3), but the internal structure of other species of this genus is unknown. Genus pseudorthograptus Legrand, 1987 Type species. Diplograptus insectiformis Nicholson, 1869. Diagnosis (after Koren’ and Rickards 1996). Pattern I species with straight (‘orthograptid’) thecae, with spinose apertures. Proximal end bears an ancora that may be very large and supports a continuous membrane. Species included. Typical species include: Pseudorthograptus insectiformis (Nicholson, 1869), P. inopinatus (Boucek, 1943) (PI. 4, figs 6-8, 1 1-12), P. mutabilis (Elies and Wood, 1907), and P. obuti (Rickards and Koren’, 1974). Remarks. Koren’ and Rickards (1996) restricted the definition of this genus to include only those taxa with spinose apertures and an ancora. It may be also be noted that P. inopinatus is aseptate, and this condition may characterize the genus and serve to distinguish it further from Petalolithus, at least some species of which possess a thin, partial median septum. Genus sudburigraptus Koren’ and Rickards, 1996 Type species. Orthograptus eberleini Churkin and Carter, 1970. Remarks. Koren’ and Rickards, 1996 erected this genus to include species with Pattern H or I development, unornamented orthograptid thecae and an unornamented, relatively unprotracted proximal end. The type species, S. eberleini, appears to be aseptate (Churkin and Carter 1970, pi. 3, fig. 2) and most probably possesses a Pattern I astogeny, although the internal and astogenetic details of none of the taxa assignable to this genus (Koren’ and Rickards 1996) are known for certain. Assuming that the Pattern I astogeny arose only once in the latest Ashgill or earliest 298 PALAEONTOLOGY, VOLUME 41 Llandovery (see Llandovery graptoloid phylogeny below) then a genus encompassing both Pattern H and I ‘ orthograptids ’ would probably include two independently evolving groups of species, although further taxonomic revisions of these forms must await analysis of new, better preserved material. Genus rivagraptus Koren’ and Rickards, 1996 Type species. Diplograptus bellulus Tornquist, 1890. Remarks. Koren’ and Rickards (1996) erected this genus, with Rivagraptus bellulus as its type species. However, their description of R. bellulus indicates the presence of a sicula at least 1 mm long and a full median septum distally, whereas the specimens described by Bjerreskov (1975) are aseptate and show a much shorter sicula. The present specimens match well with those of Bjerreskov in all respects, accounting for the differences in width that would accompany compression. The author has not had the opportunity to examine the original material of Tornquist (1890), so the question of the real nature of the proximal and internal structure of this species must await re- examination of the type specimens. If the present specimens match Tornquist’s material (i.e. if R. bellulus is aseptate with an exceptionally short sicula), then the generic diagnosis should be revised to reflect this unique development and structure, and the scope of the genus revised to encompass those species that share those features (e.g. Rivagraptus ? kayi (Churkin and Carter, 1970)). Those other species assigned by Koren’ and Rickards (1996) to this genus (e.g. R. cyperoides (Tornquist, 1897) and some new species erected by Koren’ and Rickards) that possess a much longer sicula, should be assigned to another genus (e.g. Sudburigraptus). The species that are here questionably assigned to this genus show the key Pattern I characteristics : only one primordial theca and normal differentiation of all subsequent thecae ; and a short, downward-growing portion of thl1 with a single terminal foramen at the sicular aperture (PI. 7, fig. 7). They have, however, acquired a proximal appearance quite unlike other petalolithids with their extremely short, obscured sicula and blunt proximal end (PI. 7, figs 4-6, 8, 11-13). Even in compressed form, the short, obscured sicula and blunt, rounded proximal end are evident (e.g. Tornquist 1890, pi. 1, figs 27, 29) differentiating species of this genus from other Llandovery genera. Genus glyptograptus Lapworth, 1873, emend. Type species. Diplograptus tamariscus Nicholson, 1868. Emended diagnosis. Pattern I species with glyptograptid to climacograptid thecae. Proximal end rather slender, unornamented and tapering. Rhabdosome circular to ovate in cross section, aseptate, virgula central and free or attached to bases of interthecal septa, or lateral and embedded in obverse wall. Species included. Glyptograptus tamariscus (Nicholson) (PI. 5, figs 1-6, 9) (except G. tamariscus magnus Churkin and Carter, 1970), Glyptograptus alternis (Packham, 1962), G. elegans Packham, 1962 (PI. 5, figs 10, 13; PI. 6, figs 1-3), G. enodis Packham, 1962, G. tamariscoides (Packham, 1962). Remarks. There has long been difficulty in distinguishing species of Glyptograptus from Climacograptus in Llandovery collections and arbitrary criteria have been variously employed (e.g. Packham 1962). This has resulted in what many authors have considered a phylogenetically unrealistic classification, even from the point of view of thecal morphology and rhabdosomal form alone (Rickards et al. 1977). Mitchell (1987) suggested that all the Llandovery glyptograptids and MELCHIN: SILURIAN ‘ DIPLOGRAPTID ’ GRAPTOLITES 299 climacograptids possess the same proximal development pattern (Pattern H) and he decided to include both within an expanded Glyptograptus until further information was available to distinguish more phylogenetically consistent subgroups. The present material has clearly shown, however, that some of the Llandovery glyptograptids are of the Pattern I type, including G. tamariscus, the type species, whilst others (e.g. G. nikolayevi) possess the Pattern H proximal growth form and are here grouped with the Pattern H climacograptids in the genus Normalograptus (Melchin and Mitchell 1991). Likewise, some Pattern I species such as ‘ Climacograptus' tamariscoides and ‘C.’ alternis possess climacograptid thecae and, despite the fact that they were considered by Packham (1962) to have evolved directly from the Glyptograptus tamariscus group, they were still placed in the genus Climacograptus on the basis of their thecal morphology. These forms clearly possess the same astogenetic pattern and rhabdosomal structure as Glyptograptus sensu stricto and are, therefore, placed in that genus. Koren’ and Rickards (1996) generally used the concept of Glyptograptus of Melchin and Mitchell (1991), that includes only Pattern I taxa, although several of the species that they assigned to this genus are septate with a rather blunt proximal end (resulting from early derivation of thl2) and are most probably Pattern H species assignable to Normalograptus (e.g. G. bulbus Koren’ and Rickards, 1996, G. incertus Elies and Wood, 1907, G. cf. serratus Elies and Wood, 1907 and G. tamariscus nikolayevi Obut, 1965 (= Normalograptus nikolayevi ; PI. 1, figs 4-9). Genus comograptus Obut and Sobolevskaya, 1968, emend. Type species. Comograptus comatus Obut and Sobolevskaya, 1968. Emended diagnosis. Pattern I species with at least three spines (often many) projecting outward from the sicular rim. Thecae climacograptid to pseudoglyptograptid, possibly glyptograptid, and may bear mesial and/or genicular spines, especially proximally. Rhabdosome aseptate with central virgula. Species included. Comograptus comatus Obut and Sobolevskaya, 1968 (Text-fig. 3n), C. gorbiachinensis Obut and Sennikov, 1980 (PI. 7, figs 7-13), Comograptus rhayaderensis (Rickards and Koren’, 1974) and possibly ‘ Pseudoglyptograptus ’ tabukensis Rickards and Koren’, 1974 (cf. Text-fig. 3q). Remarks. This genus remains largely unchanged from the definition of Obut and Sobolevskaya (1968), except that it has been found here to include only Pattern I species (probably not Normalograptusl serratus barbatus which appears to be a spinose variant of an otherwise normal Pattern H species). The proximal development, as seen clearly in present isolated specimens of C. gorbiachinensis and C. comatus, is typical of the petalolithids and this type of proximal end can also be seen in the uncompressed specimen of ''Pseudoglyptograptus' rhayaderensis illustrated by Rickards and Koren’ (1974, fig. 17). The long sicula exposed for a considerable length on the obverse side and the absence of a median septum, even on the obverse side, are characteristic of Pattern I species. The presence of spines on the sicular rim is also indicative of this genus. ‘ Pseudoglyptograptus ' tabukensis is less well preserved but also shows the sicular spines and in other ways is similar to C. rhayaderensis. It is, therefore, included questionably in Comograptus. Koren’ and Rickards (1996) recognized that the type species bears a Pattern I astogneny, but restricted the definition of the genus to include only those taxa bearing spines on the sicula and proximal thecae. This definition excludes those taxa listed above that do not bear thecal spines, including C. gorbiachinensis, which was assigned to this genus by Obut and Sennikov (1980). Observations on the present material suggest that the degree of thecal spine development varies between as well as within species depending on the growth stage, whereas the spines on the sicular rim formed at the time of completion of growth of the metasicula, and combined with the Pattern 300 PALAEONTOLOGY, VOLUME 41 I astogeny and thecal form, provide a more reliable guide for phylogenetic grouping of these taxa. It appears that C. comatus represents the extreme end-member of this group of Pattern I species with varying degrees of proximal spinosity. Genus agetograptus Obut and Sobolevskaya, 1968, emend. Type species. Agetograptus secundus Obut and Sobolevskaya, 1968. Emended diagnosis. Pattern I species in which a dimorphograptid appearance has been achieved either by redirection of thl2 above thl1 or suppression of the thl2 metatheca, and all the following thecae are in a normal biserial pattern. Thecae orthograptid to glyptograptid, possibly climacograptid and may bear apertural spines. Sicula relatively short, often with a long virgella. Rhabdosome aseptate. Species included. Agetograptus secundus Obut and Sobolevskaya, 1968 (Text-fig. 3dd, hh), A. primus Obut and Sobolevskaya, 1968, A. spiniferus Obut and Sobolevskaya, 1968 (PI. 7, figs 1-3, 5-6), A. tenuilongissimus Obut and Sobolevskaya, 1968, and A. zintchenkoae Obut and Sobolevskaya, 1968. In addition, Dimorphograptus anhuiensis Li, 1987, D. brevis Li, 1987, and D. hubeiensis Ni, 1978 (PI. 7, fig. 4) may be referable to this genus. Remarks. Obut and Sobolevskaya (1968) recognized that the difference between Agetograptus species and Dimorphograptus was the short sicula, not fully exposed below thl1 and the short first theca, and recognized the similarities with other Pattern I species such as Rivagraptus bellulus (see remarks of Rivagraptus above). The distinctness of Agetograptus was also recognized by Loydell (1991) and Koren’ and Rickards (1996). The genus is expanded here to include all Rivagraptus- to Glyptograptus-like Pattern I species with relatively short siculae in which there is a uniserial portion consisting of only one theca. Many of the ‘dimorphograptid’ species described from China in which the uniserial portion consists of only one theca are questionably included in this genus, such as A.? hubeiensis and A. ? cf. A.? sichuanensis (Ye, 1978), which have been found in the present collections and A.? anhuiensis and A. 1 brevis, both illustrated by Li (1987). Although Li (1987) suggested diverse origins for several of these species, his conclusions were based on thecal form and overall rhabdosomal profile. More information is necessary regarding the details of the proximal end and internal structure before the mono- or polyphyletic origin of this genus can be determined. Family retiolitidae Lapworth, 1873, emend. Emended diagnosis. Sicula reduced to absent. Thecae represented by thecal framework and/or reticulum that may show some development of continuous periderm. Ancora always present and incorporated in framework of first thecal pair. Remarks. This family comprises the groups assigned to the Retiolitinae and the Plectograptinae, which include, as far as presently known, all the Silurian ‘retiolitids’. The Ordovician forms (the ‘ archiretiolitids ’) previously included in the Retiolitidae ( sensu Bulman 1970), and the order Retiolitida of Obut and Zaslavskaya (1986), have a different proximal development pattern not involving an incora and have been included by Mitchell (1987) within the Orthograptidae (see also Bates 1990). Mitchell (1987) discussed some of the profound differences between the normal diplograptid peri- derm and the retiolitid thecal framework and reticulum, but chose to include both within the same MELCHIN: SILURIAN ‘ DIPLOGRAPTID ’ GRAPTOLITES 301 subfamily (Retiolitinae). However, recent work on the skeletal architecture of many retiolitid genera by Bates and Kirk (1978, 1984, 1992), Crowther (1981), Obut and Zaslavskaya (1986), Lenz and Melchin (1987a, 19876) and Lenz (1993, 1994) as well as many observations made by myself on both retiolitids and ancora-bearing petalolithids shows that several profound differences exist both in the early growth stages and distal architecture between these two groups. The first is the partial to total desclerotization of the sicula, considered by Fortey and Cooper (1986) and Mitchell (1987) to be the most phylogenetically conservative feature of the graptolite rhabdosome. Although some specimens of Pseudoretiolites preserve a portion of the metasicula, no retiolitids have yet been found in which a resorption foramen or initial bud of thl1 is preserved, except for the unusually sclerotized specimens of Agastograptus described by Lenz (1994), which show the foramen but not the downward growing portion of thl1. A second feature is the integration of the ancora with the basic thecal framework of the first thecal pair, which contrasts sharply with any of the known ancora- bearing petalolithids in which the ancora is not involved in the construction of the first thecae. In addition. Bates and Kirk (1992) have pointed out some ultrastructural differences between petalolithid and retiolitid ancorae. The third (and most obvious) distinction is the total apparent replacement of preservable, primary thecal periderm with the open mesh of the thecal framework and/or reticulum. Lenz (1994) has shown that, even within Late Wenlock plectograptines, the sicular and thecal astogeny is identical to that of the petalograptines (Pattern I), and that the thecal framework and reticulum are almost entirely external to the thecae themselves. Therefore, Bates’ (1990) suggestion that since the key attributes of the retiolitids arise early in astogeny, this group ought to be given subordinal status, is not supported by Lenz’s observation regarding retiolitid thecal astogeny. Lenz and Melchin (1997) have completed a phylogenetic analysis of the Silurian retiolitids and, from the point of view of their overall classification, came to two major conclusions. The first is the fact that all share the several derived characteristics (e.g. synapomorphies 10-12 on Text-fig. 5), as described above, which suggests that they represent a monophyletic clade. Ultrastructural studies on the nature of the ancora (Bates and Kirk 1992) suggest that, although this structure may have some ultrastructural differences among the Llandovery biserial graptolites, the ultrastructure is consistent within the retiolitids. The second major conclusion of Lenz and Melchin (1997) was that the Retiolitidae can be divided into two main subclades. The first includes those genera traditionally included within the Retiolitinae: e.g. Pseudoplegmatograptus, Pribyl, 1948a Retiolites Barrande, 1850 and Stomatograptus Tullberg, 1883 {Pseudoretiolites Boucek and Munch, 1944 was identified as the stem-group for both subclades). The second includes those genera assigned to the Plectograptinae ( sensu Lenz 1993) as well as Rotaretiolites Bates and Kirk, 1992 and a new taxon that shares attributes of Rotaretiolites and Paraplectograptus , which may belong to the genus Eorograptus Sennikov, 1984. Family dimorphograptidae Elies and Wood, 1908, emend. Emended diagnosis. Pattern J graptolites which may be uni-biserial or fully biserial. Sicula long (usually 1 -7—2-0 mm), fully exposed on its dorsal side. Downward growing portion of thl1 strongly reduced and does not reach down to sicular aperture, leaving a portion of sicula exposed for its full circumference. Obverse and reverse walls of thl1 both growth straight upward for all or much of their length. Rhabdosome fully or partly septate. Thecae commonly orthograptid to climacograptid but may be isolate or slightly hooked, especially in uniserial portions. Genera included. Dimorphograptus Lapworth (= Bulmanograptus Pribyl, 19486, Metadimorphograptus Pribyl, 19486), Akidograptus Davies, 1929 and Parakidograptus Li and Ge, 1981. Remarks. The descriptions of the Pattern J astogeny, and the distinction of the ‘true’ dimorphograptids from Rhaphidograptus Bulman, 1936 and Agetograptus, are discussed above in 302 PALAEONTOLOGY, VOLUME 41 the description of proximal development patterns and below in the discussion of their recognition in non-isolated graptolites. Several authors have recognized that Akidograptus and Parakidograptus do not possess a uniserial first theca (e.g. Williams 1983; Li and Ge 1981) and this led them to include these genera within Diplograptidae rather than Dimorphograptidae. Despite the fact that they have a fully biserial rhabdosome, the early astogeny (Pattern J), particularly the early upward growth of thl1, is more like that of the dimorphograptids (Pattern J') than the other diplograptid groups and they ar^ therefore, included within Dimorphograptidae here (see cladogram, Text-fig. 5). Storch and Serpagli (1993) recognized the distinction between the uniserial and the uni-biserial genera within this family at the subfamily level and that distinction is recognized here. Koren’ and Rickards (1996) distinguished Akidograptidae and Dimorphograptidae as separate families. The classification of Storch and Serpagli (1993) is preferred for these taxa because it recognizes the strong astogenetic similarities and close phylogenetic relationship between these two groups. Subfamily akidograptinae Li and Ge, 1981, emend. Emended diagnosis. Pattern J graptolites which are fully uniserial. Thecae climacograptid to orthograptid. Proximal end protracted, often bearing an ‘ancora’. Dicalycal theca 21, fully septate rhabdosome. Genera included. Akidograptus Davies, 1929 and Parakidograptus Li and Ge, 1981. Genus akidograptus Davies, 1929 Type species. Akidograptus ascensus Davies, 1929. Diagnosis. Biserial rhabdosome with protracted proximal end and early upward growth of first two thecae (Pattern J). Thecae strongly geniculate (climacograptid). Species included. Akidograptus ascensus Davies, 1929, A. anhuiensis Ge, A. cultus Mikhailova, A. gangjiawuensis Ge, A. giganteus Yang, A. macilentus Chen and Lin, 1978, A. parallelus Li and Jiao, A. priscus Hsii and A. shannanensis Yu et al. Remarks. No attempt has been made here to assess the status of the various species assigned to this genus with respect to synonymy. It is clear, however, that considerably more variability exists within both this genus and Parakidograptus in China than in other parts of the world. Akidograptus antiquus Li and Ge, 1981 is the only reported member of this family from pre- persculptus Zone strata. The holotype, and apparently only known specimen of this species, has been examined by the author (Text-fig. 3w) and is too poorly preserved to be confidently assigned to this genus. Both Akidograptus and Parakidograptus, therefore, appear to be confined to the persculptus, acuminatus and basal vesiculosus biozones. Genus parakidograptus Li and Ge, 1981 Type species. Diplograptus acuminatus Nicholson, 1867. Diagnosis. Rhabdosome with protracted proximal development (Pattern J). Thecae straight to weakly geniculate. MELCHIN: SILURIAN ‘ DIPLOGRAPTID ’ GRAPTOLITES 303 Species included. Parakidograptus acuminatus (Nicholson, 1867), P. aculeatus Yu et al., P. xixiangensis Yu et al., P. angustitubis Li, P. helixiensis Li, P. huloensis Li and P. primarius Li. Remarks. Distinction of this genus from Parakidograptus is made on the basis of thecal form. Akidograptus possesses strongly geniculate thecae whereas Parakidograptus weakly geniculate to, more commonly, straight (orthograptid) thecae. Subfamily dimorphograptinae Elies and Wood, 1908, emend. Emended diagnosis. Pattern J species with a uni-biserial rhabdosome (Pattern Y ). Uniserial portion consisting of one or several thecae, apparently achieved by redirection of theca(e) following thl. Thecae orthograptid to climacograptid, although they may be isolate or slightly hooked, especially in the uniserial portion. Biserial portion appears to be fully septate. Genus included. Dimorphograptus Lapworth, 1 876 ( = Bulmanograptus Prfbyl, 1 9486 and Metadimorphograptus Pfibyl, 19486). Genus dimorphograptus Lapworth, 1876, emend. Type species. Dimorphograptus elongatus Lapworth, 1876. Emended diagnosis. Pattern J species with a uni-biserial rhabdosome (Pattern J' ). Uniserial portion, consisting of one or several thecae, apparently achieved by redirection of theca(e) following th 1 . Thecae orthograptid to climacograptid although they may be isolate or slightly hooked, especially in the uniserial portion. Biserial portion appears to be fully septate. Species included. Typical species include Dimorphograptus elongatus Lapworth, 1876, D. confertus Nicholson, 1868, D. decussatus Elies and Wood, 1908, D. erectus Elies and Wood, 1908, and D. extenuatus (Elies and Wood, 1908). Remarks. This genus, as employed here, includes all Pattern J species with a uniserial proximal portion. Other genera have been introduced to subdivide this group according to thecal shape (e.g. Bulmanograptus , Metadimorphograptus), but many authors have not accepted them because their morphological or phylogenetic basis was considered questionable. A great deal more work needs to be done, especially to define the details of thecal form of some of the dimorphograptids, which appear to be rather complex in many species. Family monograptidae Lapworth, 1873 Diagnosis. Scandent, uniserial rhabdosomes with Pattern M astogeny. Remarks. The various cladia-bearing genera of the Monograptidae are not considered by many workers to be a monophyletic group (Rickards et al. 1977) and as many as four or more separately derived lineages may be involved. For this reason, the cyrtograptids are not separated at the subfamily level here until more is known about the relationships within and between the various cladia-bearing groups. Bulman (1970) and Fortey and Cooper (1986), as well as many other authors, have considered that the origin of thl from a sinus rather than via a resorption foramen was a distinctive and universal feature among the monograptids. Mitchell (1987) cautioned that this feature had not been observed in any of the earliest monograptids but hypothesized that its appearance was coincident 304 PALAEONTOLOGY, VOLUME 41 with the achievement of the early upward growth of thl and the uniserial rhabdosome. Isolated, compressed specimens of several Early and Mid Llandovery monograptids clearly show that thl emerges from a resorption foramen (Lukasik and Melchin 1994, 1997). It can also been seen that thl grows outward, then upward, with no downward growth component. Lukasik and Melchin (1997) designated this primitive monograptid pattern, with a resorption porus as Pattern Mr, and the more advanced development with a primary porus as Pattern Mp. The timing or mode of origin of Pattern Mp from Mr is currently unknown. LLANDOVERY GRAPTOLOID PHYLOGENY As a result of the late Ordovician extinction event, only one of the then extant graptoloid families, Normalograptidae, survived from the end of the pacificus Zone into the Early Llandovery (Melchin and Mitchell 1991). The only graptoloid species known to cross the extinction boundary (i.e. the pacficus-extraordinarius zonal boundary) are Normalograptus normalis, N. angustus, N. ojsuensis Koren’ and Mikhaylova, in Koren’ et al., 1980 and N. extraordinarius. ‘ Diplograptus bohemicus ’ Marek, 1955 has been reported from several localities in China, occurring with both pre-extinction and post-extinction faunas (Mu 1988; Melchin et al. 1991). However, Storch and Loydell (1996) have demonstrated that Diplograptus bohemicus is a junior synonym of Persculptograptus per sculp tus (Elies and Wood, 1907). Most of the Chinese specimens previously assigned to D. bohemicus are not P. persculptus, however, and are here assigned tentatively to Normalograptus cf. ojsuensis. The only Akidograptus species reported from pre-persculptus Zone strata is A. antiquus Li and Ge, 1981 from the typicus Zone (= middle pacificus Zone) in China. As noted above, the holotype (and apparently only specimen) of this species (Text-fig. 3w) is too poorly preserved to be confidently assigned to this genus. The earliest reliable report of Akidograptus is that of A. parallelus from the lowermost persculptus Zone of Shaanxi, China (Yu et al. 1988), where it predates the first occurrence of A. ascensus or Par akidograptus acuminatus. None of the pr e,-extraor dinar ius Zone taxa that have been previously assigned to Paraclimacograptus or as subspecies of P. innotatus are considered here to belong to that genus. It thus appears, from both the currently available biostratigraphical evidence and, more importantly, from the astogenetic evidence (Text-fig. 5), that the Normalograptidae were ancestral to all of the Silurian graptoloids. Text-figure 7 depicts a suggested phylogeny for the Llandovery biserial graptolites. The origin of the first species of Glyptograptus (the earliest species with a Pattern I astogeny) from a Pattern H-bearing Normalograptus species primarily involved a delay in the budding of thl2 from thl1. In addition, the style of budding of thl2 is as in all subsequent thecae, suggesting that only thl1 is primordial. Among Normalograptus species, thl2 emerged from the foramen at the downward end of pro theca 1 k In Glyptograptus tamariscus and related species, thl2 appears to have emerged from the upward-growing portion of thl1 and developed without a pronounced fusellar unconformity as in all later thecae. Based on the present evidence, this transition appears to have been accompanied by a loss of the dicalycal theca, thereby producing an aseptate (or partly septate) rhabdosome. The majority of species previously assigned to Glyptograptus from the extraordinarius Zone ( = upper ‘ bohemicus ’ Zone) have broad proximal ends, are fully septate, and, therefore, are assigned here to Normalograptus (e.g. ‘G.’ elegantulus Mu and Ni, 1983, ‘G.’ asthenus Mu and Ni, 1983, ‘G.’ daedalus Mu and Ni, 1983). Glyptograptus praetamariscus Li, 1984, from the uppermost ‘ bohemicus ’ Zone of Jingxian, Anhui, China, strongly resembles G. tamariscus in its rhabdosomal form and may be an example of one of the earliest of the Petalolithidae. Species of what appear to be Glyptograptus sensu stricto are better documented from the persculptus Zone, including several reports of G. tamariscus (e.g. Li 1984). Sudburigraptusl angustifolius (Chen and Lin, 1978), which also appears to be a Pattern I species, is found in the persculptus Zone in Arctic Canada (author’s unpublished data). Derivation of other petalolithid genera from Glyptograptus involves only changes in thecal form or proximal and thecal ornamentation. Koren’ and Rickards (1996) discussed the evolutionary relationships among those taxa here included in Petalolithidae, and most of their conclusions MELCHIN: SILURIAN 1 DIPLOGR APTID ’ GRAPTOLITES 305 text-fig. 7. Proposed phylogeny for the Llandovery Diplograptoidea and approximate generic ranges. Dashed lines indicate possible alternative line of origin. Genera of uncertain family affinites (e.g. Paraclimacograptus, Victorograptus and Corbograptus) are not shown. are consistent with the data presented here. However, they regarded the evolutionary origin of Pseudorthograptus as unknown, and raised the possibility that Suburigraptus was derived from an Ordovician species of Rectograptus. They noted that this would involve a loss of the proximal spines typical of Rectograptus but it would also require a reorganization of the early growth patterns of the first three thecae, from the Pattern G astogeny (Mitchell 1987). On the other hand, the early species of Glyptograptus and Sudburigraptus have the same astogentic development and differ only slightly in thecal form, and it is proposed that the latter genus was derived from the former. From Sudburigraptus, the derivation of Pseudorthograptus, Parapetalolithus and Rivagraptus requires only minor changes in degree of protraction of the (still Pattern I) proximal end and, in some cases, the addition of apertural spines ( Pseudorthograptus and Rivagraptus) and/or an ancora ( Pseudortho- graptus and Petalolithus). The close morphological similarity between the ancorae seen in some species of Pseudorthograptus (e.g. P. inopinatus and P. obuti) and those of the Retiolitinae strongly suggests that the earliest retiolitid ( Pseudretiolites ) evolved from either a Pseudorthograptus or possibly Petalolithus ancestor. 306 PALAEONTOLOGY, VOLUME 41 This suggestion has been questioned by Bates (1990), based on some observed ultrastructural differences in the ancorae. It is supported, however, by the thecal form of the fully sclerotized retiolitid described by Lenz (1994). As in the Petalolithidae, the evolution of different genera within the Normalograptidae involves only modification in thecal form, or, in the case of Hirsutograptus, addition of proximal and thecal spines (Koren’ and Rickards 1996). The origins of Neodicellograptus and Cystograptus are discussed in the remarks for those genera. Rhaphidograptus is discussed in the section on proximal development patterns. The oldest reliable record of the Dimorphograptidae is Akidograptus parallelus from the base of the persculptus Zone in China (Yu et al. 1988). Li and Ge (1981) and Li (1990) have discussed the origin of the akidograptines from an ancestor that would here be placed within the Normalograptidae (e.g. Normalograptus). This involves the development of a longer sicula, the emergence of thl1 from a point on the metasicula farther from the aperture, the early upward growth of thl1, and the delayed budding of thl2 (see also discussion of Pattern J astogeny). The delayed budding of thl2 is an apomorphic feature shared with the Petalolithidae (Pattern I). The presence of a complete median septum and dicalycal th2\ however, is a plesiomorphic feature retained from the Normalograptidae (Pattern H), not observed in any known Pattern I species. Although the possibility exists that the earliest species of Akidograptus and Glyptograptus achieved the delayed (non-primordial) thl2 independently, a more parsimonious solution is that Pattern J was derived from an unknown, septate Pattern I ancestor within the persculptus Zone. In this case, the petalolithid ancora and the ancora-like structures seen in some akidograptines may be homologous. In either case, both groups share ancestry among the latest Ordovician normalo- graptids. More work on isolated material from this critical stratigraphical interval is required to clarify these relationships. Since Rickards and Hutt (1970) discovered Atavograptus ceryx in the persculptus Biozone it has been widely considered that Atavograptus , the earliest monograptid genus, evolved directly from a septate species of ‘ Glyptograptus ’ (here assigned to Normalograptus). The akidograptines and Dimorphograptus were cited by Rickards (1988) as an example of ‘echoic evolution’ because their uniserial proximal end (not present in Akidograptus or Par akidograptus) was considered a later ‘pale echo’ of the uniserial stipe of Atavograptus (Rickards 1988, p. 223). Bulman (1970) noted that the elimination of thl2 from the astogenetic sequence has been a difficulty in understanding the origin of the monograptids. This question has been discussed by Mitchell (1987) and Li (1990), both of whom suggested an ancestor for Atavograptus among the akidograptines (or possibly the Petalolithidae). In fact, the transition from a Pattern H ancestor to a monograptid (Pattern M) rhabdosome requires three separate astogenetic changes to occur: the immediate outward-upward growth of the first theca; the redirection of the second theca so that it is no longer alternate; and the loss of the second thecal series distally (loss of the dicalycal theca). All these changes also involve a transition from two or three primordial thecae as seen in Pattern H to one or none in Pattern Mr. Li (1990) has correctly noted that the early upward growth of thl1 among the akidograptines is more similar to monograptid astogeny and that a derivation of Atavograptus from among the akidograptines requires less drastic astogenetic reorganization than from a Normalograptus ancestor. Li also noted strong similarities in thecal form between several akidograptine and earliest monograptid species. He considered, however, that four of the reported earliest mongraptids (Atavograptus ceryx, A. primitivus (Li, 1983), ‘ Pristiograptus' antiquatus Li, 1990 and ‘ MonograptusT sp. Bjerreskov 1975) were derived from four separate akidograptid ancestors with similar thecal forms, thus implying a polyphyletic origin for the Monograptidae. (Based on its strongly climacograptid thecal form and relatively great width in comparison with other earliest monograptids it seems likely that the single fragment assigned to Monograptusl sp. reported by Bjerreskov (1975, text-fig. 17f) is a distal fragment of a single stipe of a Normalograptus species such as N. normalis. As noted above and by a number of previous workers (e.g. Mu and Ni 1983; Williams 1983) single stipes of such species can grow to considerable lengths either as a result of MELCHIN: SILURIAN ‘ DIPLOGRAPTID ’ GRAPTOLITES 307 J1 M text-fig. 8. Schematic diagram of astogenetic pattern in the evolutionary origin of Atavograptus from a normalograptid ancestor. Note that the Pattern J species may have been derived from Pattern H through an intermediate, septate Pattern I species. See text for explanation. stipe divergence or termination of growth of one stipe.) Atavograptus primitivus and ‘ Pristiograptus' antiquatus have been shown to be synonymous (Lukasik and Melchin 1994), and this species (Text- fig. 3ll-mm) differs only slightly in thecal form from A. ceryx. Based on presently available data, there is no evidence to support a polyphyletic origin for the Monograptidae. In the transition from Pattern H to Pattern J, possibly with a septate Pattern I intermediate step, the early upward growth of thl 1 was achieved, and th2J and probably thl 2 are no longer primordial. The transition from Pattern J to J' involves only redirection of the second theca (and usually one or more subsequent thecae) above thl. Thus, two of the conditions necessary for the transition from a normalograptid ancestor to Atavograptus were achieved in Dimorphograptus. The only changes necessary to evolve from Dimorphograptus to Atavograptus are the loss of the short downward- growing portion of thl and the loss of the second thecal series distally. From the information currently available, it is not clear if the second thecal series in the Dimorphograptus species is produced directly from a dicalycal theca or if any of the thecae in the biserial portion of the rhabdosome are alternate in origin. If the second thecal series arose directly from a dicalcyal theca then suppression of the dicalycal theca results in a fully uniserial rhabdosome. Since Rickards and Hutt (1970) described Atavograptus ceryx, the principal objection to a dimorphograptid ancestor for Atavograptus has been that the earliest known species of Dimorphograptus occurs almost two zones later than the origin of Atavograptus : in the atavus Zone for the former and upper per sculp tus Zone for the latter (Rickards et al. 1977). However, Li (1987) lists three Dimorphograptus species from the acuminatus Zone. Lin and Chen (1984) have reported ‘ Rhaphidograptus ’ minutus (here assigned as Dimorphograptus ? cf. minutus ) from the middle of the persculptus Biozone, below the first occurrence of Akidograptus ascensus or Parakidograptus acuminatus. Their illustrated specimen has been examined by the author and although it is rather poorly preserved (Text-fig. 3z), it may be a true Dimorphograptus, although the sicula is much wider than is typical of this species in higher samples or of coeval akidograptines. It is too poorly preserved to see if it possesses an initial downward growing portion of thl. Its occurrence in persculptus Zone strata, however, is significant because it demonstrates the possible presence of this genus in strata coeval with or slightly earlier than the first Atavograptus. A suggested evolutionary sequence for the origin of Atavograptus is as follows (Text-fig. 8). 308 PALAEONTOLOGY, VOLUME 41 1 . A Pattern H ancestor (e.g. Normalograptus) gave rise to Pattern J (e.g. Akidograptus) by early upward growth of thl1, the late derivation of thl2 from the upward-growing portion of thl1, and general protraction of the proximal end (this may have involved a septate Pattern I intermediate step as discussed above); 2. Pattern J' ( Dimorphograptus ) developed from Pattern J by redirection of the second theca above thl and the second thecal series arises by some later dicalycal theca; 3. Pattern M ( Atavograptus ) arose from Pattern J' by loss of the downward growth of thl and loss of the second thecal series distally. The sinus and lacuna stage development of the thl porus apparently developed at some later stage in monograptid evolution. By comparison with the suggestions of Rickards and Hutt (1970), that Atavograptus be derived directly from a Pattern H ancestor, or Li (1990), that it be derived from Par akidograptus and Akidograptus along several different individual individual lineages, this phylogenetic sequence is the most parsimonious. It involves the the fewest number of synapomorphies at each step and the fewest number of parallelisms in the astogenetic development. Furthermore, with the discovery of Dimorphograptus! cf. minutus in the persculptus Biozone in China, this sequence may no longer be in conflict with the known stratigraphical ranges of the taxa involved. If Dimorphograptusl cf. minutus is not a true dimorphograptine and that genus does not arise until the overlying zone, then it may be that Atavograptus was derived directly from Akidograptus as suggested by Li (1990), and the uniserial proximal end of Dimorphograptus must have arisen independently from that of Atavograptus, also from an akidograptine ancestor. RECOGNIZING SUPRASPECIFIC TAXA IN NON-ISOLATED GRAPTOLITES Mitchell (1987) recognized that his new classification scheme, based on early astogeny, would be difficult to work with in the short term until more well preserved material was studied in detail and more species could be definitely assigned within this new scheme. He pointed out that, although the study of isolated material was necessary to define the proximal growth patterns, it is not essential to place a species within the classification once established. Another important point he noted was that, even if a species cannot be assigned with certainty to a genus within the new system, it does not diminish its utility. The species is the prime entity in biostratigraphical studies and this new classification scheme will not affect the stability of the species, only supraspecific taxa. In fact, the application of this new classification greatly enhances the usefulness of the generic and higher taxa since many have a much more limited range than the previously defined, thecal form-genera. In his tables 1 and 2, Mitchell (1987) listed the species that could definitely be placed within his new classification and pointed out some diagnostic features, recognizable in well-preserved, non- isolated specimens, that could be used to distinguish the astogenetic patterns. I emphasize some of those points here, particularly with respect to Llandovery faunas, and add some new points of distinction between the Silurian genera based on the present findings. Melchin and Mitchell (1991) have re-examined graptolite generic distributions in the Ashgill and Lower Llandovery. They have outlined criteria for distinction of the lower Ashgill, ‘pre-extinction’ faunas dominated by Pattern D-G and K genera, from the uppermost Ashgill-lowermost Llandovery, ‘post-extinction’ faunas dominated by Pattern H-J and M genera. They have also demonstrated the great utility of this new generic classification in revealing the precise level and the magnitude of the late Ordovician extinction event. Distinction between Pattern H, I and J species can be a more difficult matter since it was discovered as part of this work (Melchin and Mitchell 1991) that Glyptograptus sensu stricto (including a few species with climacograptid thecae) have a Pattern I proximal development. However, even these Pattern I species tend to have a more pointed proximal end and the early growth of thl2 is usually slightly delayed and more strongly upward than outward in comparison with a Pattern H proximal development. In specimens preserved in partial relief, a change in surface topography can often be seen at the origins of thl2 and th2x in Pattern H species but is not seen in MELCHIN: SILURIAN 1 DIPLOGR APTID ’ GRAPTOLITES 309 Pattern I. If the primordial origin of th2x can be established (this can often be seen in compressed or partial relief specimens - e.g. Text-fig. 6d,h) then the species is Pattern H, although not all Pattern H species show this. In the early growth stages, Pattern H species show th 1 1 growing ahead of thl2 (Text-fig. 3a-b), whereas in Pattern I the two grow synchronously (Text-fig. 3k-m). In addition, in some rare cases, the two foramina at the base of protheca 1 1 in Pattern H species and the list separating them can be seen pressed through the periderm of methatheca l1 in flattened specimens (Text-figs 3gg, 7m). In most compressed specimens, however, the proximal details are not clear enough for positive assignment. The principal criterion employed here, and one which is applicable to reasonably well- preserved, flattened specimens, is the presence or absence of a median septum. As noted above, as far as can be determined from the present material and by comparison with previous reports, there are no known Pattern I species with a complete median septum, although some possess a small partial median septum (always on the obverse side). Partly septate Pattern I species are mostly, if not exclusively, Petalolithus species with the typical petalolithid rhabdosomal form. Pattern H species, on the other hand, appear usually to have a complete median septum, although in many species it appears only distally. It is on this basis that I have separated Glyptograptus from Normalograptus in compressed specimens where proximal details are unclear. This method of distinction is one which can be employed on a variety of preservational types including uncompressed specimens embedded in rock (especially internal moulds) or in compressed specimens where the septum can be seen pressed through (Text-figs 3c, 6j, n, p). In specimens where the distal end is complete, the median septum can sometimes be seen projecting beyond the distal thecae (Text-fig. 6p, s). If, at the distal end, one stipe grows beyond the other, then a median septum must be present (PI. 5, fig. 9; Text-figs 3e, 6g), because in the aseptate Pattern I species the two rows of thecae must grow synchronously. In those Pattern I species in which the virgula is embedded in the obverse wall, such as Glyptograptus tamariscus ssp., the position of the virgula will be close to the edge of those compressed specimen preserved in subscalariform view (Text-fig. 3p) and the fuselli on the distal end may be seen to extend out on onto the virgula. In those species where the virgula is central and unattached, the virgula may be seen to ‘wander’ laterally along the length of the rhabdosome (Text-fig. 3dd). It must be admitted that still only a relatively small proportion of the Llandovery biserial fauna has been studied in enough detail and further work, especially with Ashgill and Early Llandovery species, may reveal fully septate petalolithids or aseptate normalograptids. The distinction based on internal structure, however, seems reasonable if one assumes that rhabdosomal architecture is, at least to some extent, a product of early astogeny. Distinction of Pattern J species from patterns H and I in non-isolated specimens is accomplished in most cases by recognition of a fully exposed sicula below thl1. In addition, there are, as yet, no known Pattern H or I species with more than one uniserial theca, whereas most Dimorphograptus species have at least two uniserial thecae. It is important to note that in many Dimorphograptus species, the space between the downward end of thl and the sicular aperture is often overgrown with later cortical deposits, although the original downward position can often be seen ‘ pressed-through ’ in compressed specimens (Text-fig. 3y). Although in a few Pattern I species thl 1 does not grow down to the sicula, this does not occur, to my knowledge, in any Agetograptus or Rhaphidograptus species. The growth of the reverse wall of metatheca 1 1 straight upward can easily be seen in well preserved akidograptines, even when compressed (Text-fig. 3j, o, r-s, u, x). On the other hand, its growth across the reverse face of the sicula is difficult to see in slender species tentatively assigned to Agetograptus such as A.l hubeiensis (Ni, 1978), although it can clearly be seen in uncompressed examples (PI. 7, fig. 4). Distinction between Rhaphidograptus and some slender Agetograptusl species is more difficult unless the fuselli can be seen over the first three thecae. For compressed material, the presence or absence of a median septum, or genicular hoods must be employed for their distinction. Acknowledgements. The author gratefully acknowledges the advice and assistance of A. C. Lenz and C. E. Mitchell throughout the course of most of this study. This work also benefited greatly from discussions with 310 PALAEONTOLOGY, VOLUME 41 T. N. Koren’, P. Legrand, Li Ji-Jin, D. K. Loydell, J. Lukasik and S. H. Williams, and the journal reviewers’ comments. A. C. Lenz and A. D. McCracken kindly provided some of the samples used in this study and R. 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On some new Llandoverian diplograptids of the eastern Baltic. 140-151, pis 1-2. In kaljo, d. and koren’, t. n. (eds). Graptolites and stratigraphy. Academy of Sciences of Estonian SSR, Institute of Geology, Tallinn, 256 pp. perner, j. 1895. Etudes sur les Graptolites de Boheme. IPeme Partie. Monographie des Graptolites de TEtage D. Prague, 31 pp., pis 4—8. pribyl, A. 1947. Classification of the genus Climacograptus Hall, 1865. Bulletin Internationale, Academie Tcheque des Sciences , 48, 1-12. — 1948 a. Bibliographic index of Bohemian Silurian graptolites. Knihovna Statniho Geologickeho Ustavu Republiky Ceskoslovenske, 22, 1-97. — 19486. Some new subgenera of graptolites from the families Dimorphograptidae and Diplograptidae. Vestnik Statniho Geologickeho Ustavu Republiky Ceskoslovenske, 23, 37-48. [In Czech with English summary], rickards, r. b. 1970. The Llandovery (Silurian) graptolites of the Howgill Fells, northern England. Monograph of the Palaeontographical Society, 123 (524), 1-108, pis 1-8. 1972. Climacograptus scalaris (Hisinger) and the subgenus Glyptograptus ( Pseudoglyptograptus ). Geologiska Foreningens i Stockholm Forhandlingar, 94, 271-280. — 1988. Anachronistic, heraldic, and echoic evolution: new patterns revealed by extinct, planktonic hemichordates. 211-230. In larwood, g. p. (ed.). Extinction and survival in the fossil record. Systematics Association Special Volume, 34. 314 PALAEONTOLOGY, VOLUME 41 rickards, R. B. and hutt, J. E. 1970. The earliest monograptid. Proceedings of the Geological Society, London, 1663, 115-119. — and berry, w. B. N. 1977. Evolution of Silurian and Devonian graptoloids. Bulletin of the British Museum ( Natural History), Geology Series, 28, 1-120, pis 1—6. — and koren’, t. n. 1974. Virgella meshworks and sicular spinosity in Llandovery graptoloids. Geological Magazine, 111, 193-204. rigby, j. 1986. A critique of graptolite classification, and a revision of the suborders Diplograptina and Monograptina. 1-12. In HUGHES c. P. and rickards r. b. (eds). Palaeoecology and biostratigraphy of graptolites. Geological Society Special Publication, 20, 277 pp. riva, j. 1988. Graptolites at and below the Ordovician-Silurian boundary on Anticosti Island, Canada. 221-237. In cocks, l. r. m. and rickards, r. b. (eds). A global analysis of the Ordovician-Silurian boundary. Bulletin of the British Museum ( Natural History), Geology Series, 43. — and ketner, k. b. 1989. Ordovician graptolites from the northern Sierra de Cobachi, Sonora, Mexico. Transactions of the Royal Society of Edinburgh: Earth Sciences, 80, 71-90. schauer, m. 1971. Biostratigraphie und Taxonomie der Graptolithen des tieferen Silurs unter besonderer Beriicksichtigung der tektonischen Deformation. Freiberger Forschungshefte, C373, Palaontologie, 1-185. sennikov, N. v. 1984. Nektorye retiolitidy (graptolity) gornogo Altaya. Akademiya Nauk SSSR, Sibirskoe Otdelenie. Trudy Instituta Geologii i Geofiziki, 584, 48-55. [In Russian]. sobolevskaya, r. f. 1974. [New Ashgill graptolites in the middle flow basin of the Kolyma River.] 63-71. In obut, A. M. (ed.). [Graptolites of the USSR.] Akademiya Nauk SSSR, Sibirskoe Otdelenie. Trudy Instituta Geologii i Geofiziki, 95. stein, v. 1965. Stratigraphische und palaontologische Unter suchungen im Silur des Frankenwaldes. Neues Jahrbuch fur Geologie und Palaontologie, Abhandlungen, 121, 111-200. stewart, s. and mitchell, c. e. 1997. Anticostia, a distinctive new Late Ordovician ‘ glyptograptid ’ (Diplograptacea, Graptoloidea) based on three-dimensionally preserved specimens from Anticosti Island, Quebec. Canadian Journal of Earth Sciences, 34, 215-228. storch, p. 1983 [a. Subfamily Akidograptinae (Graptolithina) from the lowermost Silurian of Bohemia. Vestnik Ustredm'ho Ustavu Geologickeho, 58, 295-299. — 1983/;. The genus Diplograptus (Graptolithina) from the lower Silurian of Bohemia. Vestnik Ustredm'ho Ustavu Geologickeho, 58, 159-170. — 1985. Orthograptus s.l. and Cystograptus (Graptolithina) from the Bohemian Lower Silurian. Vestnik Ustredniho Ustavu Geologickeho, 60, 87-100. — and loydell, D. k. 1996. The Hirnantian graptolites Normalograptus persculptus and ‘ Glyptograptus' bohemicus: stratigraphical consequences of their synonymy. Palaeontology, 39, 869-881. — and serpagli, e. 1993. Lower Silurian graptolites from southwestern Sardinia. Bollettino della Societa Paleontologica Italiana, 32, 3-57. suess, e. 1851. Uber bohemische Graptoliten. Naturwissenschaftliche Abhandlungen von W.Haidinger, 4, 87-134. tornquist, s. L. 1890. Undersokningar ofver Siljansomradets graptoliter, I. Lunds Universitets Arsskrifter, 26, 1-33, pis 1-2. — 1897. On the Diplograptidae and Heteroprionidae of the Scanian Rastrites-Beds. Lunds Universitets Arsskrifter, 33, 1-24, pis 1-2. tullberg, s. a. 1883. Skanes graptoliter. II. Graptolitfaunorna : Cardiolaskiffern och Cyrtograptusskiffrarne. Sveriges Geologiska Undersokning, Series C, 55, 1 — 43, pis 1-4. waern, b. 1948. The Silurian strata of the Kullatorp Core. In waern, b., thorslund, p. and henningsmoen, G. (eds). Deep boring through the Ordovician and Silurian strata at Kinnekulle, Vestergotland. Bulletin of the Geological Institute of Upsala, 32, 337-474. walker, M. o. 1953. The development of Monograptus dubius and Monograptus chimaera. Geological Magazine, 90, 362-373. williams, s. h. 1983. The Ordovician-Silurian boundary graptolite fauna of Dob’s Linn, southern Scotland. Palaeontology, 26, 605-639. — and bruton, d. l. 1983. The Caradoc-Ashgill boundary in the central Oslo Region and associated graptolite faunas. Norsk Geologisk Tidsskrift, 63, 147-191. ye, s.-h. 1978. [Class Graptolithina.] 431-686. In chengdu institute of geology and mineral resources (ed.). [Atlas of fossils of Southwest China, Sichuan Volume. Part I: Sinian to Devonian .] Geological Publishing House, Beijing. [In Chinese]. MELCHIN: SILURIAN ‘ DIPLOGRAPTID ’ GRAPTOLITES 315 yu, j.-h., fang yi-ting and zhang, D.-L. 1988. Lungmachi Formation graptolites from Sanlangpu of Xixiang, southern Shaanxi. Acta Palaeontologica Sinica, 27, 150-163. [In Chinese with English summary], zalasiewicz, j. and tunnicliff, s. 1994. Uppermost Ordovician to Lower Silurian graptolite biostratigraphy of the Wye Valley, Central Wales. Palaeontology, 37, 695-720. MICHAEL J. MELCHIN Department of Geology St. Francis Xavier University Typescript received 27 November 1992 P.O. Box 5000, Antigonish Revised typescript received 17 March 1997 Nova Scotia, B2G 2W5, Canada TEREBELLID POLYCHAETE BURROWS FROM THE LOWER PALAEOZOIC by a. t. thomas and m. p. smith Abstract. Trachyderma, as established by Phillips for specimens from the Upper Silurian of the Welsh Borderland, was triply preoccupied. Chapman described supposedly congeneric material from the Silurian of Victoria, but that material is generically distinct and Keilorites Allan was erected to accommodate it. Oikobesalon nom. nov. is erected as a replacement name for Trachyderma Phillips, which has been regarded variously as either a body fossil or a trace fossil. Based on its distinctive structure, it is interpreted here as the thin organic lining of a terebellid polychaete dwelling burrow. New illustrations and descriptions are given both of Phillips’ original specimens and of O. citrimorion from England and Canada. Chapman’s material of Keilorites is also redescribed to include burrows with a thick sediment wall. Putative gill plumes of Keilorites described by Chapman in a later paper are reinterpreted as ichnofossils comparable with certain Zoophycos. Unlike typical modern terebellids, the agent responsible for Oikobesalon may have been able to produce a new burrow after exhumation, or when required during growth. This capacity explains the morphological contrasts between Oikobesalon and previously described terebellid burrows. The Much Wenlock Limestone Formation of Wren’s Nest (Dudley, West Midlands) is well known for its diverse and well-preserved body fossil biota. The best, articulated, material comes from obrution deposits which occur at certain levels, particularly towards the top of the Nodular Beds Member (see Doming (1983) for formalization of Butler’s (1939) lithostratigraphy). Trace fossils also occur in the formation, but these have been studied less, and none has been formally described. Mr R. Foxall originally brought the Dudley specimen of Oikobesalon citrimorion (PI. 1, figs 2-3) to us for identification, but it remained undetermined until Dr A. W. A. Rushton suggested that it might have affinities with Keilorites or Trachyderma (= Oikobesalon nom. nov.): the latter suggestion proved to be correct. However, study of the type specimens and the related literature revealed a number of problems concerning the interpretation of the material and matters of nomenclature. The taxa dealt with here have been variously interpreted by previous authors: some have considered body fossils to be represented, others traces. In first describing specimens now referred to Oikobesalon, Phillips (1848, p. 331) erected two species of Trachyderma to include annelid remains differing from those of serpulids in having a large, long and flexible free external tube or covering which is membraneous or ‘ coriaceous ’ ( = leathery) rather than calcareous : clearly, Phillips considered his specimens to be ichnofossils. By contrast, Williams (1916, p. 17) thought that he recognized a small head in T. coriacea, interpreting that species as a small, but more complete, form of T. squamosa, and the latter as an adult lacking the head and tail. Chapman (1910, p. 103) considered his Australian material to be congeneric with Phillips’, and interpreted it as the parchment-like tube of a polychaete. It was for this material that the name Keilorites Allan, 1927 was erected. Chapman (1919) later reinforced his interpretation by describing what he considered to be the ‘gill plumes’ of the same animal. Howell (1962, p. W155) dealt with Keilorites ( Trachyderma was not recognized as an independent taxon), and Keiloritidae Allan, 1927, in the section of the Treatise dealing with worms, diagnosing those taxa to include worms producing perpendicular or diagonal burrows lined with membraneous material. It is therefore not clear whether Howell regarded Keilorites as a body fossil or as a trace. Neither Trachyderma nor Keilorites was mentioned in the second edition of the Treatise dealing with trace fossils (Hantzschel [Palaeontology, Vol. 41, Part 2, 1998, pp. 317-333, 3 pis) © The Palaeontological Association 318 PALAEONTOLOGY, VOLUME 4 1975), presumably because they were believed to be body fossils. Brood (1980, p. 279) considered Keilorites to represent the mucous tube of a sedentary annelid. Study of the type material of both taxa, and its re-interpretation in the context of comparable Pleistocene and Recent specimens, demonstates unequivocally that they are ichnofossils. TERMINOLOGY For convenience, the term ‘lining’ is used here in a restricted sense to refer to the layer of organic material forming the burrow wall in Oikobesalon. ‘Wall’ is used to refer to the construct of sediment externally bounding Keilorites burrows. Simple excavated burrows, where no construction has occurred at burrow boundaries, are termed ‘unwalled’. See Keighley and Pickerill (1994, p. 306) for a general discussion of burrow terminology. SYSTEMATIC PALAEONTOLOGY Ichnogenus oikobesalon nom. nov. \pro trachyderma Phillips, 1848] «o«1829 Trachyderma Latreille, p. 7 [a coleopteran], «onl829 Trachyderma Gravenhorst, p. 283 [a hymenopteran]. «o«1829 Trachyderma Wiegmann, p. 421 [a reptile]. Derivation of name. From the Greek ‘oikos', house and ‘be salon', brick; alluding to the inferred method of burrow formation. Neuter gender. Remarks. Phillips (1848, p. 331) proposed the genus Trachyderma for T. coriacea and T. squamosa from the Ludlow of the Welsh Borderland. Chapman (1910, p. 102) described supposedly congeneric material from the Silurian of Victoria, Australia, assigning his material to the new species T. crassituba and to T. cf. squamosa. Allan (1927, p. 240) noted that the name Trachyderma was a junior homonym on three counts: the senior homonym (see also Wiegmann (1834, pp. 7, 23); Sherborn (1932, p. 6554)) was used by Latreille (1829) for a genus of Coleoptera. Allan (1927) considered Phillips’ and Chapman’s specimens to be congeneric and this has been followed by most subsequent authors (e.g. Howell 1962, p. W155; Brood 1980, p. 279). Re-examination of Phillips’ and Chapman’s types, however, indicates that they are not. Both of Phillips’ species comprise elongate tubes, at least partly sediment-filled, but with a thin black lining of carbonized organic material preserved locally (e.g. PI. 2, fig. 3). The outer surfaces of the specimens show transversely fusiform wrinkles. On relatively unweathered specimens, fine, sometimes bifurcating extensions of the organic layer extend outwards into the sediment. These extensions are orientated at right angles to the tube axis (PI. 2, fig. 3). By contrast, Chapman’s specimens have a thick sediment wall (PI. 2, figs 1-2, 8) and, although some are transversely corrugated externally, they lack an organic lining with fusiform markings, and there is no trace of fine lateral projections into the surrounding sediment. These differences are here regarded as sufficient to justify separate ichnogenera. Ichnopecies included. O. coriaceum Phillips, 1848; O. citrimorion sp. nov.; O. liljevalli (Brood, 1980); O. squamosum Phillips, 1848; O. cf. squamosum Phillips (of Brood 1980). ‘ Type ’ ichnospecies. The Code of the ICZN states that genus-group ichnotaxa do not require a type species and that any type designation should be disregarded [Articles 42(b), 67(m); Ride et al. (1985)]. This has not been followed universally [e.g. Keighley and Pickerell (1994)], however, because ichnologists can find the concept of a type species just as useful as those who study body fossils. The following notes concerning the ‘type’ species of Oikobesalon are included should the relevant articles be changed in the future. THOMAS AND SMITH: POLYCHAETE BURROWS 319 Following Allan’s (1927, p. 240) erection of Keilorites for Trachyderma sensu Chapman, Bather (1927, p. 286) nominated T. squamosa as the type species of Trachyderma Phillips. However, Williams (1916, p. 17) had implicitly selected Trachyderma coriacea as the type species of the genus (ICZN Article 69a iv), a selection overlooked by subsequent authors. Diagnosis. Burrow (up to 30 mm across in compressed specimens studied) with thin organic lining. Locally, lining is linearly thickened to define transverse fusiform bands. Marginally, branched extensions of organic material extend outwards into the sediment from the thickened zones. Remarks. It is the structure of the lining that is particularly characteristic of Oikobesalon. No other ichnogenus possesses an organic lining of fusiform construction, while lacking a differentiated sedimentary wall. On the basis of Gotland material, Brood (1980, fig. 3, p. 281) reconstructed Oikobesalon as blind-ended and J-shaped. None of our specimens is complete, so we do not know if that shape is characteristic of the ichnogenus. We regard the lining structure as more significant than overall shape, however, because burrows thought to have been produced by similar means vary considerably in gross morphology. Like Brood’s material, none of our specimens shows any indication of branching, so we are satisfied that an unbranched morphology is typical of Oikobesalon. In his reconstruction of the burrow, Brood (fig. 3, p. 281) did not show the characteristic fine extensions of the organic layer into the surrounding sediment, though these are very clear in his photographs (figs 1a, e, 2a-b). Brood also argued that the lining of O. liljevalli was vesicular close to its blind end. The absence of such structures from our specimens could be due to their fragmentary condition. The morphology of the organic lining, and its likely mechanism of formation, are discussed separately below. Distribution. Lower Cambrian, Oxfordshire; Wenlock and Ludlow series of the Welsh Borderland, Gotland and Ontario. On the assumption of the synonymy of Trachyderma Phillips and Keilorites , Oikobesalon has been widely reported from sedimentary rocks ranging from Cambrian to Silurian in age : few published records seemingly refer to material closely resembling Phillips’ species, however. In an early detailed discussion of Trachyderma , Williams (1916, pp. 17-18) noted the organic lining and fusiform bands of T. coriacea and indicated their absence from many species referred by him to the genus. We have not attempted a monographic revision of the ichnogenus, but faunal lists (e.g. Holland et al. 1963, p. 156) suggest that it is widely distributed in the regressive Ludfordian facies of the Welsh Borderland. The only non-Silurian specimen we have studied which is certainly referable to Oikobesalon is BGS BDF9523 (PI. 1, fig. 5), from the Lower Cambrian of the Withycombe Farm Borehole, Oxfordshire. Oikobesalon coriaceum Phillips, 1848 Plate 1, figures 1, 4; Text-figure 1a-c 1839 Serpulites longissimus Sowerby, in Murchison, p. 608, pi. 5, fig. 1. v*.1848 Trachyderma coriacea Phillips, pp. 230, 331, pi. 4, figs 1-2. 1888 Trachyderma coriacea Phill. ; Etheridge, p. 37 [list], 1910 T. coriacea Phillips; Chapman, p. 316. 1916 Trachyderma coriacea Phillips; Williams, p. 17. v.1938 Trachyderma coriacea Phillips; Stubblefield, p. 30 [referred to Keiloritesl]. Type material. T. coriacea is based on two figured syntypes, both from the ‘ Upper Ludlow ’ ( = Whitcliffe Beds) of Hillside Farm, Woodbury Hill, Abberley district, Hereford and Worcester. BGS GSM38370 (PI. 1, fig. 1 ; Text-fig. 1b) compares quite closely with the original illustrations (Phillips 1848, pi. 4, fig. 2-2a), and this specimen is here selected as lectotype. Stubblefield identified BGS GSM38369 as the second figured syntype. That specimen is a slab with numerous fragmentary specimens, none of which resembles Phillips’ plate 4, figure 1, although the lithology suggests that the provenance is correct. Mr S. P. Tunnicliff informs us that the 320 PALAEONTOLOGY, VOLUME 41 specimen can be traced back to the 1 865 BGS catalogue, where it bears a tablet number adjacent to that for GSM38370. This is good circumstantial evidence that GSM38369 was available to Phillips, and may well have formed part of the type series, but we doubt that the slab includes the figured syntype. The paralectotype status of the material is therefore subject to some doubt. Phillips’ collection includes additional specimens (BGS GSM 105335-105337) from the type locality. These may also be paralectotypes but, again, none matches his plate 4, figure 1 . Other material. BGS GSM661, block with numerous specimens, ‘Upper Ludlow (Downton Passage Beds)’ (presumably = Whitcliffe Beds/Downton Castle Sandstone transition), north of Chances Pitch, Malvern area. BGS GSM 105333; Whitcliffe Beds, Whitcliffe, Ludlow. Description. Specimens 2-8-4-9 mm wide, and preserved as internal and external moulds in brown weathering, decalcified siltstone. All lie parallel to bedding and are interpreted as exhumed fragments. Most are straight or only gently curved, but occasional specimens are flexed more strongly. The specimens are crossed transversely by fine lines delimiting fusiform bands. These lines occur as sharp negative impressions on external moulds, and as slightly more round-topped positive features on internal ones. Hence they apparently represent places where the original organic lining, now largely weathered away, was thicker. Counting along the longitudinal mid-line, 20-24 bands occur in 10 mm. Disruption of the bands in strongly flexed specimens (Text- fig. 1a, c) implies breakage. The maximum sagittal length of the bands remains essentially constant across the size range of material studied. Locally, at specimen margins, branched extensions of organic material extend outwards into the sediment from the thickened zones (Text-fig. lc). There, the extensions are seen in section: in three dimensions, they would form transversely orientated flanges. Remarks. The exhumed nature of the specimens implies that the Oikobesalon tube was quite robust when fresh. Breakage of the strongly flexed specimens suggests significant rigidity. See below for comparisons with other species. Oikobesalon squamosum Phillips, 1848 Plate 2, figures 3-4 v*.1848 non 1888 v non 1910 1927 v.1938 non 1979 Trachyderma squamosa Phillips, pp. 230, 332, pi. 4, figs 3^4. Trachyderma ( squamosae Phill. aff.); Lindstrom, p. 6 [ = O. liljevalli\. Trachyderma cf. squamosa Phillips; Chapman, p. 104, pi. 27, fig. 5 [burrow possesses neither an organic lining nor a thick sediment one]. T. squamosa Phillips; Allan, p. 286. Trachyderma squamosa Phillips; Stubblefield, p. 32 [referred to Keiloritesl]. K. squamosus Phillips; Brood, p. 252 [ = O. liljevalli ]. Type material. Bather (1927, p. 286) selected BGS GSM38371 (figured Phillips 1848, pi. 4, fig. 3), from the Upper Ludlow (presumably Whitcliffe Beds) of Gorstley (common north-east of Linton), Hereford and EXPLANATION OF PLATE 1 Figs 1, 4. Oikobesalon coriaceum Phillips, 1848; Whitcliffe Beds, Hillside Farm, Woodbury Hill, Abberley district, Hereford and Worcester. 1, lectotype, BGS GSM38370. 4, possible paralectotype, BGS GSM 105335. Both x 2. Figs 2-3, 6. Oikobesalon citrimorion sp. nov. 2-3, holotype, DUDMG G14076; loose block from Nodular Beds Member of Much Wenlock Limestone Formation (Wenlock, Homerian), Wren’s Nest Inlier, Dudley, West Midlands; x 1-5 and x 3 6, paratype, NHM P6938; Niagara Group (Wenlock), Ontario, Canada; x 1-5. Fig. 5. Oikobesalon sp. indet.; BGS BDF9523; Lower Cambrian, Withycombe Farm Borehole, Oxfordshire; x 4. Specimens shown in figs 1 and 4 whitened with ammonium chloride sublimate ; other specimens photographed under alcohol. PLATE 1 THOMAS and SMITH, Oikobesalon 322 PALAEONTOLOGY, VOLUME 41 text-fig. 1. Camera lucida drawings of Oikobesalon coriaceum Phillips, 1848. A, c, two probable paralectotype specimens on BGS GSM661; note the disrupted banding on the right side of a, suggesting breakage of the tube during flexure, and the lateral extensions of the organic layer preserved locally in c. The spinose structure at the left of c is at a slightly higher level in the sediment and probably represents a fortuitously superimposed fragment, b, portion of lectotype (BGS GSM38370) to show fusiform banding. Scale bars represent 5 mm; stippling indicates sediment cover. Worcester, as lectotype of T. squamosa. BGS GSM38372 (figured Phillips 1848, pi. 4, fig. 4), from the Upper Ludlow, Hillside Farm, Woodbury Hill, Abberley district, Hereford and Worcester, is thus the paralectotype. Description. The following is based on the lectotype, and focuses on comparisons with O. coriaceum. The specimen is much less strongly compressed, having an oval (c. 4 x 10 mm) cross section, reflecting preservation in a more competent calcareous siltstone [uncompressed specimens of an Oikobesalon species (PI. 3, fig. 4), from the Ludlow of Ireland, show that the burrow was originally circular in cross section]. Transverse fusiform annulations are apparent, but are difficult to measure. Along the mid-line, and parallel to the tube axis, band width ranges between c. 0-5—1 -0 mm. Phillips (1848, pi. 4, fig. 3) reconstructed the lectotype as comprising a single burrow shaped like a shepherd’s crook. It is, however, just as likely that two separate specimens are THOMAS AND SMITH: POLYCHAETE BURROWS 323 represented on the slab (PI. 2, figs 3-4). The carbonized lining is more extensively preserved, and lateral extensions into the sediment are seen locally (see arrowed area on PI. 2, fig. 3). The paralectotype shows a thin carbonized lining, with fine transverse wrinkles on the external mould (PI. 2, fig. 7), but these are finer, much more closely spaced than in the lectotype, and are not clearly fusiform in shape. Remarks. Because of the contrasts described, we consider it unlikely that the lectotype and paralectotype are congeneric, and therefore base our conception of the ichnotaxon on the former specimen. O. squamosum differs from coriaceum in its greater tube width and coarser-scale transverse banding. It is possible that only a single ichnospecies is represented, and that these contrasts simply reflect differences in the size of the producing organism. Because of the preservational contrasts and the nomenclatural confusion which has surrounded these taxa in the past, we think it prudent to defer the question of possible synonymy until more material of squamosum becomes available. O. liljevalli, from the Wenlock (Hogklint Formation and Slite Group) of Gotland, is known from better, and more completely preserved, material. It resembles squamosum in overall dimensions. Brood (1980, p. 280) distinguished liljevalli by its thicker lining and by the presence of large sediment-filled vesicles posteriorly. Both these contrasts could be due to differences in quality and completeness of preservation, however. Those specimens recorded as Keilorites cf. squamosus (Brood p. 281, figs 1a, 4), from the Ludlow (Hemse Group) of Gotland, more closely resemble the lectotype of squamosum in preservation. The transverse extensions of the organic lining are longer in the Gotland specimens but, again, this could be attributed to more complete preservation. Oikobesalon citrimorion sp. nov. Plate 1, figures 2-3, 6; Text-figure 3d Derivation of name. From the Latin ‘ citrinus ’, of citron, and Greek ‘ morion', piece or portion; fancied resemblance between the holotype (PI. I, fig. 2) and a grapefruit or orange segment. Noun in apposition. Material. Holotype, DUDMG G14076; loose block from Nodular Beds Member of Much Wenlock Limestone Formation, Wren’s Nest Inlier, Dudley, West Midlands. Paratype, NHM P6938; Niagara Group (Wenlock), Ontario, Canada. Description. The British specimen (PI. 1, figs 2-3) is approximately 20 mm wide. This is likely to approximate to the original tube diameter (Briggs and Williams 1981). Large-scale fusiform bands occur; these have a maximum length of 1-6-1 -7 mm measured parallel to the tube axis. Each of these larger bands includes smaller- scale components, also transversely fusiform in shape and typically 5-8 mm wide. The Canadian specimen is slightly more weathered, but is similar in all essential respects. Its maximum width is c. 30 mm, with larger- scale fusiform bands 1 -6-3-2 mm long. Again, these contain traces of finer-scale banding within. Remarks. These specimens are substantially bigger than any of those assigned to previously described Oikobesalon ichnospecies : this probably accounts for the larger scale banding. However, specimens of O. citrimorion are distinguished by having the larger bands made up of smaller-scale subunits. Ichnogenus keilorites Allan, 1927 Remarks. Allan (1927, p. 240) erecte i the genus Keilorites , with Trachyderma crassituba Chapman as type, and included it within his family Keiloritidae. Bather (1927, p. 286) questioned whether Keilorites was intended for the Australian material alone or for all specimens previously referred to Trachyderma Phillips. However, a straightforward reading of Allan’s (1927) note indicates that he based his taxon on the Australian species and not the English specimens. The main purpose of this paper is to clarify the morphology and nomenclature of Oikobesalon. We therefore redescribe and diagnose Keilorites on the basis of the original material, without attempting a comprehensive revision of the ichnogenus. 324 PALAEONTOLOGY, VOLUME 41 Diagnosis. Unbranched, J-shaped burrow, with thick sediment wall. Transverse rugations present externally. Keilorites crassitubus (Chapman, 1910) Plate 2, figures 1-2, 8-9 v*p.l910 Trachyderma crassituba Chapman, p. 103, pi. 27, figs la-b, 2-3, non pi. 29, fig. 1 [ = unwalled burrow], 1927 Trachyderma crassituba Chapman; Allan, p. 240 [referred to Keilorites ]. 1927 T. crassituba Chapman; Bather, p. 286. Type material. Holotype specimen broken into two portions (PI. 2, figs 8-9), NMV P10330-P10331 (figured Chapman 1910, pi. 27, fig. la-b); Yarra improvement works, South Yarra. Paratypes: NMV P10333 (PI. 2, fig. 2), between Hoyte’s Paddock and Punt Road, South Yarra; P10332 (PI. 2, fig. 1), P10343 (PI. 2, fig. 10), type locality; respectively figured Chapman (1910, pi. 27, figs 2-4; pi. 29, fig. 1). All from Melbourne Formation (Lower Ludlow, nilssoni graptolite Biozone), excavations along Yarra River, South Yarra, 2-3 km east of Melbourne city centre, Victoria. Description. The holotype is shaped overall like a reclining J, with a short vertical tube and a longer horizontal one. The tube is circular in cross section, with a maximum diameter of about 17 mm. The holotype and two paratypes show a distinct sediment wall, < 5 mm thick in the holotype (PI. 2, figs 1-2, 8). Another paratype differs in being unlined (PI. 2, fig. 10). Externally, the tube surface bears coarse and irregular transverse rugations (PI. 2, fig. 9). Remarks. The lack of a sediment wall suggests that one paratype belongs to a different ichnospecies from the remainder of the type series. Material compared by Chapman (1919, p. 317) with K. crassitubus and by Chapman (1910, p. 104) with O. squamosum (PI. 2, figs 5-6, 11) similarly shows neither sediment wall nor organic lining, and we would not assign these specimens to either ichnogenus. Chapman (1910, p. 104) noted the absence of a wall in some of his specimens, attributing this to dissolution of a tube wall that he regarded as originally membraneous and compressible. When present, the burrow wall is clearly composed of sediment, so this explanation is incorrect. EXPLANATION OF PLATE 2 Figs 1-2, 8-9. Keilorites crassitubus (Chapman, 1910); Melbourne Formation (Lower Ludlow, nilssoni graptolite Biozone), excavations along Yarra River, South Yarra, 2-3 km east of Melbourne city centre, Victoria. 1, paratype, NMV P10332; Yarra improvements, South Yarra; x2. 2, paratype NMV P10333; between Hoyte’s Paddock and Punt Road, South Yarra; x2. 8-9, holotype (broken into two portions) NMV P10330-P10331 ; locality as fig. 1. 8, dorsal view of the vertical portion of the burrow and the proximal part of the horizontal portion. 9, ventral view of the horizontal portion of the tube; triangular section of wall at top left corresponds with triangular exfoliated section at bottom right of fig. 8. Both x 1-5. Figs 3-4. Oikobesalon squamosum Phillips, 1848; lectotype, BGS GSM38371; Upper Ludlow, Gorstley (common north-east of Linton), Hereford and Worcester; x 1. Arrow in fig. 3 points to lateral extensions of organic lining. Figs 5-6, 10-11. Unassigned unwalled burrows. 5-6, NMV P10334 ( Trachyderma cf. squamosa of Chapman 1910, pi. 27, fig. 5); Humevale Formation (Lower Devonian), junction of Woori Yallock Creek and Yarra River, c. 50 km east of Melbourne city centre; x 1-5. 10, NMV P10343 (paratype of T. crassituba Chapman); Melbourne Formation (Lower Ludlow, nilssoni graptolite Biozone), Yarra improvements, South Yarra, excavations along Yarra River, 2-3 km east of Melbourne city centre, Victoria; x F5. 11, NMV P10335 ( T . cf. crassituba of Chapman 1910, pi. 27, fig. 4); locality as fig. 10; x2. Fig. 7. Unassigned burrow with carbonized lining; BGS GSM38372 (paralectotype of O. squamosum)-. Upper Ludlow, Hillside Farm, Woodbury Hill, Abberley district, Hereford and Worcester; x 2. Specimen shown in fig. 3 photographed under alcohol ; other specimens whitened with ammonium chloride sublimate. PLATE 2 THOMAS and SMITH, Keilorites, Oikobesalon, unassigned burrows 326 PALAEONTOLOGY, VOLUME 41 K. crassitubus differs from O. coriaceum in lacking an organic lining of fusiform construction and in possessing a thick sediment wall. Genus zoophycos Massalongo, 1855? Zoophycos! sp. Plate 3, figures 1-3, 5-7 v.pl919 Trachyderma, sp. cf. crassituba, Chapm., et alii specierum Chapman, p. 317, pi. 13, figs 1-3, pi. 14, figs 6-12, non fig. 5 [tubular burrow]. Material. NMV P140079; Springfield Formation (Llandovery, turriculatus-crispus graptolite biozones), north of eastern end of old Keilor township reserve, Maribyrnong River, Keilor district. NMV P 1 3 1 1 8— P 13119, respectively figured Chapman (1919, pi. 14, figs 6, 10), P13120 (Chapman 1919, pi. 13, fig. 2; pi. 14, fig. 7), PI 3 121 (Chapman 1919, pi. 13, fig. 1; pi. 14, fig. 11); Deep Creek Siltstone (Llandovery), Jackson’s Creek, 4 miles (6-4 km) north-west of Keilor (probably James’s worm impression locality; see James 1920, p. 330, pi. 32). NMV P58214, P140076; same section, c. 2 km downstream (east south-east) of Organ Pipes (James’s worm impression locality), Sydenham. NMV P13135, figured Chapman (1919, pi. 14, fig. 5); Anderson Creek Formation (Silurian), near Scotchman’s Creek, Mulgrave. NMV P140081; Anderson’s Creek or Melbourne formations (Upper Wenlock-Lower Ludlow), Plenty Gorge, south of Morang. GSV (Geological Survey of Victoria, housed at NMV) 38945; probably lower part of Dargile Formation (Wenlock-Ludlow), Parish of Redcastle, Heathcote district, central Victoria, mine dumps c. 1 mile (c. 1-6 km) north-east of township. Melbourne Formation (Lower Ludlow, nilssoni graptolite Biozone), excavations along Yarra River, South Yarra, 2-3 km east of Melbourne city centre: NMV P58217-P58218, P58229-P58230, (103 feet (31 m) below surface, Domain Road sewer); P13122-P13123, figured Chapman (1919, pi. 14, figs 9, 8), (Domain Road sewer, South Yarra Sewerage Works); P13117, figured Chapman (1919, pi. 13, fig. 3; pi. 14, fig. 12), P58242, (Hawthorn main drain); P140082, (Yarra improvements); P140080, P58237, (Melbourne district). Silurian (exact age uncertain): P140077 (Russell’s Orchard, If miles (2 km) north-north-east of Langwarrin (railway) Station, Keilor district); PI 40078 (Russell’s Ground, pipetrack 1| miles (2-4 km) north-north-east of Langwarrin Station). Remarks. Chapman (1919, p. 315) described putative gill plumes (cephalic prostomial appendages), possible eyes, and other soft-part structures, attributed to Keilorites. In most specimens that we have studied, the fossils appear darker than the matrix (e.g. PI. 3, figs 1-2, 5). They are not carbonized, however, but rather consist of darker, finer grained, sediment, which contrasts with the paler host material. Other specimens occur in bleached sediment, and these are paler than the background instead of darker. Most of the material is more-or-less completely flattened, but relief is preserved in some and this facilitates reinterpretation of the specimens as ichnofossils. EXPLANATION OF PLATE 3 Figs 1-3, 5-7. Zoophycos ? sp. indet. 1, P58242; Melbourne Formation (Lower Ludlow, nilssoni graptolite Biozone), excavations along Yarra River (Hawthorn main drain), South Yarra, 2-3 km east of Melbourne city centre; x2. 2, NMV140081; Anderson’s Creek or Melbourne formation (Upper Wenlock-Lower Ludlow), Plenty Gorge, south of Morang; x 1. 3, 7, NMV PI 40076; Deep Creek Siltstone (Llandovery), Jackson’s Creek, c. 2 km downstrean (east-north-east) of Organ Pipes (James’s worm impression locality), Sydenham; the main burrow is interpreted as a hypichnial ridge; x 1-25. 5, NMV P13117; locality and horizon as fig. 1 ; x 1-5. 6, NMV P140079; Springfield Sandstone (Llandovery), north of eastern end of old Keilor township reserve, Maribyrnong River, Keilor district ; the grooves are interpreted as natural moulds of hypichnial ridges ; x2. Fig. 4. Oikobesalon sp. indet.; BGS GSM105334; Upper Ludlow, Croagh Martin, Doonquin, Dingle, western Ireland; x2. Specimens shown in figs 1-2, 5 and 7 photographed under alcohol; other specimens whitened with ammonium chloride sublimate. '•*355?./, PLATE 3 THOMAS and SMITH, Zoophycosl , Oikobesalon 328 PALAEONTOLOGY, VOLUME 41 text-fig. 2. Diagrammatic sketch of the Zoophycos- like trace fossil producing the ‘ gill plumes ’ previously attributed to Keilorites. The sinuous main burrow is essentially horizontal. Major lamellae extend left- wards and dip gently in the same direction. Secondary (minor) lamellae arise from these and are also obliquely inclined. The fine stippled area indicates the shape produced by the intersection of a horizontal surface on this complex geometry of dipping planes. The ‘ plumes ’ are typically gently curved, having a simple margin on one side, and on the other bearing branches which have one feathered margin (PI. 3, figs 1-2). Occasionally specimens occur back-to-back, with the two branched margins facing away from a central axis (PI. 3, fig. 5). Specimens which preserve relief show that the simple margin or axis marks the position of a horizontal burrow (compare PI. 3, figs 3 and 7). From this, a succession of gently inclined planes (major lamellae) arises laterally. The specimen illustrated in Plate 3, figure 6 shows that each major lamella bears a pattern of fine ridges and grooves orientated obliquely to its margins : these are taken to indicate the positions of secondary (minor) lamellae. It is the intersection of this complex surface with essentially flat bedding planes, combined with the contrast between the host sediment and the fill, that results in the frond-like appearance. In summary: the ‘plume’ axis represents the main burrow, the proximal parts of the major lamellae form the lateral branches, and the minor lamellae give rise to the one finely feathered margin on each branch. The plume-like appearance is especially marked when only the proximal parts of the major lamellae are preserved. Specimens that occur back-to-back could represent fortuitous associations or the successive reworking of sediment by the same animal on either side of the main burrow. The structure described is matched in certain types of Zoophycos, an ichnofossil in which lateral growth takes place by successive branching probings along nearly parallel lines (Simpson 1970). Arcuate forms (often termed ‘Z. cauda galli') most resemble the present material (Simpson 1970, p. 508, fig. lb), but these are thought to represent incomplete specimens which originally belonged to larger and more complex structures. In our material, the secondary laminae point obliquely backwards towards the main burrow in plan view, whereas in Simpson’s reconstruction of ‘ cauda galli' many of the secondary laminae are inclined obliquely outwards and backwards. Whilst we do not see why this should reflect any significant behavioural contrast, it seems prudent to assign our specimens to Zoophycos with question. THOMAS AND SMITH: POLYCHAETE BURROWS 329 CONSTRUCTION OF THE OIKOBESALON BURROW We have been able to match the essential features of Oikobesalon only in burrows produced by members of the Terebellidae, a family of rather large, strongly cephalized, sedentary polychaetes. Recent terebellids mostly live in blind-ended tubes (Nara 1995, p. 176), and are suspension or detritus feeders, taking diatoms and other unicellular algae, and small invertebrates (see Grasse (1959) and Fauchald and Jumars (1979) for overview of morphology and biology). The similarities in tube morphology are such that we do not doubt that Oikobesalon was produced by a terebellid. Nevertheless, contrasts exist which suggest significant differences between the Oikobesalon animal and the agents responsible for producing previously described terebellid burrows. In this section, we discuss published accounts of Recent and Pleistocene terebellid burrows, the structure of the organic lining of Oikobesalon, and then make comparisons between them. Previously described terebellid burrows Aller and Yingst (1978) studied the tube dwellings of the extant sedentary terebellid polychaete Amphitrite ornata from the Cape Cod area of Massachusetts. Specimens of A. ornata commonly range from 80 to 200 mm long, and occur in intertidal sands and sandy muds. They usually construct U-shaped tubes with an internal diameter of 5-10 mm (Aller and Yingst 1978, p. 203). The burrow wall generally consists of four or more thin (1-5—2 mm) concentric cylinders or elongated cones each of which is lined on its inner side with an organic sheet about 5 pm thick (Aller and Yingst 1978, p. 211, fig. 3). The tube wall is formed by the successive packing of fusiform, brick- like structures, made of mucus-bound sediment, which separate from each other when the burrow is dried. The bricks vary in size, commonly being 2-\ mm transversely and 0-2-0-7 mm long (parallel to the tube axis), and may extend partly or wholly through the c. 2 mm thick external sediment cylinder. Extensions of the inner, organic, burrow lining occasionally extend outwards between the bricks (Aller and Yingst 1978, p. 213). Aller and Yingst (1978, p. 231) inferred the mechanism of burrow formation using direct observation, published descriptions, and analogy with other terebellids. Sediment particles are collected by the tentacles and coated with mucus. They are then taken between the unusually pliable and muscular (Fauchald and Jumars 1979, p. 252) outer lips, worked into a small parcel with additional mucus, and packed and shaped by the lower lip onto the accreting end of the tube. The animal subsequently rotates slightly in its tube and repeats the procedure. Each of the small parcels represents one of the fusiform bricks. By this means, A. ornata can extend its tube at a rate of c. 10 mm/hour. However, the animal cannot reburrow if completely exhumed. An almost identical method of tube construction (involving the collection of mud, kneading with mucus, and shaping before construction) is known for Neoamphitrite figulus, a terebellid known from North Sea tidal flats and down to depths of 60 m (Schafer 1972, p. 345). As well as using shaped bricks, however, N. figulus may incorporate foreign fragments and mud pebbles into its tube. A tube composed of fusiform bricks is known also for N. cirrosa (Schafer 1972, fig. 204, p. 346). Schafer (1972, p. 364) briefly described a broadly similar mechanism of burrow formation in the sabellid Sabella pavonina, but in this species components are added as complete rings and so lack the distinctive fusiform shape. The multiple layered construction of the A. ornata tube reflects several episodes of tube construction: only the innermost tube and its lining represent the primary dwelling structure. The outer layers result either from slight lateral or vertical movement, or may reflect the walls of older, smaller tubes mechanically split by the animal as it grew. The latter seems particularly likely in those cases where the arc length of the outer layers in radial cross section is smaller than the next inner one (Aller and Yingst 1978, p. 232). Although the burrow of A. ornata is U-shaped, it is used much of the time as two separate vertical burrows (Aller and Yingst 1978, p. 233). The U-morphology may increase the animal’s options for escape, for switching feeding areas, or for changing its respiratory position. Other terebellids may construct U-shaped, multibranched or vertical tubes. 330 PALAEONTOLOGY, VOLUME 41 text-fig. 3. a, portion of Amphitrite ornata burrow and enlarged view of burrow wall (modified after Aller and Yingst 1979, fig. 3c-d, p. 211). B, portion of Neoamphitrite cirrosa burrow (from Schafer 1956, text-fig. 13, p. 211; scale from Schafer 1972, fig. 204, p. 346). c, portion of Rosselia socialis burrow and enlarged view of inner surface (modified after Nara 1995, fig. 7b, p. 177; partly from observations by Kikuchi). d, Oikobesalon citrimorion sp. nov.; DUDMG G14076; tracing of part of holotype. Scale bars represent 5 mm. The ichnospecies Rosselia socialis was originally described from the Lower Devonian of Germany, and subsequently has been recorded widely in strata ranging from Early Cambrian to Pleistocene in age. It was redescribed and interpreted by Nara (1995), based on well preserved material from the Middle Pleistocene of the Boso Peninsula, central Japan. There, R. socialis is abundant in shoreface to offshore deposits of the Kongochi Formation. R. socialis burrows are walled, with a central diameter of 3-1 1 mm and an outer diameter of 8-16 mm (Nara 1995, p. 172). The wall is concentrically laminated and consists mainly of mud (specimens associated with an ash layer contain ash in the burrow lining, suggesting that sediment particles were collected at the surface; Nara 1995, p. 173, fig. 6b). The burrows are often c. 0-2 m long (more rarely < 1 m) and may be vertical or inclined at angles up to 60°. Reworked specimens occur, which may be broken into blocks. The concentric lamination of the burrow wall reflects an internal variation in grain size, attributed by Nara (1995, fig. 5, p. 175) to changes in the grain size of surface sediments (from which particles were collected) caused by alternating low and high energy conditions in the environment. Each lamina in the wall consists of a hollow spindle or cone. The overall shape of the burrow is spindle- or funnel-shaped: the funnel-shaped forms occur below erosion surfaces and formed as a result of truncation. THOMAS AND SMITH: POLYCHAETE BURROWS 331 Nara did not observe the brick-like wall structures described by Aller and Yingst or Schafer (1972, p. 346). However, he noted that they were recorded by Kikuchi, in structures reassigned by Nara to R. socialis from the younger Narita Formation (Middle Pleistocene) of the Boso Peninsula (Nara 1995, p. 177, fig. 7b). Nara’s drawing represents an area less than 10 mm square, and some of the fusiform bands are incomplete. However, they range from rare examples only c. 1 mm in maximum dimension to others apparently more than 10 mm across. The supposed terebellid remains from the Ordovician of Bohemia described by Prantl (1950) consist of small shelly fossils arranged in narrow zones in the sediment. These may represent some kind of agglutinated tube, but they do not closely resemble the material dealt with here. The organic lining of Oikobesalon The existence of exhumed and broken specimens indicates that, when fresh, the lining of Oikobesalon possessed significant mechanical strength and rigidity. Because of weathering, it is not possible to estimate the original thickness of the lining in our material. However, from O. liljevalli specimens. Brood (1980) argued that the organic lining was collapsed in the fossil state, and estimated its original thickness from the thickness of spar-filled cavities left after shrinkage of the tube. The complex but regular shape of the outer surface (now preserved as a sediment mould) he figured certainly suggests that that surface was biogenically produced (Brood 1980, p. 280, fig. 2). The organic lining appears as a very thin film largely separated from the surrounding sediment by carbonate spar. In places, the surrounding spar is absent, yet the organic layer is equally thin: presumably this reflects local compaction prior to precipitation of the cement. Brood (1980, p. 279) estimated the lining thickness of liljevalli at 1 mm for a tube about 100 mm long and 10 mm wide. The organic layer in specimens of Oikobesalon is highly carbonized, and its original composition unknown. Aller and Yingst (1978, p. 233) suggested that the organic layer of A. ornata might consist principally of sulphated or phosphate-rich mucopolysaccharides. They noted that such burrow linings sometimes contain enzymes which help to inhibit colonization by other organisms. Comparisons between Oikobesalon and described terebellid burrows The distinctive fusiform banding of the organic lining of Oikobesalon and the brick-like structures found in terebellid tubes are similar in both size and shape. Characteristic of the ichnogenus are the projections of the organic layer into the sediment. These we interpret as defining brick boundaries similar to those of the modern A. ornata. As in Oikobesalon , the organic linings described from Recent material occur principally on inner surfaces and sometimes between adjacent bricks. Exhumed specimens of Oikobesalon have no sediment wall preserved in association with the lining : this may be because the sediment separated as easily from the organic layer as Aller and Yingst described for A. ornata tubes. The absence of an identifiable sediment wall from in situ specimens is more surprising, although it would be difficult to recognize if the animal was indiscriminate in its choice of grain size, and if the amount of mucus used to bind the sediment was small. It is notable that Brood’s (1980) estimate of 1 mm for the lining thickness in O. liljevalli greatly exceeds the 5 pm recorded for A. ornata. We propose that the Oikobesalon animal relied more on the thickened organic lining to maintain the integrity of its burrow, and that the surrounding sediment layer was more loosely consolidated. The mode of growth of Oikobesalon must have differed from that of Rosselia socialis and A. ornata tubes. If the agent responsible for forming Oikobesalon had lived permanently in its burrow, either a concentric pattern of organic/sediment laminae would be expected due to burrow enlargement during growth, or disruption of the organic lining would be seen where it was split to allow new packages of mucus-bound sediment to be inserted. We propose that the Oikobesalon- producing organism did not inhabit one burrow throughout life. Rather it may have been able to construct a new burrow after exhumation, or when required during growth. Although the literature sometimes reports terebellids as being entirely sessile, Fauchald and Jumars (1979, pp. 252-253) noted that some may leave their tubes when necessary, and may swim or move on the substrate by 332 PALAEONTOLOGY, VOLUME 41 peristaltic crawling or by using their tentacles. Evidently terebellids have the potential for locomotion, but few use this capacity regularly, preferring a sessile or discretely motile existence. Acknowledgements. We thank Dr A. W. A. Rushton for advice and discussion, and Mrs H. Lane for translating German and Latin text. Dr D. J. Holloway (Museum of Victoria, Melbourne, NMV), Mr C. Reid (Dudley Museum and Art Gallery, DUDMG), Mr S. P. Tunnicliff (British Geological Survey, BGS) and Mr D. N. Lewis (The Natural History Museum, London, NHM) kindly loaned material in their care. Drs Holloway, P. D. Lane, and Rushton kindly read the manuscript, and offered useful suggestions for its improvement. Mrs E. Smith and Mrs J. 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SMITH Typescript received 1 1 December 1996 Revised typescript received 7 May 1997 School of Earth Sciences The University of Birmingham Birmingham B15 2TT, UK A REVIEW OF THE CYCLOSTOMICERATID NAUTILOIDS, INCLUDING NEW TAXA FROM THE LOWER ORDOVICIAN OF OLAND, SWEDEN by ANDREW H. KING Abstract. Cyclostomiceratidae is a distinct family of early Ordovician, small, gomphoceroid to breviconic ellesmerocerid nautiloids which possess an adorally contracting aperture. The family ranges in age from Arenig to early Llanvirn and is recorded from the USA, northern Argentina, east China and Baltoscandia. This paper reviews the family’s status, origin, stratigraphical occurrence and systematics. Three new taxa are described from the lower Kundan Stage of northern Oland, Sweden: Pictetoceras oliviae sp. nov., Parcyclostomiceras paucitumidum sp. nov. and Microstomiceras holmi gen. et sp. nov. These cyclostomiceratids are extremely well preserved and extend our knowledge of the morphology, biostratigraphy and palaeogeographical distribution of the family. Microstomiceras gen. nov. is one of the smallest nautiloids described from the Lower Palaeozoic. Ellesmerocerid nautiloids are some of the oldest Lower Palaeozoic cephalopods. They evolved from the ancestral plectronocerid nautiloids in China (Anhui and Shaanxi provinces) during the late Cambrian and range into the upper Ordovician where the group is represented by a single family in the Ashgill (Rawtheyan Stage) of Cincinnati (King 1993). Following a brief ‘evolutionary explosion’ in the late Cambrian when these early cephalopods spread across northern and eastern China, Kazakhstan and central Texas, they underwent a dramatic and sharp decline in terms of both taxonomic diversity and abundance. Three of the four nautiloid orders present in the late Cambrian became extinct before the end of the period, and only a few ellesmerocerid genera survived into the early Ordovician. From these forms, there developed a rich and diverse early Ordovician ellesmerocerid fauna which has been described extensively by Ulrich et al. (1943, 1944) and Flower (1964). When compared with other nautiloid orders, the ellesmerocerids are relatively limited in the form of morphological structures that they developed within their conchs to aid buoyancy regulation. Typically, they exhibit small, narrowly camerate shells with short septal necks and thickened, layered connecting rings. The apical portions of siphuncles of many taxa contain numerous apically directed siphonal diaphragms, although this feature is not exclusive to the group. Diversity amongst the lower Ordovician ellesmerocerids is represented mainly by variations in shell form which are sufficient to provide the basis for systematic classification at family and lower taxonomic levels. The family Cyclostomiceratidae is a distinctive group of Arenig to lower Llanvirn nautiloids which exhibit typical ellesmerocerid features: they possess small, narrowly camerate conchs with achoanitic to orthochoanitic septal necks and adorally contracting apertures. Siphonal diaphragms have been recorded from at least one taxon (Mutvei and Stumbur 1971). Although the Cyclostomiceratidae has had a varied taxonomic history, the genera currently assigned to the family appear to represent a natural grouping and, following Flower (1964), are presently retained within the order Ellesmerocerida. This assignment is provisional as the cyclostomiceratid muscle scars are of general ventromyarian form (Mutvei and Stumbur 1971 ; Text-fig. 4a here) which is very different from the dorsomyarian condition known to occur in some other ellesmerocerids (Dewitz 1880). Future classifications may regard this difference as being of high taxonomic significance and, consequently, the order Ellesmerocerida may be divided further. The study of collections of early Llanvirn cephalopods from the lower Kundan Stage of Oland [Palaeontology, Vol. 41, Part 2, 1998, pp. 335-347] © The Palaeontological Association 336 PALAEONTOLOGY, VOLUME 41 text-fig. 1. a. Geographical location of the island of Oland off south-eastern Sweden, b, Northern Oland and the Ordovician bedrock geology at Halludden shore and Enerum ; the strata are limestones of Latorpian and Volkhovian (dark grey), Kundan (pale grey) and post-Kundan (no ornament) age. SWEDEN (Oland) SWEDEN (Oland) GREAT BRITAIN GREAT BRITAIN NORTH AMERICA STAGES LIMESTONE FORMATIONS SERIES GRAPTOLITE BIOZONE STAGES LASNAMAGIAN Folkeslunda (part) LLANVIRN murchisoni WHITEROCKIAN Seby Skarlov ASERIAN Segerstad KUNDAN Holen artus ARENIG hirundo VALHALLAN VOLKHOVIAN Lanna gibberulus CASSINIAN LATORPIAN Latorp nitidus deflexus (approximate) JEFFERSONIAN text-fig. 2. Lithostratigraphical and chronostratigraphical nomenclature in Sweden (Oland), compared with British and North American chronostratigraphy and biostratigraphical correlation in relation to graptolite biozones. (held in the Swedish Museum of Natural History, Naturhistoriska Riksmuseet, Stockholm and the Swedish Geological Survey, Sveriges Geologiska Undersokning, Uppsala) has revealed three new taxa of cyclostomiceratid nautiloids. The specimens, collected by Gerhard and Olivia Holm between 1895 and 1909, come from the lower Holen Limestone Formation (often referred to by Gerhard Holm as the ‘gra vaginatumkalk ’ or grey vaginatum limestone) of Halludden shore and Enerum, KING: ORDOVICIAN NAUTILOIDS 337 northern Oland where the formation is superbly exposed in the low-lying cliffs and foreshore (Text- fig. 1). Across this island, strata dip slightly to the east and, with appropriate collecting techniques using distinctive discontinuity surfaces, a high degree of stratigraphical control can be obtained. Further details of the stratigraphy (summarized in Text-fig. 2) are given by Jaanusson and Mutvei (1982). The Swedish specimens are extremely well preserved and extend our knowledge of the morphology, biostratigraphy and palaeogeographical distribution of the family Cyclostomicera- tidae, which has not been recorded from Sweden previously. It is there represented by Pictetoceras oliviae sp. nov., Paracyclostomiceras paucitumidum sp. nov. and Microstomiceras holmi gen. et sp. nov. The only other records of Cyclostomiceratidae from Baltoscandia are provided by de Verneuil (1845) and Mutvei and Stumbur (1971) who described Pictetoceras eichwaldi (de Verneuil, 1845) from the upper Kundan Stage of Estonia. The Swedish representatives of the family are slightly older. HISTORICAL REVIEW OF THE FAMILY CYCLOSTOMICERATIDAE Foerste (1925) originally proposed Cyclostomiceratidae for the genera Cyclostomiceras Hyatt, in Zittel, 1900 and Eremoceras Hyatt, 1884, believing that their siphuncle wall was characteristically holochoanitic, although no material was apparently sectioned to confirm this feature. Ulrich and Foerste (1936) added their new genus Amphoroceras , based upon Cyclostomiceras minimum (Whitfield, 1886). Later, Ulrich et al. (1943) regarded Amphoroceras as a junior synonym of Cyclostomiceras and added their new genera Buehleoceras and Bridgeoceras to the family. They also figured thin sections of the siphonal wall of Cyclostomiceras indicating that this genus actually possessed very short septal necks and thick, layered connecting rings. Ulrich et al. (1944) later added Dresseroceras to the Cyclostomiceratidae; the holotype of its type species, and the only known specimen of this monospecific genus, is represented by the internal mould of a body-chamber which bears prominent but irregularly spaced transverse annulations. The structure of the siphuncle wall remains unknown. Cecioni (1953) described the new cyclostomiceratid Paracyclostomiceras from the Llanvirn of Serrania de Zapla, northern Argentina and illustrated the detail of the siphuncle wall. In their description of nautiloids from the lower Ordovician of Virginia, Unklesbay and Young (1956) included Woosteroceras Ulrich, Foerste, Miller and Unklesbay, 1944 within the Cyclostomiceratidae, and later Balashov (1962, p. 74, pi. 5, fig. 13) included Pictetoceras Foerste, 1926, demonstrating that the connecting rings of this latter genus were of thickened ellesmerocerid type. Furnish and Glenister (1964) placed Cyclostomiceratidae in synonymy with Ellesmeroceratidae Kobayashi, 1934. This procedure united a large number of taxa with comparable siphuncular features: short achoanitic to orthochoanitic septal necks, thick-layered connecting rings and siphonal diaphragms (where known). However, the synonymy adopted by Furnish and Glenister (1964) also incorporated taxa exhibiting a wide variety of conch forms within the single family Ellesmeroceratidae and this approach is now regarded as obscuring a number of distinct lineages. The same authors regarded Dresseroceras as a synonym of the protocycloceratid genus Protocycloceras Hyatt, in Zittel, 1900, although the former genus also bears a strong morphological resemblance to other annulate protocycloceratids such as Catoraphiceras Ulrich and Foerste, 1936 and Walcottoceras Ulrich and Foerste, 1936. Flower (1964) recognized a varied series of morphotypes within the Ellesmeroceratidae ranging from orthocones and simple cyrtocones to specialized forms with contracted or ‘crested’ apertures. He used these morphotypes for descriptive purposes but his morphogroups were not intended to represent independent lineages within the family. However, he acknowledged that the diversity of taxa then assigned to the Ellesmeroceratidae was unrealistic and re-introduced a number of previously used family names including Cyclostomiceratidae Foerste, 1925 for the genera Cyclostomiceras, Paracyclostomiceras and Pictetoceras. Mainly on the basis of conch form, he retained Eremoceras, Buehleroceras and Woosteroceras within a still highly diverse family Ellesmeroceratidae, and regarded Bridgeoceras as an ellesmerocerid of uncertain affinities. He also 338 PALAEONTOLOGY, VOLUME 41 regarded Dresseroceras as a synonym of Bridgeoceras which itself was an ‘ ellesmeroceroid of uncertain position’. Mutvei and Stumbur (1971) provided a comprehensive study of Pictetoceras from the Llanvirn (Kundan; Aluojan Substage) of Estonia, and noted the presence of siphonal diaphragms and muscle-scar impressions in the type species P. eichwaldi (de Verneuil, 1845). Chen Jun-yuan (in Qi et al. 1983) described the new genus Eocyclostomiceras from the lower Ordovician of northern Jiangxi Province, east China, but assigned the taxon to the Ellesmeroceratidae. This latter genus is poorly known but available morphological and stratigraphical evidence tentatively supports assignment to the Cyclostomiceratidae. Dzik (1984) recognized that the Ellesmeroceratidae contained a diverse range of conch forms and lineages, and introduced the family Oneotoceratidae for relatively short, compressed, endo- gastrically curved shells including Buehleroceras. He also distinguished the Cyclostomiceratidae as a small group of late Arenig to early Llanvirn inflated orthoconic nautiloids but synonymized both Pictetoceras and Paracyclostomiceras within Cyclostomiceras. For reasons described below, I regard these three genera as distinct. ORIGIN OF THE FAMILY CYCLOSTOMICERATIDAE Flower (1964, pp. 123-124) regarded the Cyclostomiceratidae as being derived from the ellesmerocerid family Baltoceratidae Kobayashi, 1935 during the late Canadian (Cassinian). He noted, in particular, that the Cassinian genus Metabaltoceras Flower, 1964 was intermediate between the two families in its overall form but departed from the generalized pattern in its relatively large ventral siphuncle and sutural lobes. The fusiform shell and achoanitic septal necks in Metabaltoceras offer some support for this possible relationship. The conch cross section of taxa assigned to the Cyclostomiceratidae is usually sub-circular to compressed, and is more reminiscent of the Bassleroceratidae than the Baltoceratidae in which it tends to be slightly depressed. Bassleroceratidae had a widespread distribution in the mid to late Canadian and several genera (Avaoceras, Diaphoroceras and Lawrenceoceras Ulrich, Foerste, Miller and Unklesbay, 1944) show features reminiscent of the Cyclostomiceratidae, namely contraction of the body-chamber near the aperture and very short septal necks with thick connecting rings (Flower 1964, p. 152; Furnish and Glenister 1964, p. K148). However, the Bassleroceratidae are represented mainly by longicones and consequently, despite superficial similarities, an origin for the Cyclostomiceratidae from a bassleroceratid ancestor is thought to be unlikely. Cyclostomiceratids also bear a close external resemblance to some bathmoceratid genera described from the upper Canadian of Argentina and Bolivia by Cecioni and Flower (1985). Bathmoceratidae is a group of ellesmerocerid nautiloids characterized by inflated and greatly thickened connecting rings which project adorally or laterally towards the siphuncle; these connecting rings are commonly associated with numerous diaphragms. However, the structure of the bathmoceratid siphuncle wall is wholly unlike siphonal features known within the Cyclostomi- ceratidae. In addition, the body-chambers belonging to the bathmoceratids described by Cecioni and Flower (1985) do not appear to contract adorad which is a characteristic feature of cyclostomiceratid taxa. Consequently, there appears to be no clear evidence to link the origins of the Cyclostomiceratidae and the Bathmoceratidae, and any similarity in external conch form is regarded here to be essentially homeomorphy. A possible origin for the Cyclostomiceratidae from within the Oneotoceratidae (Dzik 1984) does, however, require serious consideration. Dzik’s (1984) interpretation of the latter family included stout breviconic or near-gomphoceroid endogastric forms in addition to distinctive, strongly cyrtoconic brevicones. The oneotoceratids appear to exhibit very short septal necks with thickened, layered connecting rings which are highly comparable to those of the Cyclostomiceratidae, although the former family generally possesses a slightly narrower siphuncle. Further evidence for deriving the Cyclostomiceratidae from the Oneotoceratidae is provided here by Microstomiceras gen. nov. which indicates that the former family may also be endogastric. KING: ORDOVICIAN NAUTILOIDS 339 Current evidence would therefore indicate that the Cyclostomiceratidae developed in the late Canadian (Cassinian) from either the Baltoceratidae (via Metabaltoceras) or more likely from gomphoceroid-breviconic forms assigned to the Oneotoceratidae. SYSTEMATIC PALAEONTOLOGY The terminology used here follows that of Flower (1964) and Furnish and Glenister (1964). The type material of newly described species is held in collections at the Swedish Museum of Natural History (Naturhistoriska Riksmuseet, RM), Stockholm and the Swedish Geological Survey (Sveriges Geologiska Undersokning, SGU), Uppsala. Class cephalopoda Cuvier, 1797 Order ellesmerocerida Flower, in Flower and Kummel, 1950 Family cyclostomiceratidae Foerste, 1925 Diagnosis. Gomphoceroid to vasiform brevicones, shell straight or with faint endogastric or exogastric curvature. Conch section sub-circular to slightly compressed or depressed, rapidly expanding over the phragmocone; aperture typically contracted but never markedly constricted. Sutures transverse or with dorsal and ventral saddles and corresponding lateral lobes. Siphuncle (sub)ventral, with achoanitic to suborthochoanitic or orthochoanitic septal necks; segments concave and outlined by thick, layered connecting rings. Siphonal diaphragms known in some genera. Remarks. Conch form within the Cyclostomiceratidae varies: Cyclostomiceras and Paracyclo- stomiceras are essentially straight brevicones (Ulrich et al. 1943, pis 31-34; Cecioni 1953, pi. 3) whilst Microstomiceras gen. nov. is clearly endogastric. Mutvei and Stumbur’s (1971) reconstruction of Pictetoceras eichwaldi (de Verneuil, 1945) proposes a straight, breviconic shell with a very large protoconch, although available evidence (based on Cyclostomiceras cassinense and C. depressum in Ulrich et al. 1943 and Microstomiceras holmi gen. et sp. nov.) indicates that the protoconch of cyclostomiceratids was, in fact, relatively small. This is consistent with Dzik’s (1984, p. 22) suggestion that the apical parts of ellesmerocerids may represent nautiloids with a small planktonic larval stage. Genera assigned. Cyclostomiceratidae is regarded here as a distinct family of breviconic ellesmerocerids containing the following taxa: Cyclostomiceras Hyatt, in Zittel, 1900; Pictetoceras Foerste, 1926; Para- cyclostomiceras Cecioni, 1953; Eocyclostomiceras Chen, in Qi et al., 1983 and Microstomiceras gen. nov. Occurrence. Arenig (upper Canadian, Cassinian) to lower Llanvirn of the USA, Baltoscandia, northern Argentina and east China. Genus cyclostomiceras Hyatt, in Zittel, 1900 (= Amphoroceras Ulrich and Foerste, 1936) Type species. Gomphoceras cassinense Whitfield, 1886; by original designation (Hyatt, in Zittel 1900, p. 611). Diagnosis. Gomphoceroid, breviconic orthocones with circular to depressed section; phragmocone expanding forward fairly rapidly, anterior half of mature body-chamber slightly contracted. Sutures and growth lines straight and directly transverse. Siphuncle small, about 15 per cent, of conch diameter, ventral in position but not marginal. Septal necks orthochoanitic, connecting rings thick and layered. Remarks. Apart from the type species C. cassinense (Whitfield), the following taxa are also assigned to the genus: C. minimum (Whitfield, 1886), C. depressum Ulrich, Foerste and Miller, 1943 and PALAEONTOLOGY, VOLUME 41 text-fig. 3. a-d, Pictetoceras oliviae sp. nov. ; lower Holen Limestone Formation, Halludden, northern Oland. a-b, ventral and left lateral views of holotype, RM Mol 58460a; x L75. c-d, ventral and left lateral views of paratype, RM Mol58441; x 2-7. e-h, Paracyclostomiceras paucitumidum sp. nov.; lower Holen Limestone Formation, northern Oland. e-f, ventral and left lateral views of holotype, SGU CeOOl, from Enerum; x 1-25. G-H, ventral and left lateral views of paratype, SGU Ce002, from Halludden; x 1-75. I-L, Microstomiceras holmi gen. et sp. nov. ; lower Holen Limestone Formation, Halludden, northern Oland. i, right lateral view of holotype, RM Mol58700; x3-3. J-L, ventral, right lateral and dorsal views of paratype, RM Mol58698; x 3-75. KING: ORDOVICIAN NAUTILOIDS 341 C. depressius Cecioni, 1953. Cyclostomicerasl vasiforme (Dwight, 1884) is of uncertain status; according to Flower (1964, p. 124), the weathered section of a Bassleroceras would produce a form analogous to the type specimen. The expansion rate and conch form of the specimen tends to confirm that its assignment to the Cyclostomiceratidae is incorrect. Occurrence. Cecioni (1953) reported C. depressius from the Arenig of Quebrada de Coquena, Purmamarca, Chile; C.? vasiforme is recorded from the Mid Canadian Rochdale Limestone of southern New York. All the remaining taxa occur in the Fort Cassin Limestone of the Champlain Valley, Addison County, Vermont or the Smithville Formation of Lawrence County, Arkansas (both occurrences are of Arenig age). Genus pictetoceras Foerste, 1926 Type species. Gomphoceras eichwaldi de Verneuil, 1845, p. 357; by original designation (Foerste 1926, p. 327). Diagnosis. Conch gomphoceroid, enlarging as far as anterior part of the phragmocone then contracting adorally. Shell section compressed; sutures inclined forward over the venter. External conch surface ornamented with weak, indistinct growth lines. Body-chamber relatively long, apertural margin with a distinct, unpaired dorsal sinus and weaker ventral sinus ; camerae narrow, 10-15 per cent, of the dorso-ventral diameter. Siphuncle circular in section, in contact with ventral wall, 20-25 per cent, of conch diameter. Septal necks orthochoanitic ; connecting rings three to four times thicker than septa and layered. Apical portions of siphuncle traversed by numerous, adorally arching calcareous diaphragms. Remarks. Pictetoceras was reviewed by Mutvei and Stumbur (1971) who regarded the genus as monospecific and described the type species, P. eichwaldi , from the upper Kundan Stage (Aluojan Substage) of the St Petersburg district and Estonia. A slightly older species, P. oliviae sp. nov., is described here from the lower Kundan of Oland. This new species is much smaller than P. eichwaldi (based on the assumption that contraction of the aperture with septal approximation is indicative of maturity in individual specimens). The type material of P. oliviae sp. nov. does not exhibit siphonal diaphragms, although it is likely that no material sufficiently apicad to contain such structures has been sectioned. Occurrence. Kundan Stage (uppermost Arenig to lower Llanvirn) of Oland, Sweden, Estonia and the St Petersburg district. Pictetoceras oliviae sp. nov. Text-figures 3a-d, 4, 6a Derivation of name. For Olivia Holm, the daughter of Gerhard Holm, who collected the holotype specimen in 1896. Material. The holotype (RM Mo 158460a) is an unsectioned conch with a complete body-chamber and several adoral camerae. Three paratypes (Mo 158441, 158457, 158460b-d) consist of incomplete sectioned phragmocones and/or body-chambers. All the type material was collected by Olivia and Gerhard Holm in 1890 and 1896, from the lower Holen Limestone Formation (lower Kundan Stage) at Halludden, northern Oland. Diagnosis. Small, slender Pictetoceras with sub-circular section and elongate body-chamber which gradually contracts adorad. Description. Conch small and slender, vasiform-breviconic with sub-circular section. Holotype is most complete specimen examined; length 24-2 mm, adoral 14-2 mm representing body-chamber. Latter relatively long (estimated 40 per cent, of total conch length) and contracting slowly towards aperture; contraction 342 PALAEONTOLOGY, VOLUME 4 text-fig. 4. Pictetoceras oliviae sp. nov.; RM Mol58441, paratype; lower Holen Limestone Formation Halludden, northern Oland, a, ventral view of base of body-chamber showing annular retractor muscle scar (ms) with indistinct lobes concentrated ventrally; x 4-6. b, shell cross section, venter and siphuncle uppermost; x 5. greater on ventral side, dorsal side only slightly concave. External shell surface smooth with very faint growth lines which trace out feeble dorsal and ventral sinuses. Maximum conch width in holotype near top of phragmocone where dorsoventral diameter is 1 2-4 mm; at apical end, dorso-ventral diameter is 10-3 mm with lateral width 9-4 mm. Body-chamber bears faint muscle-scars consisting of annular retractor scar with indistinct lobes concentrated ventrally (Text-fig. 4a). Sutures laterally transverse, becoming very weakly inclined over venter and dorsum. Average cameral height I T mm, septal concavity shallow. At base of body- chamber, siphuncle represents 26 per cent, of conch diameter, reducing to 15 per cent, at apical end. Septal necks orthochoanitic, extending apicad 0-2 camerae. Connecting rings thick and layered; inner layer (adjacent to siphuncle) dark and comparable in thickness to septa, outer layer (adjacent to camerae) paler and three to four times septal thickness (Text-fig. 6a). Remarks. P. oliviae sp. nov. differs from the type species, P. eichwaldi, in its smaller size and relatively long body-chamber. The ventromyarian muscle scars observed at the base of the body- chamber in P. oliviae sp. nov. are similar in form to those described for the type species of Pictetoceras by Mutvei and Stumbur (1971, p. 120). Occurrence. The species is known only from the lower Holen Limestone Formation (lower Kundan Stage) at Halludden, northern Oland. The specimens collected in the last century were obtained from either the Hunderumian or Valastean substages, or both. Several other specimens collected recently from Halludden are also likely to belong to this species but require further study to confirm this assignment. These specimens come from the lowermost part of the Valastean Substage (Jaanusson and Mutvei 1982, p. 16), between 0-0-05 m and 0- 1 5 m below the main discontinuity surface. Genus paracyclostomiceras Cecioni, 1953 Types species. Paracyclostomiceras floweri Cecioni, 1953; by original designation (Cecioni 1953, p. 98). Diagnosis. Similar to Cyclostomiceras but sutures undulatory with well-developed dorsal and ventral saddles and corresponding lateral lobes. Remarks. This genus is similar in overall conch form to Cyclostomiceras but is readily identified by the form of its sutures. Cecioni (1953) noted that the apertural contraction rate of Paracyclostomiceras was smaller than that known for Cyclostomiceras , and that the siphuncle was in contact with the ventral wall of the conch (according to Cecioni, the siphuncle is slightly removed from the venter in Cyclostomiceras). Apart from the type species, he also described P. depressum KING: ORDOVICIAN NAUTILOIDS 343 text-fig. 5. Polished dorso-ventral sections of conchs, all from the lower Holen Limestone Formation of northern Oland. A, Paracyclostomiceras paucitumidum sp. nov.; SGU CeOOl, holotype; Enerum. B-c. Microstomiceras holmi gen. et sp. nov. ; RM Mol 58700, holotype ; Halludden. b, x 3-75. c, detail of same ; x 7. which (as its name implies) has a more depressed conch section than P.floweri. The Swedish species, P. paucitumidum sp. nov., has a less inflated conch form and is distinctly compressed in section. Occurrence. The genus has been recorded only from the Llanvirn of Argentina and Sweden. The South American specimens were collected from Rio Las Capillas and Garrapatal, Serrania de Zapla, northern Argentina from a horizon with Hoekaspis schlagintweiti Harrington and Leanza. Associated trilobite (Hoekaspis-Famatinolithus) and graptolite ( Didymograptus bifidus-D. climacograptoides group) faunas support an early Llanvirn age (Acenolaza 1976). P. paucitumidum sp. nov. is known from the lower Kundan Stage (uppermost Arenig or lower Llanvirn) of northern Oland. Paracyclostomiceras paucitumidum sp. nov. Text-figures 3e-h, 5a, 6b Derivation of name. From Latin paucus meaning little and tumidus meaning swollen, referring to the relatively slender conch form of this species. Material. The holotype (SGU CeOOl) and paratype (SGU Ce002) consist of incomplete dorso-ventrally sectioned phragmocones with portions of the body-chamber remaining. Both specimens were collected by Gerhard Holm in 1895 from the lower Holen Limestone Formation (lower Kundan Stage) of northern Oland; the holotype is from Enerum, the paratype from Halludden. Diagnosis. Relatively slender Paracyclostomiceras with compressed section. Description. Conch slender, vasiform-breviconic with conspicuously compressed section. Body-chamber in both holotype and paratype incomplete but gradually contracting adorad. Holotype 41-9 mm long, adoral 20-5 mm representing body-chamber. Remainder of phragmocone consisting of nine camerae, each c. 2-0 mm high except for adoral camerae where septa approximated and 0-7 mm apart. Lateral compression of conch evident at apical end where dorso-ventral diameter 14-9 mm and lateral width 12-1 mm. Sutures undulatory, forming broad and conspicuous apically directed lobes; septa shallowly concave. Siphuncle ventral, sub-circular, 25 per cent, of conch diameter. Septal ridges distinct, comprising sharp, adorally directed raised lines 2-2 mm apart on venter. Septal necks orthochoanitic, extending apicad 0-25 to 0-3 camerae. Connecting rings thick and layered (Text-fig. 6b), with inner dark layer (adjacent to siphuncle) and 344 PALAEONTOLOGY, VOLUME 41 C text-fig. 6. Camera lucida drawings of the structure of the siphuncle wall; solid shading indicates septa, stippling represents layered connecting rings, A, Pictetoceras oliviae sp. nov.; RM Mol58460b, paratype. B, Paracyclostomiceras paucitumidum sp. nov. ; SGU CeOOl, holotype. c, Microstomiceras holmi gen. et sp. nov. ; RM Mo 158700, holotype. Scale bar represents 0-5 mm (a), 1 mm (b) and 0-25 mm (c). outer, paler thicker layer (adjacent to camerae). Fragments of external shell confirm conch surface to be virtually smooth with inconspicuous feeble growth lines. Paratype similar to holotype but smaller; 31-4 mm long, adoral 12-7 mm representing body-chamber; remaining 18-7 mm of phragmocone consisting of ten camerae varying in height from 1-5 mm to 1-9 mm. Remarks. Paracyclostomiceras paucitumidum sp. nov. is readily distinguished from other species assigned to the genus by its laterally compressed conch section. Occurrence. Lower Holen Limestone Formation (lower Kundan Stage; Hunderumian and/or Valastean substages) of Enerum and Halludden, northern Oland. Genus eocyclostomiceras Chen, in Qi et al., 1983 Type species. Eocyclostomiceras ventrum Chen, in Qi et al. 1983; by original designation (Chen, in Qi et al., 1983, p. 305). Remarks. Eocyclostomiceras is a poorly known genus described from incomplete, sectioned (but apparently gomphoceroid) phragmocones with the apical portion of a body-chamber preserved in the holotype of the type species. The siphuncle is relatively narrow, accounting for c. 10-15 per cent, of the conch diameter; septal necks short, probably orthochoanitic, connecting rings thick and layered. The sub-circular shell section and structure of the siphuncle wall tentatively support assignment of the genus to the Cyclostomiceratidae, although the overall conch form is unknown KING: ORDOVICIAN NAUTILOIDS 345 and more detailed comparison with other genera is not possible. Further study may prove the genus to be synonymous with Cyclostomiceras. Apart from the type species, Chen Jun-yuan (in Qi et al. 1983) also described E. subventrum (with subventral siphuncle) and E. clinoseptatum (with steeply inclined septa). Occurrence. All three species of Eocyclostomiceras are reported from the lower Ordovician (Dawan Formation or equivalent) of northern Jiangxi Province, east China. Associated cephalopods, including Hemichoanella canning i Teichert and Glenister, indicated a late Canadian (Arenig) age. Genus microstomiceras gen. nov. Type species. Microstomiceras holmi sp. nov. Derivation of name. From Greek mikro meaning little and stoma meaning mouth, referring to the small, contracted aperture of this taxon and its small conch size. Diagnosis. Very small, slightly endogastric gomphoceroid brevicone with moderate expansion rate enlarging to base of body-chamber and then contracting adorally; body-chamber 30-35 per cent, of total length. Shell surface ornamented with weak, indistinct growth lines. Conch section sub- circular to slightly compressed, sutures nearly transverse with faint inclination forward over dorsum. Camerae narrow, comprising 9 per cent, of dorsoventral diameter, siphuncle slightly removed from ventral shell wall, representing approximately 10 per cent, of conch width adorally increasing to 18 per cent, apically. Septal necks very short, suborthochoanitic to achoanitic; connecting rings thick and layered. Remarks. This monospecific genus is readily distinguished from all other cyclostomiceratids by its small size and slight endogastric curvature. Microstomiceras gen. nov. is one of the smallest nautiloids yet described from the Lower Palaeozoic. Occurrence. Lower Kundan Stage (uppermost Arenig to lower Llanvirn) of northern Oland, Sweden. Microstomiceras holmi sp. nov. Text-figures 3i-l, 5b-c, 6c Derivation of name. In honour of the eminent Swedish palaeontologist Gerhard Holm (1853-1926) who collected the type material. Material. The holotype (RM Mo 158700) is a nearly complete specimen which has been dorso-ventrally sectioned. Three paratypes are also designated: Mol 58697 is a thin section through a portion of a phragmocone and body-chamber; paratypes Mo 158698-1 58699 are sub-complete, unsectioned phragmocones with body-chamber. None of these specimens retain the apicadmost tip of the conch. All the material was collected by Gerhard Holm (in 1895 and 1909) from the ‘grey vaginatum limestone’ (lower Holen Limestone Formation) at Halludden, northern Oland. Description. Very small, slightly endogastric gomphoceroid brevicones less than 14 mm long. Holotype 11-5 mm long with maximum width 5-5 mm; body-chamber 3-9 mm long, approximately 34 per cent, of total conch length. Conch expansion rate moderate, maximum width attained at base of body-chamber. Body-chamber contracts adorally by similar amounts on dorsal and ventral sides, aperture 55-60 per cent, of maximum conch width. Conch section sub-circular, becoming slightly compressed apically. Shell surface smooth, ornamented with indistinct growth lines only. Sutures nearly transverse with slight adorally directed, broad saddle over dorsum. Siphuncle slightly removed from venter, nearly 10 per cent, of conch diameter adorad and 18 per cent, apicad. Septa shallow, average cameral height 0-5 mm; in holotype, last-formed septum approximated. Septal necks very short, achoanitic to suborthochoanitic; connecting rings thick and layered but tapering and 346 PALAEONTOLOGY, VOLUME 41 thinning slightly in apical region of camerae (Text-fig. 6c). Diaphragms not visible but apicadmost tips lacking from all conchs examined. Remarks. No specimens of Microstomiceras holmi sp. nov. examined exceed 14 mm in total length; this figure allows for the apicadmost tips of the conchs which are missing. The adoral contraction of the body-chamber and approximation of the last-secreted septa are regarded here as being reliable indicators of maturity. Consequently M. holmi sp. nov. is the smallest cyclostomiceratid known and the first member of the family known to possess a definite endogastric shell. Occurrence. Lower Holen Limestone Formation (lower Kundan Stage, Hunderumian to lower Valastean substages) at Halludden, northern Oland. CONCLUSIONS Cyclostomiceratidae is a family of short breviconic to gomphoceroid nautiloids recorded from the Arenig and Llanvirn (lower Ordovician) of the USA, Baltoscandia, northern Argentina and east China (Jiangxi Province). It is distinguished from all other ellesmerocerids by its combination of shell form, with contracted apertures and achoanitic to orthochoanitic septal necks outlined by thick connecting rings. As is common with many other Lower Palaeozoic nautiloids, the new Swedish taxa described in this paper are based on only a few specimens. Current knowledge indicates that although Cyclostomiceratidae possessed a wide palaeogeographical range, they were not common elements of early Ordovician nautiloid faunas. Consequently, it is not possible on present evidence to gauge the amount of intraspecific variation that these nautiloids may exhibit. However, the combination of distinct morphological features, excellent preservation and stratigraphical position, provides ample evidence for regarding the cyclostomiceratids from Oland as representing new and distinct taxa. In particular, Microstomiceras gen. nov. is one of the smallest nautiloids yet described from the Lower Palaeozoic. Acknowledgements. I thank Professor Valdar Jaanusson, Dr Harry Mutvei, Dr Lars Karis and Sven-Ola Nilsson for making the material available for loan from the Naturhistoriska Riksmuseet and Sveriges Geologiska Undersokning. I am grateful to my supervisors, Drs L. Cherns and J. C. W. Cope, University of Wales, Cardiff. I also thank Dr Dave Evans for useful discussions about the Cyclostomiceratidae and Marion Hoad for translating from the Spanish paper by Cecioni (1953). This work was carried out with the assistance of NERC grant GT4/86/GS/137 which is gratefully acknowledged. An anonymous referee kindly commented on the manuscript. 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Macmillan & Company Limited, London and New York, 706 pp. [Reprinted in 1937 with different pagination]. Typescript received 26 March 1997 Revised typescript received 3 July 1997 ANDREW H. KING English Nature Northminster House Peterborough PEI 1UA GINKGO FOLIAGE FROM THE JURASSIC OF THE CARPATHIAN BASIN by ZOLTAN CZIER Abstract. Mesophytic Ginkgo foliage from the Carpathian Basin (Romania and Hungary) is revised using a new statistical method for identification. The genera Ginkgoites and Baiera are suppressed in favour of Ginkgo. New combinations G. marginata and G. skottsbergii are studied for the first time using scanning electron microscopy. G. baieraeformis banaticus subsp. nov. is an Indo-European member of the Dictyophyllum- Clathropteris Flora. G. marginata banatica subsp. nov. is characteristic of the Clathropteris meniscioides Biozone (Hettangian-Sinemurian) of the European Province. G. polymorpha is of western origin, later spreading out into Siberia. G. skottsbergii europeica subsp. nov. possibly belongs to the Dictyophyllum- Clathropteris Flora that originated in the Late Triassic in eastern South-east Asia, spread to Europe in the Early Jurassic and to South America in the Mid Jurassic, where it persisted until the Early Cretaceous. The Carpathian Basin yields one of the richest Liassic floras in Europe (Czier 1990, 19946, 1996a, in press b). However, the only detailed records of Ginkgo leaves have been from the lower Liassic of the Transylvanian part of Romania and the Transdanubian part of Hungary (Text-fig. 1). The earliest illustration is of a leaf from Anina figured by Hantken (1878) as Baiera taeniata Braun. This locality, now in Romania, was part of Hungary before the First World War and known as Stajerlak or Steierdorf. Other specimens from Anina were described by Humml (1969) as Ginkgoites taeniata (Braun) Harris, and by Givulescu (1991) as Baiera polymorpha Sarny lina. Significantly, both papers included details of the cuticles. Mateescu (1958) described specimens from Svinecea Mare as B. taeniata but without cuticles. Nagy (1961) described specimens from Komlo and Pecsbanyatelep (Hungary) as Ginkgoites marginatus (Nathorst) Florin, as well as associated fructifications similar to those of living Ginkgo biloba Linnaeus. Other records of Mesophytic Ginkgo- type leaves from Romania are in species lists without descriptions or illustrations (Semaka 1961, 1962a, 19626, 1963, 1965, 1968, 1970; Oarcea and Semaka 1962; Humml 1963; Semaka et al. 1972). They are based mainly on specimens stored in the Institute of Geology and Geophysics in Bucharest, but a request to study these specimens was refused and so nothing is known of their cuticles. As cuticle information is critical, these records are of little value and are not referred to in the rest of this paper. This paper completely revises all well-documented Liassic Ginkgo- like leaves from the Carpathian Basin, including new material from Anina and §uncuiu§, and may be regarded as a synthesis of Mesophytic Ginkgo foliage from this part of Europe. Scanning electron microscopy was used for the first time with such foliage from here, and has yielded results significant for both Carpathian palaeobotany and a wider understanding of the group. IMPORTANCE OF CUTICLE STUDIES IN THE GENUS GINKGO Cuticles are essential for the identification of Ginkgo- type leaves, because biological species show so much morphological variation, as is clearly seen in the extant Ginkgo biloba. The limits of this variation are subject to genetic control but climate also has a strong effect. Kimura {in Zhao et al. 1993, p. 80) demonstrated experimentally that low levels of water supply or natural light would cause seedlings to sprout leaves in May, but they remained abnormally small until leaf-fall in the [Palaeontology, Vol. 41, Part 2, 1998, pp. 349-381, 4 pis] The Palaeontological Association 350 PALAEONTOLOGY, VOLUME 41 "Pecsbany 0 100km 1 i text-fig. 1. Localities yielding Ginkgo foliage in the lower Liassic of the Carpathian Basin. autumn. If such miniature leaves, or the rare outgrowth leaves with multidivided laminae, were preserved as fossil impressions, palaeobotanists would probably recognize them as separate Ginkgo species. Significantly, however, the cuticles remained the same. The wide morphological variation in Mesophytic Ginkgo- like leaves, particularly in the early Liassic, was almost certainly influenced largely by climate. Epidermal structure is therefore the only reliable means of distinguishing between Ginkgo species. This conclusion has at least four practical implications. 1. Leaf gross morphology must be treated with the greatest caution in Ginkgo taxonomy. Macroscopic characters alone cannot define or be used to distinguish fossil species of Ginkgo. 2. New species of Ginkgo should only be established for fossil leaves where cuticles are known. 3. Fossil Ginkgo leaves lacking cuticles should only be assigned with an ‘aff. ’ to a species for which cuticles have been described. If no such comparable species can be found, they should be determined simply as Ginkgo sp. 4. It is vital to obtain epidermal evidence for any species of fossil Ginkgo leaf diagnosed only on macroscopic characters. If no cuticles are available from the original types, that species should be rejected. No attempt should be made to establish cuticle-bearing neotypes for such species. The cuticular characters of some of the better studied Ginkgo leaves are summarized in the Appendix. However, not all of these characters are of the same taxonomic value. For instance, because the non-stomatal bands correspond mainly to the veins, their width tends to be of very low taxonomic significance. The distinction between the costal and intercostal fields probably depends mainly on the fineness of the venation, and so is again of rather low taxonomic importance. The dimensions, shape and arrangement of the epidermal cells are generally highly variable in a species, sometimes even in the same specimen, and often overlap with the variation in other species. More important are the shape of the cell walls, whether the lamina is hypostomatic or amphistomatic, and the arrangement and orientation of the stomata. The cell ornamentation (papillae and trichomes) and stomatal density and index are also of great taxonomic importance, as well as providing information about the palaeoclimate (Chaloner and Creber 1990). The most important characters are, however, those of the stomatal structure, including the shape and size of CZIER : JURASSIC GINKGO FOLIAGE 351 the guard cells, the shape, size, number and ornamentation of the subsidiary cells, and the shape of the stomatal pit. Because of their different taxonomic importance, each character is assigned a Factor of Importance (F), ranging from 1 (least important) to 10 (most important). The Factor of Importance for each of the characters studied is given in the Appendix. Not all of these cuticular characters are easily observed using light microscopy; details of the stomata can be particularly difficult (e.g. ornamentation, walls and mutual relationships between the guard and subsidiary cells). As such characters are among the most important for Ginkgo leaf taxonomy, light microscopy must be supplemented by scanning electron microscopy (SEM). The value of SEM has been clearly demonstrated in the studies of Ginkgo insolita Samylina from the Middle Jurassic of western Siberia (Samylina and Markovich 1991) and of G. manchurica from the upper Jurassic or lower Cretaceous of Inner Mongolia (Zhao et al. 1993). IDENTIFICATION OF FOSSIL GINKGO LEAVES The following is a new statistical approach to the perennial problem of identifying fragmentary plant fossils. It is used here for Ginkgo foliage but could be adapted to any group of plant fossils. The first step is to list all characters on which the identification is to be based and to assign a Factor of Importance (F) to each. Then, for each well-documented species which might be comparable, assign one of four letters to each character : T, if that species is identical to the new material in that character; N, if that species is totally different from the new material in that character; P, if that species partly agrees with the new material in that character; and U, if that character is not known in either that species or the new material. Each occurrence of T, N, P and U is then multiplied by its corresponding Factor of Importance, and then summed over the entire species. This results in four parameters, EFT, EFN, EFP and EFU, from which an Affinity Index (A) is calculated. (EFT — EFN) + (EFP + EFU) A = fp xl0°- The resulting two values for A reflect the extreme cases whereby all of the P and U values have the same influence as T (i.e. the Highest Affinity Index - AH) or they all have the opposite influence as T (i.e. the Lowest Affinity Index - AL). The next stage depends on whether cuticles are preserved in the new material. If they are, then the following decision tree should be followed through. 1 . If EFN =)= 0 for all species, go to 2 If EFN = 0 for one or more species, go to 3 2. Recalculate EFN for cuticular characters only (EFNC) If EFNC =f= 0 for all species, go to 2.1 If EFNC = 0 for one species, go to 3 ; if necessary, emend diagnosis to account for apparent discrepancy in gross morphology If £FNC = 0 for several species, go to 3 ; where AL > 0 in no species, the assignments should be with ‘ex group’ rather than ‘cf.’ 2.1 If EFN < 15 in one species, assign to that species and emend diagnosis; go to 2.1.1 If EFN < 15 in several species, select species with lowest EFN, assign to that species and emend diagnosis; go to 2.1.1 If EFN < 15 in no species, select that species with the lowest EFN; go to 2.1.2 2.1.1 If new material is from a quite different geographical area and/or stratigraphical level from the types, create new subspecies If new material is from a clearly different population, but the geographical and/or stratigraphical separation is only partly distinct, create new variety 352 PALAEONTOLOGY, VOLUME 41 2.1.2 If Al > 0, assign to that species with ‘aff. ’ If Al < 0, either continue comparisons with other species or, if all reasonable comparisons have been made, create new species 3. If AL > 0 in no species, assign with ‘cf. ’ to the species with highest AL; if several species have an equally high AL, assign with ‘ cf. ’ to species with highest AH If AL > 0 in only one species, then assign to that species If AL > 0 in several species, select that species with the highest AL; if several species have an equally high AL, assign to species with highest AH The limiting value at node 2. 1 will vary in different groups of fossils, and reflects those characters which are of low taxonomic value. In the case of Ginkgo , it has been given as 1 5, due to the low F values of the 1 1 macroscopic characters and of the widths of the stomatal and non-stomatal bands. If the new material does not have cuticles, the same four parameters EFT, EFN, EFP and EFU, and the Affinity Index (A) are calculated on the macroscopic characters alone. A simplified decision tree is then used. 1. If EFN = 0 in no species, refer it to Ginkgo sp. or Ginkgo ? sp. If EFN = 0 in one or more species, go to 2. 2. Select species with highest EFT values; if only one species has that value, assign there with ‘aff. ’. If several species have highest EFT value, assign it with ‘aff.’ to that species which is geographically and/or stratigraphically nearest MATERIAL AND METHODS The material described in this paper consists of five hand specimens, three slides and two SEM stubs. Two hand specimens were collected by the author in 1987 and 1988, from the lower Liassic of §uncuiu§, and are now in the Palaeobotanical Collection of the Jarii Cri§urilor Museum - Natural Sciences (TCMO-NS. 15364/1 and 16623/4). The other three hand specimens were collected in 1937 from the lower Liassic of Anina (other data not known) and are kept in the Palaeobotanical Collection of the Hungarian Natural History Museum, Budapest (MTM- BP. 602241 A-C). The slides (Z.C. 12-14) and SEM stubs (Z.C. 1 1 SEM, 12 SEM) are currently kept in the Bihor County Museum, Oradea, but are to be deposited in the Hungarian Natural History Museum, Budapest. Cuticles were prepared by macerating the fossil in Schulze’s reagent (HN03 plus KC103) and neutralizing with KOH. The cuticles were mounted in glycerin-jelly for light microscopy, and on a transparent film for SEM study. SYSTEMATIC PALAEONTOLOGY Phylum GINKGOPHYTA Order ginkgoales Family ginkgo ace ae Genus ginkgo Linnaeus, 1771 Type species. Ginkgo biloba Linnaeus, 1771. Remarks. It has been argued (e.g. Petrescu and Dragastan 1981) that the Ginkgoales belong to the Cordaitopsida (Gymnospermatophyta). However, I follow authors such as Boersma and van Konijnenburg-van Cittert (1991) and use the phylum name Ginkgophyta. I also follow Zhou (1991) in the use of the family name Ginkgoaceae. Ginkgo was introduced by Linnaeus (1771) for the extant maidenhair tree. Although it has also been used for fossil foliage (e.g. Heer 1876), many palaeobotanists have tended to assign such fossils CZIER : JURASSIC GINKGO FOLIAGE 353 to Ginkgoites Seward, 1919 and Baiera Braun, 1843 emend. Florin, 1936. As pointed out by Harris and Millington (1974, p. 4), however, the name Ginkgoites has been used in three different ways. 1. Seward (1919) originally proposed it for Ginkgo- like fossil leaves for which reproductive organs were unknown; in this sense, Ginkgoites has no morphological distinction from Ginkgo. 2. Florin (1936) rejected Seward’s convention and used Ginkgoites for two groups of fossils. Firstly, he used it for species judged to be too different from Ginkgo to be included in that genus. This usage is thus based on morphological distinctions, albeit undefined. Secondly, he used it for inadequately known species, especially where cuticles are unknown. Florin’s second usage is thus a pure convention, albeit not the same as Seward’s. 3. Tralau (1968) gave a clear morphological distinction: Ginkgo (and Ginkgodium Yokoyama) had leaves ‘ divided into two or more lobes by shallow notches which never reach the basal part of the lamina’; Ginkgoites (and Baiera ) had leaves ‘deeply and symmetrically divided into narrow segments’. Harris and Millington argued that although the Tralau usage was morphological, it was inapplicable in practice. For instance, at its type locality, the leaves of Ginkgo huttonii (Sternberg) Heer were either deeply divided (i.e. Ginkgoites- like sensu Tralau) or shallowly divided (i.e. Ginkgo- like sensu Tralau). Even some G. biloba trees bear leaves of both morphological type. Harris and Millington therefore proposed to suppress Ginkgoites, and I agree. Consequently, all species that have been placed in Ginkgoites must be transferred to Ginkgo. I have the same opinion about Baiera as it is difficult to distinguish from Ginkgo using cuticles (Zhao et al. 1993). Harris and Millington (1974) distinguished them on just one macroscopic character, i.e. the segments of Baiera have no more than four veins. In my view, this distinction is purely conventional without any scientific logic ; it could equally be another number of veins, such as six. Fossil Ginkgo- like foliage is usually fragmentary and represented by only a few specimens, from which the full range of morphological variation cannot be determined. G. biloba foliage is by contrast well-known, and the limits of variation can be established on entire populations. This makes Ginkgo a much more robust genus than both Ginkgoites and Baiera. As there is no essential difference between the characters of the fossil and living leaves, and Ginkgo has nomenclatural priority, there seems no reason why the name should not also be used for the fossil leaves. Ginkgoites and Baiera should therefore be suppressed in favour of Ginkgo. Ginkgo baieraeformis (Klipper) Czier comb. nov. 1971 Ginkgoites baieraeformis Klipper, p. 92, text-fig. 3; pi. 25, fig. 3; pi. 28, figs 4-6. Holotype. Specimen JK 702 (hand specimen and microscope slide), Ruhrland Museum, Essen, Germany (Klipper 1971, pi. 25, fig. 3; pi. 28, figs 4-6). Isotype JK 707 (Klipper 1971, text-fig. 3). Origin: Zirab, northern Iran; middle Liassic Shemshak Formation (Assereto 1966; Vozenin-Serra and Taugourdeau-Lantz 1985). Emended diagnosis. Leaf petiole > 20 mm long, 1-2 mm wide. Basal angle c. 60-70°. Lamina divided in to c. six or seven segments, c. 50-70 mm long. Central division very deep, reaching the top of the petiole. Ultimate segments linear to slightly oblanceolate, their free portion c. 30-40 mm long and c. 2-9 mm wide. Number of veins in widest part of segments four to fifteen. Leaf hypoamphistomatic. Distinctness of costal and intercostal fields of adaxial epidermis highly variable. Intercostal cells polygonal to slightly elongate, costal cells elongate to polygonal, both of them 20-40 pm in size. Each cell has a faint papilla. Abaxial epidermis with numerous stomata, c. 80 per mm2. Stomatal bands c. 200-215 wide. Stomata mainly longitudinally oriented, irregularly or more or less regularly arranged, forming even rows. Epidermal cells mainly polygonal, isodiametric to slightly elongate, c. 15-20 /zm x 7-15 pm in size, with straight to slightly sinuous 354 PALAEONTOLOGY, VOLUME 41 table 1. Statistical analysis of material from Anina figured by Humml (1969) as Ginkgoites taeniata. Species EFT EFN EFNC EFP EFU al Ah G. australis 18 23 23 69 80 -81 + 76 G. baieraeformis 26 10 10 31 123 -73 + 89 G. cuneifolius 19 19 18 47 105 -80 + 80 G. digitata 52 16 14 16 106 -45 + 83 G. insolita 46 36 35 36 72 -52 + 62 G. iranicus 7 17 17 34 132 -93 + 82 G. longifolius 26 14 14 56 94 -73 + 85 G. marginata 66 21 21 31 72 -31 + 78 G. parasingularis 21 14 14 60 95 -78 + 85 G. skottsbergii 47 42 42 29 72 -51 + 56 G. taochuanensis 36 28 26 35 91 -62 + 71 G. troedssonii 15 51 51 52 72 -84 + 46 G. waarrensis 30 24 24 59 77 -68 + 75 G. whitbiensis 13 18 17 61 98 -86 + 81 walls. Non-stomatal bands c. 50-70 pm wide, with cells arranged in longitudinal rows, and with elongate, straight to finely sinuous walls. Papillae present, trichomes absent. Stomatal apparatus cyclocytic, with five to eight subsidiary cells, and guard cells c. 40 / im long and c. 20 pm wide. Stomatal pit oval, elongate. Remarks. This diagnosis is partly based on the description given by Klipper (1971), with additional information derived from the specimen described by Humml (1969) as Ginkgoites taeniata. Humml’s is the only known Mesophytic specimen from the Carpathians that can be assigned to this species. It was subjected to a statistical analysis, as outlined in the earlier part of this paper (Table 1). The parameters EFN and EFNC were not zero for any of the species compared, but were less than 15 for G. baieraeformis. It is therefore assigned to the latter species, but as a separate subspecies. The nearest species appear to be G. digitata, G. longifolius and G. parasingularis. Both G. digitata and G. parasingularis have a wider basal angle and shorter segments. G. digitata also has much wider segments, more veins per segment, and a hypostomatic lamina with trichomes but not papillae ; while G. parasingularis has stomata with usually fewer subsidiary cells, and wider non-stomatal bands on the lower cuticle. G. longifolius has a longer petiole with few stomata on the abaxial surface and a lower stomatal density on the adaxial surface, much wider stomatal and non-stomatal bands, and an often distinctively stellate stomatal pit. Ginkgo baieraeformis (Klipper) Czier, comb, nov., subsp. baieraeformis Holotype. As for species. Diagnosis. Maximum width of free portion of segments no more than 5 mm; no more than six veins in widest part of segment ; epidermal cells polygonal ; adaxial epidermis with costal and intercostal fields not distinct; abaxial epidermis with irregularly arranged stomata, with no more than seven subsidiary cells. Distribution. Iran: Zirab, middle Liassic (Klipper 1971). CZIER : JURASSIC GINKGO FOLIAGE text-fig. 2. Ginkgo baieraeformis subsp. banaticus Czier subsp. nov.; Palaeobotanical Institute, Uni- versity of Graz; holotype; Anina; lower Liassic (Hettangian-Sinemurian). a, leaf silhouette; scale bar represents 10 mm. b, details of venation; scale bar represents 5 mm. Both based on Humml (1969, pi. 10, fig. 23; text-fig. 9). 355 Ginkgo baieraeformis subsp. banaticus Czier subsp. nov. Text-figure 2 1969 Ginkgoites taeniata (Braun) Harris; Humml ( non Braun), p. 401, text-fig. 9; pi. 10, fig. 23; pi. 11, figs 24—25. Derivation of name. From Banat, the type region. Holotype. Hand specimen and slides (Humml 1969, text-fig. 9; pi. 10, fig. 23; pi. 11, figs 24-25) stored at the Palaeobotanical Institute, University of Graz, Austria. Origin: Anina, Banat region, Romania; Anina Coal Formation, Clathropteris meniscioides Biozone ( sensu Czier in press a), lower Liassic (Hettangian-Sinemurian). Diagnosis. Maximum width of free portion of segments at least 4 mm; adaxial epidermis with distinct costal and intercostal fields; costal cells mainly elongate; on abaxial epidermis, stomata arranged in rows and with at least six subsidiary cells. Remarks. Humml identified this specimen as Ginkgoites taeniata {Ginkgo taeniata sensu Sikstel et al. 1971), but the nomenclature of this species is very confused and it should probably be rejected. It was first published as a nomen nudum (as Baiera taeniata) by Braun (1843). The first macroscopic description (Schenk 1867) was based on Early Jurassic material from Germany, but this may not have been conspecific with Braun’s original species concept. Antevs (1919) figured cuticles under this name, but Harris (1935) later transferred them to Ginkgoites hermelinii, which in turn has been regarded as a synonym of Ginkgo marginata (Lundblad 1959). All published records of this species to date are equivocal and there is no firm basis on which to build a coherent taxonomic concept. Schenk (1867) assigned a specimen from Anina, recorded by Andrae (1855) as Cyclopteris digitata (now Ginkgo digitata), to Baiera taeniata. However, Andrae’s specimen has never been described or illustrated and cannot be judged. Humml (1969, p. 402) stated that his specimen differs from Schenk’s (1867) illustrations and so it is difficult to see why he assigned them to G. taeniata. The analysis shown in Table 1 indicates that the specimen should rather be assigned to a new geographical subspecies of G. baieraeformis, subsp. banaticus. Distribution. Romania: Anina, lower Liassic (Hettangian-Sinemurian, Clathropteris meniscioides Zone). Ginkgo marginata (Nathorst) Czier comb. nov. 1878 Baiera marginata Nathorst, p. 51, pi. 8, figs 12(7), 13-14. 1959 Ginkgoites marginatus (Nathorst) Florin; Lundblad, p. 10, text-figs 1—4; pi. 1, figs 1-12; pi. 2, figs 1-13. 356 PALAEONTOLOGY, VOLUME 41 Holotype. Hand specimen (Nathorst 1878, pi. 8, fig. 13) and cuticles derived from it figured by Lundblad (1959, text-figs 1a, 2a-b; pi. 1, figs 1-8), are stored at the Geological Survey of Sweden, Stockholm. Origin: Halsingborg, Sweden; lower Liassic. Emended diagnosis. Leaf fan-shaped. Petiole incompletely known, at least 10 mm long (probably reaching at least 30 mm) and c. 3-5 mm wide. Basal angle c. 40-145°. Segments 20-80 mm long. Four to eight (typically eight) entire-margined ultimate segments, approximately parallel in middle part of lamina, but converging towards apex and base. Leaf apices rounded to almost obtuse or truncate; free portion of segments up to c. 35-40 mm long and l-5-7-0mm wide. Veins dichotomous; four to eight veins in widest portion of segments. Distance between veins 0-3-1 -8 mm. Leaf hypoamphistomatic; on lower surface, stomatal density c. 33-50 per mm2, stomatal index c. 2-7. Upper epidermis consists of bands of cells that are elongated parallel to veins, separating bands of isodiametric, polygonal cells; cell outlines finely sinuous. Cell ornamentation consists of a central thickening, sometimes forming papilla. Lower epidermis consists of alternating stomatal and non- stomatal bands. Non-stomatal bands c. 100-150 pm wide, consisting of more or less conspicuous rows of longitudinally oriented, almost smooth-walled, elongated epidermal cells, 25-1 14 ^m long and 13-30 pm wide. Stomatal bands c. 300-1800 pm wide, with polygonal to irregularly shaped cells, c. 30-48 pm long and c. 27-33 pm wide, whose walls are sinuous to almost straight. Stomata uniformly scattered through stomatal bands, irregularly to longitudinally oriented, and not forming distinct rows. Cyclocytic (monocyclic or incompletely amphicyclic) stomatal apparatus. Stomata sunken, oval in shape, with guard cells 36-72 pm long (mean c. 54 pm) and c. 10-20 pm wide. Each apparatus has three to eight polygonal subsidiary cells with well-developed, distinct to confluent papillae, which may conceal guard cells; stomatal pit oval or variable in shape. Trichomes, if present, exceedingly rare. Remarks. This diagnosis combines macroscopic details given by Nathorst (1878), and macroscopic and cuticular details given by Lundblad (1959). It also incorporates evidence obtained in the present study, especially from SEM, which had not hitherto been used with this species. Lundblad (1959, p. 17) showed that a number of the features mentioned in the diagnosis are variable : the size of the leaves ; the degree of cutinization of the epidermis ; the stomatal density on the upper epidermis ; the development of the central cutinized thickenings of the epidermal cells ; and the degree of exposure of the guard-cells between the subsidiary cells. The sinuosity of the cell- walls is subject to little variation, but straight-walled cells have been observed in places. Distinct papillae are generally present on each subsidiary cell, but ‘atypical’ stomata with confluent cutinized thickenings are occasionally present. I agree with all these observations, except that in the Anina material, the thickenings and papillae on subsidiary cells are as a rule confluent and are not ‘atypical’. The nearest comparison is with G. longifolius, but this has a narrower petiole, ultimate segments that are sometimes incised, an adaxial epidermis with very few stomata, costal and intercostal fields that are poorly distinct, and wider non-stomatal bands on the abaxial epidermis. G. digitata has a EXPLANATION OF PLATE 1 Fig. 1. Ginkgo marginata (Nathorst) Czier banatica subsp. nov.; MTM-BP.602241C (holotype); Anina, Banat region, Romania; Anina Coal Formation, lower Liassic (Hettangian-Sinemurian) ; x2. Figs 2-3. Ginkgo skottsbergii (Lundblad) Czier europeica subsp. nov.; Anina, Banat region, Romania; Anina Coal Formation, lower Liassic (Hettangian-Sinemurian). 2, MTM-BP.602241A (holotype); x 1-5. 3, MTM- BP. 60224 IB (paratype); x 1-8. Fig. 4. Ginkgo sp. B.; TCMO-NS. 15364/1 ; §uncuiu§, Romania; $uncuiu§ Fireclay Formation, lower Liassic (Hettangian-lower Sinemurian) ; x 2-4. PLATE 1 CZIER, Ginkgo 358 PALAEONTOLOGY, VOLUME 41 much wider basal angle than G. marginata, deeply incised ultimate segments, much shorter free portions of the segments, and more veins per segment. It also has an hypostomatic lamina, no papillae, and an elongated stomatal pit. G. skottsbergii differs in the narrower petiole, segments that are occasionally incised and have a longer free portion, its lower stomatal density and index, the wider non-stomatal bands, the absence of papillae in ordinary epidermal cells, and the rhomboidal to polygonal shape of the stomatal pit. G. whitbiensis differs in the narrower petiole, shorter segments, fewer ultimate segments, higher stomatal density, the scarcely recognizable stomatal and non-stomatal bands, the more or less isodiametric, polygonal to rectangular epidermal cells, and the presence of few papillae, restricted to the margins of the stomatal pit. Based on the analysis in Table 2, one specimen from Anina has been assigned to this species, but as a separate subspecies. Ginkgo marginata (Nathorst) Czier comb. nov. subsp. marginata 1878 Baiera marginata Nathorst, p. 51, pi. 8, figs 12(7), 13-14. 1896 Ginkgo ( Baiera ) Hermelini Hartz, p. 240, pi. 19, fig. 1. 1919 Baiera taeniata Braun; Antevs, p. 44, pi. 5, figs 20-24; pi. 6, fig. 43. 1919 Cf. Ginkgo Geinitzi\ Antevs, p. 43, pi. 5, fig. 18. 1922 Ginkgo cf. sibirica\ Johansson, p. 43, pi. 3, fig. 5; pi. 6, fig. 26; pi. 8, figs 7-9. 1922 Ginkgo sp. Johansson, p. 44, pi. 3, fig. 6; pi. 8, fig. 5. 1922 Baiera taeniata Braun; Johansson, p. 46, pi. 4, figs 7-8; pi. 8, fig. 12. 1922 Baiera cf. longifolia', Johansson, p. 45, pi. 3, figs 7-1 1 ; pi. 8, figs 3-4. 1922 Baiera sp. Johansson, p. 49, pi. 3, fig. 12. 1924 Ginkgo Hermelini ; Chow, p. 8, pi. 1, figs 13-15. 1924 Ginkgo or Baiera sp. Chow, p. 9, pi. 1, fig. 20; pi. 2, fig. 7. 1924 Baiera taeniata ; Chow, p. 9, pi. 1, figs 16-18. 1924 Baeira cf. spectabilis ; Chow, p. 11, pi. 1, fig. 19. 1935 Ginkgoites hermelini (Hartz) Harris, p. 13, text-figs 6-8; pi. 1, figs 8, 10; pi. 2, figs 5-6. 1959 Ginkgoites marginatus (Nathorst) Florin; Lundblad, p. 10, text-figs 1-4; pi. 1, figs 1-12; pi. 2, figs 1-13. non 1961 Ginkgoites marginatus (Nathorst) Florin; Nagy, p. 629, pi. 16, fig. 2; pi. 17. ? 1970 Ginkgoites marginatus (Nathorst) Florin; Semaka, p. 69 [only in list], ? 1993 Ginkgoites marginatus (Nathorst) Florin; Zhao et al., p. 89 [cited after lists of Chinese authors]. Holotype. As for species. Diagnosis. Ultimate segments lanceolate with rounded to almost obtuse apex, and no more than seven veins in widest part of segment. On abaxial epidermis, stomatal density c. 33 per mm* 2, stomatal index c. 7, and stomatal bands at least 400 pm wide. Stomata have no more than six subsidiary cells with mainly distinct papillae. Trichomes, if present, exceedingly rare. Distribution. Sweden: Halsingborg (Nathorst 1878; Lundblad 1959), Stabbarp and Skromberga (Johansson 1922), Hoor (Antevs 1919), Sofiero and Dompang (Chow 1924), Billesholm (Lundblad 1959). East Greenland: Scoresby Sound (Hartz 1896; Harris 1935). EXPLANATION OF PLATE 2 Figs 1-4. Ginkgo skottsbergii (Lundblad) Czier europaeica subsp. nov. ; lower cuticles photographed from outer side, with phase contrast; Anina, Banat region, Romania; Anina Coal Formation, lower Liassic (Hettangian-Sinemurian). 1-2, MTM-BP.602241A (holotype), slide no. Z.C.14. 1, portions of stomatal and non-stomatal bands, the former with polygonal cells and stoma oriented parallel to venation; x270. 2, stomatal apparatus, with rhomboidal stomatal pit; x650. 3^4, MTM-BP.602241B (paratype), slide no. Z.C.13; stomata with polygonal stomatal pit, and more or less overlying subsidiary cells; x 650. PLATE 2 CZIER, Ginkgo 360 PALAEONTOLOGY, VOLUME 41 text-fig. 3. A, Ginkgo marginata subsp. banatica Czier subsp. nov. ; MTM-BP. 60224 1C, holotype; Anina; lower Liassic (Hettangian-Sinemurian). B, G. aff. marginata subsp. banatica Czier, subsp. nov. ; Institute of Geology and Geophysics, Bucharest; based on Mateescu (1958, pi. 3, fig. 2; pi. 9, fig. 1); Svinecea Mare; lower Liassic (Hettangian-Sinem- urian). Scale bar represents 10 mm. table 2. Statistical analysis of specimen from Anina assigned here to Ginkgo marginata banatica. Species EFT EFN EFNC EFP EFU al Ah G. australis 23 33 29 51 83 -76 + 65 G. baieraeformis 63 32 30 22 73 -34 + 66 G. cuneifolius 23 28 24 23 116 -76 + 71 G. digitata 56 21 16 21 92 -41 + 78 G. insolita 39 61 57 45 45 -59 + 36 G. iranicus 13 37 34 18 122 -86 + 61 G. longifolius 33 17 16 61 79 -65 + 82 G. marginata 91 14 12 40 45 -4 + 85 G. parasingularis 27 27 23 47 89 -72 + 72 G. skottsbergii 78 23 22 44 45 -18 + 76 G. taochuanensis 35 37 31 29 89 -63 + 61 G. troedssonii 63 45 45 37 45 -34 + 53 G. waarrensis 30 39 35 54 67 -68 + 59 G. whitbiensis 24 22 18 60 84 -75 + 77 Ginkgo marginata subsp. banatica Czier subsp. nov. Plate 1, figure 1; Plate 3, figures 1-3; Plate 4, figure 1; Text-figure 3a Derivation of name. From Banat, the type region. Holotype. Botanical Department, Hungarian Natural History Museum, Budapest; hand specimen MTM-BP- 602241 C (PI. 1, fig. 1), microscope slide Z.C. 12, SEM stub Z.C. 12 SEM (PI. 3, figs 1-3; PI. 4, fig. 1). Origin: Anina, Banat region, Romania; Anina Coal Formation, Clathropteris meniscioides Biozone (sensu Czier in press a), lower Liassic (Hettangian-Sinemurian). Diagnosis. Ultimate segments oblanceolate with truncate apex, with at least six veins in widest part of segment. Abaxial epidermis with at least 40 stomata per mm2, Stomatal Index c. 2, and stomatal bands no more than 400 pm wide. Stomata with at least six subsidiary cells, which have confluent papillae. Trichomes absent. Description of new material. The Anina specimen has a lamina with a decurrent base, a basal angle of 90°, and eight segments per leaf. The central two segments are undivided, apparently oblanceolate in shape, 45 mm long and up to 7 mm wide, with margins entire; the apex is truncate (PI. 1, fig. 1). Other segments are once forked at varying distances (up to 10 mm) from the base. The venation consists of longitudinal veins, forking dichotomously at different positions along leaf. There are six to eight veins in the widest part of each segment. The upper cuticle is poorly preserved and only very small fragments could be prepared, which showed little detail other than stomata (PI. 4, fig. 1). The lower cuticle shows alternating stomatal and non-stomatal bands, the latter corresponding to the vein courses. The stomatal bands are 300-400 pm wide, with uniformly scattered stomata. The stomata are longitudinally to irregularly oriented and do not form rows. The normal CZIER : JURASSIC GINKGO FOLIAGE 361 table 3. Statistical analysis of material published by Mateescu (1958) as Baiera taeniata. Species SFT EFN Species SFT IFN G. australis 5 0 G. marginata 5 0 G. baieraeformis 0 1 G. parasingularis 4 3 G. cuneifolius 0 1 G. skottsbergii 4 0 G. digitata 3 1 G. taochuanensis 0 1 G. insolita 4 1 G. troedssonii 3 0 G. iranicus 3 1 G. waarrensis 2 2 G. longifolius 4 0 G. whitbiensis 0 1 text-fig. 4. Ginkgo polymorpha (Samy- lina) Czier comb. nov. Botanical Museum, ‘ Babe§ - Bolyai ’ University, Cluj-Napoca; based on Givulescu (1991, text-figs 1-2); Anina; lower Liassic (Hettangian-Sinemurian). Scale bar represents 10 mm. epidermal cells of the stomatal bands are irregularly shaped and arranged, have slightly sinuous walls, and are about 30 pm in size (PI. 3, fig. 1). The non-stomatal bands are c. 100 pm wide, and consist of more or less conspicuous rows of smooth-walled, elongated epidermal cells, longitudinally oriented and arranged in more or less clear rows; the cells of the non-stomatal bands are 25-100 pm long and 13-20 pm wide. The stomatal density on the lower cuticle is 40-50 per mm2, with a stomatal index of c. 2. The stomatal apparatus is cyclocytic (monocyclic or incompletely amphicyclic) with six to eight polygonal subsidiary cells surrounding each stoma (PI. 3, fig. 1). Well developed, mainly confluent cutinized thickenings and papillae overarch the stomata. The stomata are sunken (PI. 3, fig. 2) and oval in shape (PI. 3, fig. 3), with guard cells c. 50 pm long and 20 pm wide ; the stomatal pit is usually oval, 25-30 pm long. Remarks. The table of affinities (Table 2) show very low EFN and ZFNC values for G. marginata and clearly points to its affinities lying there. However, in view of the geographical separation of Anina from Scandinavia, the specimen has been interpreted as a geographical subspecies. Distribution. Romania: Anina, lower Liassic (Hettangian-Sinemurian, Clathropteris meniscioides Zone). Ginkgo affi marginata subsp. banatica Czier Text-figure 3b 1958 Baiera taeniata Braun; Mateescu, p. 12, pi. 3, fig. 2; pi. 9, fig. 1. 362 PALAEONTOLOGY, VOLUME 41 Remarks. Mateescu’s specimen has not yielded cuticles and so cannot be unequivocally placed in any taxon. The table of affinities worked out for the macroscopic characters (Table 3) suggests that it is best identified as G. affi marginata banatica. Distribution. Romania: Svinecea Mare, lower Liassic (Hettangian-Sinemurian, Clathropteris meniscioides Zone). Ginkgo polymorpha (Samylina) Czier comb. nov. Text-figure 4 1956 Baiera polymorpha Samylina, p. 1523, pi. 1, figs 1-7. 1963 Baiera polymorpha Samylina, p. 95, pi. 23, figs 1-3; pi. 24, fig. 1; pi. 25, figs 2-6. 1967 Baiera polymorpha Samylina, p. 142, pi. 1, figs 1-2. 1991 Baiera polymorpha Samylina; Givulescu, p. 12, text-figs 1-2; pi. 1, figs 1-3. Holotype. Hand specimen 70-34 (also microscope slides), Palaeobotanical Collection, Botanical Institute of Russia. Origin: lower course of the Aldan River, Siberia; Lower Cretaceous (Samylina 1956). Remarks. The presence of this species in the Carpathian Mesophytic is based on Givulescu (1991). The Siberian specimens came from the Upper Jurassic and Lower Cretaceous, and are thus significantly younger than Givulescu’s material. As pointed out by Givulescu (1991, p. 12), however, the Anina specimens have identical characters to the types from the Aldan River. His determination is therefore fully accepted here and the creation of a geographical subspecies is regarded as unnecessary. G. polymorpha may thus be regarded as a long-ranging species (Early Jurassic-Early Cretaceous) and is further evidence that Ginkgoales was (and still is) a slowly evolving group. Distribution. Siberia: Aldan River, Lower Cretaceous (Samylina 1956, 1963); Kolima region, Upper Jurassic (Samylina 1967). Romania: Anina, Lower Liassic (Hettangian-Sinemurian, Clathropteris meniscioides Zone). Ginkgo skottsbergii (Lundblad) Czier comb. nov. 1913 Baiera cf. australis McCoy; Halle, p. 37, pi. 4, figs 23-30; pi. 5, figs 1-6. 1971 Ginkgoites skottsbergii Lundblad, p. 237, text-figs 1-11, pi. 1, figs 1-12; pi. 2, figs 1-6. Holotype. Hand specimen (Halle 1913, pi. 5, fig. 1) and cuticles (Lundblad 1971, text-figs 8-1 1 ; pi. 2, figs 1-6) in the Section for Palaeobotany, Swedish Museum of Natural History, Stockholm. Origin: Locality c at Rio Fosiles, near Lago San Martin (Santa Cruz), Argentina; Lower Cretaceous, base of division 6, or possibly the transition between divisions 5 and 6, in the section east of Bahia de la Lancha. Emended diagnosis. Leaf cuneate to fan-shaped, bipartite and deeply digitate. Petiole up to at least 13 mm long and 0-8-2-0 mm wide. Basal angle 60-220°. Segments 10-60 mm long. Lamina usually divided by repeated dichotomies into six to twelve segments of lanceolate-linear to slightly oblanceolate shape, with rounded to obtuse apices (occasionally irregularly notched). Maximum size of free portion of segments widely variable (10-50 mm long, 2-2-6-0 mm wide). Petiole with two EXPLANATION OF PLATE 3 Figs 1-3. Ginkgo marginata (Nathorst) Czier banatica subsp. nov.; SEM views of cuticles; MTM-BP.602241C (holotype), SEM stub no. Z.C.12. 1, inner side of cuticles showing portion of stomatal band between two non-stomatal bands; x 300. 2, stomatal apparatus viewed from outer side; x 1000. 3, stomatal apparatus viewed from inner surface; x 1000. Fig. 4. Ginkgo skottsbergii (Lundblad) Czier europeica subsp. nov.; MTM-BP.602241A (holotype), slide no. Z.C.l 1 ; SEM view of stomatal apparatus viewed from inner side; x 600. All from Anina, Banat region, Romania; Anina Coal Formation, lower Liassic (Hettangian-Sinemurian). PLATE 3 CZIER, Ginkgo 364 PALAEONTOLOGY, VOLUME 41 table 4. Statistical analysis of specimens from Anina assigned here to Ginkgo skottsbergii europeica. Species EFT EFN EFNC EFP EFU al Ah G. australis 24 47 45 52 67 -75 + 51 G. baieraeformis 58 35 35 33 64 -39 + 63 G. cuneifolius 27 21 18 29 113 -72 + 78 G. digitata 34 39 33 33 84 -64 + 59 G. insolita 41 73 70 40 36 -57 + 23 G. iranicus 11 28 25 38 113 -88 + 71 G. longifolius 29 8 8 83 70 -69 + 92 G. marginata 76 25 24 53 36 -20 + 74 G. parasingularis 22 37 33 59 72 -77 + 61 G. skottsbergii 84 2 0 51 53 -12 + 98 G. taochuanensis 48 42 38 20 80 -49 + 56 G. troedssonii 50 46 46 58 36 -47 + 52 G. waarrensis 23 52 50 55 60 -76 + 45 G. whitbiensis 35 48 44 32 75 -63 + 49 veins that radiate into the segments, and repeatedly dichotomize at all levels ; number of veins in widest portion of segments four to nine. Leaf hypoamphistomatic. Upper cuticle slightly thicker than lower one, showing costal zones with cells elongated parallel to the veins, separated by zones of more or less isodiametric, polygonal cells. Costal zones less sharply demarcated in the upper cuticle than the lower one. Lower cuticle with low stomatal density (c. 12-26 per mm2) and stomatal index ( c . 1-2). Stomatal bands c. 400-460 pm wide, with irregularly scattered, mainly longitudinally (but sometimes almost transversely) oriented stomata, and mainly isodiametric, polygonal epidermal cells, 20-60 pm long and 20-40 pm wide. Non-stomatal bands c. 150-180 pm wide, consisting of rows of longitudinally oriented, straight to finely sinuous-walled, elongate-rectangular cells, 20-158 pm long and 10-45 /un wide. Papillae absent from ordinary epidermal cells. Resin and trichomes only sporadically present and usually absent. Cyclocytic (mostly incompletely dicyclic) stomatal apparatuses. Stomata sunken, oval in shape, with guard cells 46-66 pm long and 15- 20 pm wide. Stomatal slit 22-36 pm long. Subsidiary cells partly overarching the stomata, very vari- able in shape. The number of subsidiary cells in the inner ring varies between six to eight. Stomatal pits rhomboidal to polygonal, 24-53 pm long and 1 0-24 pm wide, in upper cuticle mostly surrounded by an irregular cutinized rim (rarely with distinct papillae), whilst in lower cuticle the thickenings may carry papillae. Cuticle on petiole with elongated to rectangular cells ; stomata present on both sides. Remarks. This diagnosis is based on Halle’s (1913) macroscopic description of what he called Baiera cf. australis, combined with macroscopic and microscopic data given by Lundblad (1971) following her re-study of Halle’s material, and the new SEM data presented in this paper. Lundblad recognized that it represents a new species, which she named after the late Professor Carl Skottsberg, leader of the 1907-1909 Swedish Expedition to South America on which the material had been collected. Although the table of affinities (Table 4) shows the Anina material to be very similar to the South American types, there are sufficient differences to warrant the establishment of a separate geographical subspecies. G. skottsbergii is very similar to G. marginata, but the latter has a usually longer petiole, segments with an irregularly forked to sub-acute apex, usually wider stomatal bands, and papillae on both surfaces. Ginkgo skottsbergii (Lundblad) Czier comb. nov. subsp. skottsbergii Holotype. As for species. CZIER : JURASSIC GINKGO FOLIAGE 365 Diagnosis. Ultimate segments lanceolate-linear, with rounded apex occasionally incised ; maximum length of free portion of segment 20 mm. Abaxial epidermis with isodiametric, mainly trapeziform subsidiary cells. Stomatal pit polygonal in shape. Distribution. Argentina: Lago San Martin, Lower Cretaceous (Lundblad 1971). Ginkgo skottsbergii subsp. europeica Czier, subsp. nov. Plate 1, figures 2-3; Plate 2, figures 1-4; Plate 3, figure 4; Plate 4, figures 1-3; Text-figure 5a-b Derivation of name. After Europe, where this subspecies occurs. Holotype. Botanical Department, Hungarian Natural History Museum, Budapest, hand specimen MTM-BP- 602241 A (PI. 1, fig. 2), microscope slide Z.C. 14 (PI. 2, figs 1-2), SEM stub Z.C. 1 1 SEM (PI. 3, fig. 4). Origin: Anina, Banat region, Romania; Anina Coal Formation, Clathropteris meniscioides Biozone {sensu Czier in press a), lower Liassic (Hettangian-Sinemurian). Paratype. Hand specimen MTM-BP-602241 B (PI. 1, fig. 3), microscope slide Z.C. 13 (PI. 2, figs 3-4). Diagnosis. Petiole width 2 mm, length of segments at least 50 mm. No more than nine ultimate segments with non-incised apex ; free portion of segment at least 20 mm long and 4 mm wide ; at least seven veins in widest portion of segment. Abaxial epidermis with straight-walled cells. Subsidiary cells elongated to rounded or polygonal. Trichomes absent. Description of new material. The Anina material consists of two leaves, with partly preserved petioles. The petioles are 2 mm wide and c. 10 mm long (the basal part is missing) and expand distally to form a lamina with a cuneate base (PI. 1, fig. 2). The basal angle is c. 80°. The lamina has straight lateral margins, and is deeply divided usually by three divisions into six to nine, 50-60 mm long segments. The first (central) division is deeper than the others, reaching down to the petiole. The secondary divisions are up to one-sixth of the leaf length, the tertiary divisions up to half the length. Ultimate segments lanceolate-linear to slightly oblanceolate, 4-6 mm wide, with entire margins, and rounded to obtuse apices (PI. 1, figs 2-3). Tertiary divisions may some- times be missing (PI. 1, fig. 3). The petiole has two longitudinal veins that radiate into the segments, and then repeatedly dichotomize at all levels. In the widest portion of the segments, there are seven to nine veins, with c. 15 veins per 10 mm. The upper cuticle is poorly preserved and very fragmentary, showing only a few stomata (PI. 4, figs 1-3). The lower cuticle is much better preserved, and consists of alternating c. 400 pm wide stomatal bands and c. 150 pm wide non-stomatal bands. The latter correspond to the costal zones, and are composed of elon- gated rectangular cells, 20-150 pm long and 10-45 pm wide, arranged in longitudinal rows. The cell walls are straight and thick (up to c. 5 /mi). Cells of the stomatal bands are 20-60 pm long and 20-40 pm wide, not arranged in rows, isodiametric-polygonal in shape, with smooth walls of the same thickenings as in the non- stomatal bands (PI. 2, fig. 1). Stomata are irregularly scattered and mainly longitudinally oriented. Stomatal density rather low, 12-26 per mm2, and the stomatal index is c. 1-2. The stomatal apparatuses are cyclocytic, mostly incompletely dicyclic (PI. 3, fig. 4). The stomata are oval, 48-60 pm long and 30-40 pm wide. The guard cells are sunken. The subsidiary cells vary in shape from elongated to rounded or polygonal. An inner ring of six to eight (most often seven) subsidiary cells surround and may partly overarch the stomata. The stomatal pit is rhomboidal (PI. 2, fig. 2) to polygonal in shape (PI. 2, figs 3-4), 24-53 pm long and 10-19 pm wide. Trichomes are absent, but papillae are occasionally present on the inner ring of subsidiary cells. Remarks. The table of affinities for this newly described Anina material (Table 4) shows it to belong to G. skottsbergii, but its stratigraphical and geographical separation from the type material means that it should be regarded as a geographical subspecies. Distribution. Romania: Anina, lower Liassic (Hettangian-Sinemurian, Clathropteris meniscioides Zone). 366 PALAEONTOLOGY, VOLUME 41 Ginkgo aff. skottsbergii subsp. europeica Czier Text-figures 5c-e, 6 1961 Ginkgoites marginatus (Nathorst) Florin; Nagy ( non Nathorst), p. 629, pi. 16, fig. 2; pi. 17. 1990 Ginkgoites ex gr. lepidus Heer; Givulescu and Czier, p. 13, pi. 2, fig. 1; tab. 2. 1993 Ginkgoites sp. ex gr. lepida Czier, p. 174; tab. 1. 1994a Ginkgo ex gr. lepida Heer; Czier, p. 354, tab. 2. 1995 Ginkgo ex gr. lepida Heer; Czier, p. 50, tab. 1. Description of new material. The single specimen (TCMO-NS. 16623/4) is an almost entirely preserved impression, without cuticles. The petiole is 1 mm wide, 20 mm long, and apparently complete. The basal angle is 1 50° and the segments are c. 40 mm long. The lamina is symmetrical, being divided into linear-shaped segments. The first-order (i.e. central) division is the deepest, reaching to the petiole. The resulting two primary segments are subdivided into three secondary segments. The middle of these secondary segments is entire, but the outer two are further subdivided into two. There are thus ten ultimate segments of the lamina. The free part of the segments has a maximum length of c. 26 mm and a maximum width of c. 2-8 mm. The apices of the segments, where preserved complete, show an incision in the middle. The venation is rather poorly preserved, but just shows that there are four to seven longitudinal, sometimes dichotomously forked veins in each ultimate segment. Remarks. Two groups of material are included here. There are firstly the specimens from Hungary described by Nagy (1961). Secondly, there are specimens that I collected from §uncuiu§ in Romania. The latter have previously been figured by Givulescu and Czier (1990) but the above is the first published description. They were initially identified as Ginkgoites ex gr. lepida. However, the epidermal structure is unknown in Heer’s species and thus needs to be revised before it can be regarded as a useful taxon. The statistical method for determining affinities was used for both groups of specimens (Table 5). In both groups, IFN was zero for G. skottsbergii. For the Romanian specimens, it was the only species. For the Hungarian material, 2FN was also zero for G. longifolius , but the EFT value was much lower. Consequently, both groups were assigned to the local subspecies G. skottsbergii europeica, with an ‘aff.’. Distribution. Hungary: Komlo and Pecsbanyatelep, lower Liassic (Hettangian, Clathropteris meniscioides Zone) (Nagy 1961). Romania: §uncuiu§, lower Liassic (Hettangian-Lower Sinemurian, C. meniscioides Zone) (this paper). Ginkgo sp. A Text-figure 7a 1878 Baiera taeniata Braun; Hantken, p. 63, text-fig. 9. Remarks. Hantken’s (1878) specimen originated from the lower Liassic of Anina. It has already been shown in this paper that Ginkgo taeniata (Braun) is in need of revision. The analysis of the taxonomic position of this specimen (Table 6) shows that no species gave a zero EFN value, and so it is referred to as Ginkgo sp. A. EXPLANATION OF PLATE 4 Figs 1-3. Ginkgo skottsbergii (Lundblad) Czier europeica subsp. nov. MTM-BP.602241B (paratype), slide no. Z.C.13. 1, epidermal cells with only a few stomata; x 270. 2-3, stomata with polygonal stomata! pits; x 650. Fig. 4. Ginkgo marginata (Nathorst) Czier banatica subsp. nov. ; MTM-BP.602241C (holotype), slide Z.C.12; stomatal apparatus; x650. All show upper cuticles photographed from outer side with phase contrast ; Anina, Banat region, Romania ; Anina Coal Formation, lower Liassic (Hettangian-Sinemurian). PLATE 4 CZIER, Ginkgo 368 PALAEONTOLOGY, VOLUME 41 text-fig. 5. A-B, Ginkgo skottsbergii subsp. europeica Czier subsp. nov. ; leaf silhouettes ; Anina ; lower Liassic (Hettangian-Sinemurian). A, MTM-BP.602241A (holotype). B, MTM-BP. 60224 IB (paratype). C-E, G. aff. skottsbergii subsp. europeica Czier subsp. nov.; leaf silhouettes. C-D, drawings based on Nagy (1961, pi. 16, fig. 2; pi. 17); Komlo or Pecsbanyatelep ; Hettangian. E, TCMO-NS. 16623/4; §uncuiu§ Fireclay Formation, lower Liassic. Scale bar represents 10 mm. CZIER : JURASSIC GINKGO FOLIAGE 369 table 5. Statistical analysis of material described by Nagy (1961) as Ginkgoites marginatus, and of material figured by Givulescu and Czier (1990) as Ginkgoites ex gr. lepidus. Species Nagy (1961) Givulescu and Czier (1990) EFT EFN EFT EFN G. australis 2 1 3 3 G. baieraeformis 5 1 4 3 G. cuneifolius 3 5 3 5 G. digitata 2 3 4 4 G. insolita 5 2 3 2 G. iranicus 2 2 4 3 G. longifolius 7 0 4 2 G. marginata 7 2 4 4 G. parasingularis 2 5 4 6 G. skottsbergii 10 0 7 0 G. taochuanensis 0 4 0 5 G. troedssonii 6 1 4 2 G. waarrensis 1 2 1 2 G. whitbiensis 1 5 2 5 table 6. Statistical analysis of material described by Hantken (1878) as Baiera taeniata, and of material figured by Givulescu and Czier (1990) as Baeira muensteriana. Species Hantken (1878) Givulescu and Czier (1990) EFT EFN EFT EFN G. australis 1 1 1 3 G. baieraeformis 4 1 1 2 G. cuneifolius 1 5 0 3 G. digitata 0 5 0 5 ' G. insolita 2 3 4 1 G. iranicus 2 3 1 3 G. longifolius 4 1 3 2 G. marginata 3 2 3 2 G. parasingularis 1 3 1 5 G. skottsbergii 3 2 1 2 G. taochuanensis 1 3 0 5 G. troedssonii 3 1 2 2 G. waarrensis 0 2 0 3 G. whitbiensis 2 3 2 3 370 PALAEONTOLOGY, VOLUME 41 text-fig. 7. A, Ginkgo sp. A; based on Hantken (1878, text-fig. 9); Anina; lower Liassic (Hettan- gian-Sinemurian). B, Ginkgo sp. B; TCMO- NS. 15364/1; §uncuiu§ Fireclay Formation, lower Liassic. Scale bar represents 10 mm. Ginkgo sp. B Plate 1, figure 4; Text-figure 7b 1988 Baiera sp. Czier and Popescu, p. 609, tab. 1. 1990 Baiera muensteriana (Presl in Sternberg) Saporta; Givulescu and Czier, p. 13, tab. 2. Description. Hand specimen TCMO-NS. 15364/1 is from fossiliferous horizon number 2 of the §uncuiu§ Fireclay Formation (Czier 19946), which is Hettangian to lower Sinemurian ( Clathropteris meniscioides Zone). It shows seven fragmentary leaves without petioles (PI. 1, fig. 4). The basal angle is very acute, c. 20°. The segments are > 40 mm long, but their apices are all missing so must have been longer. There appear to be two oblanceolate ultimate segments. Their free portion is up to 25 mm long and 5 mm wide. The venation consists of well-preserved, longitudinal, sometimes dichotomous veins ; in the widest part of the segment are three to six veins. No cuticles are preserved. Remarks. This specimen has been previously identified as Baeira muensteriana but this is the first published description. However, a statistical analysis of its taxonomic position (Table 6) indicates that at best it can be referred to simply as Ginkgo sp. B. DISCUSSION Czier (in press a) has found that the traditional plant biozonation cannot be used in the Carpathian Basin, and instead classified the terrestrial Liassic there into two plant zones: the Clathropteris meniscioides Zone in the lower Liassic (Hettangian and Sinemurian) and the Carpolithes liasinus Zone in the middle and upper Liassic (Pliensbachian and Toarcian). All of the Mesophytic Ginkgo foliage described to date from the Carpathian Basin came from the lower of these zones. Plant fossils in the lower Liassic of the Carpathians can be classified floristically into three main groups, plus a fourth group for taxa of uncertain floristic affinities (Czier 19966). The Ginkgo foliage can be assigned to these groups as follows. Species only known from the European autochthon Included here is Selenocarpus muensterianus (Presl) Schenk, which I have described in detail in a previous paper (Czier 1994a). Of the Ginkgo leaves, both subspecies of G. marginata belong to this group, having only been reported from the lower Liassic (Hettangian-Sinemurian) of Greenland, Sweden and the Carpathians. Species of eastern origin This corresponds essentially to the Dictyophyllum-Clathropteris Flora, originally recognized in the uppermost Triassic of China (Sze 1956; Sze and Zhou 1962), and includes species or subspecies mainly characteristic of warm and wet conditions (Text-fig. 8). I have previously argued that it first CZIER : JURASSIC GINKGO FOLIAGE 371 text-fig. 8. Palaeogeographical, palaeofloristic and palaeoclimatic context of the Carpathian Basin in the Early Jurassic. 1, palaeocontinental margins (Smith and Briden 1977). 2, boundary between Indo-European and Siberian floral provinces (Vakhrameev 1964). 3, boundary between warm and temperate regions (Krassilov 1981). 4-6, palaeoclimatic belts (Hallam 1985, 1993); 4, wet; 5, dry; 6, seasonally wet. C, approximate position of Carpathian Basin. Continuous arrowed lines show suggested migration routes for eastern floristic elements, indicating warm, wet palaeoclimate. Dashed arrowed line shows suggested migration route for western floristic elements, indicating temperate, seasonally wet palaeoclimate. arose in the Late Triassic of eastern South-east Asia (Kimura 1984) and later spread to Europe via the northern margins of the Tethys (Taugourdeau-Lantz and Vozenin-Serra 1987) during the latest Triassic and Liassic. It then migrated further west, spreading to South America by the Mid Jurassic, where it persisted until the Early Cretaceous (Czier 19946). This explains the presence of the same species in the Lower Jurassic of Europe and the Lower Cretaceous of South America. The two subspecies of G. baieraeformis are interpreted as taxa of eastern origin (i.e. members of the Dictyophyllum-Clathropteris Flora). This is supported by the fact that both subspecies occur in association with abundant Clathropteris meniscioides. G. skottsbergii also probably belongs here. Although not yet reported from the Far East, its migration from Europe in the Early Jurassic to South America in the Early Cretaceous seems to support this view. Species of western origin This consists of elements mainly characteristic of temperate and seasonally wet environments (Text- fig. 8). They appear first in the Triassic of North America and spread to Europe during the Early Jurassic. They then migrated further north-east, reaching Siberia by the Late Jurassic and Early Cretaceous (Czier 1994a). This explains the presence of the same species in the Lower Jurassic of the European palaeofloristic region and the Upper Jurassic and Lower Cretaceous of the Siberia palaeofloristic region. 372 PALAEONTOLOGY, VOLUME 41 Ginkgo polymorpha has previously been regarded as characteristic of the Upper Jurassic-Lower Cretaceous of the Siberia palaeofloristic region. However, its presence also in the Lower Jurassic of Europe (this paper) suggests that it was of western origin and only subsequently migrated eastwards to Siberia. Acknowledgements. I thank Drs Lilia Hably and Maria Barbacka, for allowing me to research material in the Palaeobotanical Collections of the Hungarian Natural History Museum (Budapest). I am also grateful to Dr Gabor Gaal, Director of the Geological Institute of Hungary (Budapest) for providing library and SEM facilities. Special thanks go to Dr J. H. A. van Konijnenburg-van Cittert (State University, Utrecht), Dr C. J. Cleal (National Museums and Galleries of Wales, Cardiff) for comments on the manuscript, and to Prof. Zhou Zhiyan (Institute of Geology and Palaeontology, Nanjing) for translating some Chinese references. I also thank Dr J. G. Douglas (Geological Survey of Victoria, Melbourne), Prof. A. Hallam (University of Birmingham), Prof. T. Kimura (Institute of Natural History, Tokyo), Prof. B. Lundblad (Stockholm), Dr I. Z. Nagy (Budapest), Dr V. A. Samylina (Komorov Botanical Institute, St Petersburg), Dr H. W. J. van Amerom (Geological Survey NRW, Krefeld) and Dr C. Vozenin-Serra (Universite Pierre-et-Marie-Curie, Paris) for literature. Finally, I thank the Soros Foundation for an Open Society for financial support. REFERENCES andrae, k. j. 1855. Beitrage zur Kenntnis der fossilen Flora Siebenbiirgens und des Banates. II : Lias-Flora von Stierdorf im Banate. Abhandlungen der Kaiser lich-Koniglichen Geologischen Reichsanstalt, 2, 27—46. antevs, E. 1919. Die liassische Flora des Horsandsteins. 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[In Russian], — 1963. [The Mesozoic flora of the lower course of the Aldan River.] Trudy Botanicheskogo Instituta Akademii Nauk SSSR, 8, 59-139. [In Russian], 374 PALAEONTOLOGY, VOLUME 41 — 1967. [The Mesozoic flora of the area to the west of the Kolyma River (the Zyrianka coal-basin), 2.] Palaeobotanika, 6, 135-170. [In Russian], — and markovich, e. m. 1991. [On the Jurassic flora of the Nazarovsk Coal Field (the western Siberia).] Botanicheskii Zhurnal, 76, 322-333. [In Russian]. SCHENK, A. 1867. Die fossile Flora der Grenzschichten des Keupers und Lias Frankens. C. U. Kreidel, Wiesbaden, 232 pp„ 45 pis. .. semaka, a. 1961. Uber die pflanzenfiihrenden Liasschichten Rumaniens (II. Danubikum). Neues Jahrbuch fur Geologie und Palaontologie, Monatshefte, 8, 389-394. — 1962a. Aspura Rheticului de la Bigar (Banat). Dari de Seama ale §edin}elor Comitetului Geologic, 45, 173-176. — 1962ft. Observa[iuni aspura florelor paleomezozoice din danubianul Banatului. Dari de Seama ale fedinfelor Comitetului Geologic, 47, 309—321. — 1963. Despre virsta forma[iunii de Schela. Comunicari ftiinfifice, Secfia Stratigrafie ( Asociafia Geologica Carpato-Balanica, Congresul V, Bucure§ti), 3, 165-173. — 1965. Zur Kenntnis der Nilssonia orientalis- Flora in den Siidkarpathen. Acta Palaeobotanica, 6, 27-39. — 1968. Williamsonia latecostata n. sp. aus dem rumanischen Lias. Argumenta Palaeobotanica, 2, 15-17. — 1970. Flora Rhaeto-Liasica de la Mehadia. Dari de Seama ale gedinfelor Comitetului Geologic, 56, 61-75. — hucia, i. and georgescu, l. 1972. Noi puncte cu plante Liasece in Formajiunea de Schela (Carpa[ii Meridionali). Studii si Cercetari de geologie, geofizica, Seria Geologie, 17, 435—440. Seward, A. c. 1919. Fossil plants. Part 4. University Press, Cambridge, xvi + 534 pp. SIKSTEL', T. a., KUZICKINA, YU, M., SAVITSKAYA, L. I., KHUDAYBERDYEV, R. and SHVETSOVA, E. M. 1971. [The history of development of ginkgophytes in Central Asia.] 62-116. In sikstel’, t. a. (ed.). [ Palaeobotany of Uzbekistan, II] Instituta Botaniki, Akademiya Nauk USSR, Tashkent. [In Russian], smith, a. G. and briden, j. c. 1977. Mesozoic and Cenozoic palaeocontinental maps. Cambridge University Press, Cambridge, 63 pp. Stirling, J. 1892. Reports on Victorian coalfields. Special Report on Coalfields, Victoria Geological Survey, 1, 11-13. sze, h. c. 1956. Older Mesozoic plants from the Yenchang Formation, northern Shansi. Palaeontologica Sinica, New Series, Series A , 139, 110-127. — and zhou zhiyan 1962. Mesozoic continental deposits of China. Scientific Press, Beijing, 180 pp. taugourdeau-lantz, j. and vozenin-serra, c. 1987. Les associations paleofloristiques Nord-Tethysiennes, indices d’un milieu tropical de l’infra-Lias au Dogger. Memoires et Travaux de TInstitut de Montpellier, 17, 295-313. tralau, H. 1968. Evolutionary trends in the genus Ginkgo. Lethaia, 1, 63-101. vakhrameev, v. a. 1964. [Jurassic and early Cretaceous floras of Eurasia and the palaeofloristic provinces of this period.] Trudy Geologo Instituta, Academiya Nauk SSSR, 102, 1-263. [In Russian], vozenin-serra, c. and taugourdeau-lantz, j. 1985. La flore de la Formation Shemshak (Rhetien a Bajocien, Iran) : rapports avec les flores contemporaines, implications paleogeographiques. Bulletin de la Societe de France, 8, 663-678. zhao, l. m., ohana, t. and KiMURA, t. 1993. A fossil population of Ginkgo leaves from the Xingyuan Formation, Inner Mongolia. Transactions and Proceedings of the Palaeontological Society of Japan, New Series, 169, 73-96. zhou zhiyan 1984. [Early Liassic plants from southwest Hunan, China.] Palaeontologica Sinica, New Series, Series A, 165, 1-85. [In Chinese], — 1991. Phylogeny and evolutionary trends of Mesozoic ginkgoaleans - a preliminary assessment. Review of Palaeobotany and Palynology, 68, 203-216. ZOLTAN CZIER Department of Natural Sciences Typescript received 20 January 1995 Jarii Cri§urilor Museum Revised typescript received 18 March 1997 3700 Oradea, Romania CZIER : JURASSIC GINKGO FOLIAGE 375 APPENDIX To help with comparing and determining the specimens described in this paper, the key foliar characters of certain Ginkgo species have been summarized in Tables 7 and 8. This is not a comprehensive analysis, but concentrates on those species for which cuticular features are well known. The systematic position of the species not described in detail in this paper and the key references are as follows. Ginkgo australis (McCoy, in Stirling) Czier, comb. nov. Basionym: Baiera australis McCoy, in Stirling, 1892, p. 12, pi. 1, fig. 2. Selected reference: Douglas (1965). Ginkgo cuneifolius (Zhou) Czier, comb. nov. Basionym Ginkgoites cuneifolius Zhou, 1984, p. 41, pi. 12, fig. 3; pi. 23, fig. 5, 5a; pi. 24, figs 1-3. Ginkgo digitata (Brongniart) Heer, 1876 Basionym: Cyclopteris digitata Brongniart, 1830, p. 219, pi. 61 bis, figs 2-3. Selected reference: Harris and Millington (1974). Ginkgo insolita Samylina, in Samylina and Markovich, 1991, p. 326, text-figs a-iu; pi. 1, figs 1-7 ; pi. 3, figs 7-9; pi. 4, figs 5-7. Ginkgo iranicus (Kilpper) Czier, comb. nov. Basionym: Ginkgoites iranicus Kilpper, 1971, p. 93, text-figs 5-6; pi. 25, fig. 4; pi. 28, figs 1-3. Ginkgo longifolius (Phillips) Harris, in Harris and Millington, 1974 Basionym: Sphenopteris longifolia Phillips, 1829, p. 148, pi. 7, fig. 17. Ginkgo parasingularis Kilpper, 1971, p. 90, text-figs 1-2; pi. 25, figs 1-2; pi. 27, figs 2-4. Ginkgo taochuanensis (Zhou) Czier, comb. nov. Basionym: Ginkgoites taochuanensis Zhou, 1984, p. 42, text-fig. 9; pi. 25, figs 1-5; pi. 34, fig. 6. Ginkgo troedssonii (Lundblad) Czier, comb. nov. Basionym: Ginkgoites troedssonii Lundblad, 1959, p. 20, text-figs 5-6, 7a-e, 8a-b; pi. 3, figs 4-12; pi. 4, figs 1-7; pi. 6, figs 6-7. Ginkgo waarrensis (Douglas) Czier, comb. nov. Basionym: Ginkgoites waarrensis Douglas, 1965, p. 23, figs 1-2, 4, 6, 9-10. Ginkgo whitbiensis Harris, 1951, p. 927, text-figs 3a-k, 4c-g. Selected reference: Harris and Millington (1974). table 7. Characters of gross morphology and adaxial cuticle of Mesophytic Ginkgo foliage, including the F value (Factor of Importance). Number of veins < 15 4-15 4-7 c. 20 4-9 - 2(5) 10 in widest part of segment CZIER : JURASSIC GINKGO FOLIAGE 377 a ‘-3 S3 § o & T3 ■S 2 St <3 -73 C7S a to a o o a O c-. 03 ■ S3 « •a a 6 ^ U ro in tj- in 1 = wu itf- 00 3 F Character G. marginata G. parasingularis G. skottsbergii G. taochuanensis G. troedssonii * G. waarrensis G. whitbiensis table 8. Characters of abaxial cuticle of Mesophytic Ginkgo foliage, including the F value (Factor of Importance). CZIER : JURASSIC GINKGO FOLIAGE 379 Arrangement of Longitudinal Longitudinal Longitudinal More or less Longitudinal Longitudinal More or less cells in non- rows rows clear rows rows clear rows stomatal band CZIER : JURASSIC GINKGO FOLIAGE 381 It is uncertain which cuticle is adaxial and which is abaxial in this species. i NOTES FOR AUTHORS The journal Palaeontology is devoted to the publication of papers on all aspects of palaeontology. Review articles are particularly welcome, and short papers can often be published rapidly. A high standard of illustration is a feature of the journal. Four parts are published each year and are sent free to all members of the Association. Typescripts should conform in style to those already published in this journal, and should be sent (with a disk, if possible) to the Secretary of the Publications Committee, Dr R. M. 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The Palaeontological Association, 1998 Palaeontology VOLUME 41 -PART 2 CONTENTS The phylogenetic position of Echmatocrinus brachiatus, a probable octocoral from the Burgess Shale WILLIAM I. AUSICH and LOREN E'. BABCOCK 193 Constructional morphology and palaeoecological significance of three Late Jurassic regular echinoids JOACHIM G. BAUMEISTER and REINHOLD R. LEINFELDER 203 The diversity and phylogeny of the paterinate brachiopods ALWYN WILLIAMS, LEONID E. POPOV, LARS E. HOLMER and MAGGIE CUSACK 221 Morphology and phylogeny of some early Silurian ‘diplograptid’ genera from Cornwallis Island, Arctic Canada MICHAEL J. MELCHIN 263 Terebellid polychaete burrows from the Lower Palaeozoic a. t. thomas and M. P. SMITH 317 A review of the cyclostomiceratid nautiloids, including new taxa from the lower Ordovician of Oland, Sweden ANDREW H. 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Cover: coalified terminal sporangia from the Lower Devonian of the Welsh Borderland containing permanent tetrads (far left) and dyads. Similar spores found dispersed in Ordovician rocks are considered the earliest evidence for embryophytic life on land (from left to right, NMW94.76G.1; NMW96.1 1G.6; NMW97.42G.4. All x 45). FURTHER OBSERVATIONS ON THE UPPER CARBONIFEROUS PTERIDOSPERM FROND MACRONEUROPTERIS MACROPHYLLA by C. J. CLEAL, J.-P. LAVEINE and C. H. SHUTE Abstract. A large specimen of Macroneuropteris macrophylla clearly shows the overtopped branching of the primary rachis branches in the upper part of the frond. This is the first unequivocal evidence of the distal architecture of this species to be published and confirms the reconstruction proposed by us in an earlier paper. In an earlier paper published in this journal (Cleal et al. 1996) we proposed a reconstruction of the Upper Carboniferous pteridosperm frond Macroneuropteris macrophylla (Brongniart) Cleal, Shute and Zodrow, 1990. This was based on some large specimens in the Department of Palaeontology, The Natural History Museum, London, which clearly showed the proximal and middle parts of this frond. However, the distal part of the frond was represented only by two relatively poor specimens, one of which had suffered considerable taphonomic distortion (our previous pi. 2, fig. 1); the other was broken just above what we interpreted as the main overtopped branch and was poorly preserved (pi. 3, fig. 2). Our proposed reconstruction of this part of the frond thus had to be speculative, based partly on this inadequate material and partly on some poorly illustrated specimens figured by previous authors. As stated in an endnote to our previous paper, while working on a totally unrelated project at the Sedgwick Museum, one of us (CJC) discovered a large, well preserved specimen, clearly showing the distal portions of two primary pinna branches, which probably represents the apical part of a single frond of this species. This is the first specimen to show unequivocally the architecture of this distal part of the frond of M. macrophylla , and allows us to complete the reconstruction of this important species. MATERIALS AND METHODS The specimen is stored in the Sedgwick Museum, University of Cambridge, UK, under catalogue number M.1449. It was collected in 1905 by the then curator, E. A. N. Arber, and is recorded as having originated from the Radstock ‘Series’ (i.e. Formation) at Camerton in Somerset. It is thus late Westphalian D in age. The specimen had some large chisel marks on the surface, presumably resulting from earlier attempts to prepare the specimen. Whilst not directly affecting the frond fragments themselves, they were ugly distractions to the final photograph. Fortunately, the Palaeontology Conservation Unit of The Natural History Museum were able to obscure these marks, prior to photography by the museum’s Photographic Studio. The photograph was taken under cross-polar illumination. The descriptive terminology used in this paper is the same as that used in Cleal and Shute (1995) and Cleal et al. (1996). In order that the specimen could be illustrated whole with the least reduction in size, it is shown in Plate 1 rotated clockwise by 90°. However, in the description below, the specimen will be assumed to be in its more usual orientation, and right-hand and left-hand will be represented in Plate 1 by lower and upper. [Palaeontology, Vol. 41, Part 3, 1998, pp. 383-386, 1 pi.] © The Palaeontological Association 384 PALAEONTOLOGY, VOLUME 41 DESCRIPTION The specimen shows the near-terminal portions of two bipinnate pinna fragments, the left-hand one (as shown in PI. 1) 163 mm long, the right-hand one 180 mm long. From their relative positions we interpret these fragments as parts of the two primary pinna branches of a single bipinnate frond. In the left-hand fragment, the primary rachis branch is c. 3 mm wide in its most proximal part. This branch produces two secondary pinnae, one on either side. The right-hand (inward-facing) secondary pinna is preserved for a length of 112 mm, the left-hand pinna for 65 mm, but both are incomplete. The angles of attachment are 40° and 50°, respectively, and the secondary rachis offset is 26 mm ; where each secondary pinna is attached, the primary rachis branch is kinked. At 53 mm above the right-hand secondary pinna, the primary rachis branch divides as an asymmetrical dichotomy at an angle of 65°. The right-hand branch of this asymmetrical dichotomy is 103 mm long and complete; the left-hand branch 70 mm long and incomplete. The right-hand pinna fragment also has an asymmetrical dichotomy, but shows less of the frond above this dichotomy but more below it than the left-hand fragment. The primary rachis branch is 133 mm long below the dichotomy and is 5 mm wide in its most proximal part. Three secondary pinnae are attached to the right- hand (outwards facing) side of the primary rachis branch, two to the left-hand side; none is completely preserved and so their length cannot be determined. On both sides of the primary rachis branch, the secondary rachis spacing is 45 mm. The secondary rachis offset ( sensu Cleal et al. 1996, table 1) is 22-26 mm. Where the more proximal of the two pinnae is attached, the line of the primary rachis branch is only slightly deflected, but at the next three attachment points there is a much greater deflection. The most proximal secondary rachis is attached at 65° to the primary rachis branch, the next three at 57°, and the fifth at 45°. The primary rachis branch eventually divides at about 95° in an asymmetrical dichotomy. The lateral pinnules are linguaeform, sub-falcate or sub-triangular in shape. Those attached to the secondary pinnae are up to 27 mm long and 7 mm wide, and spaced at about 7 mm intervals. Four or five pinnules are intercalated between adjacent secondary rachises along the primary rachis branches ; they vary from 7 mm long and 7 mm wide, to 36 mm long and 1 1 mm wide. Only one apical pinnule is preserved, which is lanceolate, 20 mm long and 10 mm wide. DISCUSSION This specimen confirms that the primary rachis branches in the distal part of Macroneuropteris fronds show a gradual transition from laterally attached to overtopped branches, culminating in an asymmetrical dichotomy. This confirms the reconstruction of the Macroneuropteris frond proposed by Cleal et al. (1996), but for which the then available specimens showing the distal part of the frond were equivocal on the architecture. Our original paper estimated the length of most fronds to be c. 0-8 metres between the main dichotomy of the primary rachis and the apex (the DAD dimension). However, we noted that two of the specimens (V.63416(a) and V.3073) seemed to have been parts of much smaller fronds, whose DAD was estimated to be nearer 0-4 metres. The main dimensions of the Sedgwick Museum specimen (primary rachis branch width 3-5 mm, secondary rachis spacing 45 mm, secondary rachis offset 22-26 mm, maximum pinnule length 27 mm) are very close to those of V. 634 16(a), suggesting that it came from a frond of similar DAD. Assuming that the two pinna branches in the Sedgwick Museum specimen were from the same frond and are more-or-less in place, it is possible to use their relative positions to get another estimate of the frond length, by extrapolating the primary rachis branches back to where they would have met (with an adjustment for the slight curvature of these rachis branches just above the dichotomy as proposed in the Cleal et al. 1996 model). This produces a frond with a DAD of about 0-4 m, which fully agrees with the estimate obtained from secondary rachis spacing and pinnule size. EXPLANATION OF PLATE 1 Macroneuropteris macrophylla (Brongniart) Cleal, Shute and Zodrow, 1990; Sedgwick Museum, M.1449; two pinna fragments, probably representing the apical part of a single frond; Camerton, Somerset; Radstock Formation (upper Westphalian D); x 0-6. PLATE 1 CLEAL et al., Macroneuropteris 386 PALAEONTOLOGY, VOLUME 41 The M. macrophylla specimens that we have studied to date therefore seem to have originated from fronds varying in size, with DADs of 0-8 m and 04 m. The smaller examples might have been the young leaves that had not fully expanded, although they do not seem to differ in texture from the fragments of larger fronds, which might have been expected if they were juveniles. Alternatively, they could be sun-leaves, a suggestion which could be tested by looking at their stomatal density compared with the larger leaves; cuticles are not preserved in Radstock fossils, but they are known for this species from the Sydney Coalfield in Cape Breton (Cleal and Zodrow 1989). Combined with the evidence described in our earlier paper, we can confirm that the Macroneuropteris frond fits with the bifurcate semi-pinnate type of architecture described by Laveine (1997) that occurred in many trigonocarpalean fronds, including Neuropteris (Brongniart) Sternberg (e.g. Zodrow and Cleal 1988) and Laveineopteris Cleal, Shute and Zodrow (e.g. Laveine 1967). It points to the close relationship between these genera, although the evidence of the cuticles (e.g. Cleal and Zodrow 1989) still points to them being kept taxonomically separate. Acknowledgements. We thank the staff of the Sedgwick Museum for facilitating access to this specimen, the Conservation Unit of The Natural History Museum, London, for preparing the specimen, and the Photographic Studio of the same institution for preparing the plate. cleal, c. J., laveine, j.-p. and shute, c. h. 1996. Architecture of the Upper Carboniferous pteridosperm frond Macroneuropteris macrophylla. Palaeontology , 39, 561-582. — and shute, c. h. 1995. A synopsis of neuropteroid foliage from the Carboniferous and Lower Permian of Europe. Bulletin of the Natural History Museum, London, Geology Series, 51, 1-52. — and zodrow, e. l. 1990. A revised taxonomy for Palaeozoic neuropterid foliage. Taxon, 39, 486-492. — and zodrow, e. l. 1989. Epidermal structure of some medullosan Neuropteris foliage from the middle and upper Carboniferous of Canada and Germany. Palaeontology, 32, 837-882. laveine, j.-p. 1967. Contribution a l’etude de la flore du terrain houiller. Les Neuropteridees du Nord de la France. Etudes Geologiques pour 1' Atlas de Topographie Souterraine, 1(5), 1-344, pis A-P, 1-84. — 1997. Synthetic analysis of the neuropterids. Their interest for the decipherment of Carboniferous palaeogeography. Reviews of Palaeobotany and Palynology, 95, 155-187. zodrow, E. L. and cleal, c. j. 1988. The structure of the Carboniferous pteridosperm frond Neuropteris ovata Hoffmann. Palaeontographica, Abteilung B, 208, 105-124, 4 pis. REFERENCES C. J. CLEAL Department of Biodiversity and Systematic Biology National Museums and Galleries of Wales Cardiff CF1 3NP, UK J.-P. LAVEINE Universite des Sciences et Technologies de Lille UFR Sciences de la Terre Laboratoire de Paleobotanique URA CNRS 1365 ‘ Paleontologie et Paleogegraphic du Paleozoi'que ’ 59655 Villeneuve d’Ascq Cedex, France C. H. SHUTE Typescript received 20 January 1997 Revised typescript received 15 July 1997 Department of Palaeontology The Natural History Museum Cromwell Road, London SW7 5BD, UK LATE TRIASSIC ECOSYSTEMS OF THE MOLTENO/LOWER ELLIOT BIOME OF SOUTHERN AFRICA by JOHN M. ANDERSON, HEIDI M. ANDERSON and ARTHUR R. I. CRUICKSHANK Abstract. A first attempt is made to integrate the plant, insect and tetrapod elements of the Late Triassic (Carnian) intracontinental, braidplain ecosystems of the Karoo Basin, South Africa. These are probably the richest known for this pivotal early Mesozoic interval when the dinosaurs, mammals, some insect orders and possibly the birds and flowering plants made their earliest appearance. Intensive sampling of 100 Molteno Formation taphocoenoses has yielded 56 genera with 206 species of plant (vegetative taxa) and 117 genera with 335 species of insect. Seven major habitats are identified and described, ranging from two types of riparian forest through open woodland to coniferous thicket, horsetail marsh and fern meadow. Each shows a distinctive plant/insect co-association. The tetrapod-vertebrate component of these associations is based on the Lower Elliot Formation, the assumed distal facies and time equivalent of the upper four members of the Molteno Formation. This is a sparse (seven taxa) early dinosaur fauna including both body fossils and track- ways. The Upper Elliot Formation has a richer tetrapod fauna and may, in future, be used to model possible missing elements of the Lower Elliot Formation. Comparison of the Molteno insect fauna with that of two other Carnian deposits, in Australia (Ipswich Basin) and North America (Newark Basin), reveals marked provinciality reflecting temperate and tropical latitudes. It is becoming increasingly evident that the Late Triassic comprises an extraordinary interval in terrestrial evolutionary history (Anderson and Anderson 1993a, 19936, 1995, in press; Benton 19936; Rogers et al. 1993; Fraser et al. 1996). We appear to be witness to the heyday of the gymnosperms in a period of explosive diversification with biodiversities suggestive of those today (Anderson et al. 1996). In these rich ecosystems midwifing the extant world, appeared the earliest dinosaurs, mammals, several insect orders and possibly also the ancestral lineages of the birds and flowering plants. The Molteno Formation offers a rare opportunity to examine rich co-associations of Upper Triassic (Carnian) plants and insects. Together with the tetrapod fauna of the largely coeval Lower Elliot Formation, we present for the first time a palaeoecological synthesis of these three major terrestrial components in the Late Triassic Karoo Basin of South Africa. The intracontinental Molteno/Lower Elliot floodplain biome is the canvas of our investigation. The plants, insects and tetrapods differ widely in abundance and have been variously sampled and described, but the available sum of data is now sufficient to allow assembly of a preliminary composite picture. The plants are by far the most commonly preserved, comprehensively sampled and fully studied. The insects follow in abundance and level of sampling and, whilst only a small proportion have been formally described, the full collection is curated to species level following a provisional taxonomy. The coeval tetrapods are rarest, with considerable preparation and description of the material remaining. As background we provide a brief review of Molteno /Elliot tectonics, depositional environment, lithostratigraphy, biostratigraphy, correlation, climate, preservation potential and biodiversity drawn from widely scattered sources. A summary account of the Molteno flora is given whilst the insects and tetrapods are discussed in more depth as the relevant information is mostly unavailable (Palaeontology, Vol. 41, Part 3, 1998, pp. 387-421, 2 pis) © The Palaeontological Association 388 PALAEONTOLOGY, VOLUME 41 text-fig. 1 . For caption see opposite. ANDERSON ET AL.: LATE TRIASSIC ECOSYSTEMS 389 or is difficult to access in the literature. The text is accompanied by a series of tables presenting a succinct account of the flora and fauna of the Molteno and Elliot formations. Following from these basic data we delineate and systematically describe - in the form of annotated figures - seven primary habitats (ecozones) recognized within the floodplain biome. The flora and fauna of each are characterized and defined. The Molteno plant and insect collection, on which this study is based, has been made by two of us (JMA and HMA) over the past 30 years and is all currently housed at the National Botanical Institute (NBI), Pretoria. The material collected before 1977 is on long-term loan from the Bernard Price Institute for Palaeontological Research (BPI), Johannesburg. Other collections are relatively minor, widely scattered and mostly from sites that have been resampled. The Elliott tetrapod data are drawn very largely from two review articles : Kitching and Raath (1984) and Olsen and Galton (1984) on body fossils and trackways respectively. A good proportion of the skeletal material derives from four intensive collecting trips made from 1978 to 1982 by Kitching and colleagues. This material is housed at the Bernard Price Institute. Little to affect this study has been accumulated since. The system adopted in naming Molteno collecting sites and assemblages was introduced and outlined in Anderson and Anderson (1983, pp. 3-4). The cryptic Umk 111 Die 2spp, for instance, provides both geographical and assemblage data : Umk 1 1 1 refers to the first recorded collecting site (of an area of less than 100 m diameter) in the Umkomaas Valley; Die 2spp indicates that two species of the foliage genus Dicroidium are dominant in the assemblage. For the full site names and map locations, see Anderson and Anderson (1983, 1989) and Cairncross et al. (1995). The term taphocoenosis or phytotaphocoenosis (for plant assemblage) is abbreviated to TC. The plant and insect specimens illustrated on Plates 1-2 and Text-figure 3 are catalogued with the prefixes: BP/2/ - Bernard Price Institute/fossil plants; or PRE/F/ - Pretoria (National Botanical Institute)/fossils. The plant and insect sections in this paper are essentially the work of Anderson and Anderson, the tetrapod compilations and their role in the ecosystems that of Cruickshank. GEOLOGICAL AND PALAEONTOLOGICAL BACKGROUND Tectonics The Molteno Formation and its supposed distal, fine-grained, red-bed facies equivalent, the Lower Elliot Formation, were laid down on a northerly prograding floodplain in an extensive land-locked foreland basin (Text-fig. 1). This was positioned towards the southern periphery of the Pangaean supercontinent and now forms a part of the Karoo Basin (Turner 1975, 1980, 1983, 1986; Visser 1984; Smith et al. 1993). To the south, the basin was bounded by a range of substantial mountains, the result of earlier destructive plate-margin activity, rising to at least 4000 m above sea level. These are thought to have supported permanent ice-fields. Tensional stresses, brought on by the commencement of the break-up of Pangaea, resulted in pulses of sedimentation accompanied by scarp retreat (Turner 1975). The major episodes of fault-controlled uplift of the largely quartzitic sediment source are reflected in the six cycles of upward-fining, sandstone-shale-coal sequences of the Molteno Formation (Text-fig. lc). Early in the period of deposition of the Molteno Formation (Bamboesberg Member, cycle 1) the source area lay to the south of the basin; subsequently (from the Indwe Sandstone Member, cycle 2 upwards) the source area shifted to the south-east (Turner text-fig. 1. Outcrop, lithostratigraphy and tectonics of the Molteno Formation, a, outcrop area of the Molteno Formation in Southern Africa, b, plan view of the Molteno basin showing areal extent of the six individual depositional cycles; only cycle 2 (the Indwe Sandstone) persists from south to north, thinning considerably, c, generalized stratigraphical column of the Molteno Formation, showing six major cycles of sedimentation, d, section through the Stormberg Basin, along line A-B marked on map (b), showing relationship of the Molteno Formation to the distal-facies-equivalent Elliot Formation; note that the Lower Elliot Formation is regarded as the time equivalent of at least the upper four cycles of the Molteno, and that the Middle and Upper Elliot Formation overlies them, b-d modified from Turner (1983), Kitching and Raath (1984) and Cairncross et al. (1995). 390 PALAEONTOLOGY, VOLUME 41 text-fig. 2. Regional palaeoenvironmental reconstruction of the Molteno Biome, showing the seven habitat types or ecozones (1-7) described in Text-figures 5-11. ANDERSON ET AL.: LATE TRIASSIC ECOSYSTEMS 391 1975; Smith et al. 1993). Later sedimentary cycles (3-6) seem to have had their northern limits controlled by incipient crustal upwarping about half way out into the basin, but this may also have been due to the degree and rate of scarp retreat. The formation reaches a maximum thickness of c. 600 m and the erosional remnant, largely overlain by younger Karoo strata, extends over an area roughly 400 km north to south and 200 km west to east. Depositional environment Bedload (braided) fluvial systems deposited the bulk of the Molteno sediments (Text-fig. 2a). A wide range of lithologies, from boulder conglomerates through a variety of sandstones to siltstones, mudstones and coals, occurs. Three primary facies are encountered: upward-fining, coarse-grained, channel-fill deposits ; upward-coarsening crevasse-splay and sheet-flood sequences, and rhythmically laminated lacustrine and marsh shales deposited in the floodplain (Cairncross et al. 1995). The high source-area relief, low winter temperatures at high palaeolatitude, strong orographic precipitation, and sparsely vegetated interfluves in the proximal, upper reaches of the mountain valleys contributed to rapid erosion and heavily loaded stream beds (Turner 1980; Smith et al. 1993). The upper levels of the Molteno Formation appear to grade distally into the Lower Elliot Formation, a fine-grained, red-bed facies laid down by meandering river systems. There may also have been intervals of low-sinuosity, meandering-river activity during deposition of the Molteno Formation at the waning of each cycle (Text-fig. 2b) when the source area was inactive and the basin was of low relief. One such case may have been towards the close of Bamboesberg Member sedimentation and before the deposition of the Indwe Sandstone Member (Turner 1975, Cairncross et al. 1995). Lithostratigraphy The lower contact of the Molteno Formation with the Burghersdorp Formation is diachronous across the basin and has proved difficult to define. It is generally taken that this contact is marked by the first occurrence of typical Molteno pebble beds or coarse-grained sandstones of characteristic bedload geometry (P. J. Hancox, pers. comm.). This is largely allied with the change in sediment colour from red/purple to grey/buff. The break marks a shift from a floodplain with ephemeral streams to a braided-river complex, and is defined by an unconformity which may be more than regional in nature (Charig 1963; Drysdall and Kitching 1963; Keyser 1973; Cruickshank 1986; Cox 1991 ; Hancox and Rubidge 1996). The upper boundary of the Molteno Formation apparently has an interdigitating relationship with the lower part of the Elliot Formation (Turner 1983; Visser 1984; Cairncross et al. 1995, fig. 2a) as indicated earlier. This, in turn, is separated from the Middle Elliot Formation by a distinct palaeosol horizon (Kitching and Raath 1984). The middle and upper components of the Elliot Formation are bracketed together and constitute a flood-basin facies of still finer-grained sediments than the Lower Elliot Formation. These retrograde southwards towards the eroded remnants of the ‘ Molteno ’ mountains. Biostratigraphy The 100 Molteno phytotaphocoenoses (TCs) or plant assemblages can be ordered, with reasonable confidence, in stratigraphical sequence. All but the last of the six cycles of the formation are fairly well represented, yet no marked biozonation is evident. A few well-defined gymnosperm taxa, Dicroidium zuberi , Gontriglossa verticillata, Pseudoctenis fissa, P. harringtoniana and Moltenia spp. are, however, confined to the Indwe Member (cycle 2). These occur fairly frequently and commonly within the member, but this may well be of more palaeoecological than biostratigraphical significance: the Indwe Member is the most prominent, arenaceous, and widespread of the Molteno members and is the only one to extend the full south-north extent of the formation (Text-fig. 1b, d). 392 PALAEONTOLOGY, VOLUME 41 The Molteno insect faunas have not, as yet, been tabulated in such a way as to assess how far they show biostratigraphical significance. Plant fossils are apparently extremely rare and fragmentary in the Elliot Formation (C. E. Gow, pers. comm.); but, based on Ellenberger (1972), there seems to be a broad correlation of a characteristically Triassic Dicroidium flora with the Lower Elliot Formation (= Lower ‘Red Beds’) and of a Jurassic-like flora with the Middle and Upper Elliot Formation ( = Upper ‘ Red Beds ’) (Ellenberger 1972, pp. 346-348 ; Kitching and Raath 1984). The Elliot Formation is divided into two biostratigraphical units, each with a distinctive tetrapod fauna. The lower division coincides with the Lower Elliot Formation and has been ascribed to the Euskelosaurus Range Zone (Kitching and Raath 1984). This fauna has a distinctly Triassic imprint, comprising temnospondyl amphibians, a possible chelonian, a gomphodont cynodont, a dicynodont, a thecondont and a large, primitive, sauropodomorph dinosaur. The presence of a primitive sauropod in the Lower Elliot Formation helps confirm its Carnian age (Benton 1993a; Padian and May 1993). The lower fauna contrasts with that of the Middle to Upper Elliot Formation, which is ascribed to the Massospondylus Range Zone. This younger zone contains a more diverse fauna, of Jurassic aspect, including advanced cynodonts, crocodiles, ornithischian dinosaurs and primitive mammals (Kitching and Raath 1984). We have incorporated a faunal summary of the Massospondylus Range Zone to provide some indication of what forms of animal life might possibly be missing from the seemingly incomplete Lower Elliot fauna. Global correlation The correlation of exclusively terrestrial Gondwana deposits against the international standard- reference sections based on northern marine sequences is always difficult. The quoted age of any particular tetrapod or plant-bearing formation is often based more on tradition than any secure framework of correlation. The ages of the Molteno and Elliot formations are by no means fixed. On the basis of earlier comprehensive systematic efforts to correlate the Karoo strata globally (e.g. Anderson and Anderson 1970, 1983; Anderson and Cruickshank 1978; Anderson 1981), we settled on a Early Carnian age for the Molteno Formation and a Late Norian/Rhaetian age for the Elliot Formation. The putative interfingering, coeval nature of the upper members of the Molteno and the Lower Elliot Formations, as accepted in this paper, was not accounted for in the earlier papers. The Burghersdorp Formation, which is separated from the Molteno Formation by an unconformity (Turner 1972; Cruickshank 1986; Hancox and Rubidge 1996), is taken to extend from the upper Lower Triassic (Spathian) to within the Anisian, whereas the Molteno Formation (and its distal equivalent, the Lower Elliot Formation) is considered to be Carnian (e.g. Gauffre 1993). A post- Anisian sedimentary break is widespread throughout southern Africa at least. It indicates a halt to basin formation, followed by uplift and erosion, and is thus likely to coincide with tensional stresses presaging the break-up of Pangaea. Although there are recently published alternative ‘dates’ (Aigner and Bachmann 1993; Retallack et al. 1993; Rogers et al. 1993; Lucas 19946) for the various stages within the Triassic, we take the period to have had a duration of c. 40 million years (within limits of a few million years) from 247 to 204 Ma (Menning 1991). The lower boundaries of the intervening stages are placed at 240 Ma for the Anisian, 234 Ma for the Ladinian, 229 Ma for the Carnian and 222 Ma for the base of the Norian. A time gap of at least 5 million years representing the post-Anisian unconformity can be recognized. If the Molteno/Lower Elliot Formations occupy the whole of the Carnian, then this depositional event would represent a slice of history of some 7 million years duration, but we have generally considered the Molteno Formation to have been laid down over a shorter period of time (e.g. Anderson 1981). If the Upper Elliot Formation is placed in the lowest Jurassic, as is traditional, then the unconformity recognized between the Lower and Upper Elliot Formations (Kitching and Raath 1984) would represent the whole of the Norian and Rhaetian (18 My). This gap might be very much reduced if the Upper Elliot Formation were to extend down into the Upper Triassic and Lower Elliot Formation up into the Norian. ANDERSON ET AL.\ LATE TRIASSIC ECOSYSTEMS 393 table 1. The Molteno flora; plant form and preferred habitat are of necessity first approximations. CLASS SUBCLASS Genera _»PR abund- ance plant form preferred habitat BRYOPHYTA Musettes HEPATOPHYTA Marchantites INCERTAE SEDIS Thallttes (+2 gen.) LYCOPHYTA Cylomeia (+1 gen.) SPHENOPHYTA (horsetails) Phyllotheca Schizoneura 2 genera Equisetum . .......... FILICOPHYTA (ferns) Drepanozamttes 1 1 genera Dictyophyllum Asplenttes miscell. (4 gen.) mosses & liverworts .... damp/shady undergrowth v. rare 1 herbaceous j floodplain wetlands occasional] i common l i horsetails; reed-l " I ; low to high dominant J rare ] j occasional I v. rare f ferns occasional v. rare J riverine and floodplain wetlands riverine forest | (varied) wide spectrum riverine forest I (varied) PINOPHYTA PINOPSIDA (conifers) Heidiphyllum Pagiophyllum . CYCADOPSIDA Pseudoctenis . Ctenis . . Mottenia . dominant . . | woody, reed-like j floodplain thicket common . . 5 large tree \ riverine & wetland v. rare .... tree open woodland cycad-like, generally small forest to woodland ; riverine forest PELTASPERMALES (seed ferns) Kurtziana (+2 gen.). . Lepidopteris 2 Dicroidium 19 Dejerseya 1 GINGKGOALES Ginkgo NEW ORDER Ginkgopbytopsis- like INCERTAE SEDIS Linguifolium Saportaea Chiropteris PENTOXYLOPSIDA Taeniopteris BENNETTOPSIDA Halleyoctenis GNETOPSIDA Gontriglossa Yabeiella Jungttes rare small tree floodplain woodland common . . med. shrub riverine forest dominant . . shrub to large tree forest to woodland common . . shrub or small tree dominant . . shrub to med. tree lake margin occasional . shrub to tall tree forest to woodland occasional herbaceous pioneer wide spectrum rare . . v. rare . common common occasional rare i herbaceous pioneer water margin herbaceous undergrowth . riverine forest j creeper wide spectrum shrub to small tree forest to woodland cycad-like open woodland . , herbaceous pioneer . . . . ! water margin . large tree riverine forest J shrub or tree Total diversity - 59 genera, 206 species. Species- based on full taxonomic review of Molteno flora. Sampling- based on the 100 sampled taphocoenoses (TCs). Frequency- the number of TCs in which the genus occurs. Abundance (the norm in the TCs in which it occurs) v. rare - 1-5 individuals rare - 5-10 individuals occasional - 10 individuals to 1 per cent, common - 1 per cent -5 per cent, dominant - dominates the communities. 394 PALAEONTOLOGY, VOLUME 4 Climate As proposed by Anderson and Anderson (1983, 19936), the climate during deposition of the Molteno Formation was governed by Pangaea forming a landmass stretching from pole to pole. This landmass formed a barrier to the westward-flowing warm equatorial currents, which would have been deflected north and south along the eastern shoreline of Pangaea, resulting in evaporation and copious precipitation along this belt. The cold West-Wind Drift would likewise have found a barrier in the opposite margin of Pangaea, resulting in a belt of temperate rainfall between palaeolatitudes 33° S and 66° S. The Molteno depositional basin, lying as it did towards the Gondwana interior at around 60° S, may have been fairly arid with warm to hot, dry summers and cold, wetter winters. Sufficient winter precipitation fell on the mountains of the Proto-Cape Fold Belt to ensure perennial flow in the major Molteno river systems, with enhanced flow and flooding in spring through melting snow and ice in the highlands. The preservation enigma The coarser-grained, grey/buff sediments of the Molteno Formation yield abundant, well-preserved plants and insects to the virtual exclusion of tetrapods (body fossils or trackways) ; the finer-grained, red beds of the Elliot yield abundant and often well-preserved tetrapods and their trackways to the virtual exclusion of plants and insects. This pattern of exclusivity, plant or tetrapod, appears to be general throughout the terrestrial fossil record : certainly it is seen all through the richly fossiliferous Early Permian to Early Jurassic Karoo strata of South Africa. There remains no fully convincing explanation for this enigmatic balance of preservation. It is well known that the macroscopic remains of plants (foliage, fruit) and tetrapod vertebrate (bone) are equally likely to be preserved in the various depositional settings (channel, crevasse splay, floodplain, lake) of the braidplain environment (Behrensmeyer et al. 1992, p. 17). It is additional factors, such as pH, drainage and oxygenation, that control the preservation of either plant or bone. Plants are best preserved where there are high levels of humic acids (i.e. low pH) coupled with poor drainage and low oxygenation (such as in the Molteno Formation), whilst bone is best preserved under alkaline conditions (i.e. neutral to high pH) coupled with high oxygenation (such as in the Elliot Formation). It remains difficult, however, to explain why the Molteno Formation should be nearly devoid of coprolites and trackways. Biodiversity The application of recently derived statistical techniques (Generalized Inverse Gaussian-Poisson Distribution - GIGP) to the observed (sampled) Molteno floral and insect diversity has yielded estimates of the corresponding preserved (potentially available) diversity (Anderson et al. 1996). Three extrapolations were made on the basis of these rich megafloral/insect co-assemblages from 100 taphocoenoses (TCs): insect species -335 observed, 7740 preserved; vegetative species -206 observed, 667 preserved; gymnosperm ovulate orders- 16 observed, 84 preserved. Further extrapolations of these results hint at global Late Triassic floral and faunal richness akin to that of the present day, which conflicts with the traditionally held model of a cone of increasing biodiversity EXPLANATION OF PLATE 1 The dominant plant genera defining habitats 1-4 of the Molteno Formation. 1-2. Dicroidium (seed fern). 1, BP/2/057; Umk 111; x 1. 2, PRE/F/1790; Mat 111; bedding plane showing forked fronds; x0-75. 3. Sphenobaiera; BP/2/4849; Bir 111; bedding plane of overlapping leaves of two species; x 1. 4. Rissikia (conifer); PRE/F/1326; Hla 213; x 1-5. PLATE 1 ANDERSON et al., Dicroidium, Sphenobaiera , Rissikia 396 PALAEONTOLOGY, VOLUME 41 through time (Anderson and Anderson 1995). This suggests a hitherto unsuspected phase of explosive plant and insect evolution in the Triassic - following the Late Permian extinction - crucial in understanding the evolution of the Mesozoic terrestrial biota (Anderson and Anderson 1993a, 19936, 1995; Anderson et al. 1996). The low frequency, abundance and observed diversity of the tetrapods in the Lower Elliot Formation preclude them from similar statistical treatment. MOLTENO FLORA The Molteno flora (Table 1) is apparently the most comprehensively sampled and richest known for the Triassic world. It has been extensively and intensively sampled from 100 taphocoenoses (from 69 localities, i.e. areas of up to 1 km in diameter) and is represented by some 30000 catalogued slabs with 300000 identifiable vegetative specimens. A comprehensive taxonomic study of this material, partly published, has revealed 56 genera with 206 vegetative species of plant (Anderson and Anderson 1983, 1985, 1989). The flora is characterized by a fairly equal range of gymnosperm and pteridophyte taxa. The former are dominated by a number of species of the ‘seed fern’ Dicroidium and by various ginkgophytes, conifers and cycads, although a wide spectrum of ovulate fruiting structures indicates a host of new gymnosperm orders making their appearance. The pteridophytes are strongly dominated by horsetails and ferns, with lycopods very rare. Mosses and liverworts are scattered. In spite of the overall diversity, it is the species of only a few genera - Dicroidium (seed fern, Peltaspermales), Sphenobaiera (Ginkgoales), Heidiphyllum (conifer, Voltziales), Equisetum (horse- tail, Equisetales) and, to a lesser extent, Rissikia (Coniferales) - that dominate the discernible plant associations (Table 1 ; Pis 1-2). It has been possible to define six plant habitats based largely on the occurrence of these genera (Cairncross et al. 1995), whilst a seventh is characterized by the rarer ferns and Ginkgophytopsis (PI. 2, figs 5-6). These seven habitats are further characterized by distinctive lithologies and insect assemblages. MOLTENO INSECTS In the continuing shift of interest from descriptive systematics to evolutionary palaeoecology, palaeobiology and related fields (Behrensmeyer et al. 1992; Tiffney 1992; Anderson and Anderson 1993a, 19936) it has become evident that the dearth of knowledge concerning fossil insects is a particularly pressing defect. This is all the more significant when it is acknowledged that the impact of insects in present-day ecosystems is no less than that of vertebrates. The discovery over the last few years, therefore, that the insects are far more plentiful in the Molteno Formation than was previously suspected is very encouraging. A systematic study of fossiliferous slabs under the stereo- microscope has revealed that virtually all Molteno phytotaphocoenoses yield a steady, if rare, return of insects (Table 2). This ubiquitous occurrence of insects has opened an entirely new perspective on the palaeoecology of the formation. Analysis of the full collection of 2056 individuals now available from 43 taphocoenoses (TCs) has led to the recognition of a clear pattern of plant/insect co-associations (Tables 3^4). EXPLANATION OF PLATE 2 The dominant plant genera defining habitats 5-7 of the Molteno Formation. 1-2. Heidiphyllum (conifer); Tel 111. 1, PRE/F/7705b; x 1. 2, BP/2/5617; bedding plane of overlapping leaves; xO-5. 3-4. Equisetum (horsetail); Gre 111. 3, PRE/F/7572a. 4, PRE/F/7577a. Both x 1. 5. Ginkgophytopsis ; PRE/F/10157b; Mat 111; showing characteristic anastomosing venation; x2. 6. fern frond; BP/2/3344b; Kan 111; x 1. PLATE 2 ANDERSON et al Molteno Formation flora table 2. Insect yield in the Molteno Formation. Records of the total insect count, as found in the field and under the microscope, for each of the 43 PALAEONTOLOGY, VOLUME 41 S3 T3 T3 O S3 « ^ <1 § 8 « | |.s I § *3 U S jg H cb a ^ C cB " ca B .5 — o ° I O iJ J O 33 O O S3 2 O O o 5 2 „ -S3 =3 '3 H £ § O S3 o '3 §111 -sc .a « f S E £ 2 o 2 c o a O j o; (yds isy) 1 II “«3I : 9, 3 o; (ejs 310) l II nog ; $ O i O; (0I3I3H)UI3J0 ; ss o ! j • (dsnbg)uju3d : s O j pr, (opo Ota) mam ; a - : •*> - (ddsjqds) 112110 P-; * ♦| • (opo 3ta) 1 1 1 1®M i a VO ; « 056 insects 3 asssemblages 5 2 !1 l | T • (0|3K>H) III 0!M \m ^ | ^ ' . (dds2 isv) IJ2 o3j I ° ”*[’"• (opo 3i i'T" (ci3 31(3) 1 1 1 WIN 2 r ^ c'i ■ (ddse 3ta)2i2BiH i s Tt i *r» (0]3 !3H) lit “3d a -.[2 r'ovf"'. (0|3 I3H) 1 16 “3J a ^ | VO ! o'!”'". (opo Did) 12P 03d ° r' « i =[’"■ (3IO/I3H) 1 1 I ora ; 2 01 01 ifiT- (0|3 (3HJ III 131 : - rn ; Tf (Op0 3tQ) III ™() 2 : 2 : a7’- (0|3I3H) I IE OH 2 (SW3!Q) I3C 03d ~ zz 01 r at— (opo 3K1) 222 uox : 2 10 27 PsT — (ci3 3K1) 1 1 1 dX3 : 2 2; S ; sT— (qnp 3IQ) 1 1 1 reiAl ; - 2 : 2 ' s' — (dsnba) in )(sv i = ’sTsT sTj— (o|3 3ta)Eir«IH i O 2 i 8 sT+^ (op I3H) 112 soy O' s; s s"-f— (0|3 I3H) III i » a[s £ - (!3H/3i(3) III in s ; s !”a (qdspiQ) 1 16 soy i » 2; 2 g (0|3i3H)IIts»V i « = 1 $ i s (dds2 oia) union i ^ 2 | 3 ; r£ (Si0/3td) HI do^i I m Si 2 i P i j (3I0/13H) 1 12 1 « ! & ! (dds2 qds) 1 1 1 n0 - insects p® lOhrs micr hrs 1 1 § § (s[BnpiAipai jo JsqumN) sjimoo pasuj prjoi 8 (S33o|qui3SSB) S3SOU3O3Oqd01 table 3. Plant-insect co-associations in the Molteno Formation, based on specimen counts. Matrix of plant data shows the abundance of the four dominant Molteno genera recorded for each taphocoenosis (TC); bold type = percentage abundance, normal type = individual count where less than 1 per cent. Matrix of insect data shows the number of individual insects attributed to each order for each of the 43 productive TCs. ANDERSON ET AL.: LATE TRIASSIC ECOSYSTEMS £ 2 « S 2 g ' S • 9 9 ' £ ' £ 2 s T" £ ' nbaPKJ nbgpiQ nbgpiQ («nN)nba (nos) 3 (ao^) qa§ (MnN) nbg (aiO)nbg III W IZZ**X l \Z TOd IZZ Q3d in mjL III op ph zu^yi op PH 1 1 1 °!M op PH op PH op PH op PH op PH op PH op PH 11^ osd 11C Q3d 1 1€ 112S«V uesev ^ JR ' " JR ' 3 3 2 S S 23 w s"- a S dds£ qds ddsj qds qdS/PH ddsjqds dds£ 3IQ 131 mi 113*0 JQ U£*H 5 in a nt'SFv a 3K3/PH 3»0/PH 3K3/qdS qnz Dia opo 3IQ opo OIQ in a III ara a III mo* £ 1 1 1 MnN S 1 1 1 pm £ 1 1 1 PD J2 opo 3K] opo 3*Q OpO OIQ SI>I/3!(3 111 WM III 00)1 333 oo)i I3frt»d 13€ °3d III III BTtO !i S ~ 3 a a $ qnp 3ia PHPK1 siHPKI op OKI 313 BIH III III PW H3z*W lll250 mm - preservation: 1 partial skull (skull) trackway unknown REPTIUA habitat lull spectrum (terrestrial) ANAPSIDA analogue: tortoise CHELONIA diet omnlvore/herbivone (scavenger, plants to inverts) AUSTROCHELYIDAE FAM. indet. association: with Massospondylus Austrochetys 1 O/H >0,6 m Episcopus preservation: t good skull trackway: frequency/abundance uncertain LEPIDOSAURIA habitat probably burrowing, dry river banks etc. SPHENODONTIA analogue: tuatara SPHENODONTIDAE diet: wide spectrum invertebrates Clevosaurus 1 1 50 mm : association: unknown (skull) preservation: 1 fair skull trackway: unknown ARCHOSAURIA CROCODYUA PROTOSUCHIA PROTOSUCHIDAE Orthosuchus 1 A habitat primarily open woodland (interfluve) Notochampsa 2 analogue gracile, fast (greyhound) Baroquesuchus 2 diet: insectivore/camivore (skull C100 mm) SPHENOSUCHIDAE l/C <0.5 m BATRACHOPODIDAE association: Pachygenelus ( 3x), Massospondylus (lx) Sphenosuchus 1 1 Batrachopus spp. preservation: v. well preserved articulated skull/skeleton Pedeticosaurus Clarences l 1 trackway: most abundant small non-dinosaur THECODONT1A 7AETOSAURIA ?Aetosaurid Indet. 2 H 3m - diet ?root & tuber eater SAURISCHIA habitat primarily open woodland THEROPODA analogue: small bipedal dinosaur PODOKESAURIDAE GRALLATORIDAE diet irtsectivore (juveniles), carnivore Syntarsus 4 C 1m GraUator association: Tritylodon (2x) Fabrosaurus (2x), etc. preservation: partial skeletons trackway: most common SAUROPODOMORPHA habitat principally riparian forest ANCHISAURIDAE analogue: small-med. facultative bipedal dinosaur Massospondylus 116 H 4m - diet medium-level browser association: Trilyl. (20x), Pacbygen. (6x), crocs (6x), etc. preservation: good, fully articulated skull/skeleton trackway: unknown ORNITHISCHIA habitat forest margin to open woodland ORNITHOPODA analogue: small dinosaur FABROSAURIDAE ANOMOEPODIDAE diet herbivore, low-level browser(to t m) Fabrosaurus 7 H 1,5m Anomoepus association: Massospondylus (3x), Synlarsus (2x), etc. preservation: good, fully articulated skull/skeleton trackway: 2nd most common HETERODONTOSAURIDAE habitat forest margin to open woodland Heterodontosaurus 5 A A analogue: small dinosaur Lycprhinus 1 T T t diet herbivore, low-level browser (to 1 m) Abiidosaurus 2 1,5m association: mostly, isolated occurrences Lanasaurus 1 1 1 i preservation: good, fully articulated skull/skeleton Lesolhosaurus 1 V V V trackway: unknown SUBORDER indet Om'ithischian indet. 9 H 1,5m - diet low-level browser SYNAPSIDA habitat forest to open woodland THERAPSIDA analogue: elephant shrew CYNODONTIA diet insectivore (arboreal or in leaf litter) TRITHELEDONTIDAE (skulls) association: Massospondylus (5x), Crocodylia (2x), etc. Tritheledon 1 1 45 mm - preservation: fragmentary jaws & teeth Pachygenetus 17 1 35 mm - trackway: unknown TRITYLODONT1DAE AMEGHINICH1DAE habitat primarily riparian forest Tritylodon 35 1,5 m Ameghinlchnus analogue: giant rodent (to 1,5 m) diet herbivore (?bark eater) association: Massospondylus (20x) & various others preservation: good, fully articulated skull/skeleton trackway: relatively abundant (7) MAMMALIA habitat forest to open woodland PROTOTHERIA analogue: nocturnal, arboreal tree shrew TRICONODONTA diet insectivore MORGANUCODONTIDAE association: Massosp. (lx), Tritylodon 1 lx), Fabros. (lx) Megazostrodon 1 , 100 mm preservation, fair to good, fully articulated skull/skeleton Erythrotherium 5 trackway: unknown PALAEONTOLOGY, VOLUME 41 INSECTS # 1 Blattodea Coleoptera Homoptera Odonata (cockroach) (beetle) (bug) (dragonfly) cockroaches : beetles : bugs : dragonflies 3 : 1 : 1 : 1 Proportional abundance (number of individuals), based on reference taphocoenosis, e g. Bir 111 TETRAPODS Capitosaurid indet. (amphibian) 4m Proganochelyid indet. Basutodon (chelonian anapsid) 0-75m (rauisuchid thecodont) 3m Theropod indet. (saurischian dinosaur) 1m ^5^ Kannemeyeriid indet. (dicynodontid therapsid) 2m Scalenodontoides (cynodontid therapsid) 15m Euskelosaurus (sauropod dinosaur) 10m text-fig. 4 Key to the insects and tetrapods of the Molteno/Lower Elliot Biome (as used on Text-figs 5-11). The tetrapod genera of the Euskelosaurus Range Zone fauna {Lower Elliot Formation ) The seven body-fossil/trackway ‘genera’ recognized here (including the single dubious trackway taxon from the Molteno Formation) are each discussed in regard to their role in the fauna and their likely habitat preferences. Relevant details are summarized systematically in the right-hand column of Table 5 (see Text-fig. 4 for thumbnail sketches). Capitosaurid indet. {amphibian). These crocodile-like aquatic animals are represented by cranial and postcranial fragments from nine sites. Trackways remain unknown. The fragmentary nature of the material indicates break-up in a high-energy flow system and, therefore, that these capitosaurids ANDERSON ET AL.: LATE TRIASSIC ECOSYSTEMS 409 were riverine and not lake dwellers. It is assumed that they were piscivores with a skull up to 1 m long and an overall body length of up to 4 m. They may possibly also have scavenged on the carcases of Euskelosaurus whose remains have been found in association with them. Proganochelyid indet ( chelonian anapsid). This taxon ( Episcopusl ) is known from just one unclear trackway at the Maclear site (Molteno Formation) described by Raath et al. (1990) and its maker is assigned with some doubt to the Chelonia. A primitive chelonian, Austrochelys Gaffney and Kitching, 1994, is known from the Upper Elliot Formation, and the present form may have been an earlier relative. The Maclear animal would have been a medium to large tortoise-like herbivore/omnivore scavenging on plants and invertebrates that probably ranged the full spectrum of habitats from forest to open woodland, although with possible preferences as indicated on Text- figures 8 and 10-11. Basutodonid {rauisuchid thecodont). Disarticulated cranial and postcranial fragments not found associated with the remains of other taxa - have been collected from ten sites. At 3 m in length this is seen as the top carnivore of the Lower Elliot fauna. Although body fossils are far less common than those of the dinosaur Euskelosaurus , trackways, identified as Brachycheirotherium (Olsen and Galton 1984; Martin 1987), are the most frequently encountered form in the Lower Elliot. The prints have a five-toed pes with V reduced, and a forward-pointing five-toed manus. Basutodon approximates very closely the size range of the extant Varanus komodoensis (Komodo dragon) and may have had similar habits. It is the largest terrestrial predator known from the Lower Elliot Formation and would have been a formidable opponent, capable of dealing with anything in the fauna with the exception of an adult Euskelosaurus , unless aged or ill. If it hunted in a similar manner to the Komodo dragon, then it would have been an ‘olfactory’ animal and could have ranged over a wide spectrum of habitats, from riverine forest to open woodland. Theropod indet ( saurischian dinosaur). Records consist of trackways ( Grallator ) only, made by a bipedal dinosaur perhaps twice the size of the small coelurosaur Syntarsus (Raath 1969), i.e. c. 1 m tall. The prey of the juveniles could have been any of the larger insects, whilst the adults would have taken the young of Euskelosaurus, Scalenodontoides, or the dicynodont. It is also tempting to believe that, in addition to the known insects and juvenile tetrapods, this animal could have preyed on such unknowns as lizards, small cynodonts and early mammals. It is portrayed in the reconstructed plant/animal assemblages as an insectivore. These speedy, gracile little dinosaurs, whose footprints are the second most common in the fauna, are seen as hunting primarily in the open Dicroidium woodland. Euskelosaurid ( sauropod dinosaur). Found at 55 sites, Euskelosaurus is by far the most common of the body-fossil tetrapods of the Lower Elliot Formation. Preservation varies from fragmentary to fully articulated animals including skull and skeleton. The latter may represent animals entombed in the mud or quicksand of the braided rivers (the necessary site details to confirm this are lacking). The number of carcases found at each site has not been recorded systematically. This was a medium- sized (10 m long), browsing quadruped dinosaur. If it were an obligate quadruped, depending only on neck mobility (Martin 1987), then it may not have been able to browse above the 5 m level; but if it were a facultative biped (being able to rear up on its hindlegs) then it may have been able to browse to as high as 7 m above ground level. The trackways assigned to Euskelosaurus are placed in the ichnogenus Tetrasauropus. These, in spite of the abundance of the body fossils, are relatively uncommon. The prints have a Brachycheirotherium-like pes with small V and manus with a falciform medially directed claw on I. Bones of Euskelosaurus are sometimes found alongside those of the riverine capitosaurid amphibians (Kitching and Raath 1984), suggesting that they were primarily browsing along the riparian forest. They would possibly have spread out as well into the open Dicroidium woodland, the more closed Sphenobaiera woodland of the lake margin and the Heidiphyllum thicket. 410 PALAEONTOLOGY, VOLUME 41 text-fig. 5. Reconstruction of Dicroidium riparian forest (type 1, mature), bordering channels in the mature basement landscape (Habitat 1). Reference taphocoenosis (TC): Upper Umkomaas (Umk 111 Die 2 spp); Text-fig. 2c. Fossiliferous bed. The deposit consists of a 2-3 m thick, dark grey, rhythmically bedded, carbonaceous shale, exposed in the bed of a small mountain stream. It crops out along strike for at least 10 m, but its full extent remains unclear. The bed is interpreted as the infill of an abandoned channel (e.g. oxbow lake) incised into the underlying Beaufort Group. Floral associations (Pis 1-2; Tables 1, 3—4). The Umk 111 flora, with 73 vegetative species (44 gymnosperm, 29 non-gymnosperm) is by far the most diverse of the 100 Molteno TCs. It is strongly dominated by a range of species of the seed fern Dicroidium (69 per cent. Heidiphyllum (7 per cent.), Rissikia (5 per cent.), Sphenobaiera (5 per cent.) and Gontriglossa (5 per cent.) follow next in abundance. Though remarkably diverse, with eight species of horsetail and 19 species of fern, the non-gymnosperms amount to less than 5 per cent, of the flora in abundance. Insect fauna (Text-fig. 3; Tables 2-4). 166 individuals, 42 species, 11 insects/10 man-microscope-hours. With 42 species, the Umk 111 fauna is of medium to high diversity, although at order level it is markedly low in diversity. These features are matched closely in the only other fauna in the collection, Lit 1 1 1, representing the mature type of Dicroidium riparian forest. The fauna shows strong domination by the three orders, cockroaches (80 individuals), beetles (63 individuals) and bugs (12 individuals), in the proportion 8:6:1. The four additional orders encountered, dragonflies, stoneflies, crickets and alderflies, occur very sparsely. The beetles are by far the most diverse group with 28 species, whilst there are only six species of bug and four of cockroach. Tetrapod fauna (Text-fig. 4; Table 5). Capitosaur amphibians most probably inhabited the river channels, whilst the forested levee supported Euskelosaurus (high-level browser), Scalenodontoides (low-level omnivore) and the kannemeyeriid dicynodont Pentasauropus (low-level browser/grazer). The last is seen as skulking in the cover of the denser bush, possibly more on the dry side of the gallery forest than close to the water. Basutodon was the predator in this habitat, its trackways ( Brachycheirotherium ) occurring alongside those of Pentasauropus. ANDERSON ET AL.\ LATE TRIASSIC ECOSYSTEMS text-fig. 6. Reconstruction of Dicroidium riparian forest (type 2, immature), bordering channels in immature landscapes (Habitat 2). Reference taphocoenosis (TC): Kapokkraal (Kap 111 Dic/Ris); Text-fig. 2a. Fossiliferous bed. The bed, up to l-3m thick, is a black, highly fissile, metamorphosed shale cleaving at 1 mm intervals. It is exposed for 30 m along a stream bank and appears to lense out towards either end. It caps a thick channel-fill sequence of bedload sandstones. Considering the lithofacies, Kap 1 1 1 may be interpreted as having been deposited under very quiet conditions in an abandoned channel within the braided river. Floral associations (Pis 1-2; Tables 1, 3-4). The phytotaphocoenosis, of medium diversity with 14 genera and 20 species (vegetative taxa), includes the seed fern Dicroidium (50 per cent.) and the conifer Rissikia (38 per cent.) as dominants and Equisetum (horsetail) (10 per cent.) as a common element. This combination of plants presumably represents both riparian forest and Equisetum stands of the river margin and adjacent sandbanks. Insect fauna (Text-fig. 3; Tables 2-4). 178 individuals, 43 species, 18 insects/ 10 man-microscope-hours. The Kap 111 faunotaphocoenosis, a medium/high diversity cockroach/beetle fauna, includes 28 genera and 43 species. The presence of dragonflies (eight individuals), protodragonflies (three individuals), Paraplecoptera (four individuals) and stoneflies (one individual), provides ample supporting evidence of deposition in a river channel. The abundance ratio between the four dominant orders, cockroaches, beetles, bugs and dragonflies, (6:6: 1 : 1), is intermediate between that seen in the mature riparian forest (e.g. Umk 1 1 1 and Lit 111) and the floodplain-lake (e.g. Bir 1 1 1 and Aas 411) faunas - reflecting well the environment portrayed for Kap 111. The beetles are, again, by far the most diverse group with 23 species, whilst there are six species of bug and three of cockroach. Tctrapod fauna (Text-fig. 4; Table 5). The fauna of this more immature forest habitat would have been very much like that of the previous ecozone. It is possible that in the more open aspects of the forest, the fauna would have included the maker of the Grallator (theropod) trackways. Kannemeyeriid indet ( dicynodontid therapsid). Based on the preserved trackways Pentasauropus , this form is seen as a large ox-like animal c. 3 m in overall length and with a short stride. The moderately common trails show sub-equal manus and pes, with five toes on each foot. By the Late Triassic the majority of dicynodonts were tuskless (Keyser and Cruickshank 1979) and it has been proposed (Cruickshank 1978) that these forms occupied ‘close-cover’ niches or were nocturnal. The overall height of this Elliot Formation animal would have limited it to feeding at about 1 m above ground 412 PALAEONTOLOGY, VOLUME 41 text-fig. 7. Reconstruction of Dicroidium woodland of the open floodplain (Habitat 3). Reference taphocoenosis (TC): Peninsula (Pen 321 Dic/Ris); Text-fig. 2a. Fossiliferous bed. The bed (0T-0-2 m) consists of a light blue-grey, moderately laminated, chertified shale and is exposed for over 100 m along a grassy hillslope. Intermittent exposures of the same stratum can be traced over at least 2-5 km, clearly suggesting deposition during flooding of the distal floodplain. Floral associations (Pis 1-2; Tables 1, 3-4). The flora, with 13 genera and 18 species, is dominated by the seed fern Dicroidium odontopteroides (50 per cent.) and the conifer Rissikia media (35 per cent.) representing a medium-diversity Dicroidium woodland in the vicinity. The presence of Schizoneura (horsetail), Equisetum (horsetail) and Heidiphyllum (conifer) in unusually low proportions indicates derivation from communities further afield. Insect fauna (Text-fig. 3; Tables 2-4). 25 individuals, 12 species, 9 insects/10 man-microscope-hours. The faunotaphocoenosis (medium-diversity beetle/bug fauna), including 11 genera and 12 species of insect, is typical for the Dicroidium woodland co-associations. It is dominated equally by bugs (seven individuals) and beetles (seven individuals), whilst the cockroaches (three individuals) are only half as commonly encountered. A few insect remains may have been washed in via flood waters, but the bulk of the fauna appears to constitute a true reflection of this habitat. The total absence of dragonflies and the other more primitive insect orders (e.g. stoneflies) corroborates a model of deposition from flood waters, with occasional ephemeral pools. Tetrapod fauna (Text-fig. 4; Table 5). Euskelosaurus (high-level browser), Scalenodontoides (low-level omnivore) and the kannemeyeriid dicynodont (low-level browser/grazer) are seen as the herbivore community in these woodlands, with Basutodon as the principal predator. The Grallator- trackway maker could have found a niche here, especially if it operated in packs in the open. There is no firm evidence (mass trackways on bedding planes) for this, however. level. It may alternatively have been a low-level ‘grazer’ (Cruickshank 1978). We visualize it as ranging through the shrubby growth of the drier, outer margins of the riparian forest, the closed Sphenobaiera woodland fringing floodplain lakes and the Heidiphyllum thicket. Cheirobrachytherium {Basutodon) and Pentasauropus trackways have been found in association (Olsen and Galton 1984), suggesting a likely predator-prey relationship. Scalenodontoides {cynodontid therapsid). These cynodontids were, apparently, relatively scarce. ANDERSON ET AL.\ LATE TRIASSIC ECOSYSTEMS 413 text-fig. 8. Reconstruction of Sphenobaiera woodland, in floodplain lake (Habitat 4). Reference taphocoenosis (TC): Birds River (Bir 111 Sph 2 spp); Text-fig. 2a. Fossiliferous bed. The buff-coloured, rhythmically bedded, richly fossiliferous shales, reaching c. 2-5 m thick, are exposed along the gently sloping bank of a farm dam. They crop out over a good 1 50 m of strike, but the full extent of the bed is hidden beneath a grass-covered soil overburden. Similar strata appear intermittently to some 500 m distance, in a stream bed and other exposures, suggesting a fairly extensive lake. Floral associations (Pis 1-2; Tables 1, 3^4). The phytotaphocoenosis (with 21 genera and 33 species of vegetative taxa) is interpreted as deriving from three distinctive communities: (1) the first heavily dominated by two species of Sphenobaiera , S. pontifolia (50 per cent.) and S. schenkii complex (35 per cent.), which characterize a medium-diversity closed-woodland community bordering a lake in the floodplain; (2) Heidiphyllum (conifer), at 10 per cent, of the assemblage, represents a more or less monospecific community of rush-like conifers colonizing sandy areas of the lake shore ; (3) certain other gymnospermous elements such as Dicroidium (seed fern), with no fruit present, and Halleyoctenis (bennettitalean), with only two detached gynoecia, may well represent the more open woodland some distance from the lake. Insect fauna (Text-fig. 3; Tables 2-4). 474 individuals, 99 species, 30 insects/ 10 man-microscope-hours. This is clearly the best sampled and most diverse of the 43 Molteno insect faunas. In the wide spread of orders represented and the proportions (3: 1:1:1) between the dominant orders, cockroaches, beetles, bugs and dragonflies, it is most like the fauna from Aas 411, the only other well-sampled Molteno insect fauna of the floodplain lake-margin. Particularly notable, also, is the relatively common occurrence of the more primitive insect orders, the mayflies (five individuals), protodragonflies (five individuals), dragonflies (47 individuals), protostoneflies (27 individuals) and stoneflies (seven individuals), that are associated with open water bodies. Tetrapod fauna (Text-fig. 4; Table 5). This is not thought to be the preferred habitat for the large herbivore, Euskelosaurus, but would provide browsing for both the dicynodont and Scalenodontoides, the former possibly more so in the denser vegetation near the water’s edge. Basutodon was once again the dominant predator, whilst the Grallator trackway maker hunted for insects amongst the vegetation. The chelonian could have been grazing on pond weeds, waterside vegetation or acting as an aquatic predator on insect larvae and small fish. Their disarticulated remains (only one good skull is known) have been recovered from only six sites and trackways remain unknown. With a skull c. 300 mm long, and therefore a body length of up 414 PALAEONTOLOGY, VOLUME 41 text-fig. 9. Reconstruction of Heidiphyllum thicket in areas of high water table in the floodplain or on channel sandbars (Habitat 5). Reference taphocoenosis (TC): Aasvoelberg (Aas 311 Hei elo); Text-fig. 2a-b. Fossiliferous bed. The bed, a 0-7 m thick, poorly laminated, light khaki/beige mudstone, is exposed uniformly for 75 m along strike .Two very similar horizons (Aas 111, Aas 211) appear at the same level at 2 km and 6 km distance. The unit grades, above and below, into palaeosols rich in roots and slender woody fragments (to 30 mm diameter), and lies above a 3^1 m thick sequence of monotonous, barren, floodplain mudstones. Aas 311 yields an autochthonous to parautochthonous assemblage associated with low-energy sheetflood deposition in the distal floodplain. Floral associations (Pis 1-2; Tables 1, 3-4). The phytotaphocoenosis is heavily dominated by the conifer Heidiphyllum elongatum (99 per cent.), with the other vegetative taxa (eight genera and nine species) being very rare. A virtually monospecific coniferous thicket in close proximity is clearly indicated. The remaining elements of the assemblage probably represent Dicroidium (seed fern) and Sphenobaiera woodland communities growing some distance away. Insect fauna (Text-fig. 3; Tables 2-4). 146 individuals, 31 species, 15 insects/10 man-microscope-hours. The faunotaphocoenosis (medium-diversity cockroach/beetle/bug fauna) includes 23 genera and 31 species. The insects, although typically fragmentary, are particularly clearly preserved. Aas 311 is the best sampled of the nine Heidiphyllum thicket co-associations thus far examined and includes a fauna typical for this type of assemblage. The cockroaches are clearly dominant, being three to four times as numerous as the beetles and bugs. The five further orders present are represented by rather few specimens. The TC is possibly a nearly clean sample of the fauna inhabiting the Heidiphyllum thicket, with little contamination from more distant habitats. The leaf litter of the coniferous thicket provides the ideal niche for the abundant cockroaches. The medium- to-high insect yield suggests a relatively low-energy flow regime, whilst the rare occurrence of dragonflies and Paraplecoptera points to the absence of permanent water. Tetrapod fauna (Text-fig. 4; Table 5). These monospecific coniferous stands might have provided good grazing and browsing for the dicynodont and Scalenodontoides, whilst harbouring a varied insect diet for the Grallator trackway maker. Basutodon could have hunted in the drier areas of this habitat. to 1-5 m, this therapsid is visualized as a small, bear-like omnivore. Its dentition, of ‘ gomphodont ’ pattern with a diastema (Gow and Hancox 1993), was apparently adapted to pulping vegetable matter. It would not have been able to crop vegetation much higher than 0-5 m above ground level ANDERSON ET AL.: LATE TRIASSIC ECOSYSTEMS 415 text-fig. 10. Reconstruction of Equisetum marsh in the floodplain (Habitat 6). Reference taphocoenosis (TC): Greenvale (Gre 111 Equsp.); Text-fig. 2a. Fossiliferous bed. The bed, up to 1 m thick, consists of rhythmically laminated grey mudstones. It is exposed for 30 m along strike in a road cutting, and occurs within a rather monotonous mudstone sequence with occasional thin siltstones. A lake or marsh in the distal floodplain is indicated. Floral associations (Pis 1-2; Tables 1, 3-4). The phytotaphocoenosis, with eight genera and ten species (vegetative taxa), is strongly dominated by Equisetum (horsetail) (97 per cent.), clearly indicating a horsetail marsh. Rare elements such as Dicroidium (seed fern) (2 per cent.) and fern (1 per cent.) presumably represent more distant communities. The absence of upright, rooted Equisetum stems indicates parautochthony rather than autochthony. Insect fauna (Text-fig. 3; Tables 2-4). Five individuals, four species, 10 insects/10 man-microscope-hours. The faunotaphocoenosis, a low-diversity beetle/bug assemblage, remains sparse, with only five individuals including four genera and four species (two species of bug, one of beetle and one scorpionfly). Although the sample is small, it appears typical of horsetail marshes in the Molteno. Cockroaches are conspicuously absent, the standing water and absence of leaf litter being an unfavourable habitat for these usually abundant insects. The relatively common occurrence of Conchostraca (three species, 15 individuals), and the appearance of pelecypods (one genus, three species, three individuals), unique for the Molteno, are further indicators of marsh conditions. Tetrapod fauna (Text-fig. 4; Table 5). The dicynodont might have been found here, but Equisetum would not have been attractive to the other herbivores, nor would there have been much to draw an insectivore. The chelonian might have ventured into this marshy setting. and was thus restricted to the foliage and fructifications of smaller shrubs and undergrowth - probably in all the described habitats except Equisetum marsh. PLANT-ANIMAL CO-ASSOCI ATIONS IN THE MOLTENO/LOWER ELLIOT BIOME The seven primary habitats (ecozones) of the Molteno Formation, characterized by distinctive plant/insect co-associations, were first outlined in Cairncross et al. (1995) together with lithofacies 416 PALAEONTOLOGY, VOLUME 41 TEXT-FIG. 11. Reconstruction of iem/Ginkgophytopsis meadow colonizing sandbars in the braided river (Habitat 7). Reference taphocoenosis (TC) : Kannaskop (Kan 1 1 1 Ast spA) ; Text-fig. 2a. Fossiliferous bed. This bed, a 0-25 m thick, massive, conchoidally fracturing, khaki mudstone, is exposed for 2-3 m along a road cutting. It lies at the base of a series of stacked channel-fill sequences, all erosively based. Kan 111 was evidently deposited under turbid conditions in a restricted channel within a sand-dominated braided river. Floral associations (Pis 1-2; Tables 1, 3—4). The low-diversity phytotaphocoenosis (five genera and seven species) is dominated by a single species of fern (63 per cent.) preserved in situ or nearly so. These are found as virtually whole plants, with fronds, rhachis and rhizomes preserved together. Equisetum (horsetail) (20 per cent.), Heidiphyllum (conifer) (10 per cent.) and Ginkgophytopsis (5 per cent.) are relatively common. The last is found with both leaves and fruit attached to fragments of herbaceous shoot. The association evidently colonized sandbanks of the braided river, the plants being preserved in place or close to their place of growth and being rapidly engulfed by sediment. Heidiphyllum thickets appear, likewise, to have flourished on the sandbanks. Insect fauna (Text-fig. 3; Tables 2-4). The Kan 111 TC is unique among the 7 habitat assemblages discussed here in that it has yielded no fauna, insect or Conchostraca. Four hours of scanning plant-bearing slabs under the microscope yielded no specimens of either category. This might be anticipated considering the high flow velocity indicated by both the sediment and the plant assemblage. Insect faunas representing this habitat remain unknown. Tetrapod fauna (Text-fig. 4; Table 5). Whereas the vegetated sandbars of the braided-river system could have supported periodic forays by the smaller tetrapod herbivores ( Scalenodontoides ), it is unlikely that the insectivore (theropod) or the larger carnivore ( Basutodon ) would be found in this habitat. The proganochelyd might well have found it rewarding foraging territory, as might the lumbering kannemeyeriid in the safety of the night hours. descriptions of vertical profiles including the reference and other significant TCs. In the present study we provide the basic insect data on which the ecozonal patterns are based (Tables 3-4) and integrate the associated coeval Lower Elliot Formation tetrapods for the first time. ANDERSON ET AL .: LATE TRIASSIC ECOSYSTEMS 417 Here we aim to synthesize the three components of the study : the flora, insects and tetrapods. The seven habitats are portrayed in a series of annotated reconstructions (Text-figs 5-11) along with succinct, comparative text on the associated flora and fauna. Each is based, in particular, on a selected reference taphocoenosis (TC): e.g. Upper Umkomaas (Umk 111 Die 2spp) for the mature type of Dicroidium riparian forest (Text-fig. 5). The incorporation of the tetrapods is based on our assessment of their likely habitat preferences as previously discussed. Thumbnail sketches (key on Text-fig. 4) of the insects, with proportions of the dominant orders, and of the tetrapods are appended, as is a line drawing of each dominant plant genus. A COMPARISON OF THREE CARNIAN BASINS The three most productive Carnian-age ‘basins’, known to us globally, that yield both good plants and insect faunas are the Karoo Basin, South Africa (Molteno Formation); the Ipswich Basin, Queensland (Ipswich Group), and the Newark Supergroup, eastern USA (Solite Quarry, Cow Branch Formation) (Fraser et al. 1996; N. C. Fraser, pers. comm.). It is interesting in the context of this paper to compare the insect faunas (Table 7) of these three areas as it throws light on the widely differing biota and ecology of the tropical and temperate latitudes of the Late Triassic. The comprehensiveness and currency of the data available are highly variable yet sufficient to highlight the magnitude of the faunal differences. Whilst it is beyond the scope of this study to attempt a synthesis of the three floras, it is clear that those of the Molteno Formation and Ipswich Group are alike and belong to the Gondwana Kingdom, whereas that of the Newark Supergroup is quite different, belonging to the Laurasian Kingdom. In particular, the two southern floras are strongly characterized by the seed fern Dicroidium, whilst the northern flora is dominated by conifers (Pagiophyllum, Br achy phy llum) and cycadeoids. In Table 7 we plot the diversity and abundance of insects per order for the 21 orders identified in the Molteno Formation (c. 60° S palaeolatitude), Ipswich Group (c. 50° S) and Newark Supergroup (c. 10° N). To attain a closer balance for the two temperate Gondwana occurrences, we include only the single richest fauna (Birds River, Bir 111, a lake deposit) from the Molteno Formation, but the full published fauna (Mt Crosby and Denmark Hill localities) from the Ipswich Group. There are differences between the two southern faunas, especially the strong presence of Neuroptera, Mecoptera and Trichoptera in Australia, but the similarities are more striking. The beetles, cockroaches and bugs are particularly prominent in each and the general spread of orders is similar. The Newark Supergroup fauna is very different (Fraser et al. 1996; N. C. Fraser pers. comm.). Most notably, the beetles and cockroaches are rare in the Newark Supergroup, whilst the flies, absent in Gondwana, are prominent and diverse, with five families already recognized. The three deposits discussed are all variations on the fluvio-lacustrine theme: the Molteno Formation having been laid down in an intracontinental basin, the Ipswich Group in a small intramontane depression and the Newark Supergroup in a series of grabens. The faunal differences in some degree reflect these environments, but the overriding factor was presumably palaeolatitude : c. 50-60° S for the two Gondwana occurrences and c. 10° N for the Laurasian occurrence. CONCLUSIONS The Molteno Formation appears uniquely rich, at least for the Triassic world, possibly the pre- Cretaceous world, in the quantity and diversity of its fossil flora. This flora is relatively well documented now and is based on the extensive collections made from 100 taphocoenoses over the past 30 years. The diversity is expressed not only in the observed taxa, but in statistical projections hinting at Late Triassic floras being as rich as those in the extant world. Only recently, though, in systematically scanning plant-bearing slabs under the microscope, have we become aware of the real richness of the associated insect fauna. Like the flora, the fauna hints at diversity akin to that of today. The insect fauna combined with the flora greatly enhances our understanding of the ecology of the Molteno Biome and its varied habitats. In that most of the 18 PALAEONTOLOGY, VOLUME 41 table 7. A comparison between two temperate and one tropical insect fauna of the Upper Triassic (Carnian), from fluvio-lacustrine basins. Faunas Molteno (S. Africa) - based only on Birds River (Bir 111). Ipswich (Australia) - based on Mt. Crosby and Denmark Hill. Newark (USA) - based on the Cow Branch fauna. The Homoptera include the Heteroptera. References to faunas Molteno - this paper. Ipswich - unpublished data Newark- Fraser etal. (1996), Fraser pens. comm. Abundance 185- individuals v' - rare vV- uncommon ✓✓✓- abundant 7 - not given in reference Palaeolatitudes Follow the Late Triassic reconstruction of Pangaea used in Lucas 1994a. Basin Insect order Common name Molteno (60'S) Ipswich (50»S) Newark (10'N) spp nos spp nos fam. nos Thysanoptera thrips - 1 ✓ Microcoryphia bristletails 1 7 Ephemeroptera mayflies 1 5 Meganisoptera protodragonflies 3 5 Odonata dragonflies 12 47 6 8 Paraplecoptera extinct 5 27 Plecoptera stoneflies 2 7 2 3 Blattodea cockroaches 5 185 18 24 1 ? Mantodea mantids 2 3 1 9 Orthoptera grasshoppers 5 13 9 43 1 ? Homoptera bugs 24 68 66 168 4 ✓✓✓ Phasmatodea stick insects 1 1 Megaloptera alderflies 1 1 Gloss elytrodea extinct 1 2 1 2 Neuroptera lacewings 2 2 12 31 Mecoptera scorpionflies 4 6 13 64 Trichoptera caddisflies 3 41 1 ? Lepidoptera butterflies 2 6 1 8 Hymenoptera wasps, bees f .... ... 1 2 Coleoptera beetles 28 56 58 70 2 ? Diptera flies 5 vv Incertae sedis - 33 Totals 99 474 192 474 15 7 orders of insect represented in the Molteno Formation are extant today, they lend much insight into the palaeoenvironment. Clear patterns of plant/insect co-associations emerge for seven primary habitats (ecozones) identified in the formation. Adding yet another dimension to the Molteno Formation is the existence of a coeval tetrapod fauna in the Lower Elliot Formation. Although relatively well sampled, the Elliot Formation material remains poorly described taxonomically and not at all faunistically. We have, with some necessary simplification, attempted to reduce the published data to a meaningful fauna and to integrate this into the known Molteno biota. As sister strata, the Molteno/Elliot formation pair, yielding plants, insects and tetrapods, offers an unparalleled window onto the Late Triassic temperate world. We paint here the first strokes of the synergistic picture played out in the Karoo Basin between these three major terrestrial groups. The potential for filling out the picture, both in the Karoo and elsewhere (e.g. the Ipswich Group, Australia and Newark Supergroup, USA), is manifold. A global inventory of Late Triassic biomes, with their habitats, flora and fauna, coupled with finely resolved global correlations will enable more explicit understanding of the evolutionary biology of this critical period. What was the real magnitude of diversity and how comprehensive was the postulated extinction event(s) pre-empting the Jurassic? Did the very scale of alternating richness and decimation invest the interval with unique potential for biological invention? The moment in Earth history was pregnant with significance. In those exceptionally diverse ecosystems of the Late Triassic emerged many major new lineages, not least the dinosaurs, mammals and possibly the flowering plants. ANDERSON ET AL.\ LATE TRIASSIC ECOSYSTEMS 419 Acknowledgements. We thank Mike Raath, Roger Smith and John Hancox for reading and commenting on earlier drafts of this paper. Bruce Rubidge, Chris Gow, Roger Smith and Nick Fraser kindly supplied information not available elsewhere. 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CRUICKSHANK Department of Geology University of Leicester, University Road Leicester LEI 7RH, UK and Leicester Museum and Art Gallery Earth Sciences Section, 53 New Walk Leicester LEI 7EA, UK Typescript received 5 July 1996 Revised typescript received 10 July 1997 PREDATION ON GRAPTOLOIDS: NEW EVIDENCE FROM THE SILURIAN OF WALES by DAVID K. LOYDELL, JAN ZALASIEWICZ and RICHARD CAVE Abstract. New evidence for predation on graptoloids is presented from collections made from the uppermost Llandovery and lower Wenlock of Wales. Mediograptus morleyae occurs in dense ovoid masses, interpreted as faecal pellets. Rhabdosomes of both M. morleyae and M. cf. inconspicuus occur folded, with a stipe length of a few thecae between folds : these specimens may have a faecal origin, or may represent rhabdosomes dropped during manipulation prior to ingestion. The predation appears to have been species specific : none of the other species present in the collections is affected. The identity of the predators is uncertain. Fossil graptoloids represent the dominant preserved macrozooplankton of the Ordovician to Lower Devonian. When alive, they presumably ‘constituted a large reserve of accessible energy within the water column, and hence a major utilizable source for pelagic or nectic predators’ (Underwood 1993, p. 195). Surprisingly, however, very little evidence has been presented to suggest that graptoloids were preyed upon (see Underwood 1993 for review). By way of explanation, Bates and Kirk (1985, p. 213) have suggested that graptolite periderm may have been ‘tough and unattractive to predators’ and that the graptoloids’ soft tissues may have been ‘poisonous, perhaps with warning coloration’. Evidence for predatorial attack on dendroid graptolites, however, appears not to be uncommon (Bull 1996), suggesting that graptolite periderm and/or soft tissue was not unpalatable to all predators. Dendroid graptolites were benthic and are characteristic of shallow marine environments, often with no graptoloid graptolites present (e.g. LoDuca 1995). It is probable therefore that organisms which fed upon dendroids would not have preyed also upon graptoloids which lived in an entirely different habitat (in the pelagic realm) and usually are found in deeper marine facies than are dendroids. NEW EVIDENCE FOR PREDATION ON GRAPTOLOIDS Description of new material New evidence for predation on graptoloids is provided by specimens from two occurrences in Wales: the uppermost Llandovery ( insectus Biozone) of the Banwy River section (Loydell and Cave 1996; material housed at the British Geological Survey, Keyworth, prefix BGS); and the lower Wenlock ( centrifugus Biozone) of a quarry south-west of Disserth (see Loydell and Cave 1993 for locality details; material collected by Jonathan H. Harris and housed at the Sedgwick Museum, Cambridge, prefix SM). All the material is well preserved, mostly as three-dimensional pyrite internal moulds with original periderm adhering. The uppermost Llandovery specimens. Mediograptus morleyae Loydell and Cave, 1996 is the most abundant graptoloid in the highest graptoloid-bearing band within the Llandovery of the Banwy River section, comprising approximately 40 per cent, of the graptoloids collected (160 specimens out of a total of 363 graptoloids; the material was collected by bulk sampling, with no collector bias). Most rhabdosomes are undistorted. Fourteen specimens, however, occur as dense, ovoid masses; another 16 rhabdosomes are folded-up, with the straight rhabdosome sections between folds (Palaeontology, Vol. 41, Part 3, 1998, pp. 423-427] The Palaeontological Association 424 PALAEONTOLOGY, VOLUME 41 text-fig. 1. Mediograptus morleyae Loydell and Cave, 1996; uppermost insectus Biozone graptoloid band (uppermost Telychian), Banwy River section, Wales; specimens showing evidence for predation, a-b, folded specimens; x 20. A, BGS RCV7168. B, BGS RCV7201. c-E, dense ovoid masses, interpreted as faecal pellets; x 10. c, BGS RCV7164. d, BGS RCV7193. e, BGS RCV7099 (two pellets). bearing two or three thecae. All these specimens can be identified confidently as M. morleyae by their very distinctive thecal morphology, still clearly visible on many specimens despite the distortion (e.g. Text-fig. 1a). The dense, ovoid masses (Text-fig. 1c-e) show less variation in dimensions (Table 1) than the folded specimens (Text-fig. 1a-b). Some of the latter have dimensions similar to those of the dense masses (e.g. BGS RCV7015, 3-5x24 mm); others, however, are significantly larger and elongated (e.g. BGS RCV7071, 7-0 x 1-7 mm). The lower Wenlock specimens. Several folded specimens of Mediograptus cf. inconspicuus (Boucek, 1931) are present in the Harris collection. Their appearance (Text-fig. 2) is similar to that of the folded specimens from the Banwy River section, although the folds are fewer and more widely spaced. Dense, ovoid masses are not present in the collection. LOYDELL ET AL.: PREDATION ON GRAPTOLOIDS 425 table 1. Maximum dimensions (in mm) of dense, ovoid masses (Mediograptus morleyae , uppermost Llandovery, Banwy River section). Accurate measurements of the other three specimens could not be made (because of damage, or the presence of other graptoloids superimposed). Specimen number Length Width BGS RCV7014 2-1 1-8 BGS RCV7015 2-1 1-4 BGS RCV7038 2-1 1-55 BGS RCV7070 2-9 2-45 BGS RCY7073 2-35 115 BGS RCV7099(1) 2-2 20 BGS RCV7099(2) 2-5 2-3 BGS RCY7 164(1) 2-45 2-4 BGS RCV7 164(2) 3-0 2-8 BGS RCV7193 2-3 1-6 BGS RCV7197 2-25 1-6 text-fig. 2. Mediograptus cf. inconspicuus (Boucek, 1931); SM X.272513; centrifugus Biozone (lower Wenlock), quarry south-west of Disserth, Wales; folded specimen. Scale bar represents 1 mm. DISCUSSION Interpretation of the material. The dense ovoid masses are, most probably, faecal pellets; their uniform, ovoid shape and similar dimensions support this conclusion. The simply folded specimens are more problematical. They too may represent coprolitic material, but alternatively perhaps represent specimens which had not passed through the gut, but were dropped during manipulation prior to ingestion. The folded graptoloid rhabdosomes would probably have reached the bottom rapidly (see Bates 1987 for discussion of graptoloid density). Species selectivity. More than 200 specimens from eight other graptoloid species (of the genera Retiolites, Monograptus, Monoclimacis and Cyrtograptus ) occur on the same bedding planes as do the predated Mediograptus morleyae specimens. None of these is folded or distorted in any way. Indeed in the entire Banwy River collection (more than 8000 graptoloids) only one other specimen (RCV3640; Monoclimacis linnarssoni (Tullberg, 1883), from the lowest part of the insectus Biozone) shows either of the features described above : in a total length of 24 mm, the rhabdosome exhibits two approximately right-angled kinks. Similarly, Mediograptus cf. inconspicuus is the only taxon within the lower Wenlock collection (many hundreds of graptoloids) to exhibit folded rhabdosomes. It would seem that these two species of Mediograptus were being selected by predators in preference to other graptoloid taxa. Possibly, this was because of their rhabdosome tenuity, which allowed them to be folded up easily. M. morleyae has a maximum dorso-ventral width of only 0-4 mm. M. inconspicuus attains greater dorso-ventral widths (0-6-0-7 mm), but prothecal widths are 426 PALAEONTOLOGY, VOLUME 41 characteristically half the dorso-ventral width at the metatheca. Rhabdosome width can be only part of the explanation for the apparent selectivity, however, as there are many other graptoloids with narrow rhabdosomes or prothecae, none of which shows signs of predation. Perhaps only these Mediograptus species inhabited the same part of the water column as the predators ; or possibly they lacked an adequate defence mechanism. Unfortunately, these hypotheses would be difficult, if not impossible, to test. Possible predators. All the material described above occurs within laminated hemipelagites, deposited under low-energy conditions. Neither shelly benthic organisms nor trace fossils are present in the uppermost insectus Band in the Banwy River or in the graptolitic horizons in the quarry south-west of Disserth. Brachiopods and other shelly benthos do occur at other horizons within the Banwy River section (Temple 1987; Loydell and Cave 1996), and bioturbation is ubiquitous throughout much of the Upper Llandovery of this section; where this has penetrated graptolitic mudstones (e.g. those of the spiralis Biozone), the Chondrites mottling is obvious. We thus consider it unlikely that there was any macrobenthos alive at the time of deposition of the hemipelagite, although it is of course possible that any bedding parallel trace fossils have been obliterated by compaction during diagenesis, and thus we cannot discount completely that the features described above are the result of scavenging of the dead graptoloids by a benthic or necto- benthic soft-bodied organism. Assuming that the graptoloids were preyed upon in the pelagic realm, what organisms could have been responsible? Graptolitic horizons in the Banwy River section have yielded a few simple coniform conodont elements. Conodonts are generally rare in graptolitic facies, and thus their occurrence here is interesting. However, the Mediograptus specimens show no evidence of any damage, other than the folding, which seems inconsistent with predation by a conodont animal (see e.g. Aldridge and Purnell 1996, p. 466). Fossil nectic predators which are encountered regularly in the graptolitic facies of Wales are nautiloid cephalopods, represented almost exclusively by orthoconic forms. Feeding by extant cephalopods is generally destructive, involving crushing or breakage by powerful jaws prior to ingestion (Fretter and Graham 1976). Despite the remarkable abundance of cephalopod jaws in some Recent marine sediments (Clarke 1962), they are generally not common in the fossil record. Frey (1989) has suggested that the ‘probable noncalcified nature of most Palaeozoic cephalopod mandibles does not indicate that Palaeozoic nautiloids were not carnivorous in habit, but that they fed primarily on soft-bodied organisms or organisms with weakly mineralized exoskeletons such as trilobites and other arthropods.’ Frey (1989) attributed damage to Ordovician trilobites to predation by nautiloids, whilst Watkins (1991) interpreted ellipsoidal masses of broken skeletal fragments and crinoid ossicles as possible cephalopod ‘cough-balls’, ejected from the stomach via the mouth. As mentioned above, the Mediograptus specimens show no signs of having been bitten, or of other breakage. Having suggested that appearance of the Mediograptus specimens described here is unlikely to be the result of predation by conodont animals or cephalopods, the implication is that predation was by a soft-bodied organism, which has left no trace in the rock record. It will be interesting to see whether the gut contents of any of the soft-bodied organisms from the recently discovered Silurian Konservat Lagerstatten in Wisconsin (Mikulic et al. 1985a, 19856) and Herefordshire, England (Briggs et al. 1996) provide further evidence for the identity of predators on graptoloids. Acknowledgements. The specimens from the Banwy River section were collected as part of a research project enabled by a N.E.R.C. Small Grant (Ref. GR9/1 129). David Evans (English Nature) is thanked for discussion of feeding by cephalopods. REFERENCES aldridge, R. J. and purnell, M. A. 1996. The conodont controversies. Trends in Ecology and Evolution, 11, 463-468. LOYDELL ET AL.: PREDATION ON GRAPTOLOIDS 427 bates, d. e. b. 1987. The density of graptoloid skeletal tissue, and its implication for the volume and density of the soft tissue. Lethaia , 20, 149-156. — and kirk, n. h. 1985. Graptolites, a fossil case-history of evolution from sessile, colonial animals to automobile superindividuals. Proceedings of the Royal Society of London , Series B , 228, 207-224, pis 1-5. boucek, b. 1931. Predbezna zprava o nekterych novych druzich graptolitu z ceskeho gotlandienu. Vestnik Statniho Geologickeho Ustavu Republiky Ceskoslovenske, 7, 293-313. briggs, d. e. g., siveter, david j. and siveter, derek j. 1996. Soft-bodied fossils from a Silurian volcaniclastic deposit. Nature , 382, 248-250. bull, e. e. 1996. Implications of normal and abnormal growth structures in a Scottish Silurian dendroid graptolite. Palaeontology, 39, 219-240. clarke, m. R. 1962. Significance of cephalopod beaks. Nature, 193, 560-561. fretter, v. and graham, a. 1976. A functional anatomy of invertebrates. Academic Press, London. frey, r. c. 1989. Paleoecology of a well-preserved nautiloid assemblage from a Late Ordovician shale unit, southwestern Ohio. Journal of Paleontology, 63, 604—620. loduca, s. t. 1995. Thallophytic-alga-dominated biotas from the Silurian Lockport Group of New York and Ontario. Northeastern Geology and Environmental Sciences, 17, 371-382. loydell, d. k. and cave, r. 1993. Distinguishing between the Wenlock graptolite biozonal indices Cyrtograptus centrifugus and Cyrtograptus murchisoni. Palaontologische Zeitschrift, 68, 437—441. 1996. The Llandovery-Wenlock boundary and related stratigraphy in eastern mid-Wales with special reference to the Banwy River section. Newsletters on Stratigraphy, 34, 39-64. mikulic, d. G., briggs, d. e. G. and kluessendorf, J. 1985a. A Silurian soft-bodied biota. Science, 228, 715-717. — 19856. A new exceptionally preserved biota from the lower Silurian of Wisconsin, U.S.A. Philosophical Transactions of the Royal Society of London, Series B, 311, 75-85, pis 1-2. temple, J. T. 1987. Early Llandovery brachiopods of Wales. Monograph of the Palaeontographical Society, 139 (572), 1-137, pis 1-15. tullberg, s. a. 1883. Skanes graptoliter II. Graptolitfaunorna i Cardiolaskiffern och Cyrtograptusskiffrarne. Sveriges Geologiska Undersokning, Series C, 55, 1-43, pis 1-4. underwood, c. j. 1993. The position of graptolites within Lower Palaeozoic planktic ecosystems. Lethaia, 26, 189-202. watkins, R. 1991. Guild structure and tiering in a high-diversity Silurian community, Milwaukee County, Wisconsin. Palaios, 6, 465—478. DAVID K. LOYDELL Geology Department University of Portsmouth Burnaby Building, Burnaby Road Portsmouth POl 3QL, UK e-mail David.Loydell@port.ac.uk JAN ZALASIEWICZ Department of Geology University of Leicester University Road Leicester LEI 7RH, UK e-mail jazl@leicester.ac.uk Typescript received 29 May 1997 Revised typescript received 5 September 1997 RICHARD CAVE Institute of Geography and Earth Sciences University of Wales, Aberystwyth, Ceredigion SY23 3DB, UK EARLY ORDOVICIAN TRILOBITES FROM DALI, WEST YUNNAN, CHINA, AND THEIR PALAEOGEOGRAPHICAL SIGNIFICANCE by ZHOU ZHIYI, WILLIAM T. DEAN and LUO HUILIN Abstract. Eleven late Arenig-Llanvirn trilobite taxa, including one new species, Neseuretus elongatus, are described from the Hsiangyang Formation east of Dali, in the eastern part of west Yunnan, China, an area that may have been part of the Indo-China Terrane. The trilobites are mostly typical representatives of Gondwana cold-water faunas, and their close biogeographical relationships with south-central Europe and the Yangtze region are discussed. Four biofacies are differentiated in relation to an environmental gradient: Cruziana Biofacies (intertidal); Neseuretus Biofacies (inner shelf); Trinucleid Biofacies (shallow outer shelf); and Cyclopygid Biofacies (deep outer shelf). The rocks of the Hsiangyang Formation are interpreted as a deepening-upwards sequence. Ordovician rocks are exposed intermittently in the eastern part of west Yunnan, an area between the Yuan Jiang-Jinsha Jiang Fault (see Lai et al. 1982) and the Lancang Jiang Fault (see Fang 1991) (Text-fig. lc). Geologically the area may have formed the northern extension of the Indo-China Terrane (Metcalfe 1988, 1992), and it is bounded to the west by the Sibumasu Terrane and to the east by the South China Block. The Early Palaeozoic strata of the terrane comprise mainly metamorphic clastic rocks, with a few macrofossils reported from Cambodia, Laos, Vietnam and eastern Thailand (Workman 1977; Metcalfe 1988, p. 106, fig. 5), but are otherwise little known (Scotese and McKerrow 1991, p. 276). On the Chinese side, Ordovician rocks, which are only slightly metamorphosed, contain a complete faunal succession and are best developed at Xiangyang, in the Dali area, where they have been investigated since 1945 (Sun 1945). The lower Ordovician is composed of clastic sediments; from the middle Ordovician onwards there is a progressive increase in carbonates, but only in the Caradoc do they become dominant. Trilobites occur only in the lower Ordovician but provide good evidence for considering the Indo-China Terrane as part of Peri-Gondwana during the Early Palaeozoic. Seven trilobite species recorded by Sheng (19746) are revised on the basis of our large collection from the measured section at the stratotype, and forms new to the area are described. AGE AND BIOSTRATIGRAPHY The term Hsiangyang Formation was introduced by Sun (1945) for the clastic rock sequence exposed near Xiangyang (Text-fig. 1). The lower part, comprising massive- to thickly bedded sandstones and quartzites, was later referred to a new lithostratigraphical unit, the Haidong Formation, by Sheng (1974a). The type section was measured for the first time in 1973 by the No. 1 Regional Geological Survey Team, Yunnan Bureau of Geology, who proposed its subdivision into members 1-3, in ascending order. Most of the sequence is exposed along the road from Jiangshang to Mingzhuang, but Member 3 is seen only near Yulongcun. The thicknesses of the members, and the boundaries between them, were modified slightly during field-work carried by Chen Tingen (Nanjing Institute of Geology and Palaeontology), Xiao Yinwen (No. 1 Regional Geological Survey Team, Yunnan) and the authors in the 1980s, and the revised succession is shown in Text-figure 2. [Palaeontology, Vol. 41, Part 3, 1998, pp. 429-460, 4 pis] © The Palaeontological Association 430 PALAEONTOLOGY, VOLUME 41 area of locality map I South China Block II Indo-China Terrane III Sibumasu Terrane a Lanchan Jiang Fault 1 b Yuan Jiang Fault text-fig. 1 . Outline maps showing position of Dali area in South-western China (b, c), and location (a) of measured sections through the Hsiangyang Formation north and east of Xiangyang. The Hsiangyang Formation is underlain conformably by the Haidong Formation, and overlain by the Tongchang Formation; it consists mainly of siltstones, shales and sandstone, with conglomerates at the top, and the total thickness is about 700 m. Largely on the basis of trilobite evidence, the age of members 1 and 2 was considered as Llanvirn by Sheng (19746) but as Arenig by Lai et al. (1982). Trilobites in our collection from members 1 and 2 are of marked Arenig-Llanvirn aspect by comparison with faunas in the Yangtze region and southern Europe (see below). The lowest fossiliferous horizon in the Hsiangyang Formation yielded Liomegalaspides blackwelderi and Neseuretus cf. tungtzuensis. The former is common in the upper Arenig of southern Shaanxi (Lu 1975, p. 128, as Isoteloides liangshanensis ) and only a single cranidium was found by ZHOU ET AL.: ORDOVICIAN TRILOBITES 43: Lithol. Units Section Tong- chang Form. rn: • O.O. a o « 5 B Lithology greyish-yellow, thick-bedded calcareous sandstones with sandy limestones at the base 127m greyish-black to greyish- green shales with fine sandstones in the lower part, and coarse sandstones and sandy conglomerates in the upper 363m greyish-green to greyish- black, medium-bedded fine sandstones and siltstones intercalated with shales 216m greyish-green to greyish- yellow, medium to thick-bedded muddy siltstones intercalated with fine sandstones and sandy shales light grey, massive to thick- bedded, fine feldspathic sandstones and quartzites text-fig. 2. Simplified columnar section through the Hsiangyang Formation, as exposed in descending order from north to south from Yulongcun to Mingzhuang to Jiangshang, near Xiangyang, showing occurrences of identified trilobite species. Li et al. (1975, p. 145, pi. 10, fig. 6, as Megistaspis sp.) in the Chaochiapa Formation of the same area, probably of mid Arenig age (Lai et al. 1982). N. tungtzuensis was recorded by Sheng (1958, p. 200, as Calymene ( Synhomalonotus ) tungtzuensis from the upper part of the Meitan Formation (late Arenig) in the border area between Guizhou and Sichuan. Since the distribution of shelly 432 PALAEONTOLOGY, VOLUME 41 faunas tends to follow shifts of facies, precise age determination based on trilobites alone can be difficult or impossible; but from their evidence it is likely that most of the rocks in Member 1 are of late Arenig age, and the base of the formation may be no older than mid Arenig. Graptolites found in association with trilobites in members 2 and 3 have been identified by Ni Yunan (Nanjing Institute of Geology and Palaeontology). They include, inter al.: Amplexograptus confertus (Lapworth), Didymograptus artus Elies and Wood and D. nanus Lapworth from Member 2 ; and Didymograptus jiangxiensis Ni and D. murchisoni Beck from the lower part of Member 3. The material, which has not yet been described, indicates that Member 2 may be correlated approximately with the D. artus Biozone (early Llanvirn) and Member 3 with the D. murchisoni Biozone (late Llanvirn). Trilobites are rare in Member 3 and all belong to the Cyclopygidae, including Cyclopyge sp., Microparia ( Microparia ) cf. prantli and Pricy clopyge obscura. M. ( M .) prantli and P. obscura have been recorded only from the Llanvirn of Bohemia (Marek 1961). Specimens of Cyclopyge sp., although poorly preserved, are closely related to C. kossleri from the Llanvirn of Bohemia (Marek 1961) and South Wales (Fortey and Owens 1987). No macrofossils were found in the highest part of the formation, and the conglomerates may have formed during regression in the latest Llanvirn. BIOFACIES AND PALAEOENVIRONMENTS The Haidong Formation, the lowest part of the Ordovician succession in the Dali area, contains no trilobite body fossils but the trace fossil Cruziana and the inarticulate brachiopod Lingulepis have been found at several levels, suggesting a littoral environment, above wave base (Crimes 1970). Most of the thickly to massively bedded arenite deposits are fine-grained and well-sorted, and low- angle cross-beds a few metres thick appear at several levels; all indicate intertidal conditions (Text- fig. 3a). Most fossils from Member 1 of the Hsiangyang Formation were found in siltstones; only bivalves are known from the basal strata, but in higher beds they are accompanied by the trilobites Neseuretus cf. tungtzuensis and Liomegalaspides. Trilobites become progressively more diverse higher in the succession, in the upper part of which Hungioides and Ogyginus make their appearance and N. cf. tungtzuensis is replaced by Neseuretus elegans. The trilobite association is characterized by Neseuretus and asaphids, indicating the Neseuretus Biofacies (cf. Neseuretus Community of Fortey and Owens 1978). The fauna represents a shallow-water, inner shelf environment (Fortey and Owens 1978, p. 238; see Text-fig. 3b). Storm-induced bioclastic beds appear at several levels, formed by abundant shelly debris that includes bivalves and a few trilobites and brachiopods. Intercalations of sandy shale resting on siltstone are largely lenticular and show wave-ripple laminations, while hummocky cross-stratification is seen locally within a few siltstone beds. The sedimentary evidence suggests, according to Prothero and Schwab (1996), that Member 1 was formed in the zone below fair weather wave base and above storm wave base. Trilobite diversity in the Neseuretus assemblage is low and no planktic taxa, such as graptolites, are known from Member 1. Most of the siltstone beds are horizontally stratified and the less weathered rocks are black ; some trilobites are preserved as complete exoskeletons, and disarticulated specimens remain unbroken. It is likely that most rocks of Member 1 were deposited under quiet conditions between intervals of storm re-working. The inner shelf may have been bordered by small, discontinuous rises that made faunal exchange incomplete, and the alternations of fossiliferous and barren beds may indicate rapid fluctuations in oxygen content. Cruziana and Lingulepis continue upwards from the Haidong Formation and have been found, although without other associated macrofossils, in a few intercalated sandstone beds in the lower part of Member 1 ; these occurrences suggest occasional relative falls in sea level during the interval represented by Member 1 . Member 2 begins with about 80 m of medium- to thickly bedded fine sandstones, in the middle of which are a few beds of sandy shale. No fossils have been found in these beds, the sand grains are mature and well sorted, and several beds show hummocky cross-stratification. The sandstones are capped by grey to black shales and siltstones, finely and horizontally laminated, and rich in ZHOU ET AL.: ORDOVICIAN TRILOBITES 433 Ogyginus Pricyclopyge Liomegalaspides — — - Microparia ( Microparia) Hungioicles Hastireinopleuridesl text-fig. 3. Model showing palaeogeographical distribution of trilobites of the Hsiangyang Formation in relation to biofacies, a, Cruziana Biofacies (intertidal shore); b, Neseuretus Biofacies (inner shelf); c, Trinucleid Biofacies (shallow outer-shelf); d, Cyclopygid Biofacies (deep outer-shelf). SL = sea-level; FWWB = fair- weather wave base; SWB = storm wave base. trilobites and graptolites. About 20 per cent, of the trilobites collected are preserved as articulated exoskeletons, a few of which are undisturbed, in situ moults (PI. 3, fig. 1 1). Others are disarticulated, but the various parts of a single individual may sometimes be found associated on the same bedding plane. All these features suggest quiet conditions of deposition well below storm wave base. The trilobite fauna consists of Hanchungolithus, Hastiremopleuridesl , Liomegalaspides , Neseuretus and Ogyginus. Compared with the fauna of Member 1, Hanchungolithus is both a characteristic new addition and a dominant element, accounting for 50 per cent, of the total specimens from this horizon, for which the term Trinucleid Biofacies is employed. Zhou et al. (1990, 1992) suggested that the Trinucleid Biofacies represents a shelf-slope environment (depth < 100 m) with a muddy or clastic substrate. A similar sequence, passing from fine sandstone to shale, appears again in the middle and upper parts of Member 2, following fluctuations in sea-level, but most of the trilobite genera are absent, except for Hanchungolithus, which is associated with Cyclopyge in an horizon at the top. Cyclopygids have been considered as mesopelagic trilobites, distributed in a depth zone of some 200-700 m (Fortey 1985). However, as pointed out by Zhou et al. (1994), on the basis of their palaeogeographical distribution there may have been a depth-induced differentiation between cyclopygids of superficially similar morphology. Of these, Cyclopyge is one of a few genera that lived at a shallower water level and may have penetrated shallower shelf areas during periods of transgression. We believe that most of the shales and siltstones in Member 2 were formed on the shallow outer shelf, and that the sandstones may represent small, low sand bars distributed along the margin of the inner shelf (Text-fig. 3c). Member 3 is made up of probable turbiditic deposits. About 40 m of argillaceous to arenaceous beds in the lower part show planar laminations, whilst shaly or muddy siltstones, sandy mudstones 434 PALAEONTOLOGY, VOLUME 41 and mudstones were rhythmically deposited. Only planktic faunas have been found, including graptolites and cyclopygid trilobites ( Cyclopyge , M. ( Microparia ), Pricyclopyge), but they are not abundant. The trilobite association indicates the Cyclopygid Biofacies which, for Fortey and Owens (1987), generally represents marine conditions about 300 m deep. However, Fortey and Owens (1987) stated that 'in more turbid epicontinental seas [light penetrated] to less than half this depth’, and Zhou et al. (1990, 1992) pointed out that the exact water depth often depends on the clarity of the water body. The turbidity current induced deposits of Member 3 may indicate generally turbid marine conditions in this area during the late Llanvirn, and from the regional facies context we infer a depth of less than 200 m. About 75 m of arenites overlying the shales are mainly poorly sorted, thickly bedded, fine conglomerates and coarse sandstones that pass laterally into fine sandstones. This set of coarse elastics is considered to represent debris flows from adjacent shallow areas during the latest Llanvirn regression (see Fortey 1984). Debris flows appear also at the top of Member 2 and in the lower part of Member 3, but are thinner. It is likely that Member 3 was deposited on the lower shelf slope or the deep outer shelf (Text-fig. 3d). In general, the succession from the Haidong Formation to the Hsiangyang Formation indicates a deepening-upwards sequence, although small-scale fluctuations in sea-level were frequent. Four facies types, separated by transitional boundaries, are differentiated in relation to the shallow to deeper water environmental gradient. FAUNAL AFFINITIES AND PALAEOGEOGRAPHICAL IMPLICATIONS Of the nine genera recorded from the late Arenig to Llanvirn Hsiangyang Formation, four ( Neseuretus , Ogyginus, Hanchungolithus and Hungioides ) are well known as typical benthic index fossils of Ordovician Gondwanaland, and their geographical distribution is summarized below. Unless otherwise stated, the relevant tectonic regions listed here are those of Scotese and McKerrow (1991, fig. 1). 1. Neseuretus. Arenig: Wales, England, Germany, south-western France, eastern Newfoundland, Morocco, Algeria, southern Turkey, and the Yangtze region of the South China Block. Llanvirn: Argentina, Bolivia, Peru, England, Spain, Morocco, Algeria, Saudi Arabia, Burma and the western part of west Yunnan (the two last-named areas belong to the Sibumasu Terrane). Llanvirn to Llandeilo: south-western England (Cornwall), north-western France, Spain, Portugal, Algeria, Tunisia and Morocco (see Fortey and Morris 1982; Dean 1985; Zhou and Dean 1989; Rabano 1990). 2. Ogyginus. Arenig: Wales, south-western France and eastern Newfoundland; Llanvirn: Wales, England, ?Spain, ?Portugal, and possibly Argentina, Bolivia and Peru (as Hoekaspis, see below); Arenig-?Llanvirn : north-western France; Llanvirn-Llandeilo : England and Wales (see Romano et al. 1986; Fortey and Owens 1987; Rabano 1990). 3. Hanchungolithus. Middle Arenig: south-western France, south-eastern Ireland and ?North Wales; upper Arenig: the Yangtze region (see Hughes et al. 1975; Zhou and Hughes 1989). 4. Hungioides. Tremadoc: the Yangtze region; Arenig: central Australia, the Yangtze region, Inner Mongolia (western marginal area of the North China Block) and ?south-western France; Llanvirn: Bohemia, Germany, Spain, Portugal and Argentina (see Rabano 1983; Zhou and Dean 1989). Two further benthic trilobite genera, Liomegalaspides and H astir emopleuridesl, are more endemic, recorded only in parts of eastern Gondwanaland. The former is known mainly from the upper Arenig to lower Llanvirn of the Yangtze region, Central and Southwest China, and the Tarim region. Northwest China. Hastiremopleuridesl is considered to represent a group of species with well-developed triangular anterior border that was confined to the Yangtze region from the Arenig to Caradoc, but probably migrated to south-eastern Turkey in the early Ashgill (see below). Mesopelagic trilobites are represented only by Cyclopyge , M. ( Microparia ) and Pricyclopyge, members of a family confined mainly to peripheral Gondwana, especially in the early Ordovician (Fortey and Owens 1987, p. 108). ZHOU ET AL.: ORDOVICIAN TRILOBITES 435 Three of the 1 1 species present are conspecific with, or closely related to, forms from the Yangtze region: Neseuretus cf. tungtzuensis, Liomegalaspides blackwelderi and Hastiremopleurides ? aff. nasutus. A further three ( Neseuretus elegans, Ogyginus daliensis and Hungioides cf. bohemicus) exhibit close relationships to south and central European species ( Neseuretus arenosus, Ogyginus armoricanus and H. bohemicus). Cyclopygid species are usually widespread, and the three species in the Dali area closely resemble coeval Bohemian forms. If the eastern part of west Yunnan formed a northward extension of the Indo-China Terrane, as deduced by Metcalfe (1988, 1992), the trilobite evidence may indicate a biogeographical connection between the South China Block, south-central Europe, and the Indo-China Terrane. Interestingly, the appearance of the above benthic trilobite genera in the Indo-China Terrane is not exactly contemporaneous with their corresponding appearance in south-central Europe or the Yangtze region. A typical example is Hanchungolithus, which occurs in the middle Arenig of south-western France and south-eastern Ireland, in the upper Arenig of the Yangtze region, and in the lower Llanvirn of the Dali area. This indicates that free migration or dispersal of trilobites was possible along the epicontinental sea on the east side of the ‘Paleotethys Ocean’ of Scotese and McKerrow (1991 ; discussion in Dean 19676, p. 23; El-Khayal and Romano 1985, p. 404). Neseuretus was interpreted by Fortey and Morris (1982) as representative of shallow, cold-water Gondwana faunas found only at high latitudes. An exception to this is the northward extension of the genus into the Yangtze Carbonate Platform, the explanation for which may involve either the northward movement of a cold ocean current into lower latitudes, or even differences in water depth. We agree with Fortey and Owens (1987) that the Neseuretus Biofacies represents an inner shelf environment. However, the palaeogeographical distribution in the Dali area (Text-fig. 3) indicates that Neseuretus itself may have had a wider tolerance range, from inner shelf to shallow outer shelf. In south-western France (Dean 1966) Neseuretus was described from graptolite-bearing mid Arenig mudstones, in association with Hanchungolithus, and more recently it was found in the upper Arenig (U. austrodentatus Zone) of western Hubei (Xiang and Zhou 1987), with Nileus, a warm-water trilobite usually considered to occupy a farther off-shelf habitat than Neseuretus. The Armorican types of clastic facies and the cold-water trilobites assemblages in the Dali area suggest that, at least in the early Ordovician, the Indo-China Terrane may have been located at a higher latitude than shown by Metcalfe (1992, fig. 4) and by Scotese and McKerrow (1991, fig. 3). It is highly likely that the Indo-China Terrane was situated closer to the south-central Europe Block than to the South China Block. West of the Indo-China Terrane, Ordovician rocks are documented in the Baoshan area, western west Yunnan (Lai et al. 1982), the Shan States (Chhibber 1934) and the Thailand-Malaysia border area (Hamada et al. 1975). Contiguity of lithological and faunal successions in the first two areas was noted by Sun and Szetu as early as 1947, and the lower Ordovician there comprises mainly elastics with only a few limestones in the upper part ; in marked contrast, the succession in the last-named area is composed essentially of carbonates. These differences were interpreted by Metcalfe (1992) as due to facies changes on a single stable shelf which belonged to the Sibumasu (or Shan-Thai) Terrane. No reliable evidence of Arenig trilobites is known from this terrane, but the Llanvirn trilobite Basilicus ( Basilicus ) satunensis (Kobayashi and Hamada, 1964, p. 208, pi. 9, figs 1-12), from Satun, near the Malaysian frontier with Thailand, exhibits close affinities with B. (B.) boehmi (Lorenz) from the coeval Machiakou Formation in North China (see Zhou and Fortey 1986, p. 180; Zhou and Dean 1989, p. 132). Llanvirn trilobites from the Baoshan area (Reed 1917; Sheng 19746) and North Shan States (Reed 1906, 1915) include, inter al., Neseuretus , Prionocheilus, Basilicus ( Basiliella ) [as Pseudobasilicus baoshanensis; see Sheng 19746, p. 101, pi. 3, fig. 3], Encrinurella and Pliomerina. Species of B. ( Basiliella ) and Pliomerina are closely similar to those from the Machiakou Formation of North China and the Tsuibon Formation of South Korea (Zhou and Fortey 1986, pp. 182, 202), whilst Encrinurella is known elsewhere only from the lower Ordovician in Australia (Legg 1976). A south-western Gonwanaland connection is also indicated by Neseuretus and Prionocheilus. On the whole, the Llanvirn trilobites of the Sibumasu Terrane differ markedly from those of the Indo-China Terrane, suggesting geographical separation of the two areas. Based on the similarity of early Ordovician nautiloids from the 436 PALAEONTOLOGY, VOLUME 41 Thailand-Malaysia border area. North China and Australia, Burrett and Stait (1987, fig. 7) and Burrett et al. (1990, fig. 4) considered the Sibumasu Terrane to be located in the tropics, in the proximity of the North China and Australia blocks. However, the trilobite evidence favours the reconstructions by Scotese and McKerrow (1991, fig. 3) and by Metcalfe (1992, fig. 4), in which the Sibumasu Terrane was rotated through 180° so that Thailand Peninsula-West Malaysia was on the palaeoequator, close to the North China Block, while the Shan States-western west Yunnan area may have been sited in a low latitudinal zone not far from the South China Block. SYSTEMATIC PALAEONTOLOGY The terminology adopted here is that of Harrington et al. (in Moore 1959, pp. 117-126), with modifications by Whittington and Kelly (in Kaesler 1997). Described and cited specimens are housed in the following institutions, with prefixes for registration numbers: BGM, Geological Museum of Beijing, Ministry of Geology and Mineral Resources; CIGM, Chendu Institute of Geology and Mineral Resources, Academy of Geological Sciences of China ; NI, Nanjing Institute of Geology and Palaeontology, Academia Sinica; SBNM, National Museum of Natural History, Prague; USNM, National Museum of Natural History, Washington, D.C. Family remopleurididae Hawle and Corda, 1847 Subfamily remopleuridinae Hawle and Corda, 1847 Genus hastiremopleurides Yin, 1980 Type species. Remopleurides (Hastiremopleurides) bijieensis Yin, 1980. Hastiremopleurides ? aff. nasutus (Lu, 1957) Plate 1, figures 19746 Remopleurides cf. dalecarlicus Holm; Sheng, p. 99, pi. 1, fig. 4a-f. Description. Cranidium pitcher-shaped in outline, weakly convex, its length 85-100 per cent, the breadth; downturned anterior tongue expands forwards slightly and has basal width about 32-35 per cent, the maximum cranidial breadth, across the mid-point of the palpebral lobe. Glabella has deeply incised, transverse SO and three pairs of faint, subparallel, equispaced lateral furrows. SI and S2 are gently sigmoidal, S3 is straighter, and all become successively shorter and weaker from SI to S3; the furrows do not reach the axial furrows, and extend slightly backwards adaxially; the distal end of SI almost coinciding with the maximum breadth of the cranidium. Occipital ring occupies 56-63 per cent, the cranidial width, and about 14 per cent, the length (sag.) of the glabella in specimens preserved in relief; it declines and becomes slightly narrower (exsag.) abaxially, and a median node is sited close to SO. Palpebral lobe strongly convex in plan, widens posteriorly and extends from SO to base of anterior tongue; palpebral or axial furrow deep. Anterior area of EXPLANATION OF PLATE 1 Figs 1-4. Hastiremopleurides ? aff. nasutus (Lu, 1957); Loc. 1, Member 2. 1, NI 127486; cranidium; x 10. 2, NI 127487; cranidium; x 7. 3, NI 127488; cranidium; x8. 4, NI 127489; cranidium; x 6. Figs 5-9, 11. Liomegalaspides blackwelderi (Weller, 1907). 5, NI 127490; cranidium; Loc. 1, Member 2; x3. 6, NI 127491; hypostoma; Loc. 2, Member 1; x 1-5. 7, NI 127492; exoskeleton, latex cast from external mould; Loc. 2, Member 1 ; x 3. 8, NI 127493; cranidium; Loc. 2, Member 1 ; x 3. 9, NI 127494; librigena; Loc. 1, Member 1; x2. 11, NI 127495; pygidium; Loc. 1, Member 2; x 1-5. Figs 10, 12-14. Ogyginus daliensis (Sheng, 19746); Loc. 1. 10, NI 127496; pygidium; Member 1 ; x 1-2; 12, NI 127497; pygidium; Member 2; x 1. 13, NI 127498; exoskeleton, meraspid degree 7; Member 2; x 6. 14, NI 127499, hypostoma; Member 2; x2. PLATE 1 ZHOU et al., Ordovician trilobites 438 PALAEONTOLOGY, VOLUME 41 fixigena narrow (tr.), triangular, depressed. Anterior border upturned, triangular in plan, bluntly pointed frontally. Border furrow deep and merges with preglabellar furrow in front of anterior glabellar tongue. The librigena as illustrated by Sheng (19746, pi. 1, fig. 4b-c) is very narrow outside the eye, flat anteriorly, and convex behind the base of the librigenal spine. Eye semicircular, its width 60 per cent, that of librigena, and its posterior half more strongly curved than the anterior half ; the visual surface declines gently at first but becomes almost vertical peripherally. Eye socle narrow, upturned, defined above and below by deep furrows. Librigenal spine slightly curved, its length at least twice that of librigena, and its broad base in-line with midpoint of eye; lateral margin joins that of anterior half of librigena in a broad curve; intergenal angle (= genal notch of authors such as Nikolaisen 1983) about 45° and deep. Remarks. Sheng (19746) compared this form with Remopleurides dalecarlicus Holm, in Warburg (1925, p. 88, pi. 1, figs 7-8; pi. 11, fig. 34), from the Upper Leptaena [= Boda] Limestone (Ashgill) of Dalarna, Sweden. Material in our collection shows the cranidium to have a broad (sag.) anterior border, a single character sufficient to exclude the species from Remopleurides. In our opinion the species is closely related to Remopleurides nasutus Lu, 1957 (p. 277, pi. 153, figs 14—15), a taxon redescribed by Lu (1975, p. 299, pi. 3, figs 15-22; pi. 4, figs 1-13) from the upper Arenig of southern Shaanxi and western Hubei, China, and later recorded from northern Guizhou (Yin, in Yin and Lee 1978, p. 519, pi. 172, fig. 2) and southern Anhui (Zhang Quanzhong, in Qiu et al. 1983, p. 196, pi. 65, fig. 6; as Remopleurides latilingulatus, placed here in synonymy with nasutus). The glabella, excluding occipital ring, is 75-80 per cent, as long as wide, and anterior tongue has width 26-43 per cent, (depending on preservation) that of glabella in our specimens; the corresponding figures in R. nasutus are 74-90 per cent, and 37-53 per cent., underlining the similarity of the cranidium in both forms. Other characters, such as the lateral glabellar furrows, palpebral lobe, occipital ring and anterior border, are almost identical in the late Arenig and Llanvirn specimens; but R. nasutus differs in the more posterior position of the librigenal spine base, which extends from the lateral margin of the librigena at a point about one-third its length from the rear. The species also resembles Remopleurides shihtzupuensis Lu, 1957 (p. 278, pi. 153, fig. 16; 1975, p. 301, pi. 4, figs 14—15) from the Shihtzupu Formation (Llandeilo) of northern Guizhou; Lu considered the latter to have a narrower anterior glabellar tongue than R. nasutus , but in the holotype (Lu 1957, pi. 153, fig. 16) its basal width is 34 per cent, that of the glabella, similar to the present material. However, the genal spine in shihtzupuensis is based on the anterior part of the librigena (Zhou et al. 1984, p. 15, fig. 3a-b), which is more advanced than in the present form. We believe that these three closely allied species may represent a new genus, the cranidium of which has a characteristic triangular anterior border. The more transverse, faint to shallow lateral glabellar furrows recall Remopleurides , and the narrow librigena with deep intergenal angle is similar in certain species of that genus ; but, in addition to the very different preglabellar area, the pygidium in R. nasutus has a much longer outer ( = first) pair of pleural spines, and a shorter inner pair. In the shape and size of the anterior border and the anterior cranidial tongue, it resembles Arator Nikolaisen, 1991, type species Robergia marianna Koroleva, 1965, from the lower middle Ordovician of northern Kazakhstan ; but the latter differs mainly in the deeply incised, less anteriorly divergent lateral glabellar furrows, and in having a rectangular pygidium with three pairs of pleural spines. The above three Chinese species are of different ages but have a similar cranidium, and local gradual morphological changes can be recognized in the librigena. They involve mainly the librigenal spine, which becomes successively more anterior in position : its base is opposite the rear part of the eye in nasutus, the earliest (Arenig) form; the middle part in the Llanvirn aff. nasutus ; and the front part in the Llandeilo shihtzupuensis. The three species may possibly form a peramorphocline in this character. Nikolaisen (1983, p. 277) suggested that some early species, such as R. nasutus and R. shihtzupuensis, may belong to an ancestral genus, which he called ‘ Robergiella s.l.\ and may have evolved into his younger genus Sculptaspis. Both species are comparable to members of Robergiella Whittington, 1959, in the form of the lateral glabellar furrows and the pygidium, but even in early species such as R. brevilingua Fortey, 1980 (p. 44, pi. 5, figs 1-8, 10-11 ; pi. 25, figs 7, 11, 13) and ZHOU ET AL.: ORDOVICIAN TRILOBITES 439 R. lundehukensis Fortey, 1980 (p. 46, pi. 5, figs 9, 12 14, 16), both from the Arenig of Spitsbergen, the anterior cranidial tongue has only a very narrow (sag.) frontal rim, and the librigena has a broader genal field between the eye socle and border. It is likely that the group of Chinese species is independent of both Robergiella and Sculptaspis. The latter is closely similar to Sculptella Nikolaisen, 1983, although, as noted by Nikolaisen (1983, pp. 267, 277), it has a thicker exoskeleton and the outer margin of the librigenal spine is at a distinct angle to the lateral border of the librigena. Species of both Nikolaisen’s genera may be compared to the group of Chinese species but differ in : the narrower anterior glabellar tongue, the longer postaxial field of the pygidium, and the form of the librigena, in which the librigenal spine is located more posteriorly and the intergenal angle is very shallow. Nikolaisen (1983, p. 266) postulated an evolutionary lineage from Remopleuridiella Ross, 1951, by way of Sculptella and Remopleurella Dean, 1963 to Amphitryon Hawle and Corda, 1847. Morphological changes affecting the librigena during phylogeny involve a rearward shift of the base of the librigenal spine, and progressive shallowing of the librigenal notch, culminating in its eventual disappearance ; these suggest that local heterochronic variation may have occurred by paedomor- phosis. If the lineage postulated by Nikolaisen proves to be correct, then, at least on the basis of the evolution of the librigena, the group of Chinese species may form a different remopleuridid lineage. Robergia striata Endo, 1932 (p. 109, pi. 38, fig. 3), from an unstated horizon at Huangbayi, southern Shaanxi, was reassigned to Remopleurides by Reed (1935), Kobayashi (1951), Whittington (1959), Lu et al. (1965), Li et al. (1975) and Chang and Jell (1983). Li et al. (1975, p. 151) reported the species from the Pagoda Formation (Caradoc) at its type locality, and similar cranidia were later described from the same formation at Liangshan, Hanzhong, southern Shaanxi (Ji 1986, p. 12, pi. 1, figs 13-14). The holotype, refigured by Chang and Jell (1983, fig. 6e-f), closely resembles cranidia in our collection, but its anterior glabellar tongue is wider, 46 per cent, the glabellar width. Nikolaisen (1991, p. 54) was inclined to refer R. striata to Sculptaspis, but the wider cranidial tongue and the shape of the anterior border suggest, rather, the nasutus-grovep. Outside China, Amphitryon ? sp. from the lower Ashgill of south-eastern Turkey (Dean and Zhou 1988, p. 643, pi. 61, figs 8-10) is closely related to the group of Chinese species; the anterior cranidial tongue is narrower (tr.) in the Turkish species, but the length of the triangular anterior border is similar to that of nasutus. Zhou et al. (1984, p. 15) assigned shihtzupuensis to Hastiremopleurides. The type species, H. bijieensis Yin (1980, p. 23, pi. 1, fig. 6) from the Chientsaokou Formation (lower Ashgill) of Bijie, northern Guizhou, has the anterior glabellar tongue more expanded frontally, with a much longer (sag.) anterior border, but is otherwise basically similar to all the species in the nasutus- group. Immature specimens of nasutus show that the length (sag.) of the anterior border increased during ontogeny (Lu 1975, p. 300). This may suggest a peramorphic increase in border length, and bijieensis might represent the latest stage of one branch in the nasutus evolutionary series. Unfortunately, except for nasutus, material is limited and species in this series are imperfectly known, so that for the time being we refer both nasutus and the present material with reservation to Hastiremopleurides. Family asaphidae Burmeister, 1843 Subfamily isotelinae Angelin, 1854 Genus liomegalaspides Lu, 1975 Type species. Isotelus usuii Yabe, in Yabe and Hayasaka, 1920. 440 PALAEONTOLOGY, VOLUME 41 Liomegalaspides blackwelderi (Weller, 1907) Plate 1, figures 5-9, 11 1907 Asaphus blackwelderi Weller, p. 560. 1907 Asaphus asiaticus Weller, p. 561. 1913 Asaphus blackwelderi Weller; Weller, p. 286, pi. 26, figs 21-22. 1913 Asaphus asiaticus Weller; Weller, p. 287, pi. 26, fig. 5. 1957 Isoteloides liangshanensis Lu, p. 279, pi. 152, figs 1-2. 1974 b Pseudoasaphus daliensis Sheng, p. 101, pi. 4, fig. la— b, f {non c-e). 1975 Isoteloides liangshanensis Lu, p. 322, pi. 9, figs 6-10; pi. 10, figs 1-11. 1975 Megistaspis sp. Li et al., p. 145, pi. 10, fig. 6. 1975 Isoteloides liangshanensis Lu; Li et al., p. 147, pi. 13, fig. 5. 1982 Isoteloides liangshanensis Lu; Zhou et al., p. 263, pi. 65, fig. 16. 1983 Megalaspides blackwelderi Weller; Chang and Jell, p. 198, fig. 3b, h-i [non figs 3a, c-g, 4j, 5e = Megalaspides taningensis (Weller)]. Holotype. Cranidium (USNM 60876) figured Weller, 1913, pi. 26, fig. 21 (see also Chang and Jell 1983, fig. 3b), from an Arenig limestone, 2-4 km upstream from Sukiapa on the Taning River, northern Sichuan. Figured specimens. One exoskeleton (NI 127492), one cranidium (NI 127493) and one hypostoma (NI 127491) from Member 1, Loc. 2; one cranidium (NI 127490), one librigena (NI 127494) and one pygidium (NI 127495) from Member 2, Loc. 1. Remarks. One cranidium, one small, compressed pygidium and three librigenae from Member 2, Loc. 1, were described by Sheng (19746) as a new species, Pseudoasaphus daliensis. The cranidium (BGM OT68-48, 49; Sheng 19746, pi. 4, fig. la-b), selected herein as lectotype, has a small palpebral lobe, its anterior margin level with the centre of the cranidium ; the glabella lacks a posterolateral glabellar furrow and a distinct occipital ring. The pygidium (Sheng 19746, pi. 4, fig. If) shows a narrow doublure. All these characters suggest that assignment of the species to Pseudoasaphus Schmidt, 1904 is incorrect. In the light of the present collection, the librigenae figured as P. daliensis by Sheng (19746, pi. 4, fig. lc-e) may belong to Neseuretus elongatus sp. nov. (see below). The new material indicates that daliensis is synonymous with Isoteloides liangshanensis Lu (1975), from the Ningkianolithus welleri Zone (uppermost Arenig) in the Siliangssu Formation of southern Shaanxi. Lu’s species is characterized by the following features: (1) the cephalon is sub-triangular in outline; (2) the glabella is broadly rounded anteriorly, constricted between the palpebral lobes and poorly defined; (3) the anterior sections of the facial suture are divergent instead of subparallel; (4) the acute posterior area of the fixigena shows no border furrow in testaceous material ; (5) the pygidium is triangular, with smooth surface and a narrow but concave doublure. Judging from better preserved material (Lu 1975, pi. 9, figs 7, 9-10; pi. 10, figs 2, 8; Li et al. 1975, pi. 13, fig. 5), the pygidium has no defined border, and the supposed ‘ border furrow ’ is seen only in compressed specimens; the width (sag.) of the anterior border of the cranidium appears to vary from wide (Lu 1975, pi. 9, fig. 8) to narrow (Lu 1975, pi. 10, fig. 2), and in some examples the border merges with EXPLANATION OF PLATE 2 Figs 1-6, 9. Ogyginus daliensis (Sheng, 19746); Member 1. 1, NI 127500; hypostoma with attached cephalic doublure; Loc. 1; x3. 2, NI 127501; cranidium; Loc. 1; x 1-2. 3, NI 127502; exoskeleton without librigenae; Loc. 2; x 2. 4, NI 127503; exoskeleton; Loc. 1 ; x 0-6. 5, NI 127504; cranidium; Loc. 1 ; x 2. 6, NI 127505; small librigena; Loc. 1; x 6. 9, NI 127506; exoskeleton; Loc. 1; x0-55. Fig. 7. Microparia ( Microparia ) cf. prantli Marek, 1961; Loc. 3, Member 3; NI 127510; pygidium; x 5. Fig. 8. Pricyclopyge obscura Marek, 1961 ; Loc. 3, Member 3; NI 127511 ; pygidium, latex cast from external mould; x2. PLATE 2 ZHOU et al Ordovician trilobites 442 PALAEONTOLOGY, VOLUME 41 the glabella (Lu 1975, pi. 9, fig. 7); all these features depend on state of preservation. Specimens from Western Yunnan exhibit similar characters and the determination can be made with some confidence. Isoteloides liangshanensis differs from the type species of Liomegalaspides, L. usuii (Yabe, in Yabe and Hayasaka, 1920, p. 57, pi. 18, fig. 9; pi. 19, fig. 8; Kobayashi 1951, p. 27, pi. 2, figs 7-8; Lu, in Lu and Chang 1974, p. 126, pi. 50, figs 1-2; Lu 1975, p. 328, pi. 13, figs 1-7) from the uppermost Dawan Formation (uppermost Arenig) of western Hubei, mainly in the less effaced axial furrows on the cranidium. The species was referred to Liomegalaspides and is considered to be a junior subjective synonym of L. blackwelderi (Weller) by Zhou et al. (in press). The holotype cranidium of the latter species, refigured by Chang and Jell (1983), agrees closely with that of liangshanensis and the sole difference, a poorly defined anterior border, may be due to the preservation of blackwelderi in limestone and liangshanensis in shale. Subfamily ogygiocaridinae Raymond, 1937 Genus ogyginus Raymond, 1912 Type species. Asaphus corndensis Murchison, 1839. Ogyginus daliensis (Sheng, 19746) Plate 1, figures 10, 12-14; Plate 2, figures 1-6, 9 19746 Hoekaspis daliensis Sheng, p. 100, pi. 2, fig. la-e; pi. 3, fig. la-e. 19746 Hoekaspis daliensis ovatus Sheng, p. 100, pi. 1, fig. 5a-d; pi. 2, fig. 2a-e. Lectotype. Selected herein: BGM OT68-29, figured Sheng (19746, pi. 2, fig. lc), an exoskeleton lacking librigenae, from Member 1 of the Hsiangyang Formation, Loc. 1. Figured specimens. Two exoskeletons (NI 127503, 127506), two cranidia (NI 127501, 127504), one pygidium (NI 127496), one hypostoma with attached cephalic doublure (NI 127500) and one small librigena (NI 127505), from Member 1, Loc. 1 ; one exoskeleton without librigenae (NI 127502) from Member 1, Loc. 2; one meraspid (degree 7) exoskeleton (NI 127498), one pygidium (NI 127497) and one hypostoma (NI 127499) from Member 2, Loc. 1. Description. Exoskeleton oval in outline, 62-72 per cent, as wide as long. Cephalon sub-semicircular, its width less than twice the length (sag.) excluding librigenal spines. Glabella gently convex, declines anteriorly towards shallow preglabellar furrow, narrows slightly until level with rear end of palpebral lobe and then expands forwards to attain maximum width 66-73 per cent, of glabellar length in most of the less compressed specimens. Lateral glabellar furrows rarely preserved, seen as faint impressions on only a few specimens (PI. 2, fig. 3). SO curves backwards near sagittal line to meet posterior band furrow of occipital ring. S1-S4 short (tr.), directed more or less adaxially, and do not reach axial furrow abaxially. S 1 elliptical, level with point 40 per cent, of glabellar length from rear; S2-S4 triangular (S4 very narrow (exsag.)), sited, respectively, opposite front, mid- point and posterior end of palpebral lobe. Baccula elongate, weakly defined by furrow adaxially, and extends along axial furrow between SO and S 1 . Occipital ring consists of pair of weakly defined, sub-triangular lateral lobes, and posterior band which narrows abaxially. Median glabellar node situated between lateral occipital lobes and immediately in front of shallow posterior band furrow. Axial furrow deep, wide; preglabellar furrow broadly curved, deep abaxially but shallower medially. Palpebral lobe reniform, well defined by distinct palpebral furrow in some specimens (PI. 2, fig. 2), its length usually 14 per cent, that of cranidium and 11 per cent, in large examples (PI. 2, fig. 9); it is generally located opposite mid-point of cranidium, but two-thirds overall length from rear in large specimens, and anterior end is close to axial furrow ; ocular ridge short, thick, runs forwards and slightly adaxially (PI. 2, fig. 2). Anterior area of fixigena narrow (tr.), adaxially declined, seen to merge frontally with anterior border in well-preserved specimens ; palpebral area slightly convex ; posterior area wide (exsag.), equilaterally triangular in outline, with convex border that is well demarcated by deep, wide ZHOU ET AL.\ ORDOVICIAN TRILOBITES 443 border furrow and narrows adaxially. Anterior border convex laterally, becoming narrower (sag.) and flatter adaxially. Anterior sections of facial suture run divergently into anterior border, where they curve adaxially to converge at 120° and meet frontally in a gentle curve; posterior sections form broadly divergent, sigmoidal curves as far as border furrow, where they turn sharply adaxially to cut posterior border. Cranidial doublure ventrally convex, narrows adaxially, and carries a few parallel, fine terrace ridges. Librigena with narrow, vertical eye socle ; lateral and posterior borders convex, well defined by deep, wide border furrows, and widen towards genal angle, where they join to form a short, broadly based librigenal spine that, in smaller specimens, is relatively longer, more narrowly based, and slightly curved inwards. Hypostoma broadly rounded anteriorly, its length three-quarters the width, with acuminate but entire posterior margin. Middle body convex, wider than long, separated from large, triangular anterior wing by shallow, broad anterior border furrow but well defined by shallow lateral border furrow and deep, wide posterior border furrow; anterior lobe sub-oval, its length 80 per cent, that of hypostoma, and its posterolateral margin slightly concave abaxially; posterior lobe crescentic, short (sag.); middle furrow V-shaped, wide, mostly deep but shallows adaxially from maculae; macula prominent, located on anterior flank of posterior lobe, nearer to sagittal line than to lateral margin. Lateral border convex, wider than posterior border. Surface, except for maculae, covered with widely spaced, arched terrace ridges, subparallel to lateral and posterior margins. Thorax with zetoidal axial furrows. Axis gently convex, 30-33 per cent, the thoracic length in large specimens, and narrows slightly from fifth ring backwards ; each axial ring is trapezoidal in plan, uniformly wide (sag.). Pleura truncated distally, with deep, spindle-shaped pleural furrow which ends opposite fulcrum. Pygidium sub-semicircular in outline, the length 51-60 per cent, the width in well-preserved specimens; in compressed examples the corresponding figure is 38—48 per cent. (PI. 1, fig. 10). Axis convex, conical, reaches paradoublural line posteriorly, and has frontal width about one-quarter that of pygidium ; articulating ring furrow distinct; six or seven axial rings and a terminal piece are visible on most material and only three rings in large specimens, but up to 1 1 rings are seen in some internal moulds. Axial furrows usually distinct, but more or less effaced in large specimens. Pleural region gently convex with six unfurrowed, distally rounded ribs; articulating half-rib ridge-like, well defined by deep, spindle-shaped first pleural furrow. Pygidial border flat or weakly convex, delimited by border furrow which appears deep or shallow, depending on preservation. Doublure narrow, 15-18 per cent, the pygidial length medially but widens slightly abaxially; inner margin subparallel to that of pygidium, and surface covered with closely spaced, fine terrace ridges subparallel to margin. A meraspid exoskeleton (PI. 1, fig. 13) is similar to the adult but differs in the larger palpebral lobe, the almost parallel-sided glabella, the presence of an intergenal angle on the librigena, and the slightly but uniformly tapered thoracic axis. Remarks. Specimens in our large collection are mostly compressed or deformed, the better preserved material forming the basis of the above description, and it is clear that the supposedly different morphological forms (for example, Hoekaspis daliensis ovatus Sheng, 19746, p. 100, which has a slightly shorter exoskeleton) found together at several stratigraphical levels belong to a single species. The lectotype selected herein for ovatus is a pygidium (Sheng 19746, pi. 2, fig. 2d) identical to some in our collection (PI. 1, fig. 10); it is 40 per cent, as long as wide, much wider than specimens preserved in relief and the result, we believe, of different preservation. Sheng (19746) referred daliensis to Hoekaspis Kobayashi, 1937 and noted only briefly that it is almost identical to H. megacantha (Leanza, 1941) (see Harrington and Leanza 1957, p. 179, figs 88-89). Differences between the two forms lie mainly in the slightly wider glabella and much fainter pygidial pleural furrows of the Argentine species. The type species of Hoekaspis , Megalaspis matacensis Hoek, in Steinmann and Hoek, 1912 from the Llanvirn of Bolivia, was re-illustrated by Ross (1965, pi. 8, figs 8-9, 12-13, 16, 19) and a neotype pygidium was designated by Pribyl and Vanek (1980, p. 26, pi. 23, fig. 2). Fortey and Owens (1978, p. 261) considered that H. matacensis differed from H. megacantha in having a wider pygidium with unfurrowed pleural field, and an extremely narrow (sag.) anterior cranidial border, and they assigned the latter species to Merlinia , a point of view contested by Pribyl and Vanek (1980, p. 29). Merlinia as established by Fortey and Owens (1978) included several Welsh Arenig species and a Llanvirn species from England described by Rushton and Hughes (1981). It is closely allied to Ogyginus and, as noted by Fortey and Owens (1987, p. 142), at least one early member of the latter genus, O. hybridus (Salter, 1866), has characters intermediate between Ogyginus and Merlinia. The cranidium of Hoekaspis megacantha 444 PALAEONTOLOGY, VOLUME 41 differs from that of the type species of Merlinia, M. rhyakos Fortey and Owens, 1978 (p. 263, pi. 5, figs 1-6; pi. 6, figs 1-5), in having a shorter glabella, more expanded anteriorly, a narrower (sag.) anterior border, and the anterior area of the fixigena merges with the abaxial part of the anterior border, seen only on a less compressed specimen figured by Harrington and Leanza (1957, fig. 89, 1). All these characters are typical of Ogyginus. In addition to the type species and H. megacantha, at least two other Llanvirn forms have been included in Hoekaspis : H. schlagintweiti Harrington and Leanza, 1942 (p. 135, pi. 1, figs 2-5, 7-9; 1957, p. 177, fig. 87, 1-6) from Argentina and H. yahuari Pribyl and Vanek, 1980 (p. 27, pi. 13, figs 1-2; pi. 14, fig. 6) from Bolivia, Argentina and Peru. All these South American species have a cephalon similar to that of Ogyginus, six ribs are visible on the pleural region of the pygidium (and can even be traced on the neotype of H. matacensis), but are usually more weakly defined compared with those in most species of Ogyginus. In our opinion the effacement of pleural furrows is not a reliable generic character and some species of Ogyginus, such as O. hybridus (Salter, 1866) (see Fortey and Owens 1987, p. 143, figs 29-32) and O. orbensis Courtessole, Pillet, Vizcaino and Eschard, 1985 (p. 44, pi. 6, figs 1-8), show similar pleural furrows. The distinctness of pleural furrows may vary during ontogeny (Fortey and Owens 1987, p. 146) or with preservation; in O. terranovicus Dean, in Dean and Martin, 1978 (p. 15, pi. 5, fig. 9; pi. 6, figs 4, 6-7) from Arenig elastics at Bell Island, eastern Newfoundland, testaceous specimens exhibit much fainter pleural furrows than internal moulds. Unfortunately, the hypostoma is not known in Hoekaspis, but judging from the rest of the exoskeleton, we believe the genus may eventually prove synonymous with Ogyginus. Hoekaspis daliensis possesses features diagnostic of Ogyginus as defined by Whittard (1964, p. 245) and by Fortey and Owens (1987, p. 142), and is transferred to the latter genus. Ogyginus corndensis (Murchison), from the Llanvirn-lower Llandeilo of west Shropshire and central Wales, was redescribed by Whittard (1964, p. 250, pi. 42, figs 2-8; pi. 43, figs 2—1 1) and by Hughes (1979, p. 126, figs 21—61, 66), who included Whittard’s varieties septenarius and novenarius in the synonymy. O. daliensis resembles the Anglo-Welsh species in many respects but differs in the more anteriorly sited palpebral lobe, the longer (exsag.) posterior area of the fixigena, and the wider thoracic axis (in large specimens about one-third the width of the thorax, compared with one- quarter). In addition, the pygidium of O. corndensis possesses eight or nine pleural ribs, compared with six or seven in O. daliensis, and has a narrower axis. Among the other species of Ogyginus listed by Fortey and Owens (1987, p. 142) and by Rabano (1990, p. 70) is the closely related O. armoricanus (de Tromelin and Lebesconte, 1876) (see Henry 1971, p. 66, pi. 1, figs 1-11, text-figs 1-2; 1980, p. 37, fig. 7, pi. 1, figs 4-5, 7) from the Arenig to, possibly, lower Llanvirn of Brittany, France. The French species is distinguished only by the slightly greater glabellar width (76 per cent, of length, compared with 66-73 per cent.), the narrower (sag.) anterior border, the smaller anterior wing of the hypostoma and, probably, the slightly larger palpebral lobe, all apparent differences that may be due to preservation. Only a few specimens of O. armoricanus have been described, the intraspecific variation is not known, and for the time being we retain O. daliensis as a separate taxon. EXPLANATION OF PLATE 3 Fig. 1. Cyclopyge sp.; Loc. 3, Member 3; NI 127509; exoskeleton; x4. Figs 2, 5. Hungioides cf. bohemicus (Novak, in Perner, 1918); Member 1. 2, NI 127507; pygidium; Loc. 2; x 3. 5, NI 127508; incomplete cranidium; Loc. 1; x 1. Figs 3—4, 6-8, 10-11. Hanchungolithus xiangyangensis Sheng, 19746; Loc. 1, Member 2. 3, NI 127513; exoskeleton; x 6. 4, NI 127514; exoskeleton; x 6. 6, NI 127515; cephalon; x 5. 7, NI 127516; lower lamella of fringe; x 6. 8, NI 127517; cephalon; x 8. 10, NI 127518; cephalon with two attached thoracic segments; x5; 11, NI 127519; exoskeleton; x 6. Fig. 9. Pricyclopyge obscura Marek, 1961 ; Loc. 3, Member 3; NI 127512; cranidium; x 3. PLATE 3 ZHOU et al. , Ordovician trilobites 446 PALAEONTOLOGY, VOLUME 41 Family dikelokephalinidae Kobayashi, 1936 Genus hungioides Kobayashi, 1936 (= Argentinops Pribyl and Vanek, 1980) Type species. Dicellocephalina bohemica Novak, in Perner, 1918. Hungioides cf. bohemicus (Novak, in Perner, 1918) Plate 3, figures 2, 5 19746 Taihungshania sp., Sheng, p. 102, pi. 4, fig. 5 Figured specimens. One incomplete cranidium (NI 127508) from Member 1, Loc. 1 ; one pygidium (NI 127507) from Member 1, Loc. 2. Description and remarks. Specimens are fragmentary and more or less compressed. The glabella narrows gently forwards, bluntly rounded frontally, with four pairs of lateral glabellar furrows which, except for S4, become fainter before reaching the axial furrow; SI is bifurcate adaxially, S4 is shortest, sited opposite adaxial end of the eye ridge. SO is deep and transverse, defining a uniformly wide (sag.) occipital ring. A prominent pair of depressed, oval alae has the anterior ends opposite the distal end of S2. Surface of the cranidium covered with dense granulation that becomes finer on the fixigena. The large pygidium described by Sheng (19746) as Taihungshania sp., from the same bed at Locality 1 as the present figured cranidium, is about 50 mm long, wider than long, with nine or ten pleural ribs in addition to the articulating half-rib. The axis has at least 1 1 well-defined rings, and the outer pair of marginal spines extends backwards with its tips about level with that of the axis. The smaller figured pygidium, 18 mm long, closely resembles the larger specimen but the two pairs of broad based marginal spines end in-line. We agree with Rabano (1983, p. 436) that such a difference is due to ontogenetic variation during the holaspid stage. The cranidium has a more uniformly parabolic glabellar outline than Hungioides mirus Lu, 1975 (p. 372, pi. 29, figs 8-15) from the upper Arenig of Hubei and Guizhou, China, and H. acutinasus Fortey and Shergcld, 1984 (p. 345, pi. 44, figs 1-7) from the Nora Formation (Arenig) of central Australia, but is generally comparable to that of H. bohemicus (Novak, in Perner 1918, pi. 1, fig. 6; see also Rabano 1983, pi. 1, figs 1-3; 1990, pi. 11, figs 1-3). The pygidium closely resembles the Bohemian lectotype (Perner 1918, pi. 1, fig. 4; selected by Marek, in Horny and Bastl 1970, p. 77, pi. 5, fig. 7), and specimens from the Llanvirn of Spain figured by Rabano (1983, pi. 1, figs 4-6; 1990, pi. 11, figs 4-7), especially in the pleural field, with nine or ten segments, and in the form of the marginal spines. Rabano (1983, p. 435) reassigned to H. bohemicus several other Llanvirn, or possibly Llanvirn, forms, including: H. bohemicus arouquensis Thadeu, 1956 (p. 11, pi. 2, figs 1-2; pi. 6, fig. 3) from Portugal, and H. novaki Kobayashi, 1936 (based on Perner 1918, pi. 1, fig. 5; see Prantl and Pribyl 1948, p. 15, pi. 2, fig. 1) from Bohemia, and considered their supposedly different characters to be the result of ontogenetic changes. Hungioides graphicus R. and E. Richter, 1954« (p. 341, pi. 1, figs 1-^4) from the Griffelschiefer (upper Arenig-Llanvirn, according to Sdzuy 1971) of Thuringia, is based on poorly preserved pygidia and thoracic segments but, as noted by Fortey and Shergold (1984, p. 348), it is closely comparable to the type species. Hungioides intermedius (Harrington and Leanza, 1957, p. 191, fig. 100, 1-8), from the Llanvirn of Argentina, was made type species of Argentinops Pribyl and Vanek, 1980, considered to be a junior subjective synonym of Hungioides (Rabano 1983; Fortey and Shergold 1984). It differs from the present form mainly in the more slender outer pair of spines, located at the posterolateral corners of the pygidium. From the above discussion the Chinese form is best compared with the Hungioides bohemicus species-group. Authorship of the species has been variously attributed by Prantl and Pribyl (1948, ZHOU ET AL.: ORDOVICIAN TRILOBITES 447 p. 14), Lochman-Balk in Moore (1959, p. 0361) and Rabano (1983, p. 436; 1990, p. 83); in the present paper we follow Rabano (1990). Family cyclopygidae Raymond, 1925 Genus cyclopyge Hawle and Corda, 1847 Type species. Egle rediviva Barrande, 1846. Cyclopyge sp. Plate 3, figure 1 Figured specimen. Exoskeleton (NI 127509) from Member 3, Loc. 3. Remarks. The material is poorly preserved but the presence of a prominent SI and a pair of circular swellings behind it suggests assignment to Cyclopyge. The figured specimen has four thoracic segments preserved and the cranidium is slightly displaced, indicating a moulted exoskeleton. The pygidium is longer and more narrowly rounded posteriorly compared with most species of Cyclopyge, but is similar to that of C. kossleri (Kloucek, 1916) from the Llanvirn of Bohemia and South Wales (Marek 1961, p. 25, pi. l,figs 14-17; Fortey and Owens 1987, p. 155, fig. 37a-b). Three pairs of pleural furrows are visible on the same specimen, a character typical of C. kossleri, but the axis of the European species is longer, almost pointed posteriorly, and has probably one more ring. Genus pricyclopyge R. and E. Richter, 19546 (= Pricyclopyge ( Bicyclopyge ) Horbinger and Vanek, 1985) Type species. Aeglina prisca Barrande, 1872. Remarks. We follow Fortey and Owens (1987, p. 181) in considering the subgenus Bicyclopyge to be a junior subjective synonym of Pricyclopyge sensu stricto. Pricyclopyge obscura Marek, 1961 Plate 2, figure 8; Plate 3, figure 9 1961 Pricyclopyge obscura Marek, p. 35, pi. 2, fig. 17; text-fig. 10. Holotype. Cranidium (SBNM BR132), figured Marek (1961, pi. 2, fig. 17), from the Sarka Formation (Llanvirn) at Sarka, Prague. Figured specimens. One cranidium (NI 127512) and one pygidium (NI 127511) from Member 3, Loc. 3. Description and remarks. Only two examples were previously known of the cranidium, which was fully described by Marek and differs from that of other species of Pricyclopyge in having an oval outline, only gently tapered to both front and rear. The present specimen agrees closely with the holotype; the median node is slightly elongate, sited in the centre of the glabella; a pair of indistinct swellings is visible near the posterior margin; and three pairs of very faint, eyebrow-shaped impressions can be traced on the posterior flanks. The pygidium in our collection is triangular in outline, about twice as wide as long, narrowly rounded posteriorly with slightly concave lateral margins. The axis occupies 25 per cent, the anterior width and 64 per cent, the length of the pygidium, and is gently tapered, with a well-defined, rim- like articulating half-ring and broadly-rounded tip; a single, transversely straight ring furrow is PALAEONTOLOGY, VOLUME 41 complete, followed by a second ring furrow that is defined only distally. The pleural field is gently declined abaxially, and the articulating half-rib is straight and ridge-like. The border is convex, uniformly wide, one-tenth of the pygidial length (sag.), well defined by a deep border furrow. Apart from its slightly shorter axis, the pygidium is almost indistinguishable from that of Pricyclopyge binodosa prisca (Barrande, 1872) (Marek 1961, pi. 1, fig. 20, as P. binodosa binodosa; Horbinger and Vanek 1985, pi. 2, figs 1-3, as P. prisca prisca; for discussion of subspecies name see: Marek 1961, p. 33; Whittard 1966, p. 287; Rushton and Hughes 1981, p. 633; and Fortey and Owens 1987, p. 181). The present pygidium also agrees closely with Chinese material described as P. prisca and P. sichuanensis by Lee (1978, p. 252, pi. 107, fig. 9 and figs 7-8 respectively) from the Llanvirn of Moli, western Sichuan, specimens of which are slightly deformed but show a pair of thoracic spines on the sixth segment. In the absence of the cranidium it is impossible to decide whether both should be assigned to P. binodosa prisca or to P. obscura. Genus microparia Hawle and Corda, 1847 Type species. Microparia speciosa Hawle and Corda, 1847. Subgenus microparia (microparia) Hawle and Corda, 1847 Microparia ( Microparia ) cf. prantli Marek, 1961 Plate 2, figure 7 Figured specimen. One pygidium (NI 127510) from Member 3, Loc. 3. Description. Pygidium sub-semicircular in outline, 76 per cent, as long as wide, moderately convex. Axis occupies 44 per cent, of pygidial width frontally and is strongly tapered; two axial rings are delimited by shallow ring furrows; distinct, rim-like articulating half-ring is defined by deep, wide (sag.) articulating furrow. Axial furrows clearly defined anteriorly and become faint behind the third axial ring. Pleural region almost featureless except for ridge-like articulating half-rib, defined by prominent anterior pleural furrow. Border narrow, visible only laterally, delimited by shallow, broad border furrow. Doublure uniformly wide (sag.), wider than border and equal to about 16 per cent, of pygidial length (sag.). Remarks. Cranidia in our collection are badly deformed. Pygidial features suggest that the form is referable to Microparia, a genus divided by Fortey and Owens (1987) into two subgenera, Microparia sensu stricto and M. ( Heterocyclopyge ) Marek, 1961. Zhou et al. (1994) considered Quadratapyge Zhou, in Zhou et al., 1977 to be a third subgenus of Microparia. Species of Heterocyclopyge and Quadratapyge have a pygidium that is straight-sided laterally, with an entire axis, and are quite different from the present form. In the outline, length/width ratio, and form of the axis, particularly in specimens of comparable size, the pygidium closely resembles that of M. (M.) broeggeri (Holub, 1912) (see Marek 1961, p. 45, pi. 3, fig. 16; Fortey and Owens 1987, p. 164, figs 44a-e, 45a-e) from the Klabava Formation of Bohemia and the upper Arenig (Fennian Stage) of South Wales, and of M. (M.) prantli Marek, 1961 (p. 40, pi. 3, figs 1^1, text-fig. 13) from the Sarka Formation (Llanvirn) of Bohemia. However, the doublure of M. (M.) broeggeri widens adaxially (Fortey and Owens 1987, p. 166) compared with its uniform width in M. (M.) prantli, and we consider our form to be closer to the latter species. Family trinucleidae Hawle and Corda, 1847 Subfamily hanchungolithinae Lu, 1963 Genus hanchungolithus Lu, 1954 Type species. Cryptolithus multiseriatus Endo, 1932. ZHOU ET AL.\ ORDOVICIAN TRILOBITES 449 Hanchungolithus xiangyangensis Sheng, 19746 Plate 3, figure 3^1, 6-8, 10-11 19746 Hanchungolithus xiangyangensis Sheng, p. 106, pi. 6, fig. 4a-i. 1989 Hanchungolithus xiangyangensis Sheng; Zhou and Hughes, p. 61. Lectotype. Selected by Zhou and Hughes (1989, p. 61). Exoskeleton BGM OT68-90, figured Sheng (19746, pi. 6, fig. 4b), from Member 2 of the Hsiangyang Formation, Loc. 1 . Figured specimens. Three exoskeletons (NI 127513-127514, 127519), two cephala (NI 127515, 127517), one cephalon with two attached thoracic segments (NI 157518), and one lower fringe lamella (NI 157516); all from Member 2, Loc. 1. Description. Exoskeleton oval in outline. Cephalon sub-semicircular, 40-53 per cent, as long as wide (excluding librigenal spines) in well preserved specimens. Glabella clavate, strongly convex, protruding slightly into the fringe anteriorly, with median node on apex at mid-length; S1-S3 oval to circular, sited abaxially, becoming successively shallower; S3 in-line with median node. Occipital ring narrow (sag.), uniformly wide, arched posteriorly and well defined by deep SO. Axial furrow deep, wide. Small, low baccula is elongate, oval, with anterior end close to S2. Cheek convex, declined both abaxially and adaxially ; lateral eye tubercle distinct, located close to axial furrow and behind line through S3 and median node; eye ridge runs slightly forwards adaxially to axial furrow ; slender genal ridge extends diagonally to posterolateral corner of cheek ; posterior border narrow (exsag.), upturned; posterior border furrow broad, deep, ends in posterior fossula. Fringe flat, narrow (sag.) anteriorly but widens gradually to posterior margin, where its breadth is twice that in front of glabella; marginal band distinct. Lower lamella is prolonged backwards at genal angle to form librigenal spine which is slightly curved inwards, its tip well beyond the posterior margin of the pygidium. Fringe pits largest frontally and become slightly smaller both inwards and laterally; they are radially arranged in weak sulci, from about R9 to R1 1, and become irregularly arranged abaxially; there are about four arcs in front of the glabella, and seven to ten pits along the posterior margin. I, and In are complete ; in specimens where the pits are clearly visible, It has 24-28 pits and In 22-24 ; pits between I, and In are mostly irregular, but a roughly regular arrangement is seen in I2 1-16 and I3 1-12. Thoracic axis well defined, strongly convex transversely, gradually tapered backwards and about 25 per cent, of thoracic width; each ring is uniformly wide (sag.) with pair of deeply incised apodemal pits at its anterolateral corners. Pleural region flat, narrows slightly backwards ; each pleura parallel-sided, horizontal for most of its length as far as fulcrum, where it turns downwards; pleural furrow wide, shallow, and almost straight. Pygidium sub-triangular, 25-31 per cent, as long as wide. Axis convex, conical, occupying 19-22 per cent, of frontal width of pygidium and reaching inner margin of border; there are five axial rings and a terminal piece, and the ring furrows become successively weaker posteriorly. Pleural region flat, with only one pleural furrow, which is shallow, widens abaxially and delimits clearly an upturned articulating half-rib. Border ridge- like in plan view, narrows abaxially, and is deflected ventrally. Remarks. More than seven Chinese species of Hanchungolithus were reviewed by Zhou and Hughes (1989), six of them of late Arenig age from the Yangtze region. H. xiangyangensis is the youngest of the seven, and its most distinctive character is the more regular arrangement of pits on the anterior and anterolateral parts of the fringe (Zhou and Hughes 1989, pp. 58, 74). Previous descriptions were incomplete, and the above account is based mainly on new material in our collection. Family calymenidae Milne Edwards, 1840 Subfamily reedocalymeninae Hupe, 1955 Genus neseuretus Hicks, 1873 Type species. Neseuretus ramseyensis Hicks, 1873. Remarks. More than 50 species have been referred to this genus, most of which were listed by Fortey and Morris (1982) and Rabano (1990). Only a few have been revised (Whittard 1960; Fortey 450 PALAEONTOLOGY, VOLUME 41 and Owens 1987 ; Rabano 1990), and both N. antetristani Dean, 1966 and N. lugneensis Courtessole, Pillet and Vizcaino, 1983 were reassigned to Pradoella Hammann, 1977 by Hammann (1983), Rabano (1990) and Courtessole et al. (1991). Nineteen species and subspecies of Neseuretus have been described from Southwest and Central China, and the species yinganensis, listed as a nomen nudum by Fortey and Morris (1982), had in fact been published as Calymenesun yinganensis Zhang, 1981 (p. 211, pi. 78, figs 3-5). Most of the Chinese species are known from only a few specimens. The present collection indicates that the presence or absence of S4 and hypostomal pits, and the form of the preglabellar area and anterior border furrow may vary within a single species and, as noted by Whittington (1966) and Fortey and Owens (1987), apparent intraspecific variation is largely dependent on preservation. In the following descriptions, most of the Chinese species are reviewed. Neseuretus birmanicus (Reed, 1906, p. 71, pi. 6, fig. 27), from the Naungkangyi Beds of the northern Shan States, Burma, was founded on a compressed cranidium. Lu et al. (1965, p. 619, pi. 128, fig. 13) and Sheng (19746, p. 112, pi. 8, fig. 2a-b, d, f, non 2c, e, g) redescribed the species using several specimens from the Llanvirn of Baoshan, western Yunnan, an area that belongs to the same structural unit (now called the Sibumasu Terrane) as the northern Shan States. The Chinese specimens indicate that, as noted by Fortey and Morris (1982), N. birmanicus Reed, 1906 closely resembles N. tristani (Brongniart, in Desmarest, 1817), redescribed in detail by Henry (1970, 1980), Sadler (1974), Hammann (1983) and Rabano (1990), but differs in the more developed anterior border furrow. This may be due to preservation, and better preserved topotype material is needed for further comparison. Burmese and Afghanistan specimens later referred to birmanicus by Reed (1915, p. 44, pi. 8, figs 1-5, as Calymene birmanica ) and by Pillet and de Lapparent (1969, p. 325, pi. 34, figs 1-10; ?pl. 35, fig. 9, as Diacalymene birmanicus) are quite different from the holotype. As noted by Dean (1967a, p. 117; 1975, p. 369) they resemble Neseuretus ( Neseuretinus ) turcicus Dean (1967a, p. 115, ?pl. 7, figs 8, 10-11 ; pi. 9, figs 1^1), from the Caradoc of south-eastern Turkey, but differ from the latter in the shorter, broadly rounded (rather than pointed) anterior border and the less convex preglabellar field. These characters, in turn, match Vietnamia douvillei (Mansuy) (see Kobayashi 1960, p. 44, pi. 5, figs 4—5) and we reassign birmanicus sensu Reed, 1915 questionably to Vietnamia. Calymene nivalis Salter, in Salter and Blandford, 1865 from the ‘middle Ordovician’ of the central Himalayas, India, was referred to Neseuretus by Dean (19676, p. 32; 1975, p. 368) and by Morris and Fortey (1985, p. 96, pi. 5, fig. 3), but may possibly be referable to Neseuretinus, as may Pharostoma malestana Wolfart (1970, p. 82, pi. 17, figs 2-7) from the middle Ordovician of east Afghanistan (Dean 1975, p. 369). Neseuretinus is possibly present in South Tianshan, formerly part of the USSR (as Calymenesun and Synhomalonotus ; see Kolobova 1978, pp. 133, 134, pi. 26, figs 1-5 and 6-11 respectively; see also Zhou and Dean 1989, p. 133). Synhomalonotus pamiricus Balashova (1966, p. 233, pi. 2, figs 12-15) from the middle Ordovician of Pamir has a glabella with swollen, wide LI and may be related to Neseuretinus or Vietnamia, but the figured specimens do not show the rest of the cranidium and identification is uncertain. Neseuretus cf. tungtzuensis (Sheng, 1958) Plate 4, figures 5, 7, 10 Figured specimens. One cranidium (NI 127528) from Member 1, Loc. 1; one cranidium (NI 127527), one librigena (NI 127526) and one pygidium (NI 127529) from Member 1, Loc. 2. Remarks. Specimens from lower levels in Member 1 of the Hsiangyang Formation are recorded here for the first time. The cranidium is almost identical with the lectotype (selected herein, BGM Loc. Sh. 173, figured Sheng 1958, pi. 7, fig. 5a) of Calymene ( Synhomalonotus ) tungtzuensis, but has a slightly more tapered glabella. The pygidium has six well-defined axial rings and six ribs; it closely resembles that in the original material (Sheng 1958, p. 200, pi. 7, fig. 5a-c), but according to Sheng’s original description the latter has at least eight distinct axial rings. The form of the glabella and ZHOU ET AL.\ ORDOVICIAN TRILOBITES 451 librigena recalls TV. shensiensis (Lu, 1957, p. 288, pi. 150, figs 13-16; 1975, p. 452, pi. 46, fig. 3; pi. 47, figs 6-1 1 ; pi. 50, fig. 1 1) from the Chaochiapa Formation (middle Arenig) of southern Shaanxi, but shensiensis has a smaller palpebral lobe, located opposite L3, and a correspondingly longer (exsag.) fixigena. The pygidium of shensiensis exhibits only four or five ribs on the inner part of the pleural region, adaxial to the fulcrum. On the basis of the glabella and preglabellar area, TV. kayseri (Kobayashi, 1951, p. 41, pi. 3, fig. 7), from northern Sichuan, may be closely related to TV. shensiensis , but the single cranidium is incomplete and difficult to interpret. Neseuretus caerhunensis Beckly, 1989 (p. 15, figs 14a— 1, 15a-d), from the upper Arenig of North Wales, is generally similar to the present form but differs in the much longer preglabellar area, wider palpebral area, and the oblique rather than transverse eye ridge. A large, well-preserved pygidium shows that the Welsh species has up to nine axial rings. TV. tungtzuensis, from the upper Arenig of northern Guizhou, is similar to a number of contemporaneous forms such as TV. concavus Lu, 1975 (p. 454, pi. 47, figs 13-15; pi. 48, fig. 1), TV. cf. shensiensis (Lu, 1975, p. 454, pi. 47, fig. 12), TV. concavus tenellus Lu, 1975 (p. 242, pi. 48, figs 2-6), TV. expansus Lu, 1975 (p. 456, pi. 48, figs 8-10) and TV. equalis Lu, in Lu and Chang, 1974 (p. 130, pi. 51, figs 13-14), all from southern Shaanxi except for TV. equalis , which is from north-eastern Sichuan. The cranidium in these species is of ramseyenis or murchisoni type, including: shorter (sag.), straight-sided, truncated glabella ; longer preglabellar area ; larger palpebral lobe, sited more posteriorly (opposite L3 and front part of L2); and shorter (exsag.) posterior area of fixigena. Judging from illustrations of TV. concavus, TV. concavus tenellus and TV. expansus, the pygidium has about eight axial rings and six pleural ribs; according to Fortey and Owens (1987) the corresponding numbers are eight to ten and seven to nine for TV. ramseyensis, and five and four for TV. murchisoni (Salter, 1865). We believe that forms in the tungtzuensis group may represent one species, and apparent differences include : the convexity of the preglabellar area and the depth of the anterior border furrow; and the presence or absence of S4 (see Lu 1975, p. 452). All of these may be the result of preservation and are probably of little specific importance, but further material of all the listed species is required. Neseuretus elegans Lee, 1978 Plate 4, figures 1^4, 6, 12, 15 19746 Neseuretus birmanicus (Reed) ; Sheng, p. 1 12, pi. 8, fig. 2c only [non 2e, g = TV. elongatus sp. nov. ; non 2a— b, d, f = TV. birmanicus sensu stricto], 1974/? Neseuretus tungtzuensis Sheng; Sheng, p. 113, pi. 8, fig. la, d-e [non lb-c = Neseuretus elongatus sp. nov.]. 1978 Neseuretus elegans Lee, p. 274, pi. 107, figs 3-5. 1978 Neseuretus leiboensis Lee, p. 274, pi. 107, fig. 10. Holotype. Cranidium (CIGM Stl96), figured Lee (1978, pi. 107, fig. 3), from the Lower Qiaojia Formation (upper Arenig-lower Llanvirn), Yanjin, north-eastern Yunnan, China. Figured specimens. One cranidium (NI 127520) from Member 1, Loc. 2; one pygidium (NI 127523) from Member 2, Loc. 2; two cranidia (NI 127521-127522); one exoskeleton (NI 127524) and one librigena (NI 127525) from Member 2, Loc. 1. Description and remarks. The species is closely allied to Neseuretus arenosus Dean, 1966 (p. 313, pi. 14, figs 1, 4—5, 7-9, 11) from the middle Arenig of the Montagne Noire, south-western France. Both have an almost identical pygidium, the pleural regions of which show five distinct ribs and a trace of a sixth, but the axis has seven well-defined rings in TV. elegans and six in TV. arenosus. The glabella of both species has the sides broadly curved and slightly convergent forwards, where the anterior margin is gently concave; the palpebral lobe is sited opposite L3 and part of L2, and the palpebral ridge is straight and transverse. TV. elegans has apparently deeper axial, pre-glabellar and glabellar furrows, and S4 is present, but these differences may be due to preservation. The preglabellar area 452 PALAEONTOLOGY, VOLUME 41 of N. arenosus occupies 24 per cent, of the cranidial length (sag.), compared with 30 per cent, in N. elegans, whilst the anterior border of the French species is slightly shorter, and for these reasons we retain the two specific names. Additional specimens from the Montagne Noire were subsequently referred to N. arenosus (Courtessole et al. 1983, p. 25, pi. 1, figs 1-9; pi. 6, figs 1-8, 11-12; see also pi. 2, fig. 15, as Platycalymene ( Platycalymene ) sp. cf. minervensis n. sp. ; Courtessole et al. 1985, p. 47, pi. 8, figs 3^4; see also pi. 8, fig. 1 1, as Platycalymene ( Platycalymene ) sp. cf. minervensis n. sp.). Most were later considered to be distinct from the holotype and redetermined as N. cf. arenosus by Courtessole et al. (1991). Well-preserved specimens assigned to N. cf. arenosus by Courtessole et al. (1991, p. 9, pi. 4, figs 5-8, text-fig. 4) agree closely with those of N. elegans , including the length of the preglabellar area. Courtessole et al. (1991, p. 10) claimed that N. cf. arenosus differs from N. arenosus sensu stricto in having a better developed preglabellar furrow, longer preglabellar area, and a shorter palpebral lobe sited further forwards, with posterior end opposite S2. However, our collection shows that at least the palpebral lobe varies in both size and position during ontogeny; it is larger and more posteriorly sited in small holaspids (PI. 4, fig. 4) and late meraspids (PI. 4, fig. 12, meraspid degree 12). If it can eventually be demonstrated that the supposedly distinctive characters of the French species are due to intraspecific variation, ontogenetic variation and preservation, we would consider N. elegans to be a junior subjective synonym of N. arenosus. Neseuretus attenuatus Gigout, 1951 (p. 289, pi. 3, figs 6-7; see also Dean 1966, p. 317, pi. 14, figs 2, 6, 12) from, probably, the Llanvirn of Morocco resembles N. elegans in many respects, but is distinguished by the longer (sag.) but narrower (tr.) preglabellar area and the more convergent anterior portions of the axial furrows. No pygidium was described for the Moroccan species, but on cranidial characters alone N. attenuatus is closer to N. tristani (neotype designated by Henry 1970, p. 6, pi. A, fig. 6) than to N. arenosus and N. elegans. Neseuretus leiboensis Lee from the Lower Qiaojia Formation of western Sichuan was based on a single cranidium. Lee (1978, p. 275) noted that the species has the anterior border slightly concave, apparently arched backwards rather than forwards, but is otherwise indistinguishable from N. elegans. Some compressed cranidia in our collection show similar deformation of the anterior border and we consider the two species to be synonymous, with N. elegans having line priority over N. leiboensis. Neseuretus elongatus sp. nov. Plate 4, figures 8-9, 11, 13-14, 16 1 974ft Pseudasaphus daliensis Sheng, pi. 4, fig. 1 c—e only. 1974ft Neseuretus birmanicus (Reed); Sheng, p. 112, pi. 8, fig. 2e, g only. 1974ft Neseuretus tungtzuensis Sheng; Sheng, p. 113, pi. 8, fig. lft-c only. Derivation of name. From the Latin, elongatus (= elongate) referring to the glabellar outline. Holotype. Cranidium (NI 127532) (PI. 4, fig. 13) from Member 2 of the Hsiangyang Formation, Loc. 1. EXPLANATION OF PLATE 4 Figs 1^1, 6, 12, 15. Neseuretus elegans Lee, 1978. 1, NI 127520; cranidium; Loc. 2, Member 1 ; x 2-5. 2-3, NI 127521; cranidium, lateral and dorsal views; Loc. 1, Member 2; x 2. 4, NI 127522; cranidium; Loc. 1, Member 2; x 4. 6, NI 127523; pygidium; Loc. 2, Member 2; x 2. 12, NI 127524; small exoskeleton; Loc. 1, Member 2; x 4. 15, NI 127525; librigena; Loc. 1, Member 2; x4. Figs 5, 7, 10. Neseuretus cf. tungtzuensis Sheng, 1958; Member 1. 5, NI 127526; librigena; and NI 127527; cranidium; Loc. 2; x 2-5. 7, NI 127528; cranidium; Loc. 1; x2-5. 10, NI 127529; pygidium; Loc. 2; x2-5. Figs 8-9, 11, 13-14, 16. Neseuretus elongatus sp. nov. ; Member 2. 8, 11, NI 127530; pygidium, paratype, dorsal and rear views; Loc. 1; x 3. 9, NI 127531, paratype cranidium; Loc. 3; x6. 13, NI 127532, holotype cranidium; Loc. 1 ; x 4. 14, NI 127533 paratype librigena; Loc. 1 ; x 5. 16, NI 127534, paratype cranidium; Loc. 1 ; x 4. PLATE 4 ZHOU et al., Neseuretus 454 PALAEONTOLOGY, VOLUME 41 Paratypes. One cranidium (NI 127534), one librigena (NI 127533) and one pygidium (NI 127530) from Member 2, Loc. 1 ; one cranidium (NI 127531) from Member 2, Loc. 3. Diagnosis. Neseuretus species with elongate glabella and narrow (tr.) frontal area of cranidium; palpebral lobe with posterior end opposite rear part of L2. Pygidial axis relatively narrow, with seven axial rings; pleural region has five furrowed ribs. Description. Frontal area has width 34-38 per cent, that of rear of cranidium. Glabella strongly convex transversely, tapers gently forwards to sharply rounded anterolateral angles and more-or-less truncate anterior margin; it occupies 25-30 per cent, the basal breadth of the cranidium, about 75 per cent, the overall length, and the width of the frontal glabellar lobe is 60-65 per cent, that across LI. Occipital ring well defined by deep, wide SO and carries median node. SI and S2 deep; SI curves back and becomes very shallow before reaching SO; S2 runs slightly backwards adaxially from the deep, broad axial furrow; S3 and S4 just visible on the flank of the glabella. Palpebral lobe has length 22 per cent, that of cranidium and extends from opposite S3 to opposite rear of L2; palpebral ridge transverse. Anterior and palpebral areas of fixigena narrow, about 10 per cent, the posterior cranidial width, and strongly declined adaxially; posterior area wide, 36-40 per cent, of maximum cranidial width, sub-triangular in outline with low, weakly convex, semicircular paraglabellar area beside axial furrow and opposite LI. Anterior sections of facial suture subparallel, only slightly convergent forwards ; posterior sections run abaxially in broad curve to cut posterior border at genal angle. Preglabellar field moderately swollen, merges with upturned anterior border, and defined abaxially by broad (tr.) abaxially curved furrows; anterior border furrow absent or broad (sag.) and shallow, depending on preservation. Hypostomal pits faint, sited at junction of axial and preglabellar furrows. Librigena has broad, convex lateral border, shallow border furrow, and gently declined librigenal field; eye socle crescentic, narrow, strongly upturned. Pygidium about three-quarters as wide as long. Axis strongly convex with frontal width less than one-third that of pygidium; it includes the articulating half-ring, seven rings defined by deep ring furrows, and the terminal piece. Axial furrows deep, wide, convergent to seventh ring furrow, beyond which they are parallel, producing a funnel-shaped outline. Pleural region divided by six pleural furrows into a ridge-like articulating half-rib, five ribs and a trace of a sixth rib, and the distal half is turned down almost vertically ; ribs become successively more strongly curved backwards, the fifth being subparallel to the axial furrow; interpleural furrows shallow proximally but deep on distal half of pleural region, where a narrow, unfurrowed marginal band is developed. Rear half of the margin (PI. 4, fig. 1 1) marked by low rim which thickens towards sagittal line, where it merges with sub-rectangular terminal piece. Remarks. Specimens from the same horizon and locality as N. elongatus were described by Sheng (19746) as either N. tungtzuensis or N. birmanicus and are identical to the new species. One of them (Sheng, 19746, pi. 8, fig. 2e) shows a complete thorax with attached pygidium; the thorax of 13 segments is consistent with that in other Neseuretus species, but the axis is narrower, occupying only one-third, or less, of the thoracic width. Of the many described species of Neseuretus, only a group of Chinese late Arenig forms is closely comparable to N. elongatus. It includes : N. intermedius Lu, 1975 (p. 455, pi. 48, fig. 7) and N. sankwaichangensis Lu, 1975 (p. 457, pi. 48, figs 1 1-13), both from the upper part of the Meitan Formation, southern Sichuan; N. planus Lu, 1975 (p. 458, pi. 46, fig. 15) from the upper part of the Meitan Formation, southern Sichuan, and the Ningkianolithus welleri Zone of the Siliangssu Formation, southern Shaanxi; N. zunyiensis Yin, in Yin and Lee, 1978 (p. 585, pi. 187, figs 4—5) from the upper part of the Meitan Formation, northern Guizhou; N. muliensis Lee, 1978 (p. 275, pi. 107, figs 12—13) from Muli, western Sichuan; N. xiadongensis Xiang and Zhou, 1987 (p. 332, pi. 39, figs 12-13) from Yichang, western Hubei; and possibly N. conicus (Kobayashi, 1951) (see Chang and Jell 1983, p. 207, fig. 6g), from north-western Sichuan, and N. convexia (sic) (Sheng, 1958, p. 201, pi. 7, fig. 6), from northern Guizhou. In all these species, as in N. elongatus, the glabella and anterior part of the cranidium are relatively narrow, the anterior and palpebral areas of the fixigena are narrow, adaxially declined, and the posterior area is wide. The pygidium illustrated for N. xiadongensis matches that of N. elongatus but appears relatively longer due to slight compression. The species listed above are distinguished, apparently, by their relatively shorter, more tapered glabella, and the more anterior position of the smaller palpebral lobe, opposite L3 and the front of ZHOU ET AL.: ORDOVICIAN TRILOBITES 455 L2. All eight are based on inadequate or poorly preserved material and supposed differences between them may reflect their state of preservation. They may form a natural group, and some could eventually prove to be synonyms. Acknowledgements. Part of the collection described in this paper was obtained during a visit to China by WTD in 1987, sponsored by Academia Sinica and the Royal Society of London. 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Records of the Western Australian Museum, 16, 593-622. — ying gongzheng and tripp, r. p. 1984. Trilobites from the Ordovician Shihtzupu Formation, Zunyi, Guizhou Province, China. Transactions of the Royal Society of Edinburgh: Earth Sciences, 75, 13-36. zhou zhiyi Nanjing Institute of Geology and Palaeontology Academia Sinica, Chi-Ming-Ssu Nanjing 210008, China W. T. DEAN Department of Earth Sciences University of Wales, Cardiff P.O. Box 914, Cardiff CF1 3 YE, UK and Department of Geology National Museum and Gallery of Wales Cathays Park, Cardiff CF1 3NP, UK LUO HUILIN Typescript received 7 January 1997 Yunnan Institute of Geological Sciences Revised typescript received 11 June 1997 Baita Road, Kunming 650011, China NEW CRETACEOUS GASTROPODA FROM CALIFORNIA by l. r. saul and r. l. squires Abstract. Two genera of subtropical to tropical, nearshore-marine nerineid gastropods, Aphanoptyxis and Nerinella, are recognized for the first time in the Cretaceous of California. A listing of Cretaceous nerineid species from between British Columbia and Baja California, an area presently north of the tropics, records 12 species of nerineids, including two new species, Aphanoptyxis californica and Nerinella santana. Aphanoptyxis andersoni nom. nov., of Early Cretaceous (Hauterivian) age from near Ono, northern California, is the earliest Aphanoptyxis recorded in the western hemisphere; A. californica sp. nov., of Late Cretaceous (Turonian) age from near the city of Hornbrook, Siskiyou Co. and Little Cow Creek valley near Redding, Shasta Co., northern California, is the youngest Aphanoptyxis recorded. Nerinella santana sp. nov. is from the Turonian of the Santa Ana Mountains near Los Angeles, southern California. No North American Pacific coast nerineid of younger than Turonian age has been found. Four species originally described as Nerinea have been reallocated to neotaenioglossan families. Two new Cretaceous cerithiform species, which resemble nerineids in having a narrow pleural angle, are : Potamidopsisl grovesi sp. nov., a possible potamidid of Early Cretaceous (Hauterivian) age from near Ono, northern California, and Diozoptyxis ursana sp. nov., a campanilid of Late Cretaceous (Coniacian-Santonian) age from south-east of Redding, Shasta Co., and Chico Creek, Butte Co., northern California. Diozoptyxis ursana is the earliest campanilid recognized from North America. This paper concerns the discovery of four new gastropod species: two nerineids, a campanilid, and a possible potamidid from non-carbonate, Cretaceous rocks in California. Both new nerineid species are of Late Cretaceous (Turonian) age. The first new species, Aphanoptyxis californica, is present in Turonian strata north-east of Redding, as well as near the town of Hornbrook near the California-Oregon border (Text-fig. 1). Specimens are plentiful. The second new Turonian species, Nerinella santana, is from the Santa Ana Mountains near Los Angeles, southern California (Text- fig. 1). Specimens are locally common. In addition, a new name, Aphanoptyxis andersoni , is provided for Nerinea archimedis Anderson, 1938, of Early Cretaceous (Hauterivian) age, from the Budden Canyon Formation near Ono, Shasta Co., northern California. Nerineid gastropods form a conspicuous and important element in Mesozoic carbonate faunas and are considered to be indicative of subtropical to tropical conditions (Sohl 1987; Barker 1990). On the Pacific coast of North America, north of the present tropics, nerineid occurrences are sparse and specimens are rare. The only area where nerineid gastropods are moderately common and diverse is Baja California, Mexico, where outcrops of biohermal limestone in the Lower Cretaceous (middle Albian) upper member of the Alisitos Formation contain five genera of nerineids (Allison 1955). Other Cretaceous nerineids have been reported from the Queen Charlotte Islands, British Columbia, Canada (Whiteaves 1884) and from the Lower Cretaceous near the town of Ono, northern California (Anderson 1938). The most distinctive and well-known morphological feature of these gastropods is the development, in most genera, of spiral folds within the body cavity of the shell (Barker 1990). The earliest nerineid reported north of Baja California on the Pacific slope is Nerinea thompsonensis Crickmay, 1933 described from the Thompson Limestone (Diller 1892) in the Mt Jura section, Plumas County, northern California. These beds are considered to be early Mid Jurassic age (Crickmay 1933). The following nerineids have been reported from the Pacific slope Cretaceous strata of North [Palaeontology, Vol. 41, Part 3, 1998, pp. 461-488, 3 pls| The Palaeontological Association 462 PALAEONTOLOGY, VOLUME 41 text-fig. 1. Index map for Pacific Slope of North America fossil sites mentioned in text. 1 - Maude Island, Queen Charlotte Islands, British Columbia; 2 -north of Hornbrook, Siskiyou Co., California; 3 - Redding area, Shasta Co., California; 4-Ono area, Shasta Co., California ; 5 - Mt Jura, Plumas Co., California; 6 -Chico Creek, Butte Co., California; 7 -Santa Ana Mountains, Orange Co., California; 8 - Punta China and environs, Baja California, Mexico ; 9 - South of Rosario (north of Mision San Fernando; south of Arenoso) to Arroyo Santa Catarina, Baja California, Mexico. SAUL AND SQUIRES: CRETACEOUS GASTROPODA 463 PACIFIC COAST CRETACEOUS NERINEID SPEOES — with occurrences between British Columbia, Canada, and northern Baja California, Mexico. C* C* Aphanoptyxis callfomlca sp. nov. Nerinoldes santana sp. nov. Aptyxiella (Aptyxiella) cf. subula (R6mer) Cossmannea (Eunerinea) pauli (Coquand) Nerinea (Plesloptygmatis) boesei Allison Nerinea (Plesloptygmatis) d.pseudoconvexa Stanton Nerinea (Plesloptygmatis) tomasensis Allison PcheHncevla d.pllgriml (Cox) sensu Allison Plesloptyxtssubfleurtausa Pchellntsev sensu Perrilllat "Nerinella maudensis (Whlteaves) Nerinella parallela (Anderson and Hanna) Aphanoptyxis andersoni nom. nov. cm Northernmost occurrence of nerineid species during the 41 °N 32 N 32 N 42°N interval of time Indicated (excluding N. maudensis). •Latitude of N. maudensis . Stratigraphical position is uncertain. 1 53°Nl text-fig. 2. Time ranges of Pacific Slope Cretaceous nerineid species. Species plotted occur between Queen Charlotte Islands, British Columbia, Canada ( c . 54° N) and Baja California, Mexico (c. 29° N). Palinspastic reconstructions are not addressed in citing latitude, but as all localities are west of the North American craton, they have been moved north relative to it and are probably north of their latitudes of deposition. If Nerinella maudensis is indeed of Albian age, the most diverse and most northern Pacific Slope occurrences are contemporaneous . America between British Columbia and Baja California. Their geological ranges are summarized in Text-figure 2. Two-thirds of the species reported are from the Alisitos Formation in Baja California, Mexico, which is of Aptian-Albian age (Allison 1955, 1974; Gastil et al. 1975). Two-thirds of the Alisitos species have been recognized as the same species or very similar to species from the Mediterranean area, Texas, or mainland Mexico. No nerineid species of younger than Turonian age has been reported from between British Columbia and Baja California. These distributions resemble those noted by Sohl (1987) for nerineoideans elsewhere in that nerineids from the Pacific coast are most diverse in the middle Cretaceous, with an abrupt decline before its end, and the species apparently had less restricted geographical ranges during the time of maximum diversity. Nerineoidea constitutes one of the two most characteristic gastropod superfamilies of Tethys (Sohl 1987), and their absence throughout the Upper Cretaceous north of Baja California Sur may be another indication of post-Turonian cooling (Saul 1986). Aphanoptyxis andersoni nom. nov., herein. Aphanoptyxis californica sp. nov., herein. Aptyxiella ( Endiatracheus ) parallela (Anderson and Hanna, 1935). Allison 1955, p. 426, pi. 43, figs 8-9. See: Nerinella parallela , herein. Aptyxiella ( Aptyxiella ) cf. subula (Romer, 1888). Allison 1955, pp. 425^126, pi. 43, figs 3^1. Middle Albian; upper member of the Alisitos Formation; Punta China, Baja California, Mexico. Cossmannea ( Eunerinea ) pauli (Coquand, 1862, p. 177, pi. 4, fig. 3). Allison 1955, p. 426, text-fig. 3d. Barremian-Aptian, Mediterranean area. Middle Albian; upper member of the Alisitos 464 PALAEONTOLOGY, VOLUME 41 Formation; Punta China, Baja California, Mexico (Allison 1955). Barremian, Agua del Burro Formation, north-east of San Juan Raya, Puebla, Mexico (Buitron and Barcelo-Duarte 1980). Cossmannea (Eunerinea) riograndensis (Stanton, 1947, p. 89, pi. 59, figs 7-10, 12-16). Perrilliat- Montoya 1968, p. 23, pi. 7, figs \-4. Upper Albian; Devil’s River Limestone of Texas (Stanton 1947). Upper Aptian-Albian; San Fernando Formation = Alisitos Formation, east of El Rosario and north of Mision San Fernando, Baja California, Mexico (Perrilliat-Montoya 1968). Nerinea riograndensis Stanton has a barely concave to slightly convex whorl profile. Specimens illustrated by Perrilliat-Montoya (1968) appear to have concave whorl sides and may be the same species as C. ( E .) pauli (Coquand) of Allison (1955). Diozoptyxis cf. pilgrimi (Cox, 1936). Allison 1955, pp. 426-427, text fig. 3c. Middle Albian; upper member of the Alisitos Formation; Punta China, Baja California, Mexico. Not Diozoptyxis of Delpey (1941) or Kollmann (1987). Fide Cox (1954), Adiozoptyxis Dietrich, 1914, is the appropriate name for this group, but because of Dietrich’s (1914) original hesitant proposal of the genus and subsequent questioning of the species name for the specimens he allocated to it (Dietrich 1925), Kollmann and Peza (1997) considered Adiozoptyxis taxonomically invalid. They suggested that Pchelincevia Lyssenko and Aliev, 1987 includes forms agreeing with Adiozoptyxis Dietrich, 1914. Nerinea pilgrimi Cox, 1936 (p. 22, pi. 3, fig. la-b) from Khamir, Iran was considered to be of Cenomanian-Turonian age. It is much more widely umbilicate than the specimen figured by Allison which is unlikely to be conspecific with Cox’s N. pilgrimi. Although Allison’s drawing (1955, text-fig. 3c) resembles Adiozoptyxis coquandiana (d’Orbigny, 1842) which is of Aptian age (Hernandez-Lascares and Buitron 1992), on Text-figure 2 this species is listed as Pchelincevia cf. pilgrimi (Cox) sensu Allison. Nerinea sp. Anderson, 1938, p. 132, pi. 9, figs 2-3. See: Aphanoptyxis andersoni nom. nov. Nerinea archimedis Anderson, 1938, p. 132, pi. 9, fig. 1. See: Aphanoptyxis andersoni nom. nov. Nerinoea maudensis Whiteaves, 1884, pp. 214-215, pi. 27, figs 2, 2a-2d. Probably Lower Cretaceous (?Albian); Haida Formation (Bolton 1965); east end of Maude Island, Queen Charlotte Islands, western British Columbia. Whiteaves indicated that it belonged in the subgenus Nerinella. See: Nerinella maudensis (Whiteaves), herein. Nerinea ( Plesioptygmatis ) boesei Allison, 1955, pp. 424—425, pi. 43, fig. 11, text-fig 3a. Middle Albian; upper member of the Alisitos Formation; Punta China, Baja California, Mexico. Nerinea ( Plesioptygmatis ) cf. pseudoconvexa Stanton, 1947. Allison 1955, pp. 423—424, pi. 43, figs 5-6. Middle Albian; Edwards Limestone and Fredricksburg Group, Texas (Stanton 1947). Upper member of the Alisitos Formation; Punta China, Baja California, Mexico (Allison 1955). Nerinea ( Plesioptygmatis ) tomasensis Allison, 1955, p. 425, pi. 43, figs 10, 12; text fig. 3b, e. Middle Albian; upper member of the Alisitos Formation; Punta China, Baja California. Mexico (Allison 1955). Upper Aptian-lower Albian; Encino Formation, Cerrode Tuxpan, southern Jalisco, Mexico (Buitron 1986, p. 27, as Ptygmatis tomasensis (Allison)). Nerinella maudensis (Whiteaves, 1884), herein. Nerinella parallela (Anderson and Hanna, 1935), herein. Nerinella santana sp. nov., herein. Plesioptyxis subfleuriausa Pchelintsev, 1953, p. 166, pi. 33, figs 3-4. Perilliat-Montoya, 1968, p. 23, pi. 7, figs 5-6. Cenomanian of Transcaucasus, Russia (Pchelintsev 1953). Upper Aptian-Albian; San Fernando Formation = Alisitos Formation; Mesa Sepultura, south of Arenoso, Baja California, Mexico (Perrilliat-Montoya 1968). Turitella parallela Anderson and Hanna, 1935. p. 26, pi. 9, figs 1-3. See: Nerinella parallela, herein. Although originally described as nerineids, the following species belong elsewhere : Nerinea dispar Gabb, 1864, p. 113, pi. 19, figs 66, 66a. Lower Cretaceous; North Fork of Cottonwood Creek; Ono area, Shasta Co., California. See: Opalia ( Claviscala ) dispar (Gabb) (Durham 1937, p. 503, pi. 56, fig. 20). Nerinea disparl Gabb. (Var.) Whiteaves, 1896, p. 127, pi. 3, fig. 4. Whiteaves, 1903, p. 363. Upper Cretaceous ; Nanaimo Group ; Hornby Island, British Columbia. See : Opalia ( Claviscala ) n. sp. SAUL AND SQUIRES: CRETACEOUS GASTROPODA 465 Durham 1937, p. 503. Probably not Opalia or Claviscala ; may be an epitoniid similar to ‘ Nerinea ’ stewarti Anderson. Nerinea robertiana Anderson 1958, p. 155, pi. 66, fig. 3. Lower Maastrichtian; upper part of the Moreno Formation; Pacheco Pass area, Fresno County, central California. See: Turritella chaneyi Merriam, 1941 (Saul 1983, p. 81). Nerinea stewarti Anderson, 1958, p. 155, pi. 30, figs 2-3. ?Middle Turonian; ?Gas Point Formation; Hickman ranch, on the Middle Fork of Cottonwood Creek, Shasta Co., northern California. A deep water, cold-seep epitoniid (W. P. Elder, pers. comm. 1997). North American Pacific slope Cretaceous campaniloideans and cerithioideans have not been much studied. The two new species described here resemble nerineids in having a narrow pleural angle. Potamidopsisl grovesi sp. nov., of Hauterivian age, is rare and occurs with Aphanoptyxis andersoni nom. nov. near Ono, Shasta Co., California. Diozoptyxis ursana sp. nov., which is similar in overall shape to Aphanoptyxis californica sp. nov., is also from the Redding Formation east of Redding, Shasta Co., California, but is younger, of Coniacian and Santonian, rather than Turonian, age. ECOLOGICAL IMPLICATIONS Nerineids are noted for their presence in Mesozoic carbonate reefal-facies rocks of the Tethyan Province (Barker 1990), but such rocks are rarely found on the Pacific coast of North America. Only in the Middle Cretaceous Alicitos Formation of Baja California, Mexico, do carbonate-reefal rocks yield nerineids. The nerineids discussed herein, however, are from coarse- to fine-grained arenaceous rocks. Habitat preference and life-style have been suggested for some nerineid Jurassic genera by Barker (1990), amongst which are Aphanoptyxis and Nerinella. Aphanoptyxis is considered to have been epifaunal and inhabited low-energy, subtidal-intertidal (in places supratidal) mud flats (Barker 1990). Nerinella was inferred to have been infaunal and lived, in addition to areas similar to those inhabited by Aphanoptyxis, in somewhat deeper water, and in higher energy locales (Barker 1990). Modern and fossil campanilids and potamidids are found in warm temperate to tropical, nearshore habitats, including sand and mud flats. Modern potamidids are especially characteristic of muddy estuarine habitats and live in vast numbers in mangroves and salt marshes (Houbrick 1984; Wilson 1993). Specimens of Aphanoptyxis californica sp. nov. occur in abundance in moderately coarse-grained sandstone north-east of Redding in Little Cow Creek valley. Their abundance and range in specimen size suggest deposition proximal to a very nearshore habitat. Aphanoptyxis andersoni nom. nov. and Potamidopsisl grovesi, both from the Budden Canyon Formation near Ono, are represented by a few, largely immature specimens. All of the P.l grovesi specimens are small and may be only the early whorls. These specimens are associated with other shallow-marine molluscs, such as the bivalve Plicatula variata Gabb, 1864, that have apparently been transported offshore into deeper water. Nerinella santana sp. nov. is locally abundant in near-shore, coarse-grained sandstone of the Baker Canyon Member of the Ladd Formation in the Santa Ana Mountains, Orange Co., southern California. Nerinella parallela was listed as common from a tuffaceous siltstone of Aptian age in the lower Alicitos Formation at Punta China, and, as less common, from tuffaceous siltstone and sandstone of Albian age in the upper Alicitos Formation (Allison 1955). This latter species apparently occurs at a number of places within the Alicitos Formation, at least as far south as Santa Catarina (near 29° 30' N) (Text-fig. 1, area 9), Baja California, Mexico. Nerineids are considered indicative of tropical conditions and the Tethyan Province (Sohl 1987), but gastropods of the families Campanilidae and Potamididae, although also present in the tropics, range into warm-temperate waters and may reflect slightly cooler conditions than those required by the nerineids. The disappearance of campanilids from European waters is indicated by Delpey (1941) to have been related to late Miocene emergences. Houbrick (1984) considered seaway 466 PALAEONTOLOGY, VOLUME 41 constrictions and trophic niche competition with the strombids to have contributed to disappearance of campanilids from European waters. The sole living representative of the Campanilidae, Campanile symbolicum Iredale, 1917, is from the Flindersian warm-temperate province along the coasts of Western Australia and South Australia (Ludbrook 1971). Several strombids recorded from the tropical northern coasts of Australia are lacking along the warm-temperate southern coasts inhabited by C. symbolicum. Whether the occurrence of C. symbolicum is restricted more by temperature or by strombid competition is unknown, but both may have an effect. Strombids of Cretaceous age are, however, unknown from North American Pacific coast deposits, which renders their probable impact on Cretaceous campanilids to be slight. In the distribution of campanilids as she recognized them, Delpey (1941) saw a migration from European waters to an Australian refuge. However, Campanile is present in the Paleocene of California and Brazil, and in the Eocene of California, Baja California, Panama, and Jamaica, and was probably pantropical in the early Tertiary (Wrigley 1940, fig. 14; Squires 1993). SYSTEMATIC PALAEONTOLOGY Abbreviations. The following abbreviations are used: CASG, California Academy of Sciences, Geology Section, San Francisco; CIT, California Institute of Technology (collections now stored at LACMIP); LACMIP, Natural History Museum of Los Angeles County, Invertebrate Paleontology Section; UCLA, University of California, Los Angeles (collections now stored at LACMIP). A slightly modified Ponder and Waren (1988) classification is used. Phylum mollusca Linnaeus, 1758 Class gastropoda Cuvier, 1797 Sublcass prosobranchia Milne-Edwards, 1848 Superorder caenogastropoda Cox, 1959 Order neotaenioglossa Haller, 1888 Superfamily campaniloidea Douville, 1904, emend. Houbrick, 1989 Family campanilidae Douville, 1904 Remarks. Campanile has long been associated with Cerithium Bruguiere, 1789, as a subgenus (e.g. Cossmann 1906), a genus within Cerithiidae (e.g. Hanna and Hertlein 1939), a genus of the subfamily Campanilinae of the Cerithidae (e.g. Wenz 1940), or as a genus of the family Campanilidae in the superfamily Cerithioidea (e.g. Douville 1904; Houbrick 1981). Houbrick (1981, 1984, 1988, 1989) reviewed earlier classifications and presented evidence, mainly from soft-part anatomy, which resulted in his exclusion of Campanilidae from Cerithioidea and its placement in Campaniloidea (Houbrick 1989). He considered the Campaniloidea to have been an earlier, major radiation from the mainstream of the stem-group giving rise to modern Cerithioidea, the radiation having as its sole surviving member the living Campanile symbolicum Iredale, 1917. Delpey (1941) derived Campanile from mid Cretaceous Nerinea and stated that Campanile was not known before the Cenomanian. However, if Houbrick (1989) is correct in regarding Campaniloidea as an early, major radiation off the stem that gave rise to Cerithioidea and Caenogastropoda, Campaniloidea would presumably have split from that stem as stem forms became classifiable as cerithioideans. The probability of as yet unrecognized Jurassic campanilids is suggested by Ponder and Waren (1988), who listed in Cerithoidea several genera having Jurassic representatives. Haszprunar (1988) considered that Campanile has characteristics which indicate affinities with the Euthyneura ( = Heterobranchia in Ponder and Waren 1988) and that Campanile probably represents a first step toward the euthyneurous level of organization, but Ponder and Waren (1988) are sceptical because undoubted euthyneurans extend back to the Carboniferous. Ponder and Waren (1988) placed Campanile in Cerithioidea, order Neotaeniglossa, but placed nerineoideans in the sublcass Heterobranchia (= Euthyneura), order Heterostropha. Houbrick (1981) considered SAUL AND SQUIRES: CRETACEOUS GASTROPODA 467 the derivation of campanilids from nerineids most unlikely because ‘ nerineids have heterostrophic protoconchs and deep anal sulci and are considered to be in the subclass Euthyneura’. Barker (1990, p. 249) defined all Nerineidae as possessing a juxta-sutural selenizone (slitband), a rudimentary siphonal canal, and heterostrophic protoconchs, but also wrote (Barker, 1990, p. 253) ‘apart from a brief mention by Bigot (1896) no nerineid protoconch has yet been adequately described or figured’. Both K. Bandel (pers. comm.) and M. J. Barker (pers. comm.) have indicated that Vaughan (1988, text-fig. 6. 1-6.3) has provided photographs of the heterostrophic protoconch of a nerineid, Polyptyxisella schicki (Fraas, 1878)?, from the Campanian of the North Alpine Gosau. Unfortunately, protoconchs of both nerineids and campanilids are difficult to recover and the teleoconchs, which may be very similar, are difficult to assign with certainty to either family (K. Bandel, pers. comm.). Houbrick (1984) suggested that a number of fossil species described under other generic names, especially Telescopium, are actually Campanile. Although Diozoptyxis Cossmann, 1896, (type species Nerinea monilifera d’Orbigny, 1842, Cenomanian of France) was described as a nerineid, Delpey (1941) classed it as a subgenus of Campanile Bayle, in Fischer, 1884. Both Delpey (1941) and Kollmann (1987) referred to the type species Nerinea monilifera d’Orbigny as their basis for classifying Diozoptyxis as a campanilid with one columellar fold which develops in the last whorl. Diozoptyxis was raised to generic status by Kollmann (1987) who examined d’Orbigny’s type specimens. In part because of the single columellar fold in N. monilifera, he considered it close to Campanile and within Campanilidae. Mustafa and Bandel (1992), referring to the unpublished thesis of Vaughan (1988), used Dioxoptyxis as did Cossmann (1906), for a genus belonging to Nerineidae, with three folds (two columellar and a palatal) and a narrow umbilicus. According to Kollmann and Peza (1997), Vaughan did not argue with Delpey’s placement of N. monilifera in Campanilidae but suggested that ICZN Article 70c (Ride et al. 1985) should be applied. Article 70c would seem to require a misidentification or misapplication of the specific name, but there is no indication that Cossmann’s N. monilifera is not that of d’Orbigny, and the type species of Diozoptyxis is apparently not a nerineid. Delpey (1941) considered that most species assigned to Cimolithium Cossmann, 1906, should be placed in Campanile ( Diozoptyxis ) but that Cerithium belgicum d’Archiac, 1847 (Cenomanian of Belgium, the type species of Cimolithium ) is not a campanilid but is a high-spired Microschiza (Cloughtonia) and belongs in the family Pseudomelaniidae. Diversity of shell morphology in Campanilidae is increased by the inclusion in this family of the involute genus Itruvia Stoliczka, 1868, whose type species is Itruvia canaliculata (d’Orbigny, 1843) (Kollmann and Sohl 1980; Kollmann 1987), but as most species formerly refereed to Itruvia are Vernedia Mazeran, 1912, family Itieriidae Cossmann, 1896, of the Nerineiodea this diversity fails to decrease similarities between Campaniloidea and Nerineoidea. The type species of Campanile, Campanile giganteum Famarck, 1804 (by subsequent designation, Sacco 1895; Eocene, Calcaire Grossiere, Paris Basin, France), has two strong folds on its columella and parietal and basal tubercules, but Delpey (1941) followed Iredale (1917) in considering Campanile symbolicum Iredale, 1917 to be the type species. Campanile symbolicum lacks the two strong folds on the columella of C. giganteum, and Delpey suggested the use of Campanilopa Iredale, 1917 (type species C. giganteum) for the giant campaniles which she considered arose in about the Santonian and ranged through the Oligocene. Species of late Tertiary age have one or no folds, as does the modern Australian species. Houbrick (1981) did not consider the number of folds diagnostic in Campanile, and Delpey (1941) and Kollmann (1987) included Cretaceous species having one fold in Campanilidae. Houbrick’s (1981, 1988, 1989) delineation of Campanilidae is based on soft-part anatomy, unavailable in Pacific coast Cretaceous specimens. Shell features that pertain to Campanilidae include the overall elongate, turrited-conoidal shape; the short anterior canal; simple outer lip; the thick calcified periostracum that produces a finely pitted and striated shell surface; and a growth line that is opisthocline across the whorl flank and curves forward toward the aperture near the posterior suture. The anal, sulcus of campanilids is less deep and less narrow than that of nerineids and is not as tightly juxtaposed to the suture. 468 PALAEONTOLOGY, VOLUME 41 As Houbrick (1984) has noted, the whole spectrum of Campanile-\ike fossil forms is in need of a thorough revision, and he suggested that Campanilidae was more diverse in the Tertiary than indicated by Delpey (1941), but he mentioned only Dirocerithium Woodring and Stenzel, in Woodring, 1959 by name. Cretaceous genera that resemble campanilids and might belong in this family include Macrocerithium Stephenson, 1952 (type species Cerithium tramitense Cragin, 1893, Cenomanian, Woodbine Formation of Texas) and Nudivagus Wade, 1917 (type species Nudivagus simplicus Wade, 1917, Maastrichtian, Ripley Formation, Coon Creek, McNairey Co., Tennessee). Serratocerithium Vignal, 1897, based on Cerithium serratum Bruguiere, 1792 of the Paris Basin Eocene, was included by Wenz (1939) in Campanilinae, but its shell lacks the finely pitted and striated surface of Campanile. Another Tertiary genus having a form and growth line similar to that of Campanile is Perucerithium Olsson, 1929, based on Cerithium ( P .) restinense Olsson, 1929, of the Peruvian Eocene. In general, Mesozoic cerithiform gastropods are poorly known. Reasons for this lack of knowledge include poor preservation, the gastropods’ probable preference for very shallow- water habitats that are less commonly preserved than more offshore habitats, and the misperception that such gastropods are poor age indicators and unrewarding to study. This is the first allocation of a Cretaceous North American species to the Campanilidae. Genus diozoptyxis Cossmann, 1896 (emend. Delpey, 1941, and Kollmann, 1987) Type species. Nerinea monilifera d’Orbigny, 1842, by original designation; from the Cenomanian of France. Remarks. Although, as previously mentioned, Diozoptyxis was originally described by Cossmann (1896, 1906) as a nerineid with three internal folds, it has been recognized as a campanilid by Kollmann (1987) and Kollmann and Peza (1997) based on the characteristics of d’Orbigny’s specimens of the type species Nerinea monilifera. The California specimens share with species assigned to Diozoptyxis , as recognized by Delpey (1941), Kollmann (1987) and Kollmann and Peza (1997), an overall sculpture pattern, single columellar fold, and a sigmoidal growth line. Cossmann (1896) gave Diozoptyxis two columellar folds, but Delpey (1941), Kollmann (1987) and Kollmann and Peza (1997) agree that it has but one. Kollmann (1987) characterized Diozoptyxis as having a low whorl height to diameter ratio, two noded carinae, and a weak fold on the lower part of the columella. Furthermore, this fold is only developed in the last whorl (Kollmann and Peza 1997). Allison (1955) reported Diozoptyxis cf. pilgrimi from the middle Albian. His figure is a drawing of a section through his only specimen, a fragment of a large individual having two columellar folds, a labral fold, and a wide umbilicus. It is not a Diozoptyxis in the sense of Delpey (1941) and Kollmann (1987). The fold pattern and the umbilicus are similar to those of the ill-proposed Adiozoptyxis Dietrich (1914, 1925) and to Pchelincevia Lyssenko and Aliev (1987) which has for its type species Nerinea renauxiana d’Orbigny, 1842, the species that Pchelintsev (1965) incorrectly tried to substitute for Nerinea monilifera d’Orbigny, 1842 as type species of Diozoptyxis. EXPLANATION OF PLATE 1 Figs 1-6. Diozoptyxis ursana sp. nov. 1-4, LACMIP loc. 10905, Bear Creek, California. 1-2, LACMIP 7908, holotype, x 1 -7 ; 1 , apertural view ; 2, abapertural view. 3-4, LACMIP 7909, paratype ; x 2-2 ; 3, apertural view ; 4, abapertural view. 5, LACMIP 7910, paratype; LACMIP loc. 23621, Chico Creek, California; apertural view; x 3. 6, LACMIP 7911, paratype; LACMIP loc. 15797, Bear Creek, California; latex peel; x 1-9. Figs 7-10. Potamidopsisl grovesi sp. nov.; North Fork of Cottonwood Creek, California. 7-8, CASG loc. 62583; latex peels. 7, CASG 67884.01, holotype; x 7-3. 8, CASG 67885.01, paratype; x9-2. 9, CASG 67885.03, paratype; CASG loc. 62606; x 6. 10, CASG 67885.02, paratype; CASG loc. 62583; x5-5. All specimens coated with ammonium chloride. PLATE 1 SAUL and SQUIRES, Diozoptyxis, Potamidopsisl 470 PALAEONTOLOGY, VOLUME 41 Diozoptyxis ursana sp. nov. Plate 1, figures 1-6 1959 Telescopium n. sp. Saul, p. 116, pi. 10, fig. 8. 1959 Tympanotonus n. sp. Saul, p. 117, pi. 10, fig. 11. 1959 Potamidesl sp. Saul, p. 117, pi. 10, fig. 10. Derivation of name. The specific name is derived from Latin for bear ursus, reflecting the occurrence of this species in the Bear Creek drainage. Holotype. LACMIP 7908. Type locality. LACMIP loc. 10905, Bear Creek, Shasta Co., California, latitude 40° 33' 54" N, longitude 121° 54' W. Paratypes. LACMIP 7909 from LACMIP loc. 10905; 7910 from LACMIP loc. 23621; 7911 from LACMIP loc. 15797. Diagnosis. A Diozoptyxis with the posterior carina prominent and having larger nodes, the anterior one weaker with smaller, weaker nodes becoming obsolete. Description. Shell medium sized, turrited-conical with an elongate and narrow upper spire; pleural angle 20-25°. Protoconch unknown. Teleoconch consisting of more than nine whorls with noded posterior carina at posterior suture and subordinate barely noded anterior carina posterior to rounded basal angulation ; whorl flanks concave between posterior and anterior carinae, rounding abruptly into convex base ; base with about three weak, equidistant medial spirals. Growth line strongly opisthocline across whorl side and on to base, reversed at posterior carina. Columella thick, bearing one fold near the base. Aperture rhomboidal? with slightly twisted, short anterior canal ; outer lip unknown. Dimensions of holotype. Height 36-6 mm, diameter 16-8 mm. Remarks. The single fold on the columella of this species is suggestive of Diozoptyxis. The whorl diameter/height ratio is 2-3. Diozoptyxis ursana resembles Diozoptyxis monilifera (d’Orbigny) (Cossmann 1896, pi. 2, fig. 5) but has larger nodes on its posterior carina and weaker anterior nodes. Diozoptyxis ursana is similar in overall shape to Aphanoptyxis californica from which it differs in having larger, fewer, more persistent nodes on the posterior carina; the posterior carina slightly farther from the suture; the basal angulation more rounded and the base more convex; and a relative narrower and less twisted columella. Although poor preservation makes observation of the anterior canal and columellar fold difficult, some specimens suggest that the anterior canal is longer than in A. californica. Aphanoptyxis californica has a single parietal fold on the posterior part of the body whorl. Because in most specimens of D. ursana the shell is leached and partially peeled away, specimens of D. ursana are difficult to separate from those of A. californica. Diozoptyxis ursana appears to lack the spiral sculpture of A. californica. Diozoptyxis ursana has been found in two areas: near the base of the Bear Creek Sandstone Member of the Redding Formation in the Bear Creek area, Shasta Co. ; and in the Musty Buck Member of the Chico Formation on Chico Creek, Butte Co., California. In the Bear Creek area, specimens are common but usually leached, somewhat flattened, and difficult to extract. That so few specimens are at hand for study is a reflection of their preservation rather than their abundance : LACMIP loc. 10905 - three specimens, LACMIP loc. 15758 - three specimens, LACMIP loc. 15761 one specimen, LACMIP loc. 15797 -one specimen, LACMIP 15944 -three? specimens. At LACMIP loc. 15944 leached and flattened molluscs are associated with carbonized plant remains. The molluscs include, in addition to D. ursana , two other kinds of cerithiform gastropods, namely a Pyrazusl and a potamidid or batillariid. Ammonites from overlying beds of this member provide a Coniacian age (Haggart 1986) for the marine part of this member, and Haggart (1986) inferred SAUL AND SQUIRES: CRETACEOUS GASTROPODA 47: that the depositional environment of this part of the member was shallow marine (inner shelf). The specimens of D. ursana at these localities are in coarse-grained, porous sandstone beds in lenses of coquina associated with abundant plant remains, and they and another undescribed cerithiform gastropod are the largest specimens. These D. ursana show a characteristic outline with each whorl projecting more than the previous one and having a stronger projection than that of A. calif ornica. Flattening of the specimen causes them to have a much wider pleural angle than A. calif ornica. Despite this poor preservation, a sigmoidal growth line, opisthocline across the anterior portion of the flank, is discernible on several specimens. In the Chico Creek area, specimens of D. ursana were collected at LACMIP Iocs 23621 (two specimens), 23622 (one specimen), and 23625 (one specimen) in the Musty Buck Member of the Chico Formation approximately 100 m below occurrences of Baculites capensis Woods, 1906 (Saul 1959). All of these specimens are of early Santonian age (Matsumoto 1960; Haggart and Ward 1984). Russell et al. (1986) inferred that the depositional environment of this member in the Chico Creek area was the seaward edge of a delta complex. Specimens of D. ursana from these localities are small fragments with poor to moderately good preservation. Distribution. Northern California, vicinity of Bear Creek, Shasta Co., Redding Formation, Bear Creek Sandstone Member; and Chico Creek, Butte Co., Chico Formation, Musty Buck Member. Stratigraphical range. Coniacian and lower Santonian. Family potamididae H. and A. Adams, 1854? Genus potamidopsis Munier-Chalmas, in Chedeville, 1904 Type species. Potamidopsis tricarinata (Lamarck, 1804) [Cerithium], by original designation; from the Eocene, Bartonian, ‘Sables Moyen’, Paris Basin, France. Potamidopsis! grovesi sp. nov. Plate 1, figures 7-10 Derivation of name. The species is named after Lindsey T. Groves in recognition of his assistance. Holotype. CASG 67884.01. Type locality. CASG loc. 62583, North Fork Cottonwood Creek, Shasta Co., northern California; latitude 40° 28' 12" N, longitude 122° 36' 40" W. Diagnosis. A questionable Potamidopsis with a very protruding medial carina. Description. Shell small, high spired, aciculate, multi-whorled, with flaring antemedial carina. Pleural angle about 13°. Whorl profile above and below carina concave, base concave, anterior canal short; edge of carina rippled by elongate nodes ; whorl with a cord posterior to carina, a cord anterior to carina, and a weak cord at posterior suture ; anterior cord strong, at base of whorl ; posterior cord about midway between carina and suture. Suture at basal cord. No axial sculpture. Inner whorl shape round, without folds. Columella thick. Growth line appears prosocline at posterior suture with broad medial sinus, deepest near carina. Aperture unknown. Measurements. Holotype CASG 6788.01: height 10 mm, diameter 3 mm, height of largest whorl 1-3 mm. Paratype CASG 67885.01 from CASG loc. 62583: height 9-5 mm, diameter 2 mm. Paratype CASG 67885.02 from CASG loc. 62583: height 11 mm, diameter 1-75 mm. CASG 67885.03 from CASG loc. 62606: height 1 1-6 mm, diameter 4-2 mm. Remarks. Available specimens (five) are small and may all be juveniles. There are several from the type locality. Some are preserved as exquisite natural moulds; others have the shell preserved. The suture is against the basal cord and a moderate cord of the succeeding whorl is appressed to the 472 PALAEONTOLOGY, VOLUME 41 basal cord. The narrow pleural angle and rather thick columella suggest nerineids, but unlike most high-spired nerineids P. ? grovesi has a convex whorl profile, made even more so by the flaring carina, and a suture that is at a narrower part of the whorl. The elongate nodes of the carina are not apparent posterior to the carina, but they have a short abapical expression. Growth lines are difficult to discern on these small specimens, but irregularities of the whorl surface suggest a growth line with a broad medial sinus. The new species is surprisingly similar to Potamidopsis tricarinatus crispiacensis Boussac, 1905 (Lutetian and Bartonian stages, Paris Basin, France). Potamidopsis! grovesi differs from P. tricarinatus crispiacensis in having fewer more elongate nodes on the carina and stronger and unnoded cords posterior to the carina. Pot amides! grovesi also resembles Campanile ( Diozoptyxis ) ataxense (d’Orbigny) (Delpey 1941, p. 10, fig. 10) from the Santonian of Corbieres, France, but the strong carina of P. ! grovesi is more medially placed. The associated fauna at the type locality of P. ! grovesi includes the bivalves Nanonavis breweriana (Gabb, 1864), Plicatula variata Gabb, 1864, and a gastropod ‘ Potamides' diadema Gabb, 1864. Potamidopsis has been known previously only from late Paleocene and early mid Eocene brackish-marine strata in France (Gilbert 1962) and early mid Eocene brackish-marine strata in southern California (Squires 1991). Distribution. Northern California, Budden Canyon Formation, Ogo Member (CASG Iocs 62583 and 62606). Stratigraphical range. Lower Cretaceous (Hauterivian). Subclass heterobranchia Gray, 1840 Order heterostropha Fischer, 1885 Superfamily nerineoidea Zittel, 1873 Family nerineidae Zittel, 1873 Genus aphanoptyxis Cossmann, 1896 Type species. Cerithium defrancii Eudes-Deslongchamps, 1843, by original designation; Middle Jurassic (Bathonian), Aubigny, France. M. J. Barker (pers. comm.) has shown us that Fischer (1969) considered C. defrancii Eudes-Deslongchamps, 1843 non Deshayes, 1833 to be a synonym of Cerithium langruensis d’Orbigny, 1850. Diagnosis. Turrited-conical, multi-whorled nerineids of moderate size, with concave whorls; carina adjacent to suture, and weaker spiral ribs on the whorl face. Interior with no palatal or columellar plaits. No umbilicus. Columella terminated by a twisted anterior canal. Remarks. The geological range of genus Aphanoptyxis is given as Middle Jurassic (Bathonian) to Lower Cretaceous (Urgonian) in Wenz (1940). The Urgonian, a diachronous, white-limestone facies EXPLANATION OF PLATE 2 Figs 1-2. Aphanoptyxis andersoni nom. nov. = Nerinea archimedis Anderson, 1 938 ; North Fork of Cottonwood Creek, California. 1, CASG 66460.02, holotype; CASG loc. 66460 (= CASG loc. 1353, in part); abapertural view; x 1-5. 2, CASG 67886.01, holotype; CASG loc. 62583; latex peel; x9-2. Figs 3-10. Aphanoptyxis californica sp. nov. 3-4, LACMIP 7912, holotype; LACMIP loc. 10761; x 1-9. 3, apertural view; 4, abapertural view. 5, LACMIP 7913, paratype; LACMIP loc. 10761; x2-6. 6, LACMIP 7914, paratype; LACMIP loc. 10761; right-side view, low-level lighting shows opisthocline growth lines; x3-3. 7, LACMIP 7915, paratype; LACMIP loc. 10761; apical area; x6. 8, LACMIP 7916, paratype; LACMIP loc. 24649; upper spire; x 41. 9, LACMIP 7917, paratype; LACMIP loc. 24649; apertural view showing twisted columella; x2. 10, LACMIP 7918, paratype; LACMIP loc. 24649; interior view; x31. All specimens, except that in figure 10, coated with ammonium chloride. PLATE 2 SAUL and SQUIRES, Aphanoptyxis 474 PALAEONTOLOGY, VOLUME 41 of southern Europe, typically carries a Tethyan fauna rich in corals, rudists, and nerineas. Its age is predominantly Barremian to early Aptian, but, in places, ranges into the early Albian (Gignoux 1955; Ager 1980). Pchelintsev (1965) gave the range of Aphanoptyxis as Bathonian through Tithonian, but Kollmann (1976) extended the geological range of the genus into the late Albian. Aphanoptyxis californica extends the geological range of the genus into the Upper Cretaceous Turonian Stage. Aphanoptyxis andersoni nom. nov. Plate 2, figures 1-2 1938 Nerinea archimedis Anderson, p. 132, pi. 9, fig. 1 [ non Nerinea archimedi d’Orbigny, 1842]. 1938 Nerinea sp. Anderson, p. 132, pi. 9, figs 2-3. Holotype. CASG 66460.02. Anderson’s hypotypes of Nerinea sp. CASG 66460.03-66460.04 from CASG loc. 66460. Type locality. CASG 66460 (= CASG 1353 in part), North Fork Cottonwood Creek, Shasta Co., northern California; latitude 40° 28' 12" N, longitude 122° 36' 40" W. Remarks. Nerinea archimedis Anderson is a junior homonym of Nerinea archimedi d’Orbigny, 1842, a species from the Lower Cretaceous of Europe. We herein place Anderson’s species in Aphanoptyxis and rename it as Aphanoptyxis andersoni nom. nov. Specimens of A. andersoni are rare and none available shows a better cross section than those of Anderson (1938, pi. 9, figs 2-3). Neither CASG 66460.03 or 66460.04 is cut parallel to the columella; both are broken at low angle to the columella giving Anderson an impression of a wider pleural angle than that in CASG 66460.02. In addition to the specimens figured by Anderson (1938), a specimen (CASG 67886.01) from CASG loc. 62583, consisting of the early whorls of this species is figured. It is associated with Plicatula variata Gabb, 1864 and Potamidopsisl grovesi sp. nov. Of available specimens, only the holotype CASG 66460.02 is of comparable size to A. californica , and the others are smaller and less complete. The two species are very similar : Aphanoptyxis andersoni differs from A. californica in lacking the median spiral cord on the early adult whorls, in having finer nodes, and in having a pleural angle near 14° rather than 18°. Distribution. Near Ono, Shasta Co., northern California, Budden Canyon Formation, Ogo Member. Stratigraphical range. Lower Cretaceous, Hauterivian. Aphanoptyxis californica sp. nov. Plate 2, figures 3-10 Derivation of name. The species is named for the state of California. Holotype. LACMIP 7912. Type locality. LACMIP loc. 10761, Little Cow Creek valley, Shasta County, northern California; latitude 40° 40' 22" N, longitude 122° 8' W. Paratypes. LACMIP 7913-7915 from LACMIP loc. 10761; 7916-7918 from LACMIP loc. 24649. Diagnosis. An Aphanoptyxis with a noded carina at posterior suture, a low medial spiral cord, and an anterior cord at the angle between whorl side and base ; carina more prominent on adult whorls than on juvenile whorls, medial spiral rib obsolete on adult whorls. Description. Shell medium sized (up to 38-7 mm high), turrited-conical, multi-whorled (about 14 whorls), with an elongate and narrow upper spire. Pleural angle about 18°. Very early whorls (approximately first 13 mm of SAUL AND SQUIRES: CRETACEOUS GASTROPODA 475 growth) nearly flat-sided, later whorls concave, with deepest part medially. Protoconch unknown. Sculpture at diameter 0-5 mm to 2-3 mm of four noded spiral cords, each with numerous nodes; sutural cord finely noded, at suture ; posterior cord strongest, most coarsely noded ; medial cord weaker and more finely noded ; basal cord barely as strong as posterior cord, nodes stronger than on medial and smaller than on posterior cord; sculpture at diameter 2-3 mm to 4-8 mm of coarsely noded posterior cord; medial cord becomes band of collabral (opisthocline) riblets; basal cord barely visible, nearly overlapped by succeeding whorl; sculpture at greater diameters becoming obsolete, basal cord overlapped by suture; posterior cord protruding on adult whorls. Base of body whorl slightly convex with faint spirals, a slight depression adjacent to anterior carina followed by spiral row of low nodes. Aperture small, wider than high ; columella short and rising to form sharp rim bordering posterior side of anterior canal. Anterior canal strongly twisted, almost at right angle to columella, and well defined by strongly raised borders. Outer lip unknown. Whorls without interior plaits, except for a single parietal plait on posterior portion of body whorl. Whorl interiors with posterior constriction, resembling a gutter. Interior of columella complexly layered. Growth lines indistinct, opisthocline? across whorl flank and especially on anterior slope of posterior carina, looping? sharply forward across posterior carina. Dimensions of holotype. Height 38-7 mm, diameter 12 mm. Remarks. Specimens are moderately numerous, and preservation is poor to moderately good. Many of them are weathered and abraded. The shell surface tends to peel, and growth lines are obscure except on the base. Nearly all of the specimens are missing the early whorls. The holotype has the greatest height of any specimen found. A fragment from LACMIP loc. 10780 has the greatest diameter (15-5 mm) of any specimen found. An inferred complete specimen of the new species is estimated to be approximately 45 mm high and approximately 16 mm wide. A whorl with diameter of 11-3 mm is 4-6 mm high, giving a ratio of 2-5. The sculpture changes from early to later whorls. Uppermost whorls have a noded spiral thread next to the posterior suture, a noded spiral cord forming a posterior carina, a less angulate noded spiral cord on the medial part of the whorl, and a noded spiral thread next to the anterior suture. Nodes on the medial cord of these early whorls start out as beads, then change into opisthocline, short, axial ribs at a diameter of about 3-5 mm. Middle spire whorls have a swollen noded spiral carina next to the posterior suture and a fading band of riblets on the medial part of the whorl. The spiral cord next to the anterior suture becomes a low unmoded swelling. Later whorls have an unnoded, much projecting, tabulate carina next to the posterior suture and the rest of the whorl is smooth, concave-sided, with a slight spiral swelling next to the anterior suture. In the Hornbrook area, Siskiyou Co., ten specimens of the new species were collected at a single locality in Shasta Valley, LACMIP loc. 27228, from the Osburger Gulch Sandstone Member of the Hornbrook Formation. Nilsen (1984) reported the age of this member in Shasta Valley as Turonian, based on abundant molluscan fossils, including ammonites, bivalves, and gastropods, and he considered that this member was deposited under high-energy, shallow-marine conditions. The Osburger Gulch Sandstone Member specimens of A. calif ornica are poorly preserved but show the prominent spiral carina next to the posterior suture. In Little Cow Creek valley, Shasta Co., the new species was found at four localities in the Bellavista Sandstone Member of the Redding Formation: LACMIP 10761, 10780, 10784, and 24649. These localities are also plotted on a generalized geological map in Jones et al. (1978, fig. 5). The age of this member is Turonian, based on ammonites (Jones et al. 1978; Haggart 1986). Haggart (1986) inferred that the depositional environment of the member was inner to middle shelf. Specimens are most abundant at LACMIP loc. 24649 [ — UCLA loc. 4649 of Jones et al. 1978], where about 100 were collected, including some upper spire fragments. The specimens were in a coquina, faunally dominated by the new species. About 40 specimens, including some upper spire fragments, were collected at LACMIP loc. 10784 [= CIT loc. 1009 of Jones et al. 1978]. Of these specimens, about one-half are small fragments. Nearly all of the larger specimens are abraded. Their sculpture is much reduced, and the whorls are flat sided with only low spiral bands. This locality is stratigraphically the lowest of four localities, and the specimens were subjected to abrasion caused 476 PALAEONTOLOGY, VOLUME 41 by agitated-water conditions associated with deposition of the basal part of the member. Sixteen specimens were collected at LACMIP 10761 [= CIT loc. 1439 of Jones et al. 1978]. This locality is stratigraphically the highest of four localities and represents the deepest water and least agitated- water conditions of the member. Specimens from this locality were subjected to the least amount of abrasion. They are the best preserved specimens of A. calif omica available. Only four specimens were collected at LACMIP loc. 10780 [= CIT loc. 1193 of Jones et al. 1978]. They are badly corroded, but one moderately well preserved specimen shows some abrasion. The new species is very close to A. andersoni from the Lower Cretaceous (Hauterivian Stage) of Cottonwood Creek, Shasta Co., northern California. In addition to differences mentioned under A. andersoni , Aphanoptyxis calif omica differs from A. andersoni in the following features: carina stronger and more strongly noded, and medial spiral rib stronger on early adult whorls. The two species are so similar that slightly weathered specimens of the two are indistinguishable. Aphanoptyxis calif omica closely resembles Aphanoptyxis excavata (Brongniart 1822, pi. 9, fig. 10; Kollman 1976, pp. 173-174, pi. 2, figs 13-16; pi. 3, figs 17-19) from the Lower Cretaceous (middle Albian) of Poland and Lower Cretaceous (upper Albian) of France and England (Kollmann 1976). Aphanoptyxis calif omica differs from A. excavata in having whorls that are wider than high, a noded posterior carina, and, on the early whorls a medial spiral cord or band of riblets. The new species also resembles Aphanoptyxis aff. sturi (Stolickza) Kollmann (1982, p. 351, pi. 2, fig. 35; pi. 4, fig. 56) from the Upper Cretaceous (Cenomanian) of Romania and Greece and Upper Cretaceous (Turonian) of Bulgaria (Kollmann 1982). Although poor preservation makes comparison with Aphanoptyxis aff. sturi difficult, Aphanoptyxis californica differs by having a medial spiral cord or riblets on the early whorls and a less heavily noded carina on the adult whorls. The new species resembles Aphanoptyxis bladonensis Arkell (1931, pp. 618-619, pi. 50, figs 8-13) from the upper Great Oolite in England of Middle Jurassic, Bathonian age (Gignoux 1955 ; Harland et al. 1990), aspidoides zone (M. J. Barker, pers. comm.). The new species differs from A. bladonensis by having a medial spiral cord or riblets on the early whorls and a projecting carina on the much more concave adult whorls. Aphanoptyxis californica also somewhat resembles Macrocerithium tramitense Cragin, 1893 (p. 222; Stephenson 1952, p. 160, pi. 37, figs 23-29) from the Upper Cretaceous (Cenomanian) Lewisville Member of the Woodbine Formation in north-eastern Texas. The genus Macrocerithium is known solely from this species, which has been reported only from Texas. Macrocerithium tramitense , whose growth lines are very similar to those of A. californica, might be a nereinid. A study of the interior of M. tramitense or recovery of a protoconch, both presently unknown, should greatly assist in its classification. The new species differs from M. tramitense in the following features: spiral cords on upper spire more strongly noded, no fine intermediate spiral riblets on upper spire, broader pleural angle, sides of adult whorls concave, spiral carina next to the posterior suture on adult whorls much more heavily noded and more projecting, posterior part of twisted anterior canal much stronger. The adult whorls of M. tramitense have subdued sculpture which may result from abrasion. In fact, Stephenson (1952) noted that most of the specimens of M. tramitense are corroded. If the abraded adult specimens of the new species from LACMIP loc. 10784 are compared with M. tramitense, then the adult whorls of the two species show a greater similarity, in that they both have a low spiral rib next to the positive suture and they both have flatfish whorls. Also like A. californica, M. tramitense is found abundant in shallow-marine coquinas that are faunally dominated by it. The new species resembles the figures of Cerithium depressum (Zekeli 1852, p. 1 16, pi. 24, figs 6-7) from the Rondobach part of the Gosau Group, north-eastern Alps, west-central Austria. Summesberger (1985) assigned this part of the Gosau Group to the Upper Cretaceous (Santonian). Aphanoptyxis californica has a narrower pleural angle, a flatter whorl profile, and a weaker less noded medial spiral rib on the later whorls. Distribution. Northern California: Hornbrook Formation, Osburger Gulch Sandstone Member, just south of the California-Oregon border, Siskiyou County (LACMIP loc. 27228); and Redding Formation, Bellavista SAUL AND SQUIRES: CRETACEOUS GASTROPODA 477 Sandstone Member, Little Cow Creek valley, Shasta County (LACMIP Iocs 10761, 10780, 10784, 24649). Stratigraphical range. Upper Cretaceous (Turonian). Genus nerinella Sharpe, 1850 (= Nerinoides Wenz, 1940; non Nerinella Nardo, 1847 (ICZN Opinion 316; 1954)) Type species. Nerinea dupiniana d’Orbigny, 1842, by original designation; Lower Cretaceous (Hauterivian), France. Diagnosis. Slender, acicular multiwhorled nerineids of moderately large length but small diameter, with concave whorl profile, protruding sutural ridges (suture between two spiral ribs), and granulate spiral costae. Interior with one palatal plait, one or two columellar plaits, and a weak or absent parietal plait. No umbilicus. Remarks. Wenz (1940) provided the new name Nerinoides for Nerinella Sharpe, 1850 non Nardo, 1847, and he considered Nerinoides to be a subgenus of Aptyxiella Fischer, 1885. Kase (1984) recognized Nerinoides Wenz as a distinct genus. Cox (1951) applied for an ICZN ruling that would conserve Nerinella Sharpe, 1850. Nerinella Sharpe, 1850 was subsequently placed on the Official List of Generic Names in Zoology , and its type species Nerinea dupiniana d’Orbigny, 1843 was placed on the Official List of Specific Names in Zoology (ICZN 1954). Nerinella is, in general, longer and more slender than Nerinea. According to Abbass (1963), on some specimens of Nerinella, the columellar and parietal folds virtually disappear. The geological range of Nerinella is lowermost Jurassic (Hettangian) to uppermost Cretaceous (Maastrichtian) (Wenz 1940). Three Pacific Slope species are here included in Nerinella. Nerinella parallela (Anderson and Hanna, 1935) 1934 [l]Nerinella sp. Nagao, p. 251, pi. 38, figs 8-10. 1935 Turritella parallela Anderson and Hanna, p. 26, pi. 9, figs 1-3. non 1942 ‘ Turritella sp. cf. T. parallela ’ Anderson and Hanna; Popenoe, p. 179 [= Turritella hearni Merriam, 1941], 1955 Aptyxiella ( Endiatricheus ) parallela (Anderson and Hanna); Allison, p. 426, pi. 43, figs 8-9. 1958 Nerinea parallela (Anderson and Hanna); Anderson, p. 155. Remarks. As indicated by Allison (1955), who collected this species near Punta China from several localities in the Alisitos Formation from both the lower and upper members, the recorded locality information (Burckhardt 1930, p. 259) is misleading, and the species has not subsequently been found in the ‘Catarina’ = Rosario Formation. Although Anderson and Hanna (1935) gave the age as ‘Late Cretaceous’, and the locality as ‘2 miles east of Puerto Catarina’ [= Santa Catarina Landing], Baja California, the species has not been recovered from rocks of Late Cretaceous age nor from outcrops within 2 miles of Santa Catarina Landing. Their material was probably from the Alisitos Formation, which crops out more than 3-2 km (2 miles) north, south, and east of Santa Catarina Landing, Baja California, Mexico, and is of Early Cretaceous, Aptian-Albian age. Allison (1955) considered Nerinea quadrilineata Stanton, 1947, of Aptian to late Albian age, from the Edwards Limestone and Glen Rose Limestone, south-west of Forth Worth, Texas, to be a synonym of A. ( E .) parallela. In overall shape, type of sculpture, and internal structures, N. quadrilineata appears to be a Nerinella, but judging from Stanton’s figures, it differs from N. parallela in having a more concave whorl profile, the spiral ribs weaker, more widely spaced, more finely beaded, and of more nearly equal strength, and a well developed sutural ridge. Nerinella parallela has a straighter whorl profile, coarser sculpture, and a narrower pleural angle than Nerinella maudensis (Whiteaves, 1884). If N. maudensis is of Albian age, then N. parallela is the earliest known Nerinella from the Pacific coast of North America. 478 PALAEONTOLOGY, VOLUME 41 Beaded ribs and a narrow pleural angle make Nerinella parallela more similar to N. santana than to N. maudensis. Nerinella parallela lacks the strong sutural ridge of N. santana and has more, less strongly beaded spiral ribs. Distribution. Baja California, Mexico. Stratigraphical range. Aptian-Albian. Nerinella santana sp. nov. Plate 3, figures 1-6 Derivation of name. The species is named for the Santa Ana Mountains. Holotype. LACMIP 7919. Type locality. LACMIP loc. 8170, Santa Ana Mountains, Orange County, southern California; near latitude 33° 30' N, longitude 117° 30' W. Paratypes. LACMIP 7920-7923, all from the same locality. Diagnosis. A Nerinella with four noded spiral cords bearing ten or eleven nodes; interior with a strong palatal plait and a medial columellar plait. Description. Shell elongate, length in excess of 80 mm at 5 mm diameter, multiwhorled, whorls wider than high (height of whorls about 60 per cent, of diameter), incremental angle of whorl sides extremely small, pleural angle about 5°. Very early whorls nearly flat sided, later whorls concave, with deepest part medially. Protoconch unknown. Aperture unknown. Sculpture of four noded spiral cords, each with ten or eleven nodes : anterior (first) cord forming basal keel of whorl, slightly weaker than second cord ; second cord near anterior quarter line, strongest, bearing largest nodes ; third cord near posterior quarter line, weakest with finest nodes ; fourth cord at suture, tightly appressed to first (basal) cord, commonly slightly stronger than the first cord. Interior with a strong palatal plait near mid whorl, a medial columellar plait, and possibly an anterior columella plait. Columella moderately thick. Dimensions of holotype. Height 43-9 mm, diameter 8-7 mm. Remarks. Although occurrences are rare, specimens are locally abundant, and preservation is good. The specimens are in a single block of sandstone and show preferred orientation (PI. 3, fig. 3). The longest specimen, height 76-9 mm, is incomplete both apically and basally and has a maximum diameter of 5-4 mm. The specimen with the greatest diameter, 10-5 mm, is also broken apically and basally, but its diameter indicates that this very slender species would have exceeded 150 mm in height. The hand specimen containing the new species was collected as float, but the lithology - coarse- grained, very micaceous quartz sandstone - indicates that the stratigraphical horizon is probably a sandstone in the Baker Canyon Member of the Ladd Formation. The sedimentological details of EXPLANATION OF PLATE 3 Figs 1-6. Nerinella santana sp. nov. ; LACMIP loc. 8170; Santa Ana Mountains, California. 1, LACMIP 7919, holotype; abapertural view; x2-4. 2, LACMIP 7920, paratype; x2-2. 3^1, LACMIP 7921, paratype; 3, hand specimen showing preferred orientation of specimens ; x 0-93 ; 4, apical area of specimen shown in upper middle part of figure 3; x 4-8. 5, LACMIP 7922, paratype; interior view; x 4-4; 6, LACMIP 7923, paratype ; interior view ; x 5-7. All specimens, except those in figures 5-6, coated with ammonium chloride. PLATE 3 SAUL and SQUIRES, Nerinella PALAEONTOLOGY, VOLUME 41 this member indicate a fluctuating, moderate to high-energy, lower to upper shoreface palaeoenvironment associated with a fan-delta setting (Cooper et al. 1982). A late Turonian age for the member is indicated by the ammonites Subprionocyclus normalis (Anderson, 1958) and Subprionocyclus cf. neptuni (Geinitz, 1849) (Saul 1982). Associated fossils at the type locality of the new species are an undescribed cerithioidian? gastropod and bivalves, including specimens of ribless small pectinids, Crassatella gamma Popenoe, 1937, and an impression of Alleinacin sulcata (Packard, 1922). This last-named bivalve species is an abundant and characteristic faunal element in the Baker Canyon Member (Popenoe 1937; Squires and Ritterbush 1981). Nerinella santana is much more strongly sculptured than the type species, N. dupiniana. Nerinella santana is similar to Nerinella quadralineata (Stanton, 1947, p. 88, pi. 62, figs 1-2) from north- eastern Texas in the upper part of the Glen Rose Limestone, of early Albian Age (Stephenson et al. 1942). Nerinella santana differs from N. quadralineata in having a wider (5° rather than 3°) pleural angle and fewer spiral cords. Despite its name, N. quadrilineata has five to six cords rather than the four of N. santana. Both species appear to have one fewer cord than is actually present because the first and last cords are tightly appressed, with only the fine line of the suture between them to indicate that what seems to be one cord is actually two cords. The exterior of the new species is similar to that of Nerinea flexuosa Sowerby (1832, pi. 38, fig. 16; Bronn 1836, p. 563, pi. 6, fig. 19; Goldfuss 1844, p. 47, pi. 177, fig. 7; Zekeli 1852, p. 38, pi. 5, fig. 5 ; Tiedt 1958, p. 504, text-fig. 1 1 as Aptyxiella ( Acroptyxis ) flexuosa ) from the Upper Cretaceous of Austria. Internally, the new species differs from N. flexuosa by having much weaker columellar folds. The interior of the new species resembles both Nerinella stantoni Cragin (1905, p. 98, pi. 21, figs 6-9; Shimer and Shrock 1944, p. 495, pi. 203, figs 9-11) from the Upper Jurassic of Texas and Nerinea ( Nerinella^. ) decipiens Stanton (1947, p. 82, pi. 60, figs 1-3) from the Lower Cretaceous of Texas. Like the new species, these two Texas species have a palatal fold on the medial part of the outer wall surface, but the new species differs by having a weak columellar fold. Externally, the new species differs from N. stantoni by having spiral cords that are much stronger, fewer in number (three rather than four), and noded. Externally the new species differs less from Nerinea ( Nerinellal ) decipiens by having noded spiral cords and stronger spiral cords. The interior of the new species resembles Cossmannea imlayi Sohl, 1965 (pp. D23-D24, pi. 4, figs 1-8) from the Middle Jurassic of central and southern Utah. Internally, Cossmannea imlayi has a palatal fold on the medial part of the outer wall surface and a very low, rounded, obscure columellar fold. The palatal fold persists from the earliest whorls, but the columellar fold does not develop until a late growth stage. Externally, the new species differs greatly from C. imlayi by having prominent sculpture rather than smooth whorls with a swollen sutural area. Sohl (1965) placed his species in the genus Cossmannea with some misgivings because his species lacked the strong columellar fold that is diagnostic of Cosmannea. It is possible that Sohl’s species belongs in the genus Nerinella. Nerinella santana has fewer and much more prominent spiral ribs, noded ribs, a weaker palatal plait, a medial columellar plait, and a thinner outer wall than does Nerinella maudensis (Whiteaves). Distribution. All specimens are from a single piece of float consisting of coarse-grained sandstone, probably derived from the Baker Canyon Member of the Ladd Formation, Santa Ana Mountains, Orange County, southern California. Stratigraphical range. Upper Cretaceous (Turonian). Nerinella maudensis (Whiteaves, 1884) 1884 Nerinaea maudensis Whiteaves, p. 214, pi. 27, figs 2, 2a-2d. Remarks. Whiteaves’ description and figures suggest that his placement of this species in Nerinella is correct. Whiteaves (1884) reported Nerinaea maudensis from brittle and very friable shale at the east end of Maude Island, opposite Leading Island in Skidegate Inlet, Queen Charlotte Islands, SAUL AND SQUIRES: CRETACEOUS GASTROPODA 481 western British Columbia. On the geological map of McLearn (1949), this imprecise locality could plot in either the Yakoun Formation or the Haida Formation. Bolton (1965) listed the type specimens as being of Early Cretaceous age and from the Haida Formation. Haggart (1992) considered the Yakoun Formation to be of Mid Jurassic, Bajocian age, and the Haida Formation to range from the Early Cretaceous to the Late Cretaceous (Albian to mid Turonian). Other than Bolton’s (1965) catalogue of the type specimens, we have seen no further report of the occurrence of this species, although Whiteaves (1884) said that it was not uncommon. According to J. W. Haggart (pers. comm.) the ‘brittle and very friable shale’ is probably the Haida Formation, and the species may be of Albian age. Acknowledgements. Lindsey T. Groves (LACMIP) provided access to collections and obtained some hard-to- find literature. Klaus Bandel (Geologisch-Palaontologisches Institut und Museum, Universitat Hamburg) and Heinz Kollmann (Naturhistorischen Museum in Wien) generously shared their knowledge of nerineids with us. James Haggart (Geological Survey of Canada) considerately looked for records that Nerinella maudensis had been collected by Canadian Survey geologists. 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Proceedings of the Malacological Society of London, 24, 97-112. zekeli, l. f. 1852. Die Gastropoden der Gosaugebilde in den nordostlichen Alpen. Kaiserlich-koeniglichen Geologischen Reichsanstalt, Abhandlungen, 1(2), 1-124, pis 1-24. zittel, k. A. 1873. Gastropoden der Stramberger Schichten. Palaeontographica : Beitrage zur Naturgeschichte der Vorwelt. Supplement Band 2, 3, 193-373. L. R. SAUL Natural Elistory Museum of Los Angeles County 900 Exposition Boulevard Los Angeles California 90007, USA Typescript received 18 April 1997 Revised typescript received 28 July 1997 R. L. SQUIRES Department of Geological Sciences California State University, Northridge California 91330-8266, USA APPENDIX Cited fossil localities The localities are listed in groups corresponding to the following (arranged north to south) geographical areas in California : Hornbrook, Cottonwood Creek, Little Cow Creek valley. Bear Creek, Chico Creek, and Santa Ana Mountains. Hornbrook LACMIP 27228. SW 1 /4, SW 1/4 Sec. 33, T47N, R7 [or 6?]N, U.S. Geological Survey, 15-minute, Hornbrook Quadrangle, 1955, Shasta Valley, Siskiyou County, northern California. Collector: M. Gaona, June, 1984. Hornbrook Formation, Osburger Gulch Sandstone Member. Age: Late Cretaceous, Turonian. Cottonwood Creek U.S. Geological Survey, 15-minute Ono Quadrangle, 1952, Shasta County, northern California. Budden Canyon Formation, Ogo Member. Age : Early Cretaceous, Hauterivian. CASG 62606. In stream bottom of the North Fork of Cottonwood Creek, downstream from the Ono Bridge and stratigraphically below the section exposed in first large bluff (north side of creek) downstream from the bridge. Locality is 59-7 m (196 ft) stratigraphically above the mouth of Rector Creek. SAUL AND SQUIRES: CRETACEOUS GASTROPODA 487 CASG 62583. Downstream from the base of section of first bluff described above and 24 m (80 ft) stratigraphically above the base of section exposed in this bluff. Little Cow Creek Valley U.S. Geological Survey, 15-minute, Millville Quadrangle, 1953, Shasta County, northern California. Redding Formation, Bellavista Sandstone Member. Age: Late Cretaceous, Turonian. LACMIP 10761 [= CIT 1439]. Upper part of Bellavista Sandstone Member, north side of Little Cow Creek, near north-east corner SW 1 /4 Sec. 31, T33N, R2W, latitude 40° 40' 22" N, longitude 122° 8' W. Collector: W. P. Popenoe, March 19, 1940. LACMIP 10780 [= CIT 1 193]. Thin conglomerate beds interbedded with massive drab sandstone cropping out on east side of Stinking Creek Valley, estimated as 7-5 m stratigraphically above Triassic-Cretaceous contact, 2353 m (7720 ft) N70° 20' W from south-east corner Sec. 6, T32N, R3W. Collectors: W. P. Popenoe and Ahlroth, June, 21, 1936. LACMIP 10784 [= CIT 1009]. Near base of Bellavista Sandstone member, sandstone cropping out on a small hill on the east bank of Willow Creek about 0-40 km (0-25 mi.) above its confluence with Salt Creek and about 91 m (300 ft) east of the creek channel, NE 1/4, NE 1/4 Sec. 34, T33N, R3W. Collectors: W. P. Popenoe and Scharf, August 11, 1931. LACMIP 24649 [= UCLA 4649]. Gritty sandstone cropping out on east bank of Stinking Creek, 122 m (400 ft) west and 305 m (1000 ft) south of north-east corner Sec. 1, T32N, R4W. Collector: W. P. Popenoe, May 19, 1961. Bear Creek U.S. Geological Survey, 15-minute, Whitmore Quadrangle, 1956, Shasta County, northern California. Redding Formation, Bear Creek Sandstone Member. Age : Late Cretaceous, Coniacian. LACMIP 10905. Massive sandstone in bed of Bear Creek, approximately 305 m (1000 ft) due west of the south- east cor. Sec. 6, T31N, R1E, U.S. Geological Survey, 15-minute, Whitmore Quadrangle, 1956, Shasta County, northern California. Collectors: W. P. Popenoe and W. M. Tovell, September 10, 1941. LACMIP 15758. (P 63-36) Along Ponderosa Way east of Di Hill, descending into Snow Creek, 0-32 km (0-2 mi.) south-east of road fork, 450 m east, 480 m south of north-west corner Sec. 18, T31N, R1E, Whitmore 15' Quadrangle, Shasta Co., northern California. Collector: W. P. Popenoe, August 17, 1936. LACMIP 15761 [= UCMP M7244]. Shell bed in fine-grained sandstone on both banks of Bear Creek, 270 m north, 245 m east of south-west corner Sec. 5, T31N, R1E, Whitmore Quadrangle, Shasta Co., northern California. Collector: Jim Haggart, December 1, 1983. LACMIP 15797. (Continental Oil HS2) Southeast slope Blue Mtn, North Fork Bear Creek, SE 1/4 Sec. 6, T31N, R1E, Whitmore Quadrangle, Shasta Co., California. LACMIP 15944. North side of North Fork Bear Creek, spoil pile of Alberta-Bakersfield pipeline, about on section line and almost at south-east corner Sec. 6, T31N, R1E, Whitmore Quadrangle, Shasta Co., California. Collectors: L. R. Saul, R. B. Saul, and Lanny Fisk, June 23, 1993. Chico Creek U.S. Geological Survey, 15-minute, Paradise Quadrangle, 1953, Butte County, northern California. Chico Formation, Musty Buck Member. Age: Late Cretaceous, Santonian. Collectors: L. R. Saul and R. B. Saul, August, 1952. LACMIP 23621 . Micaceous grey sandstone cropping out in upper part of meadow east of Chico Creek County Road, 625 m (2050 ft) south and 701 m (2300 ft) west of north-east corner Sec. 12, T23N, R2E. Age: early Santonian. LACMIP 23622. Coarse-grained grey sandstone containing black pebbles, about 268 m (880 ft) above west side of Chico Creek, 244 m (800 ft) north, 427 m (1400 ft) east of south-west corner Sec. 1, T23N, R2E. Age: early Santonian. LACMIP 23625. East bank of Chico Creek, 91 m (300 ft) north of right-angle bend in Chico Creek, 610 m (2000 ft) north, 290 m (950 ft) east of south-west corner Sec. 12, T23N, R2E. Age: late Santonian. Santa Ana Mountains U.S. Geological Survey, 15-minute, Santiago Peak Quadrangle, 1954, Orange County, southern California, Ladd Formation, Baker Canyon Member. Age: Late Cretaceous, Turonian. LACMIP 8170 [= CIT loc. 1828]. Creek at road junction, Aliso Creek, Trabuco Oaks, Santa Ana Mountains, Orange County, southern California. Collector: C. R. Stauffer. PALAEONTOLOGY, VOLUME 41 NOTE ADDED IN PROOF Illustrations of heterostrophic protoconchs of two species of nerineids are in kowalke, v. t. and bandel, k. 1996. Systematik and Palaookologie der Kiistenschnecken der nordalpinen Brandenberg-Gosau (Oberconiac/ Untersanton) mit einem Vergleich zur Gastropodenfauna des Maastrichts des Trempbeckens (Siidpyrenaen, Spanien). Mitteilungen der Bayerischen Staatssammlung fur Palaontologie und historische Geologie, 36, 15-71, pis 1-10. REDESCRIPTION OF LEMOINE’S (1939) TYPES OF CORALLINE ALGAL SPECIES FROM ALGERIA by J. aguirre and j. c. braga Abstract. The type material of eight coralline algal species of the 27 established by Lemoine (1939) from the Cretaceous and Cenozoic of Algeria is preserved in Emberger’s Collection at the University of Nantes. This is one of the very few extant collections of the original fossil material of Mme Lemoine, probably the most influential and prolific author of coralline algal palaeontology in this century. The study of this collection highlights the importance of re-documentation of type material of fossil taxa defined decades ago with descriptions and illustrations focused on characters different from those considered diagnostic in modern taxonomy. We redescribe and illustrate the conserved types and revise their taxonomic adscription and nomenclature. Archaeolithothamnium brevium, A. liberum and Lithophyllum Glangeaudi are assigned to Sporolithorr, Mesophyllum Sancti Dionysii and M. curtum are confirmed as belonging to Mesophyllum , and Lithothamnium Betieri to Lithothamnion\ whilst the absence of relevant characters in the M. Ehrmanni and Lithophyllum Sigi types prevents any certain inclusion in the currently accepted coralline genera. These results illustrate the risks of using names of taxa established long ago without reassessing their precise circumscription and the necessity of avoiding the use of taxa with no preserved type material. The taxonomy of fossil coralline red algae is under revision as a consequence of new taxonomic criteria proposed both in the botanical and palaeontological literature (Braga et al. 1993 ; Braga and Aguirre 1995). The original diagnostic characters of many taxa are ambiguous or meaningless according to the modern criteria used for delimiting taxa from the species to family level (Bosence 1983; Braga and Aguirre 1995; Aguirre et al. 1996). Revision of the original collections has to be undertaken to redescribe the type material, pointing to the characters used in modern classifications, and to illustrate as much as possible of the relevant features of the types. However, the type material of many fossil coralline algal taxa is not conserved or cannot be located at present. This is probably the main difficulty in taxonomic studies of fossil coralline algae as the illustrations and original diagnoses for many fossil genera and species are inadequate for assessing their actual circumscription. In addition, interpretations of a particular species by later authors do not always coincide, which renders the selection of a neotype very subjective and arguable. All this makes the analysis of the few preserved original collections very important for coralline algal studies. Modern descriptions and illustrations of the taxa from these type collections should be the preferential basis for taxonomic assignments that must attempt to avoid specific and generic names devoid of precise meaning due to the lack of both adequate original descriptions and any type material to assess their actual nature. Here we present a redescription of the types of eight nongeniculate coralline algal species established by Lemoine (1939) from Algeria, conserved in Emberger’s Collection at the University of Nantes. Lemoine (1939) described 27 new species among the 61 she identified in the algal samples collected by Drs Ehrmann, Dalloni, Welsch, Glangeaud, Laffitte and Flandrin during production of the Geological Map of Algeria (first series). Emberger’s Collection includes material collected by Ehrmann and Laffitte. As far as we know no other types of species established by Lemoine from fossil Algerian samples are preserved or can be located at the moment and none exists in Lemoine's own collection at the Musee Nationale d’Histoire Naturelle de Paris (M. Ardre, pers. comm. 1991). Lemoine (1939) based her description of nongeniculate coralline species on the following attributes: (1) external morphology, (2) thallus dimensions and morphology, (3) size of the [Palaeontology, Vol. 41, Part 3, 1998, pp. 489-507, 3 pls| © The Palaeontological Association 490 PALAEONTOLOGY, VOLUME 41 ‘ hypothallus ’ and ‘ perithallus ’ cells, and (4) conceptacle dimensions. The last character was impossible to apply in some species due to the lack of any reproductive structures. Photographs concentrated on the external appearance of the algal plants and text figures on the cell and conceptacle dimensions. These characters may be irrelevant or ancillary in the modern taxonomy of coralline species. We attempt to describe and illustrate the most relevant features in modern taxonomy of each group to which these species belong, thus completing the information already given by Lemoine (1939). MATERIALS AND METHODS We have examined the specimens and the thin sections from the collections of Ehrmann, Glangeaud and Laffitte from Algeria studied by Lemoine (1939). The samples from the original collections are labelled with Lemoine’s hand script, except for sample 11 (corresponding to A. brevium). The samples and thin sections were subsequently renumbered, probably by Emberger, who cut some additional thin sections. We have also cut 17 thin sections from the original specimens to examine relevant characters in those species where they were not observable in the original thin sections. In the taxonomic descriptions we follow Chamberlain et al. (1988) in orientation and nomenclature of cell and reproductive structure dimensions, and Woelkerling et al. (1993) in growth-form terminology. SYSTEMATIC PALAEONTOLOGY Division rhodophyta Wettstein, 1901 Class rhodophyceae Rabenhorst, 1863 Order corallinales Silva and Johansen, 1986 Family sporolithaceae Verheij, 1993 Genus sporolithon Heydrich, 1897a Type species. Sporolithon ptychoides Heydrich, 1897a, p. 67, pi. 3, figs 15-23; text-figs 2-3. Basionym: Lithothamnium erythraeum Rothpletz, 1893, p. 5. Sporolithon brevium (Lemoine) Aguirre and Braga, comb. nov. Plate 1, figures 1-3 Basionym. Archaeolithothamnium brevium Lemoine (Materiaux pour la Carte Geologique de L’Algerie. lre Serie Paleontologie (1939), p. 43, pi. 1, fig. 4, text-figs 4-5). Type material. Lemoine (1939), when describing the species, referred to several samples from the Turonian of Mansourah, Monts des Aures, Algeria, collected by R. Laffitte. Of these, only two algal nodules (rhodoliths) are preserved, together with a thin section, in Emberger’s Collection at Nantes. Lectotype. Lemoine (1939, p. 43) did not designate a type and the example figured by Lemoine (1939, pi. 1, fig. 4; text-figs 4-5) does not seem to be preserved. According to Articles 9.2 and 9.9 of the ICBN (Greuter 1994) we designate here sample 11 (thin section no. 860) from Emberger’s Collection as the lectotype from the original material. This is a piece (47 x 40 x 40 mm) cut from a fruticose plant with radial organization, which grew on shell fragments. Protuberances, sometimes branched and laterally coalescent, are up to 22 mm long and up to 5 mm wide. The other rhodolith of the type collection, measuring 45 x 42 x 21 mm, has a similar external appearance. Vegetative anatomy. The lectotype plant has a dorsiventral and monomerous thallus organization with a plumose ventral core (PI. 1, fig- 1) of constant thickness (42-72 pm). Cell filaments in the core run parallel to the substrate, and branch to produce new filaments that curve outwards in the peripheral region towards the thallus surface. In the protuberances the filaments become radially arranged (PI. 1, fig. 2). Both in crustose portions of the thallus and in protuberances, new plumose cores arise from the peripheral filaments and facilitate table 1 . Growth form, protuberance, cell and conceptacle dimensions, and other relevant characters in the species studied, n = number of measures ; s.d. = standard deviation. AGUIRRE AND BRAGA: CORALLINE ALGAE 491 (N T* O cO OO ^ T) +1 £ g UO 09 ^ ON (N OO Tt +17 r- m ON OO Oh *3 5 o 13 o r- co co / eeJtLi sj \ ' 0K\ hm\ 1/0°^ 2I Sundre Formation Hamra Formation Burgsvik Formation Eke Formation Hemse Group Klinteberg Formation Mulde Formation Halla Formation Slite Group Tofta Formation Hogklint Formation L + U Visby formations text-fig. 1. For caption see opposite. CHERNS: SILURIAN POLYPLACOPHOR A 547 text-fig. 2. Schematic diagram of intermediate sclerite of Chelodes showing standard measurements and terminology in dorsal (left), ventral (right) and posterior (middle) views. L = length; ML = median length; W = width; AL = apical length; H = height; A = apical angle; J= jugal angle; al = anterolateral and pi = posterolateral portions of lateral margins; cf = central shell field; If = lateral shell field. (‘Project on Silicified Fossils from Gotland’). Chitons occur in samples from only four localities: three from the Wenlock, at Mollbos (Mollbos-1, Grid Reference Rikets nat RN 637645 165970; Liljedahl 1984), Klintebys (Klintebys 1, RN 636515 164685; Laufeld 1974) and Krakfot (Krakfot- 1; RN 638020 167295; Frykman 1989); and one from the Ludlow, at Angvards (Angvards-4, RN 631953 164607). These, and all other localities on Gotland that have yielded chitons, are shown in Text-figure 1. Chelodes in museum collections come from Klinteberget, Gannvik, Bursvik and Rone (but probably not Atlingbo - see discussion of C. gotlandicus). Terminology and measurements (Text-fig. 2). Standard measurements were taken with the dorsal median line mounted horizontally; length, median length, and width were measured in dorsal or lateral view, height in transverse profile, and apical length along the median length. The plates of the chiton shell are referred to here as sclerites rather than valves, since the latter term is more appropriate to organisms with paired shells that enclose soft parts. The total and median lengths differ by the amount of embayment of the anterior margin; the term anterior sinus is not appropriate in these chitons, which lack the sutural laminae of modern forms. Apical and jugal angles were measured in dorsal and posterior views, respectively. Where the posterior apex is rounded through abrasion, the apical angle is taken as the angle between the posterolateral margins. Changing shape of the sclerites through their progressive elongation results in convex posterolateral margins; for larger shells, estimates of apical angles in worn specimens are typically lower than measurements obtained from better preserved specimens. The jugum is the dorsal median ridge or rounded area, and the jugal angle is that formed by the side slope areas (Hoare and Smith 1984). text-fig. 1. Geological map of Gotland showing stratigraphical units and localities yielding chitons (□ with italicized names) from both previous museum (RM) and new silicified collections. 548 PALAEONTOLOGY, VOLUME 41 The term anterolateral margin is used here to describe the posteriorly directed corners and continuation of the anterior margin around to the point where the anterior growth lines cross on to the ventral surface. The posterolateral margin continues from that point to the posterior apex; along this margin, growth lines cross along the entire length. Shell fields are triangular areas of the dorsal surface delimited by a radial ridge or fold from adjacent areas ; if present, there is usually a central field flanked by lateral fields, and the former may include a medial, jugal field. In the systematic descriptions that follow, the measurements and ratios given are means, unless stated otherwise. SYSTEMATIC PALAEONTOLOGY Class polyplacophora de Blainville, 1816 Subclass paleoloricata Bergenhayn, 1955 Order chelodina Bergenhayn, 1943 Family mattheviidae Walcott, 1886 Genus chelodes Davidson and King, 1874 Type species. Chelodes bergmani Davidson and King, 1874, p. 167, pi. 18, figs 14, 14a-d, by original designation, from the Silurian (Wenlock) of Gotland. Revised diagnosis (emended from Runnegar et al. 1979, p. 1388). Wedge-shaped to cordate, arched intermediate sclerites with posterior apex; becoming elongate, massive. Ventral apical area flattened, up to more than half the length, anterior rim elevated slightly above smooth ventral surface. Growth lines across dorsal surface and ventral apical area, sometimes with ridged and granulate dorsal ornament. Shell fields lacking to well-defined. Remarks. Runnegar et al. (1979) incorporated the molluscan class Mattheva Yochelson, 1966 into the Polyplacophora, and the family Chelodidae Bergenhayn, 1943, including Chelodes, into the family Mattheviidae Walcott, 1886. Also included in Mattheviidae were the genera Calceochiton Flower, 1968, Hemithecella Ulrich and Bridge, 1941 and Matthevia Walcott, 1885. Smith and Hoare (1987, p. 7) retained the family Chelodidae to include other paleoloricate taxa not assigned to more narrowly defined families in the order Chelodina, e.g. Eochelodes Marek, 1962. Stinchcomb and Darrough (1995) questioned the polyplacophoran affinities of Cambrian-Ordovician hemithecellids from the Ozark area of the USA and erected a new molluscan order, Hemithecellitina ; they also suggested that some elongate species of Chelodes might be included therein. Mattheviids differ from gotlandochitonids in having sclerites longer than wide (Bergenhayn 1943, 1955; Smith 1960; Smith and Toomey 1964; Runnegar et al. 1979). Further consideration of taxonomy among the EXPLANATION OF PLATE 1 Figs 1-2. Chelodes bergmani Davidson and King, 1874; Klinteberg Formation, upper Wenlock (Homerian), Silurian; Klinteberget, Gotland. 1, holotype, RM Mo6027; intermediate sclerite; a-e, dorsal, ventral, right lateral, posterior and anterior views respectively; x3. 2, RM Mo6028; intermediate sclerite; a-c, dorsal, ventral and anterior views respectively; x 3; d, detail of dorsal surface, showing granular ornament; x 15. Fig. 3. Chelodes cf. bergmani ; RM Mo 160.056; Halla Formation, upper Wenlock (Homerian), Silurian; Klintebys-1, Gotland; intermediate sclerite; a-e, dorsal, ventral, right lateral, posterior and anterior views respectively; x3. Fig. 4. Chelodes gotlandicus Lindstrom, 1884; RM Mo6029; Hamra Formation, upper Ludlow, Silurian; Gannvik, Grotlingbo, Gotland ; intermediate sclerite ; detail of dorsal surface showing granular ornament ; x 15. PLATE 1 CHERNS, Chelodes 550 PALAEONTOLOGY, VOLUME 41 paleoloricates will await description of the remainder of the Gotland chitons. As currently understood, Chelodes is a broadly defined genus of wide morphological variability and with a long stratigraphical range (lower Ordovician-upper Silurian/Lower Devonian) and wide geographical distribution (Sweden, Britain, Czech Republic, North America, Australia). Runnegar et al' s (1979) emended diagnosis for the genus included a deep anterior embayment on body sclerites, and an apical length of one-third to one-half of the sclerite length. However, the type species of Chelodes, C. bergmani Davidson and King, 1874, is characterized by a straight anterior margin. The North American Silurian species C. raaschi (Wenlock-Ludlow; Kluessendorf 1987) has an apical length greater than half the shell length. Chelodes bergmani Davidson and King, 1874 Plate 1, figures 1-2 v*1874 Chelodes bergmani Davidson and King, p. 167, pi. 18, figs 14, 14a-d. v.1884 Chelodes bergmani Davidson and King; Lindstrom, p. 51, pi. 2, figs 1-8, 16-17. 1885 Chelodes bergmani Davidson and King; Fischer, p. 878. 1897 Chelodes bergmani Davidson and King; Etheridge, p. 68. vp.1943 Chelodes bergmanni [sic] Davidson and King; Bergenhayn, p. 298. vp.1955 Chelodes bergmanni [sic] Davidson and King; Bergenhayn, p. 12, pi. 1, figs 3a-b; pi. 2, fig. 2 [reconstruction]. 1960 Chelodes bergmani Davidson and King; Smith, p. 149, fig. 34, 5a [reconstruction], 5b-c [cop. Bergenhayn 1955], 1975 Chelodes bergmani Davidson and King; Van Belle, p. 123, pi. 1, fig. la-b [cop. Bergenhayn 1955], 1977 Chelodes bergmani Davidson and King; Sirenko and Starobogatov, p. 31, figs la-b, 2a [reconstruction; cop. Bergenhayn 1955]. 1987 Chelodes bergmani Davidson and King; Smith and Hoare, p. 15. Material and locality. Two intermediate sclerites (one broken) : RM Mo6027 holotype (by monotypy) and RM Mo6028; Klinteberget, Gotland; Klinteberg Limestone Formation, upper Wenlock (Homerian), Silurian; Inassa/ludensis biozones. Revised diagnosis (emended from Bergenhayn 1955, p. 12). Wedge-shaped, low arched intermediate sclerites with transverse to weakly embayed anterior margin, elongate becoming massive. Ventral apical area nearly half of length, anterior margin rounded, concave, slightly raised. Weak granular ornament, strong, rounded growth lines. Shell fields lacking or weak. Description (with measurements for holotype). Large (length 18-2 mm), wedge-shaped, elongate (length/width ratio 1 -47) and massive intermediate sclerites with low arching. Anterior margin transverse, straight to weakly embayed (median length/length 0-99), rounding strongly into short, straight, slightly divergent anterolateral margins, tapering along long posterolateral margins, more rapidly from around mid-length to blunt posterior apex (apical angle 58°; PI. 1, fig- la). Rounded growth ridges, weak granular ornament patchily preserved (PI. 1, fig. 2d). Shell fields absent, or very weak with narrow, downward-sloping lateral fields (?P1. 1, fig. lc). Apical length/length at least 0-44, with rounded concave anterior margin and growth lines; margin raised slightly above smooth, thickened ventral surface (PI. 1, fig. lb). Longitudinal medial low furrow in anterior part of ventral surface, flanked by thickened lateral shell pads (PI. 1, fig. lb). Longitudinal profile gently convex dorsally, with slight geniculation at around mid-length (PI. 1, fig. lc), side slopes fairly shallow. Transverse profile rounded, lunate, with marked ventral thickening (PI. 1, figs ld-e, 2c); jugal angle 124°, height/length 0-28. Remarks. Davidson and King (1874)’s description was based only on the holotype, supplied by Lindstrom, and was appended to a description of trimerellid brachiopods, although their preferred assignment was to an operculate rugose coral. Lindstrom (1884) subsequently described C. CHERNS: SILURIAN POLYPLACOPHORA 551 bergmani as a chiton (within the Gastropoda), figured both the Klinteberg specimens (Lindstrom 1884, pi. 2, figs 1-8) and noted also one specimen from Grotlingbo (Gannvik; ?Hamra Formation, upper Ludlow). Bergenhayn (1955), also included in the species other, younger specimens, which in his earlier paper (Bergenhayn 1943, p. 298) he noted as coming from Gannviken (= Gannvik; RM Mo6029, Mo6030; Hamra Formation, upper Ludlow), and later (Bergenhayn 1955, p. 12) from Burgsvik (‘Bursvik’, RM Mo6025, Mo6030; upper Burgsvik/ Hamra Formation, upper Ludlow), but he did not identify Lindstrom’s Gannvik specimen. Lindstrom (1884, p. 51) noted ‘traces of punctuate ornamentation ’ on the growth lines, indicated on the figure of the holotype (Lindstrom 1884, pi. 2, fig. 1). That specimen shows coarse sporadic pitting near the anterior, although this is apparently a secondary, solution feature. However, on the other Klinteberg specimen (Mo6028), there is weak, fine granular ornament patchily preserved parallel to growth lines near the anterior (PI. 1, fig. 2d). C. bergmani is characterized by an elongate, wedge-shaped form, almost straight anterior margin with no more than very slight medial embayment, only gentle transverse arching, and an apical length close to half the length. These specific characters are evident only in the holotype and the topotype. From Bergenhayn’s (1943, 1955) younger material, specimen RM Mo6030 was not figured and is now missing, but Mo6029 is assigned to C. gotlandicus (Lindstrom 1884, pi. 2, figs 18-21; PI. 2, fig. 2). RM Mo6025 is very worn, including its anterior edge, but a specific assignment to C. bergmani seems questionable; although growth lines are poorly preserved, they show some anterior embayment (median length/length 0-90), and the apical length/length is 0-39. On museum labels, Bergenhayn identified two further sclerites from Grotlingbo as C. bergmani (RM Mo6033, Mo6034); although both are worn and small, they lack features characteristic of that species. An extended stratigraphical range for the species beyond that of the type locality (i.e. upper Wenlock) through the Ludlow cannot therefore be confirmed. Chelodes cf. bergmani Davidson and King, 1874 Plate 1, figure 3 Material and locality. One silicified intermediate sclerite, RM Mo 160.056; Klintebys, Gotland; Halla Formation, upper Wenlock (Homerian), Silurian. Description. Small (length 11-5 mm), wedge-shaped and elongate (length/width 1-58) intermediate sclerite with blunt posterior apex (apical angle 74°), anterior margin straight, transverse (median length/length 0-98). Rounding strongly into short, straight anterolateral margins that are parallel to weakly divergent, long, gently tapering, posterolateral margins, slightly convex. Ornament of growth lines only. Shell fields lacking. Apical length/length 0-32, with rounded to V-shaped, concave anterior margin; ventral surface smooth, little thickened. Lateral profile straight dorsally, side slopes short, tapering to apex. Jugal angle 100°; transverse profile with jugal ridge flattening anteriorly, becoming rounded; height/length 0-26. Remarks. This specimen is similar to C. bergmani in its wedge-shaped, elongate form, which lacks the anterior embayment of other Gotland Chelodes species, in having a blunt apex, relatively short side slopes, and a fairly long apical area. However, this apical area is shorter than in C. bergmani , the anterolateral margins correspondingly somewhat longer, and the specimen is small and little thickened. A length-width graph (Text-fig. 6) of growth stages in this specimen illustrates the narrow form (length/width 1 -58) compared with C. gotlandicus (length/width 1T6). Other Chelodes specimens from the same locality, all of which are beekitized and poorly preserved, include two broad cordate sclerites, probably Chelodes actinis sp. nov. (described below). The Klintebys- 1 locality is in the Halla Formation (late Wenlock), and thus is similar in age or only slightly older than the Klinteberg Limestone at Klinteberget. PALAEONTOLOGY, VOLUME 41 552 Chelodes gotlandicus Lindstrom, 1884 Plate 1, figure 4; Plate 2; Text-figure 3 vp*1884 Chelodes gotlandicus Lindstrom, p. 51, pi. 2, figs 9-27. 1897 Chelodes gotlandicus Lindstrom; Etheridge, p. 69. vp.1943 Chelodes gotlandicus Lindstrom; Bergenhayn, p. 298. v.1955 Chelodes gotlandicus Lindstrom; Bergenhayn, p. 9, pi. 1, figs 1, 2a-b; pi. 2, fig. 1 [lectotype selected]. v.1955 Chelodes variegatus Bergenhayn, p. 13, pi. 1, fig. 4; pi. 2, fig. 3 [reconstruction], v.1955 Gotlandochiton later odepressus Bergenhayn, p. 17, pi. 1, fig. 8; pi. 2, fig. 5 [reconstruction]. v.1955 Gotlandochiton troedssoni Bergenhayn, p. 19, pi. 1, fig. 9; pi. 2, fig. 7 [reconstruction]. 1960 Gotlandochiton laterodepressus Bergenhayn; Smith, p. 150, fig. 34, 8 [cop. Bergenhayn 1955], 1960 Gotlandochiton troedssoni Bergenhayn; Smith, p. 150, fig. 34, 7 [cop. Bergenhayn 1955], 1975 Gotlandochiton troedssoni Bergenhayn; Van Belle, pi. 1, fig. 7 [cop. Bergenhayn 1955]. 1977 Chelodes gotlandicus Lindstrom; Sirenko and Starobogatov, p. 31. 1977 Chelodes variegatus Bergenhayn; Sirenko and Starobogatov, p. 31. 1977 Gotlandochiton laterodepressus Bergenhayn; Sirenko and Starobogatov, p. 31, fig. 2b [cop. Bergenhayn 1955], 1977 Gotlandochiton troedssoni Bergenhayn; Sirenko and Starobogatov, p. 31. 71987 Morphotype B Kluessendorf, p. 439, pi. 1, fig. 4. 1987 Chelodes gotlandicus Lindstrom; Smith and Hoare, p. 30. 1987 Chelodes variegatus Bergenhayn; Smith and Hoare, p. 58. 1987 Gotlandochiton laterodepressus Bergenhayn; Smith and Hoare, p. 38. 1987 Gotlandochiton troedssoni Bergenhayn; Smith and Hoare, p. 56. Material and locality. Twenty-six intermediate sclerites from Grotlingbo (Gannvik), Burgsvik (Bursvik) and Rone, Gotland; upper Hemse Group-lower Hamra Formation, upper Ludlow, Silurian; lectotype RM Mo5098 from Gannvik, lower Hamra Formation, upper Ludlow. Syntypes RM Mo5099-6001, 6003-6011, 6015-6020, 6025-6026, 6029, 6032-6034, 6036. Diagnosis (emended from Bergenhayn 1955, p. 9). Cordate and arched intermediate sclerites with anterior embayment and blunt posterior apex; dorsal low radial folds defining broad elevated central shell field flanked by narrower lateral fields ; ornament of rounded ridges and grooves, and growth lines, sometimes fine granular ornament; ventral apical area around one-third of sclerite length. Description. Large, heart-shaped and arched, fairly broad intermediate sclerites (lectotype length 19-3 mm; mean length 12-65 mm, s.d. = 3-63 mm, n = 22; length/width 1-16, s.d. = 0-27, n = 19) with marked anterior embayment (median length/length 0-91, s.d. = 0-04, n = 22), rounding anterolaterally into fairly short, convex, divergent to parallel anterolateral margins, then into longer, gently convex posterolateral margins that taper to blunt posterior apex; apical angle 80° (s.d. = 17°, n = 18). Dorsal shell fields; broad, elevated and triangular central field flanked by low radial folds, 0-66 of width (s.d. = 0-1 1, n = 15), narrower and downward sloping lateral fields ; central field with weak low folds elevating a jugal field in RM Mo6029 (PI. 2, fig. 2a-c). Ornament EXPLANATION OF PLATE 2 Figs 1-4. Chelodes gotlandicus Lindstrom, 1884; upper Ludlow, Silurian; Gotland. 1, holotype, RM Mo5098; Hamra Formation; Gannvik, Grotlingbo; intermediate sclerite; a-e, dorsal, ventral, right lateral, posterior and anterior views respectively; x 3. 2, RM Mo6029; intermediate sclerite; Hamra Formation; Gannvik, Grotlingbo; a-d, dorsal, ventral, left lateral and posterior views respectively; x3. 3, RM M06OO6; intermediate sclerite; Hamra Formation; Burgsvik (Bursvik); a-c, dorsal, right lateral and anterior views respectively; x 3. 4, RM M06OIO; intermediate sclerite; ?upper Hemse Group; Rone; a-b, dorsal and left lateral views respectively; x 3. PLATE 2 CHERNS, Chelodes 554 PALAEONTOLOGY, VOLUME 4 text-fig. 3. Chelodes gotlandicus Lindstrom, 1884; upper Ludlow, Silurian; Gotland, a, RM Mo6009; ?upper Hemse Group; Rone; ventral view; x 3. B, RM Mo6020; Hamra Formation; Gannvik, Grotlingbo; left lateral view; x 3. c-F, RM Mo6036; Hamra Formation; Gannvik, Grotlingbo; dorsal, ventral, right lateral and posterior views, respectively; x 5. g-h, RM M06OII; ?Hamra Formation; ?Gannvik, Grotlingbo. G, left lateral view; x 3. H, detail of ornament; x 15. of growth ridges and furrows, and growth lines, mostly better preserved in lateral shell areas (PI. 2, figs lc, 3b, 4b). Fine granular ornament parallel to growth lines well preserved in M06OII (Text-fig. 3g-h), patchily preserved and weak in RM Mo6029 (PI. 1, fig. 4). Apical length/length approximately 0-33 (s.d. = 0-05, n = 5) ; anterior margin rounded and concave to V-shaped, slightly elevated. Ventral surface smooth, thickened, developing shallow medial anterior furrow flanked by lateral shell pads. Lateral profile slightly convex dorsally, convex anterior to anterolateral margin, posterolateral margin less convex, tapering ; side slopes fairly deep to deep. Transverse profile arched, rounded ; jugal angle 84° (s.d. = 17°, n = 19), jugal field flattening anteriorly; height/length 0-44 (s.d. = 0-08, n = 18). Remarks. C. gotlandicus was described by Lindstrom (1884), based on more extensive material than C. bergmani, using a type series of specimens from Grotlingbo (Gannvik), Burgsvik and Rone, and from Visby (Kalens kvarn; Hogklint Formation, lower Wenlock). He noted that both C. bergmani and C. gotlandicus occurred at Grotlingbo (Gannvik), although it is not known which specimens from this locality he assigned to C. bergmani (see above). Bergenhayn (1943, p. 298) selected two of Lindstrom’s specimens as the type (RM Mo5098, Mo5099), and later (Bergenhayn 1955) one of CHERNS: SILURIAN POLYPLACOPHORA 555 them, which represents the lectotype (RM Mo5098; Lindstrom 1884, pi. 2, figs 11-15; Bergenhayn 1955, pi. 1, fig. 1; PI. 2, fig. 1). Compared with C. bergmani, C. gotlandicus has more arched, broader, heart-shaped sclerites with a marked anterior embayment, and C. bergmani has shallow, wedge-shaped sclerites with an almost straight anterior margin, and a longer apical area. Lindstrom (1884, p. 51) noted the variable shape of sclerites in C. gotlandicus , from elongate to broad. He described marked ridges on the dorsal surface coincident with growth lines, and two longitudinal grooves that delimit the central area from narrower lateral shell areas. The latter are features evident only in the better preserved sclerites, e.g. the apical portion of the lectotype, and in RM Mo6029 which shows, in addition, a low jugal, radial fold within the central field (Lindstrom 1884, pi. 2, figs 18-21 ; PI. 2, fig. 2a, c). The fairly evenly spaced, ridged ornament is preserved more commonly on the lateral shell fields, becoming eroded from the arched central field of several specimens. The fine, granular ornament described above, which appears similar to that in C. bergmani (PI. 1, fig- 4 cf. PI. 1, fig. 2d), is rarely preserved and, in more worn specimens, the shell between growth ridges appears smooth. In his revision of Gotland chitons, Bergenhayn (1955) erected the species C. variegatus for two intermediate sclerites from Lindstrom’s type series of C. gotlandicus ; the holotype (RM M06OII ; Lindstrom 1884, pi. 2, figs 9-10; Text-fig. 3g-h) is alleged to come from Atlingbo (Slite Group, Wenlock) and a paratype from Grotlingbo (RM Mo6005 ; Gannvik), but there is some confusion over Atlingbo as the type locality. The locality given in Lindstrom’s (1884, pi. 2, figs 9-10) plate description is Grotlingbo, and Lindstrom’s (1884, pp. 52, 16-17) description and distribution table show that his C. gotlandicus material, including this specimen, came only from Grotlingbo, Burgsvik and Visby. The locality Atlingbo (which is one of Lindstrom’s gastropod localities, in the older, Slite Group) is given on the boxed museum label now with this specimen, but the museum label on the specimen itself shows Grotlingbo subsequently altered to Atlingbo. The preservation of the specimen and matrix lithology are similar to other Grotlingbo (Gannvik) specimens. C. variegatus was distinguished from other Chelodes species by its distinct medial and lateral shell fields, the latter curved down ventrally, and by equally spaced growth ridges, and from C. gotlandicus by the lobe-and-saddle form of the anterior margin and pronounced growth ridges. The holotype is partially embedded in limestone, with only the left side of the dorsal shell exposed, and the ventral surface obscured. The emended diagnosis given here for C. gotlandicus emphasizes the distinction of central (medial) and lateral shell fields, and of pronounced growth ridges as ornament. These features characterize Bergenhayn’s (1955) two C. variegatus specimens, both of which are somewhat compressed laterally but fall within the range of variation of C. gotlandicus. The holotype has fine granular ornament, similar to, but better preserved than that observed on RM Mo6029 (see above). The second specimen of C. variegatus (RM Mo6005) is worn and appears smooth between growth ridges. One or perhaps both specimens of C. variegatus come from the C. gotlandicus type locality at Gannvik, and C. variegatus is regarded here as a junior synonym of C. gotlandicus. Bergenhayn (1955, p. 10, pi. 1, fig. 2a-b; Text fig. 3a) figured and described one specimen (RM Mo6009) as a tail sclerite. Re-examination of the specimen shows that the poorly preserved plate is compressed laterally, distorting the ventral surface, which was the side figured as dorsal. The ventral apical area is evident in Bergenhayn’s (1955) figures. The new silicified collections from Gotland include no additional chiton material from Ludlow localities, and no C. gotlandicus. Lindstrom’s collections are apparently all intermediate sclerites, unless possibly one notably elongate (length/width 1-58 cf. average for species 1T6), arched and narrow sclerite (RM M06OO6; PI. 2, fig. 3), unfortunately embedded in matrix so that the ventral side is obscured, represents a tail plate (see discussion under C. actinis below). Lindstrom’s specimens from Visby (Kalens qvarn = Kolens kvarn) together with several from Grotlingbo (Gannvik), which he had included in C. gotlandicus , were reassigned by Bergenhayn (1955) to the new genus Gotlandochiton. This, with type species G. interplicatus Bergenhayn, 1955, was characterized by intermediate sclerites that are wider than long, with distinct shell fields, and with jugal to complete overlap along the anterior margins between sclerites. Gotlandochiton laterodepressus Bergenhayn, 1955 was based on a single intermediate sclerite from Grotlingbo 556 PALAEONTOLOGY, VOLUME 41 (Gannvik) embedded in limestone matrix with only the left dorsal side exposed (RM Mo6020; Bergenhayn 1955, pi. 1, fig. 8; Text-fig. 3b). The left side of the (broken) sclerite is wider than long, differentiated into a slightly elevated, triangular central field which has a broad anterior margin and tapers to the apex, and narrower lateral area with rounded anterolateral margin, long straight posterolateral margin tapering rapidly to the apex. Growth lines are more accentuated across the lateral area as shallow ridges and furrows. Across the anterior margin, curvature of the growth lines suggests a shallow embayment (cf. Bergenhayn’s (1955, p. 17) description as straight). Bergenhayn (1955) distinguished this species on the basis of the much wider than long form, depressed lateral area and ornament of ridges and furrows. The redescription of C. gotlandicus herein emphasizes as specific features the development of shell fields, and ridged ornament, which is more commonly evident on the less abraded, lateral areas. The holotype of G. laterodepressus, as well as showing these features, appears to have some anterior embayment as found in C. gotlandicus, and it comes from the type locality of the latter (indeed, it was originally one of Lindstrom’s (1884) syntypes for C. gotlandicus ). There is a large variation in length/width in C. gotlandicus, and although the G. laterodepressus specimen is notably short and wide after compression, all other shell features suggest that G. laterodepressus should be regarded as a junior subjective synonym of C. gotlandicus. Gotlandochiton troedssoni Bergenhayn, 1955 was based on two small, worn intermediate sclerites from Grotlingbo (Gannvik; RM Mo6032, Mo6036). Bergenhayn (1955, p. 19) noted also an unnumbered Riksmuseum specimen of a half sclerite from ‘Landspitze von Grotlingbo’, not now identifiable among the collections. Bergenhayn’s (1955) diagnosis was of intermediate sclerites half as long as wide, with anterior and posterior margins obtuse-angled and parallel, distinct medial and lateral shell fields, and complete overlap along the anterior margin between adjacent plates. He noted strong growth ridges parallel to the lateral margins. The two sclerites are wider than long, and there is a medial embayment of the broad anterior margin. The short anterolateral (= lateral) margins are rounded and convex, curving into long, straight, rapidly tapering posterolateral (= posterior) margins transected by growth lines. The posterior apex in both examples is worn; only RM Mo6036 (Text-fig. 3c-f) shows any indication of a ventral apical area, as a poorly defined broad triangular band a minimum of 0-22 of the length of the sclerite. The worn dorsal surface shows a slightly elevated central shell field, flanked by narrower lateral areas on which growth ridges and furrows are better preserved (Text-fig. 3c; Bergenhayn 1955, pi. 1, fig. 9). These dorsal shell features and embayed anterior margin occur in C. gotlandicus, from which the transverse form of these small sclerites is the only notable difference. The apparently rounded, broad shape to the apex can be ascribed to abrasion. The form of C. gotlandicus sclerites is very variable, only reliably becoming longer than wide with age (PI. 2; Text-fig. 6). The type localities of C. gotlandicus and G. troeddsoni are the same, and the latter is considered here to be a junior subjective synonym of the former. From Lindstrom’s (1884) collections, the Visby and Kalens kvarn (Text-fig. 1) specimens are retained within Gotlandochiton. On the assumption that Bergenhayn’s (1955) C. variegatus holotype is from Grotlingbo, not Atlingbo (see above), the stratigraphical range of C. gotlandicus is restricted to the upper Ludlow. EXPLANATION OF PLATE 3 Figs 1-3. Chelodes actinis sp. nov. ; Halla Formation, upper Wenlock (Homerian), Silurian; Mollbos-l, Gotland. 1, holotype, RM Mo 160.004; intermediate sclerite; a-e, dorsal, ventral, right lateral, posterior and anterior views respectively; x 3. 2, RM Mo 159.802; intermediate sclerite; a-e, dorsal, ventral, right lateral, posterior and anterior views respectively; x 3. 3, RM Mol59.858; intermediate sclerite; a-e, dorsal, ventral, right lateral, posterior and anterior views respectively; x 3. PLATE 3 CHERNS, Chelodes 558 PALAEONTOLOGY, VOLUME 41 text-fig. 4. Chelodes actinis, sp. nov. ; Halla Formation; upper Wenlock (Homerian), Silurian; Mollbos-l, Gotland; head sclerites; dorsal, ventral, left lateral, anterior and posterior views respectively; x5. a-e, RM Mol59.818. f-j, RM Mol60.003. Chelodes actinis sp. nov. Plates 3-6; Text-figure 4 Derivation of name. From the Greek aktis, a ray, with reference to the weak dorsal radial folds. Material and locality. One hundred and fourteen (102 used in biometric data) intermediate sclerites, and two head sclerites from Mollbos, Gotland; Halla Formation, upper Wenlock (Homerian), Silurian; Rm Mol59.802-159.824, 159.858-159.864, 159.869-159.873, 159.875, 159.895, 159.902-159.903, 159.905-159.910, 159.918-159.919, 159.922, 159.926-159.935, 159.938-159.941, 159.943, 159.945-159.947, 159.950-159.951, 159.953, 159.957-159.959, 159.961-159.967, 159.970-159.971, 159.975-159.982, 159.985, 159.988-159.995, 160.003-160.008 (160.004 is holotype), 160.012-160.015, 160.018, 160.021-160.024, 160.027, 160.031. Three intermediate sclerites from Klintebys-1, Gotland; Halla Formation, upper Wenlock (Homerian); RM Mol60.042, 160.054-160.055. CHERNS: SILURIAN POLYPLACOPHORA 559 Diagnosis. Cordate and arched intermediate sclerites, shallow anterior embayment, pointed posterior apex; low radial folds giving weak definition of narrow lateral and broad central shell fields, and jugal field; ornament of fine growth lines; ventral apical area about one-third of length. Head sclerites fairly small, ovoid, elongate, weakly arched; transverse anterior margin, posterolateral margins tapering, becoming transverse ; posterior apex slightly elevated ; low dorsal radial folds, slightly elevated central shell field, lateral folds flanked by shallow furrows; ornament of fine growth lines; fairly short, transverse ventral apical area. Description. Intermediate sclerites cordate and arched, highly variable in form, from broader to more elongated (holotype length 17-8 mm; mean length 11-58 mm, s.d. = 5-23 mm, n = 83; length/width 112, s.d. = 0-13, n = 71), anterior margin with shallow embayment (median length/length 0-96, s.d. = 0-03, n = 79). Rounded anterolateral corners, fairly short parallel anterolateral margins, curving into gently convex, long posterolateral margins tapering to pointed posterior apex; apical angle 76° (s.d. = 11°, n = 84). Maximum width anterolateral, well in front of mid-length. Ornament of fine growth lines (PI. 5, fig. 2f); pronounced growth increments on some sclerites show anterior embayment maintained throughout growth, variable elongation relative to broadening of sclerite, although generally becoming longer than wide, whereas smaller sclerites and younger growth stages commonly wider than, or as wide as, long (Pis 3-5; Text-fig. 5). On better preserved sclerites, weak dorsal radial folds from apex indicating fairly narrow lateral and broad central fields, the latter with low medial fold representing rounded jugal field; however, fields poorly defined, sometimes with additional radial folds within fields (e.g. PI. 3, fig. la, lc; PI. 5, figs la, 2a, 2f). Ventral surface concave, flexed gently medially; apical area with slightly raised, concave anterior margin, rounded to broadly flexed medially, apical length/length variable, mean 0-34 (s.d. = 0-08, n = 78; e.g. PI. 3, figs lb, 2b). Marked growth increments record expansion and elongation of apical area (PI. 3, figs lb, 2b; PI. 4, fig. lb; PI. 5, fig. lb). Shallow groove more or less developed beneath apical margin and, in some larger, thickened sclerites, continuing inside the anterolateral and anterior margins (e.g. PI. 3, fig. 2b; PI. 4, figs 2b, 3b). Ventral surface outside apical area smooth, in larger sclerites becoming thickened and sculpted towards anterior into lateral pads outside shallow median longitudinal groove (PI. 4, fig. 3b, d-e). Lateral profile wedge-shaped, side slopes fairly shallow to deep (e.g. PI. 3, figs lc, 2c cf. 3c; PI. 5, fig. lc cf. 2c). Dorsally gently convex to straight, or rarely slightly concave (PI. 5, fig. 2c) ; anterior to anterolateral margin convex, smoothly rounded; posterolateral margin fairly straight, tapering across apical area to apex. Posterior transverse profile arched and rounded dorsally, ventrally more flexed across jugum, side slopes tapering laterally; jugal angle 109° (s.d. = 6°, n = 98); height/length ratio 0-35 (s.d. = 0-04, n = 74). Anterior transverse profile more rounded ; median longitudinal groove and secondary lateral shell pads evident on ventral surface of thickened sclerites (PI. 4, fig. 3e; PI. 3, fig. 2e). Head sclerites (based on two specimens: RM Mol 59. 8 18, 160.003; Text-fig. 4) mean length 10-55 mm, ovoid, elongate (length/width 1-61, s.d. = 0-17, n = 2), weakly arched. Transverse anterior margin rounding into gently convex, longer anterolateral margins, which round into short, tapering posterolateral margins becoming transverse to posterior, slightly elevated apex; apical angle 180°. Low rounded radial folds from apex to anterior and lateral margins, flanked by shallow rounded furrows; low elevated central field (0-37 of width, s.d. = 0-07, n = 2) and less well defined pair of narrower lateral folds. Ornament of fine growth lines, parallel to anterior and anterolateral margins, crossing posterolateral margins. Ventral apical area (preserved only on RM Mol59.818) fairly short, apical length/length 0-22, flattened to slightly concave; transverse anterior margin slightly raised, curving anteriorly close to posterolateral margins. Ventral surface smooth and concave, with shallow and weak radial folds ; median furrow flanked by narrower lateral pair, reflected in low folds of dorsal surface. Lateral profile shallow ; dorsal low ridge straight, shell deepest at posterolateral corners, anterolateral margin tapering slightly anteriorly. Transverse profile flexed across median ridge, jugal angle 1 18° (s.d. = 7°, n = 2) flattening anteriorly; anterior edge showing weak corrugation. Tail sclerite unknown. Remarks. This species differs from both C. bergmani and C. gotlandicus in having an ornament of fine growth lines only. In addition, it differs (Table 1) from C. bergmani in having broader and more arched, heart-shaped sclerites with an anterior embayment and a pointed broader apex, low dorsal radial folds which define weak shell fields, and a shorter ventral apical region. Compared with the cordate species C. gotlandicus, C. actinis shows weaker definition of central and lateral shell fields, oblique, shallower arching, a shallower anterior embayment and pointed apex. C. raaschi Kluessendorf, 1987 from the Wenlock-Ludlow Racine Dolomite of North America has a narrower, more elongate form (Table 1), much longer apical area, and more acute apex than 560 PALAEONTOLOGY, VOLUME 41 C. actinis. C. bohemicus (Barrande, 1867), from the upper Wenlock (basal Homerian, lundgreni Biozone) of Bohemia (Barrande 1867, p. 175, pi. 16, figs 19-28) is a large, weakly cordate species that has well-defined, dorsal, low radial folds delineating narrow lateral fields and a broad elevated central field with a jugal fold, and there is an ornament of fine growth lines together with elongate granules. The relatively large numbers of robust specimens from Mollbus might reasonably be expected to include tail sclerites. Two fairly small specimens with markedly different form from the intermediate sclerites are interpreted as head sclerites (Text-fig. 4); by comparison with other chitons, tail sclerites are commonly more similar in morphology to the intermediate sclerites, although typically with a raised apex, or mucro. For the early Ordovician C. whitehousei, Runnegar et al. (1979, pi. 2, figs 36-38, 54-59) figured triangular to rectangular, arched sclerites of similar size to the intermediate sclerites as representing the tail sclerites. In the late Cambrian Matthevia variabilis, the tail sclerites by comparison with the conical intermediate sclerites are shorter and laterally compressed, and they and the head sclerites each occur in the ratio of 1 : 5 against the intermediate sclerites (Runnegar et al. 1979; see discussion of C. actinis below). Bergenhayn (1960) described, but did not figure, laterally compressed valves with an elevated mucro as tail valves for the early Ordovician C. intermedius, and figured, without description, a broken specimen showing few features which he identified as a tail valve of Chelodes‘1 sp. indet. (Bergenhayn 1960, p. 175, text-fig. 1, figs 17-18). Tail sclerites are not recognized among the other Gotland (Silurian) Chelodes species (see above for discussion of the supposed tail sclerite for C. gotlandicus (RM Mo6009), identified by Bergenhayn 1955). C. gotlandicus sclerites are variable in length and transverse profile, and compared with the broad and fairly gently arched form of the holotype and several other specimens, RM M06OO6 is long, relatively narrow and acutely arched (PI. 2, fig. 3; cf. figs 1-2, 4). Barrande’s (1867) figured specimens of Silurian C. bohemicus from Bohemia are similarly variable in form, including one elongate specimen with a notably more tightly arched and narrow form than the other specimens (Barrande 1867, pi. 16, fig. 23). However, these individual specimens of the two species are within the general range of intraspecific variation, not greatly different from others, and may still represent intermediate sclerites. For C. actinis , there is a similarly wide variation in form and, except where the head sclerites are included, graphical plots of the various shell parameters do not distinguish subgroups of data (e.g. length/width in Text-fig. 5). The lateral dorsal profile of sclerites is commonly slightly convex to straight, rarely slightly concave so that the apex becomes elevated (Pis 3-6, all figs c). One specimen showing the latter characteristic is RM Mo 159. 951, which also has notably deep side slopes and well- defined shell fields including a jugal fold (PI. 5, fig. 2c-d; cf. Pis 3-6, all figs c-d). Within C. gotlandicus , RM Mo6029 (PI. 2, fig. 2) is comparable in most respects, although the apex is not raised. However, again there is insufficient distinction from other specimens to identify any group of particular morphological characteristics as representing tail plates. The new silicified collections include a group of small, broad and triangulate sclerites that lack any anterior embayment, are only shallowly arched and have a short, wide apical area. These sclerites occur as single specimens among collections with C. actinis, which suggests that they could represent the tail sclerites of that species, yet their morphology is considerably different both from the C. actinis intermediate sclerites and from the tail sclerites proposed for other members of the EXPLANATION OF PLATE 4 Figs 1-3. Chelodes actinis sp. nov.; Halla Formation, upper Wenlock (Homerian), Silurian; Mollbos-l, Gotland. 1, RM Mol59.971; intermediate sclerite; a-e, dorsal, ventral, left lateral, posterior and anterior views respectively; x 3. 2, RM Mol59.922; intermediate sclerite; a-e, dorsal, ventral, left lateral, posterior and anterior views respectively; x 3. RM Mo 159.946; intermediate sclerite; a-e, dorsal, ventral, left lateral, posterior and anterior views respectively; x 3. PLATE 4 CHERNS, Chelodes 562 PALAEONTOLOGY, VOLUME 41 20 — text-fig. 5. Length-width graph for intermediate and head sclerites of Chelodes actinis sp. nov. + j+ I I 10 — 5 — □ head sderites + 0 5 10 15 20 25 Length (mm) Mattheviidae (described above). Alternatively, these plates are sufficiently distinct to represent a separate genus. Derivation of name. From Latin spica, ear of grain, to describe the raised granular ornament. Type species. S. pilatis sp. nov. Diagnosis. Cordate, elongate, arched intermediate sclerites with pointed posterior apex, strong, coarse granular dorsal ornament; becoming thickened. Long tapering posterolateral margins; ventral apical area V-shaped, strongly flexed and about one-third of length at midline, tapering outwards along posterolateral margins. Low dorsal radial folds, narrow central and broader lateral shell fields weakly defined. Spicuchelodes pilatis gen. et sp. nov. Plate 7 Derivation of name. From the Latin pilum, javelin, to describe the slender pointed apex. Material and locality. Nineteen mostly fragmental intermediate sclerites; Klinteberg Formation, upper Wenlock (Homerian), Silurian; Krakfot, Gotland. RM Mo 160.062 (holotype)-l 60.079. Diagnosis. As for the genus. Figs 1-3. Chelodes actinis sp. nov.; Halla Formation, upper Wenlock (Homerian), Silurian; Mollbos-l, Gotland. 1, RM Mo 160. 005; intermediate sclerite; a-e, dorsal, ventral, left lateral, posterior and anterior views respectively; x 4. 2, RM Mol59.951 ; intermediate sclerite; a-e, dorsal, ventral, right lateral, posterior and anterior views respectively; x4; f, detail of dorsal surface, showing ornament; x8. 3, RM Mo 159.869; intermediate sclerite; a-e, dorsal, ventral, left lateral, posterior and anterior views respectively; x 5. spicuchelodes gen. nov. EXPLANATION OF PLATE 5 PLATE 5 CHERNS, Chelodes 564 PALAEONTOLOGY, VOLUME 41 Description. Beekitized specimens showing the posterior, apical portions of cordate, thickened intermediate sclerites, some with prominent coarse, spaced granular dorsal ornament arranged along growth lines (PI. 7, figs la, 2a, d). Sclerites low arched, elongate and fairly slender (length/width 1-23, s.d. = 0T3, n = 2), with an embayed anterior margin (median length/length 0-93, s.d. = 0-04, n = 2) and short, rounded anterolateral corners. Posterolateral margins long, fairly straight, tapering slowly to posterior, pointed and acute apex (apical angle 54°, s.d. = 6°, n = 8). Low radial dorsal folds delineating weak shell fields, elevating narrow central field across embayment, lateral fields broader (PI. 7, fig. 2a). Ventral apical area V-shaped, with strong, angular to slightly rounded posterior flexure, apical length/length 0-36 (s.d. = 0-00, n = 2), tapering outwards along posterolateral margins, extending to well beyond midlength (PI. 7, figs lb, 2b, 3b, 4a). Anterior rim slightly elevated above smooth, concave ventral surface, which has median depression corresponding to central field (PI. 7, fig. 3b). Ventral surface becoming thickened, median pad flanked by two shallow furrows extending into groove beneath flexure of apical rim (PI. 7, fig. 4a). Lateral profile shallow, wedge-shaped ; straight dorsally, straight tapering posterolateral margin, embayed anterior margin rounding into short anterolateral margin. Transverse profile only gently arched and rounded, jugal angle 109° (s.d. = 9°, n = 4), height/length 0-30 (s.d. = 0-02, n = 2) (PI. 7, figs lc, 2c, 3d, 4b). Remarks. In spite of the poor preservation and largely fragmented material, the well-developed, coarse granular ornament, and acutely V-shaped apical area that extends anteriorly along long posterolateral margins distinguish S. pilatis from all Chelodes species, and justify the erection of a new genus. The cordate, elongate and thickened shell with a posterior apex, and presence of weak shell fields indicate, however, a close relationship with Chelodes. SILICIFICATION OF GOTLAND CHITONS The large Chelodes sclerites from Mollbos show a pattern of silicification in which the skeletal rims are formed by fine quartz crystals that grow inward normal to the surface (e.g. Schmitt and Boyd 1981, pattern 1). Crystal size increases inwards, and fibrous and drusy megaquartz fill the cavity where opposing layers meet. Where incompletely filled, the jagged margin of the inner edge results from growth of individual quartz crystals. Any original internal shell structure is lost, although surface details are well preserved. The original skeletal aragonite may have been replaced earlier by a fill of sparry calcite either after dissolution or by calcitization. In specimens from Klintebys, the shell is preserved in a coarser quartz mosaic, beekitized, with consequently poor preservation of detail. Replacement by quartz growing into a mould formed in coarser or less well cemented sediment could explain this, although reworking before or after replacement might also affect preservation. The S. pilatis specimens from Krakfot are patchily beekitized, with loss of surface detail (Schmitt and Boyd 1981, pattern 4). However, some specimens still preserve a distinctive dorsal ornament, and the grain size of the surface quartz except for the beekite discs is much finer than the internal shell fill, as at Mollbos. The material is fragmented, and it is apparent from the fine-grained entire surfaces forming many of the broken edges of sclerites that fragmentation preceded silicification. All the chiton material appears to have been silicified after formation of dissolution cavities, i.e. EXPLANATION OF PLATE 6 Figs 1-5. Chelodes actinis sp. nov. ; Halla Formation, upper Wenlock (Homerian), Silurian; Mollbos-l, Gotland ; five intermediate sclerites from one sample, interpreted as belonging to the same individual ; a-d, dorsal, ventral, left lateral and posterior views respectively; x 3. 1, RM Mol59.926. 2, RM M0159.928. 3, RM Mol59.927. 4, RM Mol59.929. 5, RM Mol59.930. PLATE 6 CHERNS, Chelodes 566 PALAEONTOLOGY, VOLUME 41 by delayed replacement. The specimens maintain thickness, which suggests that replacement preceded significant compaction. Higher silica concentrations would have favoured rapid precipitation of chalcedony and fine quartz, whereas the coarser internal fabric in shells indicates slower precipitation and lower silica concentrations. The good preservation of surface detail in specimens from Mollbos, particularly for originally aragonitic shells, suggests early cementation of the micritic carbonate sediment. GROWTH IN C. ACTINIS AND OTHER CHELODES SPP. C. actinis has a heart-shaped outline that in small specimens is as wide or wider than long, but with increasing size becomes more elongate. The length-width relationship, shown in Text-figure 5, is significantly non-linear (using correlation coefficient). Similar relationships are shown for median length-width measured in individual sclerites of C. gotlandicus and C. cf. bergmani (Text-fig. 6). Stepped growth increments, resulting from variable rates of growth, illustrate the changing proportions of lateral to anterior extension (Pis 3-6). Length and height of sclerites also have a significantly non-linear relationship. Apical length and length are less significant: many larger, elongate specimens have relatively long apical areas (e.g. PI. 3, fig. 2b), although there is wide variation (cf. PI. 3, fig. lb). Growth lines across the apical area, including marked growth increments which can be matched to those on the dorsal surface, record the increasing length. By contrast, the degree of embayment of the anterior margin (i.e. median length/length ratio) remains consistent throughout the population, and on individual sclerites (as recorded by growth lines). Growth style is demonstrated here for the large population of C. actinis, using a range of shell parameters. For the smaller population of C. gotlandicus, where length, width and height are the only parameters yielding sufficient data, length and width have a significantly nonlinear relationship, but length and height do not produce a significant correlation coefficient. The comparable graphs for individual sclerites of C. gotlandicus and C. cf. bergmani (Text-fig. 6) suggest that similar growth style also characterizes C. bergmani. The apical area, adjacent to the apex on the ventral surface, represents an extension of the dorsal shell (tegmentum) and, in at least most chitons, is found in all sclerites except the tail (Smith and Toomey 1964). It typically has a raised rim above the smooth ventral surface (hypostracum), which becomes thickened generally as well as more locally, particularly anteriorly. Growth of the shell is thus mixoperipheral, the growth lines continuing from the dorsal shell across the lateral margins onto the ventral apical area, and involving anterior growth away from the apex on both dorsal and ventral surfaces. The isolated silicified sclerites of C. actinis demonstrate that successive major growth increments involved secretion of a new marginal band around the flattened cone form of the shell. Each new marginal increment protrudes beyond the existing shell, and also enlarges the apical area. In the more massive, calcite preservation of C. gotlandicus and C. bergmani, these details of growth are less clear, although both smaller and larger growth increments are evident (e.g. PI. 1, fig. 2a; PI. 2, fig. 4a). The growth bands indicate variable rates of shell secretion, with fine-, medium- and large-scale cycles representing different periodicities. The Gotland Silurian chitons represent low latitude assemblages, so that marked fluctuations in growth due to climate may be less probable than through periodic spawning, as in living molluscs (e.g. Pannella and MacClintock 1968). Living chitons attain sexual maturity after one to a few years, and then spawn annually. They reach mature size at or after sexual maturity. Typically the Gotland Silurian chitons show two to five marked steps in growth, decreasing in spacing and extent after two or three, which therefore are probably annual increments. Smaller growth bands, represented by fine growth lines and subtle colour banding produced by their periodic crowding (e.g. PI. 5, fig. 2a, f ), might represent daily and lunar cyclicity. CHERNS: SILURIAN POLYPLACOPHORA 567 table 1 . Comparative biometric data for intermediate sclerites of Silurian Chelodes spp. Chelodes sp. (no. of intermediate sclerites in data) Length/ width Median length/length Apical length/length Height/length Apical angle Jugal angle C. actinis (101) 112 0-96 0-34 0-35 76° 109° C. bergmani (1 or 2) 1-47 0-99 0-44 0-28 58° 129° C. cf. bergmani (1) 1-58 0-98 0-32 0-26 74° 100° C. gotlandicus (26) 116 0-91 0-33 0-44 80° 84° C. raaschi (holotype only) 2-0 0-60 40° SCLERITE VARIATION WITHIN ONE INDIVIDUAL OF CHELODES ACTINIS Five intermediate sclerites (RM Mo 159.926-1 59.930) in one sample from Mollbos, showing a similar, distinctive growth increment on both dorsal and ventral surfaces, may have belonged to the same individual (PI. 6, figs 1-5 ; Table 2). All also show weak colour-banding on a more minor scale, and fine growth lines. These sclerites vary in size by at least 10 per cent, (means and s.d. of length, width, height and apical length), but ratios of shell parameters (length/width, apical length/length, height/length) are more consistent. The mean apical and jugal (PI. 6, all figs d) angles also show low variation. Weak dorsal shell fields (broad central and narrow lateral fields) are more evident on three sclerites (PI. 6, figs 1-3), and the lateral dorsal profile varies from weakly convex to straight or weakly concave (PI. 6, figs lc, 3c, 4c). On the heart-shaped ventral surface, where all plates have a distinct anterior and anterolateral rim around the more thickened central area, two of the sclerites show a longitudinal median furrow between thickened pads (PI. 6, figs 4b, 5b), on the latter (PI. 6, fig. 5b) with an additional median pad flanked by two furrows extending into the shallow groove beneath the apical area (cf. PI. 4, fig. 3b). The total complement of sclerites in this animal is a minimum of seven, at least five intermediate plus head and tail plates. Recent chitons have eight plates, six intermediate that vary in size along the body but are similar in form, and a head and tail plate that, morphologically, may differ considerably from the intermediate plates and from each other (e.g. Text-fig. 7). Fossil chitons belonging to the extinct order Paleoloricata (Upper Cambrian-Upper Cretaceous) differ from the Neoloricata (Carboniferous-Recent) in the lack of sutural plates formed from a middle shell layer, the articulamentum. Articulated fossil specimens are rare but, where known, those from both orders had eight plates (e.g. Hoare and Mapes 1989; Rolfe 1981). Rolfe (1981) identified a very small, eighth sclerite in the upper Ordovician Septemchiton grayiae (Woodward, 1885), previously thought to have only seven sclerites {= S. vermiformis Bergenhayn, 1955; Rolfe, 1981), and upon which the paleoloricate suborder Septemchitonina Bergenhayn, 1955 was founded. Hyman (1967, p. 121) had noted that seven sclerites appear in the late trochophore stage of chiton ontogeny, the eighth developing later, and thus pointed to Septemchiton as representing an early phylogenetic state. Among population of isolated sclerites, Runnegar et al. (1979) estimated the sclerite complement in upper Cambrian M. vafiabilis as seven (1:5:1), and accepted this as the total, based on comparison with a seven-plated Septemchiton. They followed Hyman (1967) in suggesting that the late ontogenetic acquisition of the eighth, tail plate observed in some living chitons (Okuda 1947) might have phylogenetic significance, although their data point to one fewer intermediate plates rather than lack of a tail plate. The population of isolated head and intermediate sclerites of C. actinis does not yield further information on the sclerite complement, but in one sample (PI. 6) at least five intermediate sclerites may have belonged to the same animal. The order of these plates along the body remains unclear; on Plate 6, they have been arranged according to development of shell fields and degree of sculpting of the ventral surface. The largest sclerites in Recent Chiton are typically around the third to fifth. 568 PALAEONTOLOGY, VOLUME 41 with size diminishing to front and rear (Text-fig. 7). However, in the measured Recent specimen, the shell parameters do not vary altogether consistently (Table 3). Rolfe (1981) measured length of sclerites in articulated specimens of S. grayiae, and noted a marked increase through sclerites 1 to 4, then fairly similar lengths for sclerites 4 to 8 with 6 being the longest. Variation between individuals and taxa preclude any one shell dimension being taken to specify sclerite position among isolated specimens. MUSCULATURE IN CHELODES ACTINIS AND SPICUCHELODES PILATIS In living chitons, the musculature is complex, repeated on each intermediate sclerite, and modified on the head and tail sclerites (e.g. Hyman 1967). Multiple muscles, attached to the edges, insertion and sutural plates, hold the sclerites and can draw them closer together. Two groups of muscles run from the anterior edge down into the body-wall beneath the sclerite in front, one group cushioning the overlap of sclerites between the sutural plates and ventral posterior margin in front, and one group running marginally between sclerites from the sutural plates on to the lateral edge of the sclerite in front. From the ventral surface, which lacks evident muscle insertion sites, muscles pass into the mantle and foot. The mantle commonly embeds and partly covers the sclerites. In paleoloricate chitons, which lack an articulamentum with sutural plates, there is limited evidence of the musculature. Runnegar et al. (1979) interpreted deep ventral pits in late Cambrian Matthevia as housing dorsoventral muscles from shell to foot, but doubted whether adjacent plates were connected. They suggested an evolutionary progression in shell form from the tall conical plates of M. variabilis towards flattening in early Ordovician C. whitehousei. Associated with this, the ventral muscle attachment sites evolved from M. variabilis with a deep anterior and posterior cavity per plate, through M. walcotti which has a single, posterior cavity, to early Ordovician Hemithecella and only some C. whitehousei in which the posterior cavity is much reduced. Other Chelodes, including the species from the Gotland Silurian, lack any ventral muscle pit. In C. actinis, although the relative length of the apical area varies between sclerites, the shape of the smooth ventral surface anterior to it remains fairly similar, cordate anteriorly, convex laterally and tapering to a rounded posterior. On the sclerites which show more sculpted thickening, the ventral surface shows a longitudinal median depression or furrow between two thickened pads anteriorly, and a narrow median pad flanked by two shallow longitudinal furrows beneath the raised rim of the apical area (PI. 4, fig. 3b, d-e; PI. 6, fig. 5b; also, for S. pilatis, PI. 7, fig. 4a). A distinct marginal rim around the ventral surface, outside the more general thickening, continues from the slight groove beneath the apical rim (e.g. PI. 3, fig. 2b). The depressed areas of the sculpted ventral surface, and its rim, may have housed muscles for attachment to the body-wall and to adjacent sclerites. The pattern of localized thickening of sclerites may have accommodated paired muscles extending beneath the apical rim, median longitudinal and anterior muscles (e.g. PI. 4, fig. 3b). The pattern beneath the apical rim differs from the deep to shallow median cavity below the apical area described above from late Cambrian and early Ordovician hemithecellids, Matthevia spp., and C. whitehousei (Runnegar et al. 1979; Stinchcomb and Darrough 1995). In most Recent neoloricate species, the apical area is much reduced compared with that of Palaeozoic paleoloricates such as Chelodes , where it occupies up to half or more of the sclerite length. Furthermore, its length and width represent the extent of overlap of successive sclerites in EXPLANATION OF PLATE 7 Figs 1-4. Spicuchelodes pilatis gen. et sp. nov. ; Klinteberg Formation, upper Wenlock (Homerian), Silurian; Krakfot-1, Gotland; intermediate sclerites. 1, RM Mo 160. 063; a-c, dorsal, ventral and posterior views respectively; x 5. 2, RM Mol60.062, holotype; a-c, dorsal, ventral and posterior views respectively; x 5; d, detail of dorsal surface showing ornament; x 10. 3, RM Mol60.074; a-d, dorsal, ventral, right lateral and posterior views respectively; x 5. 4, RM Mol60.075; a-b, ventral and posterior views respectively; x 5. PLATE 7 CHERNS, Spicuchelodes 570 PALAEONTOLOGY, VOLUME 41 table 2. Biometric data for five intermediate sclerites of Chelodes actinis sp. nov. interpreted as belonging to the same individual, RM Mol59.926-159.930, Mollbos-l (PI. 6). *broken. Dimension PI. 6 RM Mo 159.926 fig. 1 RM Mo 159.928 fig. 2 RM Mo 159.927 fig. 3 RM Mo 159.929 fig. 4 RM Mo 159.930 fig. 5 Mean s.d. n Length (mm) 12-2 12-4 131 12-3 11-8 12-36 0-47 5 Width (mm) 12-4 11-5 111* 11-2 1 1-3 11-6 0-55 4 Length/width 0-98 1-08 M0 104 1-05 0-05 4 Apical length (mm) 3-3 4-2 4.4 3-8 2-5 3-64 0-76 5 Apical length/length 0-27 0-34 0-34 0-31 0-21 0-29 005 5 Height (mm) 4-6 3-8 4.4 4-6 4-2 4-22 0-38 5 Height/length 0-38 0-31 0-30 0-37 0-36 0-34 0-04 5 Apical angle (°) 92 92 92 89 93 91-6 1-52 5 Jugal angle (°) 109 117 107 113 116 1 12-4 4-34 5 + O H++ .<>oo text-fig. 6. Median length-width graphs for in- dividual intermediate sclerites of Chelodes gotlandicus (RM Mo6029 and Mo6015) and C. cf. bergmani (RM Mol60.056). + / - aa + C. gotlandicus (RM Mo6029) 0 C. gotlandicus (RM M06OI 5) A C. cf. bergmani (RM Mo 160.056) “ ' 1 T r 8 12 Median length (mm) text-fig. 7. Recent Chiton sp. from the Red Sea; x 1. a, dorsal view of articulated specimen, head sclerite slightly askew in preservation, plates set into spiculate muscular body wall, b, isolated head, intermediate and tail sclerites, note sutural plates for articulation on intermediate and tail sclerites. CHERNS: SILURIAN POLYPLACOPHORA 571 table 3. Biometric data for individual sclerites of Recent Chiton sp. from the Red Sea. Sclerite Length (mm) Width (mm) Height (mm) Apical length (mm) Apical angle (°) Jugal angle (°) Head 7-3 14-9 5-4 2 11-7 17-6 6-8 3-5 115 110 3 9-6 211 7-0 3-6 120 112 4 10-7 21-2 7-5 4-0 121 114 5 8-5 20-2 6-9 2-5 151 117 6 7-5 19-8 60 2-2 125 118 7 7-4 18-5 4-9 2-0 168 126 Tail 6-4 14-7 4-3 — Mean 2-7 9-23 19-73 6-67 2-97 133-33 116-17 s.d. 2-7 1-75 1-44 0-90 0-84 21-21 5-67 life, indicating the degree of imbrication of the commonly massive Chelodes sclerites. It seems unlikely that overlapping plates would not have been connected by muscles, by contrast to Matthevia where convex posterior faces to the conical sclerites indicate a lack of contact (Runnegar et al. 1979). In Chelodes, the close proximity of the apical rim to the anterior edge of the partly covered next sclerite, each with sculpted muscle attachment sites, makes muscular attachment between the sclerites probable. The degree of flexibility of the body was limited by the weight and size of the plates, as well as their musculature. The large, massive plates of Chelodes provided effective armour, but also restricted movement. The facies relationships and distribution of Gotland Silurian chitons indicate life habits and ecology comparable to Recent assemblages (Cherns 1996). Living chitons are mostly sluggish, intertidal animals, creeping across rocky surfaces to feed, and relying on the plated shell and strength of adhesion against the substrate for protection. Acknowledgements. I thank Dr L. Jeppsson (Lund University) for providing the silicified collections of Gotland chitons, and for his kind hospitality, Professor M. G. Bassett (National Museum and Gallery of Wales, Cardiff) for discussion and critical review of the manuscript, and for providing darkroom facilities at NMW, Professor R. D. Hoare (Bowling Green State University, Ohio) for critical review of the manuscript, and Mrs G. Evans (NMW) for drafting Text-figure 2. 1 am grateful to the Palaeozoology Section, Naturhistoriska Riksmuseum, Stockholm for loan of museum specimens. REFERENCES barrande, J. 1867. Systeme Silurien du Centre de la Boheme. Premiere partie: recherches paleontologiques, 3, Classe des Mollusques. Order des Pteropodes. Published by the author, Prague and Paris, xv+179 pp., pis 1-16. bergenhayn, j. r. m. 1943. Preliminary notes on fossil Polyplacophoras from Sweden. Geologiska Fbreningens i Stockholms Forhandlingar , 65, 297-303. — 1955. 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Some molluscan Problematica from the Upper Cambrian-Lower Ordovician of the Ozark Uplift. Journal of Paleontology, 69, 52—65. ulrich, e. o. and bridge, j. 1941. Hemithecella expansa. In butts, c. Geology of the Appalachian Valley in Virginia, Pt. 2. Bulletin of the Virginia Geological Survey, 52, 19-20, pi. 68. van belle, r. a. 1975. Sur la classification des Polyplacophora: 1. Introduction et classification des Paleoloricata, avec la description de Kindbladochiton nom. nov. (pour Eochiton Smith, 1964). Informations de la Societe Beige de Malacologie, Serie 4, 5, 121-131, pi. 1. CHERNS: SILURIAN POLYPLACOPHORA 573 walcott, c. D., 1885. Notes on some Paleozoic pteropods. American Journal of Science, 30, 17-21. — 1886. Studies on the Cambrian faunas of North America. Bulletin of the United States Geological Survey, 30, 223-225, pis 32-33. woodward, h. 1885. On a new species of Helminthochiton from the Upper Bala (Silurian) of Girvan, Ayrshire. Geological Magazine, 22, 352-358, pi. 9. yochelson, E. L. 1966. Mattheva, a proposed new class of mollusks. Professional Paper of the United States Geological Survey, 523-B, B 1-9, pi. 1. LESLEY CHERNS Typescript received 15 January 1997 Revised typescript received 23 June 1997 Department of Earth Sciences University of Wales, Cardiff Box 914, Cardiff CF1 3 YE, UK NOTES FOR AUTHORS The journal Palaeontology is devoted to the publication of papers on all aspects of palaeontology. Review articles are particularly welcome, and short papers can often be published rapidly. A high standard of illustration is a feature of the journal. Four parts are published each year and are sent free to all members of the Association. Typescripts should conform in style to those already published in this journal, and should be sent (with a disk, if possible) to the Secretary of the Publications Committee, Dr R. 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Non-members may obtain Nos 39-58 (excluding 44) at cover price from Blackwell Publishers Journals, P.O. Box 805, 108 Cowley Road, Oxford OX4 1FH, UK, and older issues from the Marketing Manager. For all orders of Special Papers through the Marketing Manager, please add £1-50 (U.S. $3) per item for postage and packing. PALAEONTOLOGICAL ASSOCIATION PUBLICATIONS Special Papers in Palaeontology For full catalogue and price list, send a self-addressed, stamped A4 envelope to the Marketing Manager. Numbers 2-47, excluding 44, are still in print and are available together with those listed below : 48. (for 1992): Contributions to acritarch and chitinozoan research. Edited by s. G. molyneux and k. j. dorning. 139 pp., 28 text-figs, 22 plates. Price £40 (U.S. $80). 49. (for 1993): Studies in palaeobotany and palynology in honour of Professor W. G. Chaloner, F.R.S. Edited by M. E. collinson and a. c. scott. 187 pp., 38 text-figs, 27 plates. Price £50 (U.S. $100). 50. 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Price £45 (U.S. $90). 56. (for 1996): Fossil and Recent eggshell in amniotic vertebrates: fine structure, comparative morphology and classification, by k. e. mikhailov. 80 pp., 21 text-figs, 15 plates. Price £35 (U.S. $70). 57. (for 1997) : Cambrian bradoriid and phosphatocopied arthropods of North America, by david j. siveter and m. williams. 69 pp., 8 text-figs, 9 plates. Price £30 (U.S. $60). 58. (for 1997) : Himalayan Cambrian trilobites, by p. a. jell and n. c. hughes. 113 pp., 10 text-figs, 32 plates. Price £40 (U.S. $80). Field Guides to Fossils These are available only from the Marketing Manager. Please add £100 (U.S. $2) per book for postage and packing plus £1-50 (U.S. $3) for airmail. Payments should be in Sterling or in U.S. dollars, with all exchange charges prepaid. Cheques should be made payable to the Palaeontological Association. 1. (1983): Fossil Plants of the London Clay, by m. e. collinson. 121 pp., 242 text-figs. Price £7-95 (U.S. $16) (Members £6 or U.S. $12). 2. (1987): Fossils of the Chalk, compiled by e. owen; edited by a. b. smith. 306 pp., 59 plates. Price £11-50 (U.S. $23) (Members £9-90 or U.S. $20). 3. (1988): Zechstein Reef fossils and their palaeoecology, by n. hollingworth and t. pettigrew. iv+75 pp. Price £4-95 (U.S. $10) (Members £3-75 or U.S. $7-50). 4. (1991): Fossils of the Oxford Clay, edited by D. M. martill and J. d. Hudson. 286 pp., 44 plates. Price £15 (U.S. $30) (Members £12 or U.S. $24). 5. (1993): Fossils of the Santana and Crato Formations, Brazil, by d. m. martill. 159 pp., 24 plates. Price £10 (U.S. $20) (Members £7.50 or U.S. $15). 6. (1994): Plant fossils of the British Coal Measures, by c. j. cleal and b. a. thomas. 222 pp., 29 plates. Price £12 (U.S. $24) (Members £9 or U.S. $ 1 8). 7. (1996): Fossils of the upper Ordovician, edited by d. a. t. harper and a. w. owen. 312 pp., 52 plates. Price £16 (U.S. $32) (Members £12 or U.S. $24). © The Palaeontological Association, 1998 Palaeontology VOLUME 41 • PART 3 CONTENTS Further observations on the Upper Carboniferous pterid©ip&ft frond Macroneuropteris macrophylla ■ ' . W C. J. CLEAL, J.-P. LAVEINE and C. H. SHUTlfU V Late Triassic ecosystems of the Molteno/Lower Elliot biome of southern Africa , ; JOHN M. ANDERSON, HEIDI M. ANDERSON and ARTHUR R. I. CRUICKSHANK Predation on graptoloids: new evidence from the Silurian of Wales DAVID K. LOYDELL, JAN ZALASIEWICZ and RICHARD CAVE Early Ordovician trilobites from Dali, west Yunnan, China, and their palaeogeographical significance ZHOU ZHIYI, WILLIAM T. DEAN and LUO HUILIN New Cretaceous Gastr California L. R. S AUL and R. L. Redescription of Lemo’ from Algeria 39) types of coralline algal species j. Aguirre and j. c. bra'ga The applicdtibns of stromatoporoid palaeobiology in palaeoepvi ronmental analysis STEPHEN KERSHAW Chelodes and closely related Polyplacophora (Mollusca) from the Silurian of Gotland, Sweden LESLEY CHERNS 383 387 423 429 461 489 509 545 Printed in Great Britain at the University Press, Cambridge ISSN 0031-0239 HECKMAN Jil BINDERY INC. |SI JULY 99 Bound -To-Pte? ^-MANCHESTER,