JUNE 1982 ISSN 0303-2515 CAPE TOWN INSTRUCTIONS TO AUTHORS 1. MATERIAL should be original and not published elsewhere, in whole or in part. 2. LAYOUT should be as follows: (a) Centred masthead to consist of Title: informative but concise, without abbreviations and not including the names of new genera or species Author’s(s’) name(s) . Address(es) of author(s) (institution where work was carried out) Number of illustrations (figures, enumerated maps and tables, in this order) (b) Abstract of not more than 200 words, intelligible to the reader without reference to the text (c) Table of contents giving hierarchy of headings and subheadings (d) Introduction j : ; (e) Subject-matter of the paper, divided into sections to correspond with those given in table of contents (f) Summary, if paper is lengthy (g) Acknowledgements (h) References (i) Abbreviations, where these are numerous 3. 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For books give title in italics, edition, volume number, place of publication, publisher. For journal article give title of article, title of journal in italics (abbreviated according to the World list o, Scientific periodicals. 4th ed. London: Butterworths, 1963), series in parentheses, volume number, part number (only if independently paged) in parentheses, pagination (first and last pages of article). Examples (note capitalization and punctuation) BULLOUGH, W. S. 1960. Practical invertebrate anatomy. 2nd ed. London: Macmillan. FISCHER, P.—H. 1948. Données sur la résistance et de le vitalité des mollusques. J. Conch., Paris 88: 100-140. FiscHER, P.-H., DuvaL, M. & Rarry, A. 1933. Etudes sur les échanges respiratoires des littorines. Archs Zool. exp. gén. 74: 627-634. Koun, A. J. 1960a. Ecological notes on Conus (Mollusca: Gastropoda) in the Trincomalee region of Ceylon. Ann. Mag. nat. Hist. (13) 2: 309-320. Konan, A. J. 196056. Spawning behaviour, egg masses and larval development in Conus from the Indian Ocean. Bull. Bingham oceanogr. Coll. 17 (4): 1-51. THEELE, J. 1910. Mollusca: B. Polyplacophora, Gastropoda marina, Bivalvia. In: SCHULTZE, L. Zoologische und anthropologische Ergebnisse einer Forschungsreise im westlichen und zentralen Suid-Afrika 4: 269-270. Jena: Fischer. Denkschr. med.-naturw. Ges. Jena 16: 269-270. (continued inside back cover) ANNALS OF THE SOUTH AFRICAN MUSEUM ANNALE VAN DIE SUID-AFRIKAANSE MUSEUM Volume 89 Band June 1982 Junie Part 5 Deel LOWER CRETACEOUS (MIDDLE ALBIAN) AMMONITES FROM DOMBE GRANDE, ANGOLA By MICHAEL R. COOPER Cape Town Kaapstad The ANNALS OF THE SOUTH AFRICAN MUSEUM are issued in parts at irregular intervals as material becomes available Obtainable from the South African Museum, P.O. Box 61, Cape Town 8000 Die ANNALE VAN DIE SUID-AFRIKAANSE MUSEUM word uitgegee in dele op ongereelde tye na gelang van die beskikbaarheid van stof Verkrygbaar van die Suid-Afrikaanse Museum, Posbus 61, Kaapstad 8000 OUT OF PRINT/UIT DRUK 1p 2(0=3)) 528), 3 (1225425. Sh b= pri) S(L=Se Se 129) 6(1, t.-p.i.), 711-4), 8, 9(1-2, 7), 10(1-3), 11(1-2, 5, 7, t—p.i.), 15(4-5), 24(2), 27, 31(1-3), 32(5), 33, 36(2), 45(1) EDITOR/REDAKTRISE Ione Rudner Copyright enquiries to the South African Museum Kopieregnavrae aan die Suid-Afrikaanse Museum ISBN 0 86813 036 2 Printed in South Africa by In Suid-Afrika gedruk deur The Rustica Press, Pty., Ltd., Die Rustica-pers, Edms., Bpk., Court Road, Wynberg, Cape Courtweg, Wynberg, Kaap LOWER CRETACEOUS (MIDDLE ALBIAN) AMMONITES FROM DOMBE GRANDE, ANGOLA By MICHAEL R. COOPER National Museum, Bulawayo (With 31 figures) [MS accepted 3 March 1982] ABSTRACT Two stratigraphically separated Middle Albian faunules, dominated by Douvilleiceras and Oxytropidoceras respectively, are described from the environs of Dombe Grande. The wide range of continuous variation within these assemblages has an important bearing on the taxonomy of these forms. The phylogeny of the Mojsisovicziinae is discussed, and the following new taxa are created: Mortoniceratoides gen. nov., Oxytropidoceras (Mirapelia) subgen. nov. and O. (Benavidesites) subgen. nov. Middle Albian biostratigraphy outside the Boreal Realm is discussed. CONTENTS PAGE IntroductionS-c50 eee 265 Repionaligcolopyean- asses 267 SyStematics fee auc eet oe 270 Accvottheitaunatare nn rae eee 309 SUMMARY seein ee ea ae 312 Acknowledgements ............. 312 IReLeLenCeSey Henn cei Si) INTRODUCTION Choffat (in Choffat & De Loriol 1888) was the first to record ammonites from the lower part of the Albian succession of Angola, describing and figuring an ‘Acanthoceras’ mamillare (Schlotheim) (= Douvilleiceras mammillatum aequinodum (Quenstedt)) (Choffat & De Loriol 1888: 71, pl. 3 (fig. 1)) from the Dombe Grande area. The specimen was said to have come from the ‘Couches a Pholadomya pleuromyaeformis’, but as these beds are almost certainly of Aptian age (Howarth 1965; Cooper 1976) this is an error. Howarth (1965) described a small collection of Douvilleiceras made in 1930-1 by Alexan- dre Borges from the Dombe Grande region, and recorded the species D. mammillatum var. ?aequinodum (Quenstedt) and D. orbignyi Hyatt, thereby suggesting the presence of upper Lower Albian (D. mammillatum Zone) strata. Cooper (1976) described the bio- and lithostratigraphy of the region. The present collections come from the immediate vicinity of Dombe Grande 265 Ann. S. Afr. Mus. 89 (5), 1982: 265-314, 31 figs. ANNALS OF THE SOUTH AFRICAN MUSEUM 266 “speol judsoidas soul] UdyoOIg ‘polaquinu santRso] Sunosjyoo yyM ‘dew Ayypeoo7T “[ “34 of > ay Ni . PpUDAD aquog LOWER CRETACEOUS AMMONITES FROM ANGOLA 267 (Fig. 1), and well above the beds containing Pholadomya pleuromyaeformis Choffat. Prefixes to catalogue numbers refer to material in the following institutions: BMNH British Museum (Natural History), London NHMP Natural History Museum, Paris OUM Oxford University Museum, Oxford SAM South African Museum, Cape Town USNMNH_ USS. National Museum of Natural History, Smithsonian Insti- tution, Washington Measurements are in millimetres, with dimensions, as a percentage of the diameter, in parentheses. REGIONAL GEOLOGY The late Mesozoic succession in the Cuanza basin has been named the Cuanza Group (Cooper 1976). At Dombe Grande in the extreme south of the basin (12°54’S 13°13’E), the base of the Cuanza sequence is formed by the Dombe Formation, a unit of coarse clastics and lagoonal deposits with inter- bedded evaporites. The disconformably overlying transgressive deposits of the ‘Formacao com Pholadomya’ (Neto 1960, 1961) attain a thickness of about 100 m and comprise a basal member of oolitic limestones, calcarenites and siltstones capped by calcareous siltstones rich in Pholadomya pleuromyaeformis and other bivalves (Fig. 2C-F). Also present at this level are the echinoids Salenia dombeensis De Loriol and Pygurus africanus De Loriol, and the molluscs Neithea shawi Pervinquiere, Retusa malheiroi (Choffat), Panopea gurgitis (Brongniart), Lithophaga praelonga (d’Orbigny), Nerita malheiroi Choffat, ‘“Natica’ feioi Choffat, Actaeonella (Trochactaeon) cordeiroi (Choffat), Actaeon lenzi Choffat, Ampullina (Pseudamaura) bulbiformis (J. Sowerby), Pinna robinaldina dOrbigny, Cylindrites? delgadoi Choffat, and Tylostoma peschueli Choffat. Marine regression is reflected in the succeeding ‘Formagao com Nerinea’ (Fig. 1, locality 2), a lithologically highly variable unit spanning some 400 m and comprising red and yellow lagoonal clastics yielding fossil wood, the gastropods Nerinea capelloi Choffat (Fig. 3G-—H) and Cerithium monteiroi Choffat, and an indeterminate ammonite (fide Neto 1961). The ‘Formacao com Nerinea’ are overlain, perhaps disconformably, by limestones and marls at the base of the Cuio Formation, the lower beds of which have yielded the faunas described herein. The two assemblages, which were picked up mainly as surface scree, are stratigraphically separated at locality 4 (Fig. 1), with the Oxytropidoceras fauna occurring to the north-east and thus from the younger beds. Upward the sequence becomes increasingly unfossiliferous, and calcarenites and grits (Fig. 1, locality 1) span much of the 268 ANNALS OF THE SOUTH AFRICAN MUSEUM Fig. 2. A-B. Puzosia bistricta (White), SAM-—PCA2649, x 1. C—F. Undetermined bivalves from the ‘Couches a Pholadomya’, Reinecke Collection, South African Museum, X 1,5. LOWER CRETACEOUS AMMONITES FROM ANGOLA Fig. 3. A-B. Oxytropidoceras (Mirapelia) buarquianum (White), SAM-—PCAS5445, an individ- ual transitional to douglasi morphotypes. C-D. Puzosia bistricta (White), SAM-PCA3474. E. Inoceramus gr. anglicus Woods, SAM-PCA3443, from the Douvilleiceras assemblage. F. Birostrina? cf. coptensis (Casey), SAM-PCA2664, from the Oxytropidoceras assemblage. G-H. Nerinea capelloi Choffat. G. SAM-PCAS5S448, x 1,5. H. SAM-PCA5450, x 1,5. All X 1 unless otherwise stated. 270 ANNALS OF THE SOUTH AFRICAN MUSEUM remainder of the Middle Albian. These sediments are interpreted as reflecting marine regression. The Cuio Formation attains a thickness of some 200 m and is succeeded by bioclastic and oolitic limestones and calcarenites (Fig. 1, localities 3, 6) yielding a low Upper Albian fauna including Prohysteroceras wordiei Spath and Mortoniceras spp. This unit is to be correlated with the Catumbela Member of the Cabo Ledo Formation to the north, reflecting the early late Albian (Hysteroceras orbignyi Zone) transgression. SYSTEMATICS Subclass AMMONOIDEA Zittel, 1884 Family Douvilleiceratidae Parona & Bonarelli, 1897 Discussion Since the lineage Procheloniceras — Cheloniceras — Eodouvilleiceras > Douvilleiceras represents a single phyletic lineage, the subfamily Chelonicerati- nae should be included in the synonymy of the nominate subfamily. Subfamily Douvilleiceratinae Parona & Bonarelli, 1897 Genus Douvilleiceras de Grossouvre, 1894 Type species Ammonites mammillatus Schlotheim, 1813; subsequent designa- tion of I.C.Z.N., Opinion 422, 1956 Discussion Casey (1962: 260) has given a detailed diagnosis and discussion of this genus, to which little may be added. The genus Trinitoceras was erected (Scott 1940: 1016) for very large douvilleiceratids in which the *. . . douvilleiceratid sculpture is evident up to or beyond a diameter of 200 mm. Costae are multituberculate as in Douvilleiceras, but the umbilical tubercles are greatly exaggerated in size, forming large bullae on the umbilical margin at the ends of alternate costae. On later whorls costae lose all trace of tuberculation but retain, irregularly, their alternate primary and secondary arrangement. On the latest whorls shown, the ribs are nearly equal, except that the occasional secondary (marked only by the fact that it does not reach the umbilicus) is intercalated between the primaries. The whorl section, degree of evolution, and the umbilical area do not differ greatly from like features of well-known species of Douvilleiceras.’ It is clear from the above description that the genus Trinitoceras is based upon the gigantic shells that accompany virtually all Douvilleiceras populations; thus D. leightonense Casey, D. cheloniceratiforme Tavani, D. restitutum Ander- son, and D. charshangense Mirzoyev are all typical Trinitoceras. However, the fact that Trinitoceras and Douvilleiceras everywhere occur together as well as the fact that they are indistinguishable in their early ontogenetic stages and LOWER CRETACEOUS AMMONITES FROM ANGOLA Di attain maturity at vastly different diameters, suggests to the writer that the differences are those between sexual dimorphs. Trinitoceras is here considered to be based upon Douvilleiceras macroconchs, and Casey (1962) is followed in regarding it a synonym of Douvilleiceras. Up to now almost fifty trivial names have been applied to Douvilleiceras; these include D. mammillatum (Schlotheim) and its varieties paucicostatum Parona & Bonarelli, praecox Casey, baylei Spath and aequinodum (Quenstedt), D. inaequinodum (Quenstedt), D. pseudinaequinodum Collignon, D. orbignyi Hyatt, D. clementinum (d’Orbigny), D. solitae (d’Orbigny), D. tarapacaense Etayo-Serna, D. abozaglio Etayo-Serna, D. ivernoisi (Coquand), D. spiniferum (Whiteaves), D. rex (Scott), D. reesidei (Scott), D. grandense (Scott), D. adkinsi (Scott), D? dunlapi (Scott), D. quitmanense Scott, D. spathi Scott, D. cuchillense Scott, D. muralense Stoyanow, D. aurarium Anderson, D. res- titutum Anderson, D. offarcinatum (White), D. euzebioi (Maury), D. ser- gipense Beurlen, D. multinodosum Hubach, D. benonae Besairie, D. spinosum Tavani, D. albiense (Tavani), D. variabile Tavani, D. cheloniceratiforme Ta- vani, D. scabrosum Casey, D. alternans Casey, D. pustulosum Casey, D. leigh- tonense Casey and its variety pringlei Casey, D. magnodosum Casey, D. subleightonense Mirzoyev, and D. charshangense Mirzoyev. The extreme range of morphological variation exhibited by most assem- blages is emphasized by the splitting of the British collections into fourteen taxa (Casey 1962), those from Texas into eleven species (Scott 1940), and the Somali collections into eight species (Tavani 1942, 1949), and this seems to suggest genetic polymorphism. Thus Casey (1962: 263) has noted that all the mostly endemic species of Douvilleiceras recorded from southern England ‘. . . come from a limited range of strata and they constitute a closely interconnected plexus that in former days would have been interpreted (perhaps correctly) as one very large, highly variable species’. Unfortunately Casey’s revision, coming at a time when it was the practice to base species on very narrowly defined limits, suffers from oversplitting, since recent studies of ammonite populations (Kennedy & Cobban 1976) suggests that such variation is not extraordinary. In addition, Mirzoyev (1967: 54) has also commented that ‘... all species of Douvilleiceras are closely interrelated and could have been treated as a single very extensive and varied species; but investigators concerned with this group of ammonites have made efforts to discover differences, based entirely on the frequency, degree of development and modifications of the conch sculpture in the course of its development’. Casey (1962), in his revision of the British species of Douvilleiceras, laid much emphasis on the width of the ventral sulcus, number of notches per rib, and the ontogenetic stage at which ornament change occurred as taxonomic criteria. However, many writers have noted that the number of notches increases with diameter, while Collignon (1963), Mirzoyev (1967), and McLearn (1972) have all reported specimens with different numbers of notches on opposing flanks. Consequently, this criterion is considered to be of very Dif?) ANNALS OF THE SOUTH AFRICAN MUSEUM limited taxonomic significance, if at all. Both the width of the ventral sulcus and the ontogenetic stage at which morphological changes occur are relative charac- ters that are unlikely to stand up to population analysis, especially when it is considered that many of the taxa so defined are contemporaneous, occurring together in the same bed. As such, the writer believes Douvilleiceras to display genetic polymorphism and thus high intraspecific variability. Stratigraphically Douvilleiceras ranges from the top of the Leymeriella tardefurcata Zone (Leymeriella regularis Subzone) into the lower part of the Middle Albian (Lyelliceras lyelli Subzone of the Hoplites dentatus Zone). During this period it attained a cosmopolitan distribution and is currently reported from North America (British Columbia, California, Arizona, Texas, New Mexico), South America (Peru, Columbia, Brazil), Africa (Gabon, Angola, Zululand, Mozambique, Somalia), Madagascar, Asia (eastern Carpa- thians, northern Caucasus, western and central Kopet Dag, Bol’shoy Balkhan, Tuarkyr, Mangyshlak, Badkhiz Islands, southern Gissar Range, Afghanistan), Europe (southern England, France, Switzerland, ?Germany, Poland, Bulga- ria), and Japan. Douvilleiceras mammillatum aequinodum (Quenstedt, 1849) Figs 4A-B, 6C-G, 7D, G-I, 8A-B, 9A-C, E, 10C—D, F-H, 12A-B, 17A Ammonites monile aequinodus Quenstedt, 1849: 137, pl. 10 (fig. 2). ? Ammonites offarcinatus White, 1887: 219, pl. 23 (fig. 4 only). Acanthoceras mammillare (Schlotheim) Choffat (in Choffat & De Loriol), 1888: 71, pl. 3 (fig. 1). Douvilleiceras monile var. aequinodum (Quenstedt) Breistroffer, 1947: 65. ? Douvilleiceras cheloniceratiforme Tavani, 1949: 38, pl. 8 (fig. 6). ? Douvilleiceras monile (J. Sowerby) Benavides-Caceres, 1956: 442, pl. 43 (figs 1-4). ? Douvilleiceras restitutum Anderson, 1938: 175, pl. 54 (fig. 2). Douvilleiceras mammillatum var. aequinodum (Quenstedt) Casey, 1962: 271, pl. 40 (fig. 5), pl. 41 (figs 5-7), pl. 42 (fig. 10), figs 94a-c, 95a—b, 102d, 103a—b. Howarth, 1965: 343, pl. 1 (figs 1-4). ? Douvilleiceras albense Spath, Collignon, 1963: 112, pl. 284 (fig. 1243). Douvilleiceras sp. B, Beurlen, 1970: 460, pl. 4 (figs 3-4), figs 16-17. ? Douvilleiceras spinifer'um (Whiteaves) McLearn, 1972: 62, pl. 28 (fig. 1 only). Douvilleiceras cf. mammillatum (Schlotheim) Young, 1974: 184, pl. 4 (figs 1, 3, 6). Material Fifty-seven specimens, SAM-—PCA2639, 3409, 3417, 3427, 3429-3431, 3434, 3439-3440, 3442, 3456, 3459-3460, 3462-3464, 3467, 3469, 3471-3473, 3476-3480, 3482, 3484-3487, 3490-3491, 3493-3494, 3499, 3501, 3503, 3509-3511, 3516-3518, 3520, 3522-3523, 3526-3527, 3529-3530, 3532, 3534, and 3536, all preserved as limestone steinkerns. Description This taxon is the most abundant component of the Douvilleiceras fauna, although many of the specimens are fragmentary and most are more or less eroded, having been picked up as surface scree. This erosion gives a number of LOWER CRETACEOUS AMMONITES FROM ANGOLA 273 Fig. 4. A-B. Douvilleiceras mammillatum aequinodum (Quenstedt), SAM—PCA3434. C-D, F. Douvilleiceras inaequinodum (Quenstedt). C-D. SAM-PCA3435, a juvenile showing very fine intercalated ribs. F. SAM-PCAS5451, a badly eroded fragment showing three intercalated ribs between main ribs. E. Nerinea capelloi Choffat, SAM-PCA5449, x 1,5. G. Douvilleiceras variabile Tavani, SAM-PCA3448. All x 1 unless otherwise stated. 274 ANNALS OF THE SOUTH AFRICAN MUSEUM Fig. 5. A-B. Oxytropidoceras (Oxytropidoceras) roissyanum (d’Orbigny). The original of D’Orbigny’s (1841) protograph, NHMP. C—D. Douvilleiceras mammillatum mammillatum (Schlotheim). The neotype, BM—C12491. Both x 1. Photos: W. J: Kennedy. LOWER CRETACEOUS AMMONITES FROM ANGOLA LYS specimens the appearance of having had very much narrower ribs than, in fact, they probably had. The shell is moderately evolute (umbilicus 32,5-39% of the diameter), with rather inflated whorls, and a subreniform depressed whorl section. In all the better preserved material the ventral sulcus is, or appears to have been, rather narrow. The number of notches to each rib varies with ontogeny, with about 5 at 30 mm diameter increasing to 8-9 at about 60 mm diameter. Up to about 40 mm diameter the ribs tend to be simple, distant and rursiradiate, commonly with 10-14 ribs per half whorl. However, several of the more densicostate juveniles have 16 ribs per half whorl. Beyond this diameter intercalation and bifurcation becomes increasingly common, generally with 16-20 rather uniform ribs per half whorl. One individual, SAM-PCA3417, retains simple ribbing to 62 mm diameter, whereas SAM—PCA3431 has very fine, nontuberculate intercalatories between main ribs at about 40 mm di- ameter, only to loose them with further growth. The tuberculation of this subspecies is very reduced, typically with the lateral tubercle subdued and bullate. In SAM—PCA3472, however, main ribs bear a prominent lateral tubercle and, up to 35 mm diameter, alternate with fine nontuberculate interca- latories. Beyond this diameter all the ribbing becomes uniform and the lateral tubercule is much reduced and bullate. In SAM—PCA3435, the early whorls are strongly tuberculate and distantly ribbed but, at 47 mm diameter, there is a sudden and dramatic reversion to normal aequinodum-type ornament. SAM— PCA3430 connects typical aequinodum-type morphologies to the large macro- conch fragments (SAM-—PCA3408, 3410-3411, 3414, 3425, 3433, 3465, 3483, 3500) in the collection. Measurements No D H W W/H U SAM-PCA3427 Ws 29 34 29569) SAM-PCA3429 83 35 45 LS) PAY (EPA) SAM-PCA3431 ? 82, 3i/ LENG ? SAM-PCA3434 70 26 32 DS (8s) SAM-—PCA3527 51 19 Dil Petit 18 (35,3) Discussion Quenstedt (1849) described two species of Douvilleiceras, D. aequinodum and D. inaequinodum. Since the latter species is typically lower Middle Albian (Casey 1962), it may be reasonable to assume this is also the level of D. aequi- nodum. Such a supposition tends to be supported by their coexistence in the eodentatus Nodule Bed (Bed e of Destombes et al. 1977) (Fig. 12A—D, G-H) at Bully, Pays de Bray, France, and also in Angola. Since the Angolan D. mam- millatum material is dominated by aequinodum morphotypes, with no undoubted individuals of D. mammillatum s.s. (Fig. 5C-D), it seems reason- able to assume that a genuine shift in population structure has occurred when 276 ANNALS OF THE SOUTH AFRICAN MUSEUM Fig. 6. A. Douvilleiceras inaequinodum (Quenstedt), SAM—PCA3535, a juvenile. B. Oxytro- pidoceras (Mirapelia) buarquianum (White), SAM-PCA3765, a typical juvenile. C-G. Dou- villeiceras mammillatum aequinodum (Quenstedt). C. SAM—PCA3427. D-E. SAM-—PCA2639. F-G. SAM-PCA3431. All x 1. LOWER CRETACEOUS AMMONITES FROM ANGOLA Fig. 7. A-C. Douvilleiceras inaequinodum (Quenstedt). A. SAM-PCA3466. B-C. SAM-— PCA3437, a typical example. D, G-I. Douvilleiceras mammillatum aequinodum (Quenstedt). D. SAM-PCA3479. G. SAM-PCA3481. H-I. SAM-PCA3527, a typical juvenile with fine, distant, simple ribs. E-F. Douvilleiceras variabile Tavani, SAM—PCA3496. All x 1. 278 ANNALS OF THE SOUTH AFRICAN MUSEUM compared with the typical mammillatum Zone assemblages of D. mammillatum (cf. Casey 1962). It is for this reason, and because D. aequinodum can arguably be regarded as typically Middle Albian, that the writer has used Quenstedt’s name at subspecific level. As noted by Casey (1962) aequinodum morphotypes are also abundant in the mammillatum Zone of England, but at this level coexist with, and are connected by transitions to, D. mammillatum s.s., D. mammillatum var. praecox Casey, and D. monile (J. Sowerby). Since there is, in the writer’s opinion, but a single biological taxon involved in the latter list, the various nominal forms are merely morphotypes within a single poly- typic species. Disregarding the nomenclatural problems, it is clear that the Angolan population of D. mammillatum is substantially different from that at Copt Point, Folkestone, and thus warrants subspecific distinction. Both Douvilleiceras restitutum Anderson and D. cheloniceratiforme are based upon macroconchs whose inner whorls suggest they may belong here. Similarly, the hypotype of D. spiniferum (Whiteaves) figured by McLearn (1972, pl. 28 (fig. 1)) also shows few features to distinguish it from typical aequinodum morphotypes. In addition, one of White’s (1887, pl. 23 (fig. 4)) syntypes of D. offarcinatum shows a rib density that suggests possible reference to Quenstedt’s taxon. Douvilleiceras variabile Tavani, 1949 Figs 4G; 7E-F; 8C_D) 9G, 11C_—De ISAn IS, 22 Ammonites mammillaris Schlotheim, d’Orbigny, 1841: 249, pl. 72 (fig. 5 only). Douvilleiceras variabile Tavani, 1949: 37, pl. 10 (figs 1-2). ? Douvilleiceras pseudinaequinodum Collignon, 1963: 120, pl. 288 (fig. 1249). Douvilleiceras monile (J. Sowerby) Collignon, 1963: 118, pl. 287 (fig. 1248). Douvilleiceras aff. baylei Spath, Collignon, 1963: 118, pl. 287 (fig. 1247). Douvilleiceras subleightonense Mirzoyev, 1967: 59, pl. 8 (figs 1-3). ? Douvilleiceras sp. B, McLearn, 1972: 67, pl. 13 (fig. 1), pl. 16 (fig. 1). Material Four specimens, SAM—PCA3422, 3447-3448 and 3496, all preserved as internal moulds. Description In shell form, this species is very similar to the last but with substantially different ornament. In the Angolan material, ornament comprises well- developed main ribs ornamented with a distinct umbilical tubercle, a pro- nounced mid-lateral tubercle and bullate ventral tubercles that weaken beyond about 45 mm diameter and are lost at about 60 mm diameter. At about this stage a small tubercle also appears between the umbilical and mid-lateral tubercle, and the ventral tubercles bear three notches. There are, therefore, eight notches per rib. Between these long ribs are invariably one, sometimes two intercalatories that do not connect with the umbilicus and lack mid-lateral tubercles. These ribs tend to be somewhat finer than the main ribs and give rise to the typical ‘variable’ ornament of this species. LOWER CRETACEOUS AMMONITES FROM ANGOLA 279 Fig. 8. A-B. Douvilleiceras mammillatum aequinodum (Quenstedt), SAM-PCA 3429. C-D. Douvilleiceras variabile Tavani, SAM-PCA3447. Note the alternating long and short ribs and prominent lateral tubercle typical of this species. Both x 1. 280 ANNALS OF THE SOUTH AFRICAN MUSEUM Fig. 9. Whorl sections of Douvilleiceras. A-C, E. Douvilleiceras mammillatum aequinodum (Quenstedt). A. SAM-PCA3417. B. SAM-—PCA3433. C. SAM-PCA3479. E. SAM-PCA 3431. D, F, H. Douvilleiceras inaequinodum (Quenstedt). D. SAM—PCA3535. F. SAM-— PCA3437. H. SAM-PCA 3466. G. Douvilleiceras variabile Tavani, SAM-PCA3496. All x 1. LOWER CRETACEOUS AMMONITES FROM ANGOLA 281 Measurements No D H W W/H U SAM-PCA3496 51 19 22 1,16 19 (37) Discussion Douvilleiceras variabile Tavani seems to be based upon the inner whorls of a macroconch, showing the irregular ornament of the early growth stages, with 1-2 weak ribs between main ribs, and the more regular ornament of the macroconch on the adoral half of the last whorl. Tavani’s (1949) species is undoubtedly very close to D. mammillatum (Schlotheim), and D’Orbigny’s (1841, pl. 72 (fig. 5)) Ammonites mammillaris seems to be a typical example of this species. Indeed, even in the present collection, several individuals seem to combine the characters of D. variabile and D. mammillatum aequinodum (Fig. 15E). This tends to suggest that D. variabile is merely another morpho- type within a polytypic D. mammillatum. While this is the writer’s belief, opposition to the gross ‘lumping’ that such synonymies would involve from one of the referee’s of this paper has led to the adoption of a somewhat more cautious approach. Douvilleiceras variabile is here maintained as a distinct species because the writer does not believe in sympatric subspecies. Douvilleiceras subleightonense Mirzoyev is a gigantic macroconch attaining some 600 mm diameter, whose inner whorls show the irregular ribbing typical of this species, and it may reasonably be included here. The Douvilleiceras sp. B of McLearn (1972, pl. 13 (fig. 1), pl. 26 (fig. 1)) is another macroconch that may belong here. Yet another macroconch whose inner whorls are reminiscent of this species is D. pseudinaequinodum Collignon. Douvilleiceras ivernoisi (Coquand) (Pictet & Renevier, 1854, pl. 2 (fig. 1)) is somewhat similar to D. variabile, but lacks the pronounced lateral tubercle. Douvilleiceras inaequinodum (Quenstedt, 1849) Figs 4C-D, F, 6A, 7A-C, 9D, F, H, 10E, 11A, 12C-D, G-H Ammonites mammillaris Schlotheim, d’Orbigny, 1841: 249, pl. 73 (figs 1-3 only). Ammonites monile inaequinodus Quenstedt, 1849: 138, pl. 10 (fig. 1). Douvilleiceras inaequinodum (Quenstedt) Parona & Bonarelli, 1897: 95, pl. 4 (fig. 6), pl. 13 (fig. 6). Collignon, 1950: 46, fig. 2; 1963: 114, pl. 285 (fig. 1245). Casey, 1962: 282, fig. 95c. Douvilleiceras orbignyi Hyatt, 1903: 110. Casey, 1962: 279, pl. 40 (figs 6-8), pl. 42 (figs. 12-13). Howarth, 1965: 345, pl. 1 (fig. 5). Douvilleiceras mammillatum var. baylei Spath, 1923: 70, pl. 5 (fig. 4). Douvilleiceras aff. inaequinodum (Quenstedt) Spath, 1923: 73, pl. 4 (fig. 5). ? Douvilleiceras cf. inaequinodum (Quenstedt) Scott, 1937: 35, pl. 6 (figs 3-4), fig. 1. Douvilleiceras alternans Casey, 1962: 282, pl. 42 (fig. 1), fig. 1021. ? Douvilleiceras magnodosum Casey, 1962: 284, pl. 42 (fig. 4), fig. 102k. ? Douvilleiceras charshangense Mirzoyev, 1967: 54, pl. 7 (figs 1-5). ? Douvilleiceras sp. A, McLear, 1972: 67, pl. 12 (fig. 1). Douvilleiceras cf. orbignyi Hyatt, Young, 1974: 188, pl. 5 (figs 9-10). 282 ANNALS OF THE SOUTH AFRICAN MUSEUM Fig. 10 A-B. Oxytropidoceras (Mirapelia) buarquianum (White), SAM-—PCA2656, a douglasi morphotype which very closely approaches O. mirapelianum (d’Orbigny), x 0,75. C—-D, F-H. Douvilleiceras mammillatum aequinodum (Quenstedt). C. SAM-—PCA3494. D. SAM-PCA 3503. F. SAM-PCA3527. G. SAM-PCA3499. H. SAM-PCA3518. E. Douvilleiceras inae- quinodum (Quenstedt), SAM—PCA3504. All x 1 unless otherwise stated. LOWER CRETACEOUS AMMONITES FROM ANGOLA “< hy GGL OIE ee, sD ~ i tas iaaaicr | ~tameatapes 3 a ini } Fig. 11. A. Douvilleiceras inaequinodum (Quenstedt), SAM-PCA3458, a specimen showing the increased number of intercalatories in maturity. B. Oxytropidoceras (Mirapelia) sergipense (White). Front view of SAM—-PCA5444. C-D. Douvilleiceras variabile Tavani, SAM-PCA3422. E. Plagiostoma sp., SAM-PCA5490, from the Oxytropidoceras assemblage. All x 1. 284 ANNALS OF THE SOUTH AFRICAN MUSEUM Material Eighteen specimens, SAM—PCA3435-3438, 3444, 3451, 3453, 3456-3458, 3466, 3492, 3495, 3498, 3504, 3512, 3525, and 3535, all preserved as limestone steinkerns. Description This is a rather common species in the Angolan fauna. The shell is generally moderately evolute, inflated, with a subreniform, depressed whorl section. The umbilicus is rather wide, with steep umbilical walls and well-rounded shoulders. Ornament comprises sparse, distant, slightly rursiradiate ribs, which are narrower than the interspaces and alternate weak and strong. The strong main ~ ribs are ornamented with small umbilical tubercles, a prominent lateral tubercle, and exaggerated ventral bulges, each with three spiral notches. In juveniles, only two spiral notches are present on the ventral bulges. With ontogeny, a small tubercle appears between the umbilical and mid-lateral tubercle and another between the latter and the ventrolateral bulges. Thus, there may be up to eight crenulations per rib in adults. The fine intercalated ribs, usually one and rarely two, between main ribs generally lack discernible ornament (on the weathered internal moulds), but in some individuals develop a small but distinct mid-lateral tubercle. In the early growth stages (Figs 4C-D, 12G—H) the intercalated ribs may be absent or so fine that there is difficulty in distinguishing this species from D. mammillatum s.s. There are probably about 7-8 main ribs per half whorl. The ventral sulcus is moderately broad and rather deep. Discussion Casey (1962) considered D. inaequinodum to be a typical Middle Albian species, distinguished from the earlier D. orbignyi Hyatt and D. alternans Casey in having two, not one, fine intercalatories between main ribs. However, material from the /sohoplites eodentatus nodule bed at Bully, Pays de Bray, France (Fig. 12C—D), shows that at least some individuals of D. inaequinodum have but a single fine intercalated rib between main ribs. In view of this, and because Casey (1962) has noted transitions between D. alternans and D. orbig- nyi, the latter two species are included in the synonymy of D. inaequinodum. Until the population structures of the mammillatum Zone assemblages are better known, it is perhaps prudent to retain orbignyi as a subspecies for these forms, as D. inaequinodum orbignyi Hyatt. Family Anisoceratidae Hyatt, 1900 Genus Protanisoceras Spath, 1923 Type species Hamites raulinianus d’Orbigny, 1842; by original designation Protanisoceras sp. Fig. 13B Material A single fragment, SAM-—PCA3461, preserved as a limestone steinkern from the Douvilleiceras assemblage. LOWER CRETACEOUS AMMONITES FROM ANGOLA 285 Fig. 12. Douvilleiceras spp. from the I. eodentatus Nodule Bed, Bully, Pays de Bray, France (Bed e of Destombes et al. 1977). A-B. Douvilleiceras mammillatum aequinodum (Quen- stedt), OUM-KZ976. C-D, G-—-H. Douvilleiceras inaequinodum (Quenstedt). C-D. OUM-KZ982. G-H. OUM-KZ981. E-F. Douvilleiceras mammillatum mammillatum (Schlotheim), OUM-KZ979. All x 1. 286 ANNALS OF THE SOUTH AFRICAN MUSEUM Fig. 13. A. Douvilleiceras variabile Tavani, SAM-PCA3472. B. Protanisoceras sp., SAM- PCA3461. C—D. Venezoliceras acostae (d’Orbigny), syntypes. in the D’Orbigny Collection, NHMP. E-F. Mortoniceratoides rigidus (Spath), the holotype, BM—C34879. All x 1. LOWER CRETACEOUS AMMONITES FROM ANGOLA 287 Fig. 14. A-C. Puzosia bistricta (White), the lectotype, designated herein, USNMNH 12102, from Porto dos Barcos, Mariom, Sergipe, Brazil. D-E. Oxytropidoceras (Mirapelia) mirapelia- num (d’Orbigny), NHMP-5758, in the D’Orbigny Collection, from Clar, France. F-G. Oxytropidoceras (Oxytropidoceras) carbonarium (Gabb), the holotype of O. cantianum Spath, BM-C12501, from the D. cristatum Zone at Folkestone. 288 ANNALS OF THE SOUTH AFRICAN MUSEUM Fig. 15. A-B. Oxytropidoceras (Mirapelia) buarquianum (White), the lectotype, designated herein (after White 1887). C-—D. Puzosia bistricta (White), copy of White’s (1887) original illustration. E. Douvilleiceras cf. variabile Tavani, SAM—PCA3435. Note the abrupt change from a variabile to an aequinodum-type ornament. All x 1. LOWER CRETACEOUS AMMONITES FROM ANGOLA 289 Description The short curved fragment gives the impression of having had a com- pressed, elliptical whorl section. Ornament comprises rather broad, low, rursi- radiate ribs, wider than the interspaces, each bearing a distinct ventrolateral tubercle. There are about three ribs in a distance equal to the whorl height. Discussion The available specimen is too fragmentary to warrant comparison with the many described species of Protanisoceras, but does provide the first record of this genus from Angola. Family Desmoceratidae Zittel, 1895 Subfamily Puzosiinae Spath, 1922 Genus Puzosia Bayle, 1878 Type species Ammonites mayoriana d’Orbigny, 1842 (= replacement name for A. planulatus J. de C. Sowerby non Schlotheim 1820 nec Schuebler 1830); by subsequent designation Puzosia bistricta (White, 1887) Figs 2A-B, 3C-D, 14A-C, 15C-D, 16, 17B-C, 18C-D, 19A-B Ammonites bistrictus White, 1887: 216, pl. 23 (figs 5-8). Ammonites hopkinsi Forbes, White, 1887: 213, pl. 21 (figs 1-3), pl. 22 (fig. 5). Puzosia welwitschia Choffat (in Choffat & de Loriol), 1888: 68, pl. 2 (fig. 4). Puzosia garajauana Maury, 1930: 289; 1936: 234, pl. 20 (figs 1-3). Beurlen, 1970: 446, pl. 1 (figs 1-3), figs 1-2. Puzosia rosarica Maury, 1936: 236, pl. 26 (figs 2-3). Beurlen, 1970: 446, pl. 1 (figs 4-5), figs 3-6. Material Thirty specimens, SAM—PCA2623, 2625-2626, 2636, 2638, 2649, 2652, 2660-2661, 3412, 3415-3416, 3419-3421, 3424, 3426, 3429, 3432, 3434, 3449, 3452, 3474-3475, 3635, 3749, 3751, 3753, 3757, all preserved as limestone steinkerns and mostly from the beds with Douvilleiceras. Description Shell moderately large, compressed, with a moderately narrow umbilicus (21-27 % of the diameter). The umbilical walls are steep, with evenly rounded shoulders, and the flanks slightly convex, almost flat. Maximum width is just below mid-flank and the whorl section (Fig. 16) is elliptical. There are generally about 7-8 straight, prorsiradiate constrictions per whorl, which flex forward just before crossing the venter. Characteristically, the whorls show an increase in inflation immediately after a constriction. The constrictions are broad and shallow, typically with a peculiar wedge-shaped rib intercalated across the 290 ANNALS OF THE SOUTH AFRICAN MUSEUM Fig. 16. Whorl sections of Puzosia bistricta (White). A. SAM-—PCA2626. B. SAM-PCA3412. Both x 1. venter in the middle growth stages. Because of the nature of preservation, the true characters of the ribbing are difficult to assess. They first appear on the outer parts of the flanks at about 60-80 mm diameter, and coarsen and become more prominent across the venter with age. On SAM-—PCA2623 there are twenty fine ribs between successive constrictions whereas on SAM—PCA2649 there are only seven. Discussion Puzosia welwitschia Choffat is clearly conspecific with the Ammonites hopkinsi figured by White (1887), which was later renamed Puzosia garajauana by Maury (1930). They almost certainly merely represent the middle and adult growth stages, respectively, of P. bistricta (White) (Fig. 14A—-C). Puzosia rosarica Maury occurs with P. bistricta and is based upon juvenile material which probably does not warrant specific separation. There are few species of Puzosia with which this highly distinctive Middle Albian species may be confused. Family Brancoceratidae Spath, 1933 Subfamily Mojsisovicziinae Hyatt, 1903 Genus Oxytropidoceras Stieler, 1920 Type species Ammonites roissyanus d’Orbigny, 1841; by original designation Discussion The most comprehensive treatment of this genus is that of Young (1966). He included Androiavites Collignon (1936) in the synonymy of Adkinsites and provided the following emended diagnosis of Manuaniceras: ‘Ammonites with LOWER CRETACEOUS AMMONITES FROM ANGOLA 291 few whorls, which are much higher than wide; there are many flat ribs at some stage in the ontogeny, and ribs may be single or bifurcating at one or more positions at the umbilicus or on the flank’ (p. 95). Unfortunately, however, flat-topped ribs are not a feature of Manuaniceras manuanense (Spath) (Fig. 31B) and hence cannot be used in the formulation of a diagnosis of this taxon. As Young (1966) rightly pointed out, Manuaniceras is a direct descendant of the Oxytropidoceras roissyanum group, which mainly differs in showing rib bifurcation at various levels on the flank. The differences are slight and the writer finds little use for the genus/subgenus Manuaniceras which is here included in the synonymy of Oxytropidoceras s.s. As noted by Young (1966), and is clear both from the stratigraphic record and described species of Oxytropidoceras, the history of this taxon is one of parallel evolution between two species groups. The O. mirapelianum (d’Orbigny) (Fig. 14D-E herein) plexus comprises O. mirapelianum (d’Orbigny), O.evansi (Spath), O. douglasi Knetchel, O. buarquianum (White), O. sergipense (White), O. packardi Anderson, O. boulei Collignon, O. paucituberculatum (Collignon), and O. colcanapi Collignon. These are all coarsely ribbed species without bifurcation or intercalation of the simple ribs. To this group the writer would assign the strongly derived species of O. salasi Young, O. stenzeli Young, and O. pandalense Young in which the adult whorls become densicostate, with occasional bifurcation and intercalation, and thus homoeomorph ‘Manuaniceras’. The other species group is that of O. roissya- num (d’Orbigny) in which the ribs are fine, with frequent bifurcation at or above the umbilical edge, and which includes all the described ‘Manuaniceras’ species of Young (1966). Since these two plexi appear almost simultaneously at the base of the Middle Albian (Owen 1971) and evolved in parallel until their final extinction in the early late Albian, the writer believes they merit sub- generic distinction. The writer proposes, therefore, the new subgenus Oxytropidoceras (Mirapelia) to include all those coarse-ribbed species assigned to the mirapelianum plexus above, with Ammonites mirapelianus d’Orbigny as type species. Oxytropidoceras (Mirapelia) sergipense (White) provides the root- stock from which the typical coarse-ribbed species of Venezoliceras (of which Tarfayites Collignon (1966) is a synonym), such as V. venezolanum (Stieler), V. acostae (d’Orbigny) (Fig. 13C-D), V. heueri Young, V. obscurum Young, V. texanum Young, V? chihuahuaense (Bose), V. kiowanum (Twenhofel), V. umsinenense (Van Hoepen), V. bituberculatum (Collignon), V. madagasca- riense (Collignon), V. robustum (Renz) and V. clavicostatum (Renz), are derived. However, as noted by Young (1966) and Renz (1968), there is a second group of Venezoliceras, typified by Venezoliceras harrisoni Benavides-Caceres, in which the early and middle growth stages show dense, bifurcating, nontuberculate ribbing, with a flank tubercle developed only at relatively large diameters. This group, which also includes V. acutocarinatum (Shumard), V. multicostatum (Renz), V. intermedium (Renz), and V. karsteni (Stieler), seems to have its ancestry in ‘Manuaniceras’ and, as such, its similar- 292 ANNALS OF THE SOUTH AFRICAN MUSEUM Fig. 17. A. Douvilleiceras mammillatum aequinodum (Quenstedt), SAM—PCA3423, a macro- conch fragment, X 0,67. B-C. Puzosia bistricta (White), SAM—PCA5447, x 1. LOWER CRETACEOUS AMMONITES FROM ANGOLA 293 Fig. 18. A-B. Oxytropidoceras (Mirapelia) sergipense (White), SAM-—PCAS5444. C-D. Puzo- sia bistricta (White), SAM—PCA3420. Both x 1. 294 ANNALS OF THE SOUTH AFRICAN MUSEUM Fig. 19. A-B. Puzosia bistricta (White), a specimen in the South African Museum. C-E. Oxytropidoceras (Mirapelia) buarquianum (White). C. SAM—PCAS5446, a douglasi morpho- type. D-E. SAM-PCA3603, a salasi morphotype. All x 1. LOWER CRETACEOUS AMMONITES FROM ANGOLA 295 ity to the V. acostae group is due to convergence. Consequently, the writer proposes the new subgenus Oxytropidoceras (Benavidesites), with type species Venezoliceras harrisoni Benavides-Caceres (1956: 460, pl. 53 (fig. 6)), for this homoeomorphic development. The origins of Adkinsites are obscure; Young (1966) would derive this taxon from Dipoloceras, but this view is unacceptable to the writer. They could represent derivatives of the more densely ribbed O. (Mirapelia) species or of paucicostate Oxytropidoceras s.s., or of both. This taxon is not present in the Angolan material and hence the writer defers judgement. Because of its obscure, and perhaps polyphyletic origins, Young (1966) is followed in treating Adkinsites as a genus, of which Androiavites Collignon (1936) is a synonym. Fig. 20. Mojsisoviczia cf. ventanillensis (Gabb). A reconstruction based upon BM-C78865, from the Middle Albian of Zululand. x 1. 296 ANNALS OF THE SOUTH AFRICAN MUSEUM Mortoniceras (Pervinquieria) rigidum Spath (1933: 413, figs 142, 144f) (Fig. 13E-F herein) is recorded from Bed VIII (=D. cristatum Zone) at Folkestone and is, as such, the earliest described species of Mortoniceras. It differs from the latter genus, however, in having rather fine, distant ribs with a steep adoral surface and a sloping adapical surface, lacking any sign of a mid-lateral tubercle, and in lacking the doubling of the ventrolateral tubercle so typical of Mortoniceras. Indeed, the characters of ornament ally M. rigidum with the Mojsisovicziinae and it seems likely that M. rigidum is closely allied to, and perhaps descended from Adkinsites. Since the origins of Mortoniceras are generally thought to lie in Dipoloceras (Wright in Arkell et al. 1957), the similarities are due to convergence. It is proposed, therefore, to make M. rigi- dum Spath the type species for the new genus Mortoniceratoides. It differs from Adkinsites in having a subquadrate whorl section, low ventral keel, and with a symmetrically bifid first lateral saddle. As discussed by Kennedy & Cooper (1977), Mojsisoviczia and Falloticeras are closely allied and, on the basis of the available evidence, Falloticeras may reasonably be considered a neotonous offshoot of Mojsisoviczia. From their first appearance (Fig. 20), the ribs of Mojsisoviczia are coarse and simple and the origins of this taxon seem to lie in O. (Mirapelia) sergipense (White) or a closely allied form. Dipoloceras is believed by Spath (1931) to have descended from Oxytropi- doceras, and is included in the Mojsisovicziinae by Wright (in Arkell et al. 1957). However, the inflated whorls, low ventral keel and strong spiral ornament suggest a closer relationship with the Mortoniceratinae, to which subfamily Dipoloceras is here referred. The suggested phylogeny within the Mojsisovicziinae, as here interpreted, is shown as Figure 21. Oxytropidoceras (Mirapelia) buarquianum (White, 1887) Figs 3A-B, 6B, 10A-B, 15A-B, 19C-E, 22D-E, 23A-D, F-G, 24-25, 27 Ammonites buarquianus White, 1887: 222, pl. 24 (figs 3-4 only), pl. 25 (figs 7-8). Schloenbachia cf. roissyana (d’Orbigny) Douvillé, 1906: 147, pl. 4 (fig. 3). Schloenbachia aff. belknapi (Marcou) Douvillé, 1906: 148, pl. 2 (fig. 4). Schloenbachia cf. belknapi Bose (non Marcou) Douglas, 1921: 269, pl. 17 (figs 1-2). Schloenbachia cf. chihuahuaensis Bése, Douglas, 1921: 269, pl. 17 (fig. 3). Oxytropidoceras buarquianum (White) Maury, 1936, pl. 19 (figs 2-3), pl. 25 (figs 5-6). Oliveira & Leonardos, 1943, pl. 27 (fig. 7). Young, 1966: 89, pl. 38 (figs 1-3). Beurlen, 1970: 464, pl. 5 (figs 1-2), fig. 18. ? Oxytropidoceras colcanapi Collignon, 1936: 182, pl. 18 (fig. 7), fig. 12k. ? Oxytropidoceras sp.juv., Spath, 1930: 61, pl. 9 (fig. 18). Oxytropidoceras packardi Anderson, 1938: 198, pl. 50 (fig. 1). Oxytropidoceras douglasi Knetchel, 1947: 106, pl. 24 (figs 1-4), pl. 25 (figs 1-2), pl. 26, pl. 27 (figs 2-3), pl. 28 (fig. 1). Young, 1966: 88, pl. 10 (figs 1, 5), pl. 36 (figs 3-4), pl. 37 (figs 4-5). ? Oxytropidoceras involutum Beurlen, 1952: 162, fig. 3. ? Oxytropidoceras (Manuaniceras) involutum Beurlen, 1970: 465, pl. 5 (fig. 4). Oxytropidoceras sp. A, Beurlen, 1970: 464, pl. 5 (fig. 3). LOWER CRETACEOUS AMMONITES FROM ANGOLA 297 Laraiceras Venezoliceras O. (Mirapelia) Mortoniceratoides Adkinsites O. (Oxytropidoceras) O. (Benavidesites) Falloticeras Mojsisoviczia Fig. 21. A suggested phylogeny of the Mojsisovicziinae. Material Forty-five specimens, including SAM-—PCA2617-2618, 2621-2622, 2627-2630, 2632, 2637, 2640-2645, 2648, 2651, 2654, 2659, 2663, 2665-2667, 2669, 2673-2674, 2676, 2678, 2693, 3603-3604, 3755, 3762 and 3765, all pre- served as limestone steinkerns. Description The Angolan population is polytypic, with morphotypes agreeing exactly with O. buarquianum (White), O. packardi Anderson, O. douglasi Knetchel, O. salasi Young, and two specimens very closely approaching O. mirapelianum (d’Orbigny). The relationship between these morphotypes is shown in Figure 26. Because of this wide range of intraspecific variation, no single description will fully cover all morphotypes and hence they are described separately. Two specimens, SAM—PCA2656-2657, very closely approach O. mirapelia- num (d’Orbigny) and, with a typological approach, would be referred to that species. The Angolan examples (Fig. 10A—B) are, however, insensibly con- 298 ANNALS OF THE SOUTH AFRICAN MUSEUM Fig. 22. A. Douvilleiceras variabile Tavani, D’Orbigny’s (1841, pl. 72 (fig. 5)) protograph, x 0,5. B-C. Mojsisoviczia delaruei (d’Orbigny), NHMP-5761, one of D’Orbigny’s syntypes from Clar, France. D-E. Oxytropidoceras (Mirapelia) buarquianum (White), SAM-—PCA2641, a rather densely ribbed douglasi morphotype, thus transitional to salasi variants. All x 1 unless otherwise stated. LOWER CRETACEOUS AMMONITES FROM ANGOLA 299 Fig. 23. A-D, F-G. Whorl sections of Oxytropidoceras (Mirapelia) buarquianum (White). A. SAM-PCA2656, a douglasi morphotype. B. SAM-PCA2644, a douglasi morphotype. C. SAM-PCA3603, a salasi morphotype. D. SAM-PCA2693, a typical buarquianum morpho- type. F. SAM-PCA2622, a douglasi morphotype. G. SAM-PCA2641, a douglasi morpho- type. E, H. Whorl sections of O. (M.) sergipense (White). E. SAM-PCA5444. H. A unnumbered specimen in the South African Museum. All x 1. 300 ANNALS OF THE SOUTH AFRICAN MUSEUM Fig. 24. Oxytropidoceras (Mirapelia) buarquianum (White), SAM-—PCA3418, a douglasi mor- photype, X 1. LOWER CRETACEOUS AMMONITES FROM ANGOLA 301 Fig. 25. Oxytropidoceras (Mirapelia) buarquianum (White). A-B. SAM-PCA2693, the typical variant. C. SAM-PCA2674, a douglasi morphotype. D. SAM—PCA2665, a rather eroded, finely ribbed variant. All x 1. 302 ANNALS OF THE SOUTH AFRICAN MUSEUM salasi buarquianum 3 (7%) 3 (7%) 2 (4%) 6 (13%) douglasi 29 (64%) 2 (4%) sergipense mirapelianum Fig. 26. Interrelationships between the Oxytropidoceras (Mirapelia) buarquianum morphotypes and closely allied species. Figures given are the number of morphotypes in the present collection followed, in parentheses, by the percentage which they constitute. nected to O. douglasi morphotypes and differ from D’Orbigny’s (1841) species (Fig. 14D-E) in being slightly less inflated and in having the ribs somewhat thicker at the umbilical margin. The O. douglasi morphotypes are the most abundant in the present collection and show the following features: shell compressed, evolute (umbili- cus 24-28 % of the diameter), with a compressed, lanceolate whorl section and a prominent, sharp, high, siphonal keel. The umbilicus is rather wide and shallow, with fairly steep umbilical walls and evenly rounded shoulders at moderate diameters. The umbilical walls become increasingly inclined with growth and, in maturity, the umbilical shoulder is gently rounded and indis- tinct. At this stage, the outer whorl covers about 15 per cent of the ribbing of the preceding whorl. Maximum width is slightly below mid-flank in most individuals. Ornament comprises simple, generally flexuous ribs, which arise at the umbilical seam but only become prominent on the flanks. All ribs are slightly prorsiradiate, steepest adorally and convex adapically, and broaden towards the ventrolateral shoulders where they swell but do not form tubercles. LOWER CRETACEOUS AMMONITES FROM ANGOLA 303 Fig. 27. Oxytropidoceras (Mirapelia) buarquianum (White). The suture line, somewhat simplified by erosion, of SAM-PCA2693, a douglasi morphotype. Approx. X 2. There are 13—20 ribs per half whorl. A somewhat eroded suture-line is shown as Figure 27. O. buarquianum morphotypes are insensibly connected to O. douglasi morphotypes (Fig. 3A—B). Typically (Fig. 25A-B), this morphotype is strongly compressed, with 22-32 broad, low, weak ribs per whorl, and an indistinct umbilical wall. It is perhaps worth noting that it is a ‘law’ of polytypic ammonite species that the compressed variants are weakly ornamented, and that strength of ornament increases with inflation. Two examples, SAM-—PCA 3603-3604, show the rather dense, straight ribs of O. salasi Young, becoming projected near the venter (Fig. 19D-E), and are connected by intermediates to O. douglasi. These O. salasi variants show a low umbilical wall, broad convex flanks and a lanceolate whorl section, and were clearly rather evolute. Although the siphonal keel is not preserved, it certainly stood well above the venter. The dense, narrow, simple ribs are distinctly prorsiradiate and only very slightly flexuous, with at least twenty-two ribs per half whorl. The ribs swell slightly at the ventrolateral shoulders and curve strongly forward to meet the siphonal keel. Discussion The Angolan material shows an insensible transition between O. buarquia- num (White) and O. douglasi Knetchel and they are synonyms. It is unfortun- ate that White’s (1887) species has priority because the O. douglasi morpho- types predominate. There is little to separate O. packardi Anderson from the O. douglasi morphotypes and it should also fall into synonymy. Several of the Angolan morphotypes are extremely close to O. mirapelianum, which is a broadly contemporaneous European species. However, until the population 304 ANNALS OF THE SOUTH AFRICAN MUSEUM structure of D’Orbigny’s (1841) species is better understood, they are main- tained as specifically distinct. As already noted, there are O. salasi morphotypes within the Aswalen material, which are connected by transitions to O. douglasi morphotypes, but they constitute only 4 per cent of the present material. Because of this, and because Young (1966) had over 300 specimens of O. salasi from the Key Valley Marl, the Texas form is maintained as a distinct species. Occasional O. salasi morphotypes within the Angolan population merely indicate that O. salasi is descended from an O. buarquianum ancestor by a major change in population structure. Oxytropidoceras stenzeli Young (1966: 93, pl. 22 (fig. 1), pl. 26 (fig. 1), pl. 34 (fig. 1), pl. 35 (fig. 4), figs 7h, 18c) is a Middle to low Upper Albian species that may not bear separation from O. salasi. Collignon (1936) recorded O. mirapelianum, O. colcanapi Collignon, O. boulei Collignon, and O. bravoense Collignon (non Bose) from the same level and locality (Berambo) in the Middle Albian of Madagascar. His O. colcanapi is certainly very close to O. buarquianum, although the true affinities of the Madagascan material must await reassessment at the population level. The species of Oxytropidoceras figured by Reyment (1955) from Nigeria are all poorly preserved juveniles with the simple, flexuous ribbing of O. (Mirapelia). Additional and better preserved material is required for a satisfac- tory identification. Oxytropidoceras chihuahuaense (Bose) (1910: 73, pl. 5 (figs 3-4), pl. 7 (figs 3-4), pl. 8 (figs 1-2)) was assigned by Young (1966) to Venezoliceras, but the absence of a flank tubercle clearly places it in O. (Mirapelia). The lectotype is the original of the specimen figured by Bose (1910, pl. 7 (figs 3-4), pl. 8 (fig. 1)), which shows rather rigid, slightly prorsiradiate single ribs that broaden ventrally and terminate in weak ventrolateral swellings. These features are within the range of variation of the Angolan material, but since BOése’s species is, in Texas at least (Young 1966), dated as upper Middle Albian—lower Upper Albian, it is maintained as distinct. Oxytropidoceras involutum Beurlen is based upon immature material that is very close to typical examples of this species. It is likely to prove a synonym of O. buarquianum. Oxytropidoceras (Mirapelia) sergipense (White, 1887) Figs 11B, 18A-B, 23E, H, 28 Ammonites sergipensis White, 1887: 221, pl. 24 (figs 1-2). Pervinquieria sergipensis (White) ee 1930: 294; 1936: 236, pl. 24 (figs 3-4). ? Oxytropidoceras buarquianum (White) Maury, 1936: 250, pl. 9 (fig. 1 only). Oxytropidoceras mauryae Beurlen, 1952: 162, fig. 3. Dipoloceras sergipense (White) Young, 1966: 20, 22, 24. Oxytropidoceras (Venezoliceras) sergipense (White) Renz, 1968: 630. Oxytropidoceras (Androiavites) mauryae Beurlen, 1970: 468, pl. 6 (fig. 1). Non Mortoniceras sergipensis (White) Beurlen, 1970: 468, pl. 6 (figs 2-4), fig. 19. LOWER CRETACEOUS AMMONITES FROM ANGOLA 305 Fig. 28. Oxytropidoceras (Mirapelia) sergipense (White). A-B. White’s (1887) origi- nal illustration. C—D. The original of White’s illustration, herein selected as lecto- type, in the Natural History Museum, Rio de Janeiro. Photo: P. Bengtson. Both x 1. 306 ANNALS OF THE SOUTH AFRICAN MUSEUM Material Six specimens in the South African Museum, SAM-—PCA3755, 3765, and 5444, together with three unnumbered examples. All are preserved as lime- stone steinkerns. Description The shell is rather inflated and moderately evolute, with the outer whorl covering about 25 per cent of the preceding whorl. The umbilicus is moderately wide (32-35% of the diameter) and fairly shallow, with steep umbilical walls and evenly rounded shoulders. Intercostally the whorl section is oval, com- pressed, whereas costally it is subquadrate (Fig. 23E, H). Ribs begin at the umbilical seam and, across the flank, are slightly flexuous and prorsiradiate, terminating in prominent ventrolateral tubercles that are projected forward on the venter. There are thirty ribs on the outer whorl. The flanks are convex and converge slightly towards the venter, with maximum width about one-third of the way up the flanks. The keel is not preserved but must have stood high above the venter. Discussion The confusion surrounding the generic status of White’s (1887) species is evident from the synonymy. It is, indeed, very close to Venezoliceras, as noted by Renz (1968), but lacks the development of flank tubercles. On the other hand, it is also very similar to the more inflated Oxytropidoceras douglasi morphotypes with which it coexists, differing only in the very pronounced development of ventrolateral tubercles. In gross morphology and stratigraphic position, therefore, O. (M.) sergipense is intermediate between O. (Mirapelia) and Venezoliceras. Phylogenetically, it is perhaps worth noting that Young (1966) assigned this species to Dipoloceras, while Spath (1932) referred such typical O. (Mirapelia) species as O. evansi (Spath), and even O. mirapelianum (d’Orbigny) itself, to Dipoloceras. As such, it seems likely that the origins of Dipoloceras also lie in O. (Mirapelia) of the sergipense group. Oxytropidoceras (Androiavites) mauryae Beurlen shows the same promi- nent ventrolateral tubercles and simple ribbing as O. (M.) sergipense and is here regarded as conspecific. The specimen figured by Beurlen (1970) is an Upper Albian Mortoniceras (Angolaites) with distinct umbilical and doubled ventrolateral tubercles. Oxytropidoceras (Mirapelia) sergipense (White) is very close to certain species of Mojsisoviczia (Figs 20, 22B—C), from which it is readily distinguished by its greater compression and the absence of a lateral tubercle. In this respect the figured but undescribed material of Mojsisoviczia aff. delaruei (d’Orbigny) (Spath 1930: 61, pl. 9 (figs 13, 16)) closely resembles the present species, since a lateral tubercle is not evident in the illustrations. It seems reasonable to assume that the ancestry of Mojsisoviczia lies in O. (Mirapelia) of the sergipense group. pidoceras) boesei Knechtel, SAM—PCAS5452, x 1. < fe) ) Z < = O a4 Ly n jaa = Z, 2) g 2 < N =) fe) ea S) LOWER CRET 29. Oxytropidoceras (Oxytro Fig. 308 ANNALS OF THE SOUTH AFRICAN MUSEUM Oxytropidoceras (Oxytropidoceras) boesei Knechtel, 1947 Figs 29-31A Oxytropidoceras (Manuaniceras) bosei Knechtel, 1947: 109, pl. 27 (fig. 1). ? Manuaniceras uddeni Young, 1966: 95, pl. 12 (figs 1, 4-5), pl. 13 (fig. 1), pl. 16 (figs 1, 3), figs 10b, 12b. Material Three specimens, SAM—PCA5452-5453 and an unnumbered example in the South African Museum, preserved as limestone steinkerns. Description The Angolan material comprises several rather eroded internal moulds of body chamber fragments that, because of scaphitoid-uncoiling of the body chamber, appear to be more evolute (umbilicus 33% of the diameter) than the earlier growth stages actually were. The shell is strongly compressed, with a lanceolate whorl section (Fig. 30) and broad, convex flanks. Maximum width is about one-third of the way up the flanks. Although the siphonal keel is not preserved, it certainly stood well above the venter. Ornament comprises dense, flexuous flank ribs that arise at, or close to, the umbilical seam and pass forward across the flanks. The ribs are narrower than the interspaces with a steep, concave, adoral surface and a sloping, convex, adapical face. They frequently bifurcate close to the umbilical seam, but only rarely at, or above, mid-flank. There are 8-9 ribs along the venter in a distance equal to the whorl height. There is no sign of bullae on any part of the flanks. Fig. 30. Oxytropidoceras (Oxytropidoceras) boesei Knechtel. Whorl sections. A. SAM-PCAS5452. B. SAM-PCAS5453. x 1. LOWER CRETACEOUS AMMONITES FROM ANGOLA 309 Discussion Oxytropidoceras (Manuaniceras) boesei Knetchel was based upon frag- mentary material, without proper description, which shows no features to distinguish it from the Angolan material. The Texas species, Manuaniceras uddeni Young, which coexists with O. (M.) buarquianum, is very close to the present material. It is said to differ in the presence of a few very weak bullae at the umbilical shoulder, and sometimes also at the point of bifurcation or intercalation of a rib. Since the presence of such bullae is likely to be markedly affected by state of preservation, M. uddeni is probably a synonym of O. boesei. Oxytropidoceras roissyanum (d’Orbigny) (Fig. 5A-B) is difficult to com- pare with the present species because the known material of both species represents vastly different growth stages. So far as can be judged, O. roissya- num is much more inflated, with stronger, more robust ribs, about as wide as the interspaces, and does not show bifurcation above the umbilical shoulder. Oxytropidoceras applanatus Collignon (1936: 183, pl. 16, (fig. 5)) is doubtfully distinct from O. roissyanum. Oxytropidoceras manuanense (Spath) (1921: 281, pl. 25 (fig. 1)) (Fig. 31B) resembles the present species in lacking flattened ribs, but differs in that nearly all ribs bifurcate at some level on the flanks and in the effacement of ribbing in maturity. Oxytropidoceras cantianum Spath (Fig. 14F—G) is an Upper Albian (Dipo- loceras cristatum Zone) species that is based upon a juvenile showing strongly branching ribs. It closely approaches the example figured by Young (1966, pl. 7 (figs 4, 6)) as ‘probably M. carbonarium (Gabb)’, and Owen (1971) seems to be right in regarding it a synonym of O. carbonarium. Oxytropidoceras aroeirium Maury (1936: 251, pl. 26, (fig. 7)) is, to judge from the description, very close to the present species. Unfortunately, the writer has not seen the illustrations of this species and thus further comment is unjustified. AGE OF THE PRESENT FAUNA Douvilleiceras mammillatum (Schlotheim) has long been considered diag- nostic of the uppermost biostratigraphic zone in the Lower Albian, to which it gives its name. Thus, the rich Douvilleiceras faunas from the rest of the world are almost invariably assigned to the zone of D. mammillatum and considered to be of late early Albian age. Despite the fact that Douvilleiceras has long been known to persist into the Middle Albian (Casey 1962; Owen 1971; Destombes et al. 1977), including D. mammillatum itself (Fig. 12E-F), this has never been a problem in the boreal realm where the incoming of Hoplites forms an easily recognizable and diagnostic base to the Middle Albian. Outside the hoplitinid faunal province, however, no such aid is available and the problem of 310 ANNALS OF THE SOUTH AFRICAN MUSEUM SAM-PCAS5453.__B. Oxytropidoceras (Oxytropidoceras) man- uanense (Spath), SAM-—2726, a paratype. LOWER CRETACEOUS AMMONITES FROM ANGOLA Sila the Lower—Middle Albian boundary is far more complex. These problems led Young (1966) to suggest that Lyelliceras may date a younger level in South America than it does in Europe. Contrary to Young’s (1966) opinion, however, the writer feels that Lyelliceras is critical to the problem of the Lower—Middle Albian boundary, in view of its widespread geographic distribution and com- mon association with hoplitinids in the boreal realm. In the Anglo-Paris basin, the type region for the Albian Stage, Owen (1971) recognized the following subdivisions of the Middle Albian: Anahoplites daviesi Subzone Euhoplites lautus Z BOP eS, AUS ONE | Euhoplites nitidus Subzone Euhoplites meandrinus Subzone Mojsisoviczia subdelaruei Subzone Dimorphoplites niobe Subzone Euhoplites loricatus Zone | Anahoplites intermedius Subzone Hoplites spathi Subzone Hoplites dentatus Zone Lyelliceras lyelli Subzone Isohoplites eodentatus Subzone In the Anglo-Paris basin, Douvilleiceras inaequinodum (Quenstedt) does not range above the eodentatus Subzone, while Oxytropidoceras (Mirapelia) mirapelianum (d’Orbigny). is a constituent of the Hoplites spathi Subzone (Owen 1971). Moreover in Peru, Benavides-Caceres (1956) records Oxytropi- doceras ‘douglas in association with Lyelliceras lyelli (d’Orbigny). There can also be little doubt that the Angolan Oxytropidoceras fauna is strictly contem- poraneous with those from the Texan zone of O. salasi, and it is certainly also represented in Brazil (White 1887; Maury 1936; Beurlen 1970). As such, the Lyelliceras lyelli Subzone is represented in the south-central Atlantic region by Oxytropidoceras buarquianum (White) and/or Lyelliceras lyelli (d’Orbigny), and their associated species. The underlying beds in Angola, dominated by Douvilleiceras mammillatum aequinodum (Quenstedt) and D. inaequinodum (Quenstedt), are thus certainly to be correlated with the /sohoplites eodentatus Subzone of the Anglo-Paris basin. It is perhaps worthy of note that O. mirape- lianum (d’Orbigny) is a replacement name for Ammonites cristatus Quenstedt (non DeLuc) and, as such, Quenstedt (1849) was dealing with a faunal horizon closely comparable, and probably strictly contemporaneous, with those at Dombe Grande. As such, the Dombe Grande faunas are here regarded as of basal Middle Albian age, to be correlated with the Isohoplites eodentatus and Lyelliceras lyelli Subzones of the European succession. The absence of lyelliceratids and brancoceratids is enigmatic. Since Oxytropidoceras species are relatively long- lived, the Oxytropidoceras (M.) buarquianum faunule may prove to range somewhat higher. The fact that many of the Douvilleiceras assemblages from around the world could now prove to be of basal Middle Albian age suggests 312 ANNALS OF THE SOUTH AFRICAN MUSEUM that the late early Albian eustatic transgression (Cooper 1977) might actually have peaked during the earliest Middle Albian. SUMMARY Two Middle Albian faunules rich in numbers, but poor in species, are described from the vicinity of Dombe Grande, Angola. The lower faunule, which is correlated with the I[sohoplites eodentatus Subzone of the European sequence has yielded Douvilleiceras mammillatum aequinodum (Quenstedt), D. inaequinodum (Quenstedt), D. variabile Tavani and Puzosia_bistricta (White). The upper faunule has yielded Oxytropidoceras (Oxytropidoceras) boesei Knechtel, O. (M.) buarquianum (White), O. (M.) sergipense (White), Puzosia bistricta (White), Protanisoceras sp. and a Hamites sp., and is to be correlated with the Lyelliceras lyelli Subzone of the Anglo-Paris basin. Mojsiso- vicziinid phylogeny is discussed, and the following new taxa introduced: Morto- niceratoides gen. nov., Oxytropidoceras (Mirapelia) subgen. nov. and O. (Bena- videsites) subgen. nov., while Manuaniceras is included in the synonymy of Oxytropidoceras S.s. ACKNOWLEDGEMENTS I am grateful to Dr W. J. Kennedy for providing me with photographs of D’Orbigny’s type material, and to Dr P. Bengtson for photographs of the Brazilian material. 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SYSTEMATIC papers must conform to the Jnternational code of zoological nomenclature (particularly Articles 22 and 51). Names of new taxa, combinations, synonyms, etc., when used for the first time, must be followed by the appropriate Latin (not English) abbreviation, e.g. gen. nov., sp. nov., comb. Nnov., syn. nov., etc. An author’s name when cited must follow the name of the taxon without intervening punctuation and not be abbreviated; if the year is added, a comma must separate author’s name and year. The author’s name (and date, if cited) must be placed in parentheses if a species or subspecies is transferred from its original genus. The name of a subsequent user of a scientific name must be separated from the scientific name by a colon. Synonymy arrangement should be according to chronology of names, i.e. all published scientific names by which the species previously has been designated are listed in chronological order, with all references to that name following in chronological order, e.g.: Family Nuculanidae Nuculana (Lembulus) bicuspidata (Gould, 1845) Figs 14-15A Nucula (Leda) bicuspidata Gould, 1845: 37. Leda plicifera A. Adams, 1856: 50. Laeda bicuspidata Hanley, 1859: 118, pl. 228 (fig. 73). Sowerby, 1871: pl. 2 (fig. 8a—b). Nucula largillierti Philippi, 1861: 87. Leda bicuspidata: Nicklés, 1950: 163, fig. 301; 1955: 110. Barnard, 1964: 234, figs 8-9. Note punctuation in the above example: comma separates author’s name and year “semicolon separates more than one reference by the same author full stop separates references by different authors figures of plates are enclosed in parentheses to distinguish them from text-figures dash, not comma, separates consecutive numbers Synonymy arrangement according to chronology of bibliographic references, whereby the year is placed in front of each entry, and the synonym repeated in full for each entry, is not acceptable. In describing new species, one specimen must be designated as the holotype; other speci- mens mentioned in the original description are to be designated paratypes; additional material not regarded as paratypes should be listed separately. The complete data (registration number, depository, description of specimen, locality, collector, date) of the holotype and paratypes must be recorded, e.g.: Holotype SAM-—A13535 in the South African Museum, Cape Town. Adult female from mid- tide region, King’s Beach Port Elizabeth (33°51’S 25°39’E), collected by A. Smith, 15 January 1973. Note standard form of writing South African Museum registration numbers and date. 7. SPECIAL HOUSE RULES Capital initial letters (a) The Figures, Maps and Tables of the paper when referred to in the text > ‘ e.g. *... the Figure depicting C. namacolus...’; ‘... in C. namacolus (Fig. 10) . (b) The prefixes of prefixed surnames in all languages, when used in the text, if not preceded by initials or full names e.g. Du Toit but A.L.du Toit; Von Huene but F. von Huene (c) Scientific names, but not their vernacular derivatives e.g. Therocephalia, but therocephalian Punctuation should be loose, omitting all not strictly necessary Reference to the author should be expressed in the third person Roman numerals should be converted to arabic, except when forming part of the title of a book or article, such as “Revision of the Crustacea. Part VIII. The Amphipoda.’ Specific name must not stand alone, but be preceded by the generic name or its abbreviation to initial capital letter, provided the same generic name is used consecutively. Name of new genus or species is not to be included in the title: it should be included in the abstract, counter to Recommendation 23 of the Code, to meet the requirements of Biological Abstracts. "WANT 3 9088 01206 6858 MICHAEL R. COOPER LOWER CRETACEOUS (MIDDLE ALBIAN) AMMONITES FROM DOMBE GRANDE, ANGOLA