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The corresponding author will normally receive a copy of the edited manuscript on which deletions, additions, and changes can be made and queries answered. Only one set of page proofs will be sent. All desired corrections of type must be made on the single set of page proofs. Changes in page proofs (as opposed to corrections) are very expensive. Author-generated changes in page proofs can only be made if the author agrees in advance to pay for them. THIS PUBLICATION IS PRINTED ON ACID-FREE PAPER. aeOlOflY UBRAI^fY FIELDIANA Geology NEW SERIES, NO. 32 Pachypleurosaurs (Reptilia: Sauropterygia) from the Lower Muschelkalk, and a Review of the Pachypleurosauroidea Olivier Rieppel Department of Geology Field Museum of Natural History Roosevelt Road at Lake Shore Drive Chicago, Illinois 60605-2496 U.S.A. Lin Kebang Redpath Museum McGill University Montreal, Quebec H3A 2K6 Canada Accepted June 1, 1995 Published December 29, 1995 Publication 1473 PUBLISHED BY FIELD MUSEUM OF NATURAL HISTORY © 1995 Field Museum of Natural History Library of Congress Catalog Card Number: 95-70458 ISSN 0096-2651 PRINTED IN THE UNITED STATES OF AMERICA Table of Contents Abstract 1 zusammenfassung 1 Introduction 1 Systematic Paleontology 2 Phylogenetic Analysis 21 Definition of Characters 24 Genera and Species of Pachypleuro- SAUROIDEA in THE MIDDLE AND UPPER Triassic 34 Historical Biogeography of the Pachypleurosauroidea 36 The Paleoeoology of Pachypleurosaurs . . 40 Acknowledgments 40 Literature Cited 41 Appendix: Mateiual Included and Institutional Abbrevl\tions 43 List of Illustrations 1 . Casts of holotype oi Anarosaums pumilio Dames 3 2. Charitosaurus tschudii Meyer 4 3. Skull of Anarosaurus pumilio Dames (cast of holotype) 5 4. Skull of Anarosaurus pumilio Dames ... 5 5. Gastral ribs of Anarosaurus pumilio Dames 7 6. Pubis of Anarosaurus pumilio Dames .. 7 7. Humerus and femur of Anarosaurus pumilio Dames 8. Holotype of Anarosaurus heterodontus n. sp 9 9. Left premaxilla of Anarosaurus hetero- dontus n. sp 9 10. Skull of Anarosaurus heterodontus n. sp 10 1 1 . Holotype of Dactylosaurus gracilis Giirich 12 12. Holotype of Dactylosaurus schroederi Nopcsa 13 13. Dactylosaurus gracilis Giirich from the lower Muschelkalk of Gogolin, Upper Silesia (Gomy Slask, Poland) 14 14. Dactylosaurus gracilis Giirich, humerus, from the lower Muschelkalk of Bobrek near Beuthen 14 1 5. Right forelimb of Dactylosaurus gracilis Giirich 15 16. SVxAl of Dactylosaurus gracilis Gurich ..16 17. Pectoral girdle of Dactylosaurus gracilis Giirich 17 18. Pubis of Dactylosaurus gracilis Gurich ..18 1 9. Humerus of Dactylosaurus gracilis Giirich 18 20. Manus and pes of Dactylosaurus gracilis Giirich 19 21. Sauropterygia indet. from the lower Muschelkalk of Gogolin, Upper Silesia (Gomy Slask, Poland) 21 22. Strict consensus tree of sauropterygian interrelationships 23 23. Unrooted network for Placodus, Pachy- pleiu-osauroidea, and selected represen- tatives of Eusauropterygia 31 24. The single most parsimonious tree for pachypleurosaur interrelationships rooted on the monophyletic Eusau- ropterygia 32 25. Strict consensus tree for pachypleuro- saurs and selected eusauropterygians, rooted on an all-0 ancestor 33 26. Strict consensus tree for Placodus, pachy- pleurosaurs, and selected eusauroptery- gians, rooted on an all-0 ancestor 33 27. Strict consensus tree for pachypleuro- saur interrelationships, rooting the pachypleurosaurs plus selected eusau- ropterygian taxa on Placodus 34 28. Reconstructions of Anarosaurus pumilio and Dactylosaurus gracilis 37 8 List of Tables 1. Measurements of the humerus of Anaro- saurus pumilio Dames 8 2. Measurements of the femur of Anarosau- rus pumilio Dames 8 3. Body proportions in Pachypleurosauroi- dea 11 4. Measurements of the humerus of Dactylosaurus gracilis Giirich 18 5. Measurements of the limb bones of Dac- tylosaurus gracilis 19 6. Data matrix for 14 taxa and 50 charac- ters 24 m Pachypleurosaurs (Reptilia: Sauropterygia) from the Lower Muschelkalk, and a Review of the Pachypleurosauroidea Olivier Rieppel Lin Kebang Abstract The type material of all pachypleurosaurs from the lower Muschelkalk is redescribed and pachypleurosaur systematics are reviewed. Three species of lower Muschelkalk pachypleuro- saurs are recognized, Anarosaurus pumilio Dames, Anarosaurus heterodontus n. sp., and Dac- tylosaurns gracilis Giirich. A cladistic analysis based on 50 characters shows Keichousaurus to be the sister-taxon to all other pachypleurosaurs; Dactylosaurus is the sister- taxon to Anaro- saurus plus the Serpianosaurus-Neusticosaurus clade; Anarosaurus is the sister-taxon to the Serpianosaurus-Neusticosaurus clade; Serpianosaurus mirigiolensis is the sister-taxon to Neus- ticosaurus. The genus Neusticosaurus includes four species, A^. edwardsii, N. peyeri, N. pusillus, and N. toeplitschi. The stratigraphic and biogeographic relations of pachypleurosaurs indicate that pachypleurosaurs reached the European epicontinental sea (Muschelkalk Basin) by invasion from the east in Anisian times, and that a faunal interchange was possible between the Muschel- kalk Basin and the southern Alpine intraplatform basin facies at least during late Anisian and Ladinian times. Zusammenfassung Das Typusmaterial aller Pachypleurosaurier aus dem unteren Muschelkalk wird neu be- schrieben. Drei Arten von Pachypleurosauriem lassen sich im unteren Muschelkalk feststellen: Anarosaurus pumilio Dames, Anarosaurus heterodontus n. sp., und Dactylosaurus gracilis Gur- ich. Eine kladistische Analyse weist Keichousaurus als Schwestergruppe aller anderen Pachy- pleurosaurier aus; Dactylosaurus ist die Schwestergruppe von Anarosaurus und der Serpiano- saurus-Neusticosaurus-Linie; Anarosaurus ist die Schwestergruppe der Serpianosaurus-Neus- ticosaurus-lAme; Serpianosaurus mirigiolensis ist die Schwestergruppe von Neusticosaurus. Die Gattung Neusticosaurus umfasst vier Arten: A^. edwardsii, N. peyeri, N. pusillus, und A^. toe- plitschi. Stratigraphische und biogeographische Beziehungen zeigen, dass die Pachypleurosaurier das Germanische Becken von Osten her kommend im Unteren Anis erreichten. Zwischen der Germanischen und der Alpinen Trias fand zumindest warend dem spaten Anis und dem Ladin ein Faunenaustausch statt. Introduction lesia (Dactylosaurus gracilis, Giirich, 1 884) and in the lower Middle Triassic of China (Young, 1958, The Pachypleurosauroidea (Pachypleurosauri- 1965). The clade has not been recorded beyond dae) constitute a monophyletic clade of the sau- the upper Ladinian (upper Middle Triassic), per- ropterygian radiation (Rieppel, 1987, 1989; Storrs, haps lower Camian (lower Upper Triassic), de- 1991; Sues, 1987) that first appears in the lower- posits in the southern Alps (Ca' del Frate, Italy: most Muschelkalk (lower Anisian) of Upper Si- Tintorietal., 1985). Pachypleurosaurian anatomy FIELDIANA: GEOLOGY, N.S., NO. 32, DECEMBER 29, 1995, PP. 1-44 1 is well known for the Middle Triassic taxa abun- dantly represented in uppermost Anisian and lower Ladinian deposits at Monte San Giorgio, Switzerland (genera Neusticosaurus and Serpiano- saurus: Carroll & Gaskill, 1985; Rieppel, 1989; Sander, 1989), but the interrelationships of pa- chypleurosaurs in general still remain poorly un- derstood. This results from the relatively poor knowledge of earlier representatives of the clade. Of these, only a guttapercha cast of the holotype of Dactylosaurus schroederi Nopcsa (1928) from the Muschelkalk of Gross-Stein, Upper Silesia, has recently been restudied (Sues & Carroll, 1985; Dactylosaurus schroederi Nopcsa is considered a junior synonym oi Dactylosaurus gracilis Giirich: see below). A second pachypleurosaur from the lower middle Muschelkalk, Anarosaurus pumilio Dames, 1890, from Remkersleben in Saxony, has not been restudied since Arthaber's (1924) and Nopcsa's (1928) contradictory comments on its morphology (a reconstruction of the skull was pub- lished by Carroll, 1981, Fig. 32a). Since the early original description of pachy- pleurosaurid taxa from the lower Muschelkalk (lower to middle Anisian), new material has ac- cumulated in various museum collections, the identification of which remains problematic until the diagnoses of the originally described taxa are refined. It is the purpose of this paper to pull to- gether all available information on the original type material of pachypleurosaurs from the lower Muschelkalk. A redescription of the original type material will also provide the basis for a review of pachypleurosaur interrelationships and the re- construction of their evolutionary and paleobio- geographic history. Systematic Paleontology Sauropterygia Owen, 1860 Pachypleurosauroidea Huene, 1956 Pachypleurosauridae Nopcsa, 1928 Definition— A monophyletic group including the common ancestor of Anarosaurus, Dactylo- saurus, Keichousaurus, and all of its descendants. Diagnosis— Small to medium-sized Sauropter- ygia with the preorbital region of the skull longer than the postorbital region; frontal with concave lateral edge, entering the dorsal margin of the or- bit; broad parietal skull table; mandibular artic- ulation at level with occipital condyle; quadrate with concave posterior margin; ectopterygoid ab- sent; trough on dorsal surface of retroarticular pro- cess present; anterior teeth not strongly procum- bent; posterior process on interclavicle rudimen- tary or absent; radius slightly longer than ulna; iliac blade absent (i.e., reduced to narrow dorsal process). Distribution— Middle Triassic of China and Europe (Tethyan Province). Anarosaurus Dames, 1890 Type SPECIES—Aruirosaurus pumilio Dames, 1890. Generic Diagnosis— A small pachypleurosaur with a spatulate expansion of the tooth crown; a high dorsal vertebral count (25 or 26); an open obturator foramen in the pubis; pubis with a dis- tinct anteroventral spine; and a distinctly elon- gated femur (femur length/standard length = 1.55). Distribution— Lower and middle Muschelk- alk, central Europe. Anarosaurus pumilio Dames, 1890 1890 Anarosaurus pumilio. Dames, p. 74, PI. 1, text figs. 1,2. 1899 Anarosaurus pumilio, Schrammen, p. 408, PI. 25, Fig. 8. 1910 Anarosaurus pumilio, Jaekel, pp. 325, 335, text fig. 1 . 1924 Anarosaurus pumilio, Arthaber, pp. 480- 483, text figs. 12a, b, 13. 1928 Anarosaurus pumilio, Nopcsa, pp. 30-31, 43, PI. 4, Figs. 1, 2. 1935 Anarosaurus pumilio, Zangerl, pp. 64-65, 68. 1959 Anarosaurus pumilio, Kuhn-Schnyder, p. 652. 1981 Anarosaurus pumilio, Carroll, text fig. 32a. 1985 Anarosaurus pumilio. Sues and Carroll, p. 1349. 1987 Anarosaurus pumilio, Rieppel, pp. 1110, 1115-1116. 1993 Anarosaurus pumilio, Rieppel, p. 10. Holotype— The holotype was originally housed at the Institut und Museum fiir Geologic und Pa- laontologie, Georg-August-Universitat, Gottin- gen, but can no longer be located today (lost or HELDIANA: GEOLOGY Fig. 1 . Casts of the holotype o{ Anarosaurus pumilio Dames, deposited by Nopcsa in the British Museum (Natural History). A, Dorsal view (bmnh R-5691); B, ventral view (bmnh R-5866). Scale bar = 20 mm. destroyed during World War II; H. Jahnke, in litt. 1991). Two casts are available at this institution (Orig. Nr. 409-1). The specimen came from the orbicularis beds near Remkersleben, approxi- mately 15 km west of Magdeburg. The orbicularis beds were assigned to the top of the lower Mu- schelkalk by Dames (1890), but are now consid- ered the base of the middle Muschelkalk (Hag- dom, 1991). Arthaber (1924) describes a guttapercha cast of the holotype in the Natural History Museum, Humboldt University, Berlin (mb R. 57.1-3, dor- sal view; mb R. 58, ventral view), deposited by Jaekel (1910) after further preparation of the ho- lotype. Additional casts (Fig. 1) were deposited by Nopcsa in the British Museum (Natural History) (BMNH R-5691, dorsal view; bmnh R-5866, ven- tral view). Other casts are kept at the Institut fur Geowissenschaften, Martin-Luther-Universitat, RIEPPEL AND KEBANG: PACHYPLEUROSAURS Fig. 2. Charitosaurus tschudii Meyer. A, Cast of the Esperstadt specimen (original of Meyer, 1851, PI. 31, Fig. 22; MB R. 62); B, cast of the Querfurt specimen (original of Meyer, 1851, PI. 31, Fig. 23; mb R. 61). Scale bar = 20 Halle (M4/12, skull only), and at the Staatliches Museum fur Naturkunde, Stuttgart (smns 59073). Diagnosis— Same as for genus, but about half the size of Anarosaurus heterodontus, homodont dentition with eight teeth in premaxilla, and a weak sculpturing of dermal skull bones. Locus Typicvs— Orbicularis beds (middle Muschelkalk) of Remkersleben, 15 km west of Magdeburg, Germany. Distribution— Lower middle Muschelkalk, Anisian, Europe. Comments— Anarosaurus pumilio was origi- nally described by Dames (1890). Schrammen (1899) found Anarosaurus to be closely compa- rable to Cymatosaurus, perhaps because of the spatulate expansion of the tooth crown. Jaekel (1910) reconstructed the skull of ^4 narosaurus after further preparation of the holotype, and used An- arosaurus (as well as Simosaurus) in support of his argument that sauropterygians are a subgroup of the Diapsida. Arthaber (1924) criticized Jae- kel's (1910) reconstruction of the skull, and pre- sented new vertebral counts in his redescription of Anarosaurus. He also noted the similarity of the pubis of Anarosaurus to other, isolated elements from the lower Muschelkalk referred to '''Macro- tracheW by H.v. Meyer (1847-1855). Nopcsa ( 1 928) rejected Arthaber's ( 1 924) vertebral counts in Anarosaurus, and compared the taxon to Dac- tylosaurus. He considered the skull to be very sim- ilar in both genera, but found differences in the postcranial skeleton to support the generic dis- tinction of the two taxa. In 1 958, Huene described a second species, "^«- arosaurus" multidentatus, from the lower Anisian of the Lechtaler Alps, Austria. The specimen con- sists of a lower jaw characterized by an elongate symphysis and a heterodont dentition. In a recent redescription of the holotype, the species has been referred to the genus Cymatosaurus (Rieppel, 1995). In 1838, Meyer reported the collection of two lower jaw fragments (left dentaries), one from the Saurierkalk (lower middle Muschelkalk) of Esper- stadt, the other from the orbicularis beds (lower middle Muschelkalk) of Querfurt. The original of the Esperstadt specimen was kept in Dresden, that from Querfurt was kept in Jena. Both specimens are now lost, but casts of both specimens are pre- served in the Staatliches Museum fiir Naturkunde in Stuttgart (smns 80082-83), and in the Hum- boldt Museum in Berlin (mb R. 61-62) (Fig. 2). The specimens first reported in 1838 were rede- scribed as lower jaws of fishes by Meyer (1851), who renamed them Charitodon tschudii. Chari- todon {Charitosaurus) tschudii resembles Anaro- saurus in tooth structure, with a constricted base and an expanded crown, but the tooth crown of Anarosaurus is more distinctly lanceolate than the rather bulbous tooth crown of Charitosaurus. At the present time, Charitosaurus tschudii must re- main a nomen dubium. Morphological Description— The holotype of Anarosaurus pumilio is known from casts only. The original specimen consisted of part (dorsal view) and counterpart (ventral view). The Institute and Museum of Geology and Paleontology in Got- tingen holds two casts of the dorsal view that differ in size; measurements of limb bones taken from one cast (Go 409- lb) being consistently smaller than those taken from the other (Go 409- la). Oth- er casts kept at the natural history museums in Berlin, London, and Stuttgart (see above) yield different values again, indicating the limited ac- FIELDIANA: GEOLOGY Fig. 3. Cast of the skull of Anarosaurus pumilio Dames (holotype) (Institut fiir Geowissenschaften, Mar- tin-Luther-Universitat, Halle, M4/12). Scale bar = 20 mm. curacy of those casts. Unless noted otherwise, the measurements given below are from the Gottingen cast. Go 409- la. The skull (Figs. 3, 4) is incompletely preserved, partially crushed, and (or) destroyed by prepara- tion. In dorsal view, both premaxillae, the right maxilla, right prefrontal, and most of the skull table are well exposed. The distance from the tip of the snout to the posterior margin of the skull table (as preserved) is 34.5 mm, the distance from the tip of the snout to the posterior margin of the supraoccipital (as preserved) is 38 mm. The lon- gitudinal diameter of the (right) orbit is 1 3 mm, the longitudinal diameter of the upper temporal fossa is 5 mm (right) and 4.5 mm (left), respec- tively. The premaxilla forms the anterior and antero- FiG. 4. Skull of Anarosaurus pumilio Dames (holotype). A, Drawing of the cast kept at the Institut und Museum fur Geologic und Palaontologie, Georg-August-Universitat, Gottingen, Orig. Nr. 409-1); B, reconstruction of the skull in dorsal view. Scale bar = 10 mm. Abbreviations: ar, articular; f, frontal; m, maxilla; p, parietal; pm, premaxilla; po, i>ostorbital; pof, postfrontal; prf, prefrontal; so, supraoccipital; sq, squamosal. RIEPPEL AND KEBANG: PACHYPLEUROSAURS dorsal margin of the external naris. A slender pos- terior process entered between the external nares, but its relation to the nasal and frontal remains unknown. The posterior process of the premaxilla does not extend beyond the level of the posterior margin of the external naris. Jaekel (1910) counted four, Arthaber (1924) five premaxillary teeth, numbers that seem to refer to the incompletely preserved left premaxilla. The exact tooth count is difficult to establish on the available casts, but the completely preserved right premaxilla shows a possible maximum of eight teeth or tooth po- sitions. Dames (1890) and Jaekel (1910) showed a characteristic leaflike expansion of the crown of the premaxillary teeth, which cannot be confirmed on the cast kept at the Institute and Museum of Geology and Paleontology in Gottingen; a spatu- late expansion of the tooth crown is distinct in one anterior premaxillary tooth in the casts kept at the Staatliches Museum fiir Naturkunde in Stuttgart as well as in the casts kept at the Natural History Museum in Berlin. The remaining premaxillary teeth are about 3 mm long, slightly recurved, and pointed. The exact structure of the maxilla re- mains obscure, as does the number of maxillary teeth. Posteriorly, the maxilla forms a short slen- der process, underlying the prefrontal in the an- teroventral margin of the orbit. The prefrontal is a broad, domed element, as is typical for pachypleurosaurs. It remained broadly separated from the postfrontal along the dorsal margin of the orbit, which is formed by the slightly concave lateral margin of the frontal. The partially fused frontals are long and slender elements, but their anterior portion is missing. Posteriorly, the frontals form an interdigitating suture with the parietals in a rather forward position. Slender pos- terolateral lappets of the frontals extend backward along the medial side of the postfrontals. The pa- rietals enclose a small parietal foramen that lies midway between the frontoparietal suture and the posterior margin of the parietals. Laterally, the parietal forms the medial margin of the upper tem- poral fossa. Posteriorly, tapering processes of the parietal extend laterally on to the occiput. The upper temporal fossa in Anarosaurus has rounded contours, and is smaller than the orbit but distinctly larger than the temporal fossa in Serpianosaums and Neusticosaurus. The postfron- tal forms a considerable portion of the anterior and anteromedial margin of the upper temporal fossa, the triradiate postorbital forms the lateral margin, and the squamosal borders the temporal fossa posteriorly. The upper temporal arch is nar- row, leaving the cheek deeply "excavated." The ventral process of the left postorbital carries a facet on its anterior margin that received the dorsal end of the jugal. Details of the suspensorium and of the occiput are difficult to ascertain except for the presence of a large supraoccipital with a low sag- ittal crest. j The palate is difficult to analyze. Little can be ' seen beyond the general outlines of the major el- ements and the location of the internal nares (Car- roll, 1981). In particular, it is impossible to con- firm the presence or absence of the ectopterygoid. A distinct ventral ridge marks the lateral edge of the pterygoid along the anteromedial and medial margin of the subtemporal fossa. Lateral to the left suspensorium, the articular facet of the lower jaw is preserved in situ, with the retroarticular process extending backward behind the mandibular articulation. A distinct trough can be identified on the dorsal surface of the retroar- ticular process. The right lower jaw is exposed in ventral view but shows little morphological detail. Its total length, including the retroarticular pro- i cess, is 47.5 mm. 1 Posterior to the skull, 1 6 cervical vertebrae are preserved in articulation. Arthaber ( 1 924) counted 1 5 cervicals, but obviously omitted counting the poorly exposed atlas. In dorsal view the cervicals j show pachyostotic neural arches with a low neural I spine; the ventral surface of the centrum is orna- mented with paired longitudinal keels. The size of the cervical vertebrae slightly and gradually in- creases from front to back. The length of the cen- trum is 4.2 mm in the axis, 4 mm in the 10th cervical, and 4.8 mm in the 1 6th cervial; the width of the corresponding elements, measured across the zygapophyseal articulations, is 5 mm, 6 mm, and 8 mm, respectively. Three cervical ribs (an incomplete number) can unequivocally be iden- tified, the anteriormost one of which lies adjacent to the 1 5 th cervical vertebra and carries a distinct free anterior process close to its proximal articular head. Separated from the cervical vertebrae by a gap, a total of 14 dorsal vertebrae (13 complete, 1 in- complete) are preserved in articulation, followed by the first sacral vertebra. The dorsal vertebrae show a weak constriction of the centrum in ventral view. Within the gap between the cervical and dorsal vertebrae series, 10 (left) ribs are exposed, plus the space for one additional rib that was not completely prepared. Following the 1 6 preserved cervical vertebrae, the contours of four additional elements can be identified (see also Nopcsa, 1 928); FIELDIANA: GEOLOGY obt.f. Fig. 5. Gastral ribs of Anarosaurus pumilio Dames (holotype) (drawn after smns 59073). A, Anterior gastral ribs; B, posterior gastral ribs. Scale bar = 10 mm. all lie in front of the first exposed Oeft) rib. With a total of 1 5 vertebral elements bridging the gap between the preserved series of cervical and dorsal vertebrae, a count of 45 presacral vertebrae results. Dames (1890) counted 43 presacrals, Arthaber ( 1 924) postulated 48 presacrals, and Nopcsa ( 1 928) counted 39—40 presacrals. Since the anteriormost rib exposed within the gap between cervicals and dorsals shows the morphology of a holocephalous dorsal rib without free anterior process, we con- clude that Anarosaunis had no more than 19-20 cervical vertebrae (in agreement with Nopcsa, 1928) and 25-26 dorsal vertebrae. The standard length was defined as the length of the last four presacral centra (Rieppel, 1989; Sander, 1989), and it is 23 mm (the length of the second but last presacral centrum is 5.5 mm; the standard length is the same in the casts from Gottingen and Berlin, but it is 21.3 mm in the cast from Stuttgart). The dorsal ribs lack pachyostosis. The gastral ribs are composed of five elements each (Peyer, quoted in Zangerl, 1935), the angled medioventral element bearing a distinct anterior tip at least in the anterior and middle part of the gastral region, and two lateral elements on either side (Fig. 5). The ratio of vertebral elements to gastral ribs is 1:2. Of the three sacral vertebrae, only the anteri- ormost is preserved. However, three sacral ribs can clearly be identified, of which the second one (1 1.5 mm long) is slightly larger than the first one (10,8 mm long), whereas the third one is only in- completely preserved. The sacral ribs are slightly expanded at their proximal end. Nothing is known of the caudal axial skeleton. The pectoral girdle is poorly preserved and/or exposed, and dermal elements cannot be identified unequivocally. The right scapula is preserved in ventral view, possibly in association with a frag- FiG. 6. The pubis of Anarosaurus pumilio Dames (holotype). Scale bar = 5 mm. Abbreviation: obt.f, ob- turator foramen. mentary clavicle. The right coracoid lacks its distal portion, but shows a rounded proximal head as well as a strongly concave anterior margin oppos- ing the less distinctly concave posterior margin. Of the pelvic girdle, the ilium is not exposed. The two ischia are preserved in articulation. They show a narrow ("rod-shaped" according to Nopcsa [1928, p. 31]) acetabular portion, strongly convex anterior and posterior margins, and a widely ex- panded ventral portion with a convex ventral mar- gin. The length of the ischium is 19 mm, its prox- imal width is 6.5 mm, the minimal width is 4 mm, and the width of the ventral part is 20 mm. The pubis oi Anarosaurus shows weakly concave an- terior and posterior margins. The obturator fora- men is not closed, but rather forms an open slit at the posterior margin of the pubis close to the acetabular margin of the bone. The concavity of the central (medial) margin of the pubis results in a distinct spine protruding from the anteroventral edge of the pubis (Fig. 6). A large thyroid fenestra was developed between the pubis and ischium. The length of the pubis is 19.5 mm, its proximal width is 10 mm, its minimal width is 7 mm, the distal width is 9 mm excluding the anteroventral spine, but 1 3 mm including the latter. The humerus (Fig. 7A) is the only element of the forelimb that is preserved. The element is slightly curved with a concave medial (preaxial) margin, a well-developed deltopectoral crest, and a broadly expanded distal portion. The entepicon- dylar foramen is well set off from the distal artic- RIEPPEL AND KEBANG: PACHYPLEUROSAURS Table 2. Measurements of the femur of Anarosaurus pumilio Dames, in different casts of the holotype. ec.r nt.f. ni Proxi- Mini- mal mal Distal Length width width width Go 409- la 35.5 7.5 3 6 Go 409- lb 32 7 2.5 5 BMNH 5691 40 8 3 6.5 mbR-57.1 36 7.3 3.3 6 MB R-57.2 36 7.1 3.1 5.8 SMNS 59073 35 6.2 2.4 5.6 (Rieppel, 1993), and Serpianosaurus (Rieppel, 1989; Sander, 1989). Measurements of the hu- merus differ on the various casts, as indicated in Table 1. The femur (Fig. 7B) is the only element of the hindlimb that is preserved. The bone is distinctly elongated, slender, and weakly sigmoidally curved. The surface of the bone shows the same striation on the proximal and distal ends as does the hu- merus. The measurements of the bone differ in the different casts available, as recorded in Table 2. Fig. 7. A, Humerus of Anarosaurus pumilio Dames (holotype) (drawn after mb R. 57); B, femur of Anaro- saurus pumilio (holotype) (drawn after smns 59073). Scale bar = 5 mm. Abbreviations: ec.r., ectepicondylar ridge; ent.f., entepicondylar foramen. ular facet, indicating that the specimen is adult, and a distinct ectepicondylar groove is present. The surface of the bone shows distinct striations radiating toward its proximal and distal ends. These striations are straight rather than vermiculate, more marked, and more widely spaced than the ridges and grooves described on the humerus of Neus- ticosaurns (Sander, 1989), ''Psilotrachelosaurus" Table 1. Measurements of the humerus of Anaro- saurus pumilio Dames, in different casts of the holotype. Proxi- Mini- mal mal Distal Length width width width Go 409- la 28.5 5 4 9 Go 409- lb 25 5 3 8 BMNH 5691 31 6 4 10 mbR-57.1 28 4.7 3.5 9 MB R-57.2 28.3 5.1 3.5 8.9 MB R-57.3 28.4 4.5 3.6 6 SMNS 59073 28.5 5 3.5 8.7 Anarosaurus heterodontus n. sp. Holotype— Institut fur Geowissenschaften, Martin-Luther-Universitat, Halle (M4/12): right dentary. Schaumkalk (upper lower Muschelkalk) of Freyburg/Unstrut. Referred Materl\l— Institut fiir Geowissen- schaften, Martin-Luther-Universitat, Halle (M4/ 12): left premaxilla; Schaumkalk (upper lower Muschelkalk) of Freyburg/Unstrut. Museum Frer- iks, Winterswijk (#20778): skull; lower Muschel- kalk, Winterswijk, Netherlands. Dl\gnosis— Same as for genus, but about twice as large as Anarosaurus pumilio and characterized by a heterodont dentition, a close approximation of prefrontal and postfrontal along the dorsal mar- gin of the orbit, and a distinct sculpturing of der- mal bone surface. Locus Typicus— Schaumkalk (upper lower Muschelkalk), Freyburg/Unstrut, Germany. Distribution— Lower Muschelkalk, Anisian, Europe. Morphological Description— The holotype (Fig. 8) consists of an incomplete right dentary. The total length of the fragment is 67 mm, and therefore represents an animal about twice the size of the holotype of Anarosaurus pumilio. The den- tary bears a total of 1 9 preserved teeth, which all FIELDIANA: GEOLOGY Fig. 8. Holotype ofAnarosaurus heterodontus n. sp., right dentary (Institut fur Geowissenschaften, Martin- Luther-Universitat, Halle, M4/12). Scale bar = 10 mm. share the form diagnostic of the genus Anarosaums (i.e., a constricted tooth base and a lanceolate tooth crown). Of the preserved teeth, the anterior two are distinctly larger (4.5 mm high) than the suc- ceeding teeth (2.5 mm high). Preparation of the dentary from the ventral side revealed a narrow symphysis as is characteristic of pachypleurosaurs. Overall size, tooth morphology, and the increased size of the anterior dentary teeth render the fossil closely similar to a lower jaw reported from the lower Muschelkalk of Winterswijk, erroneously referred to Cymatosaurus (Oosterink, 1986, Foto 40). A perfectly preserved left premaxilla from the Schaumkalk of Freyburg/Unstrut (Fig. 9) has a dentition that matches the morphology diagnostic of Anarosaurus. The premaxilla bears five teeth, if a posterolateral trough is interpreted as a facet for the maxilla rather than as part of an alveolus for a sixth tooth. But even with six functional teeth on the premaxilla the number is less than the eight teeth observed on the premaxilla of Anarosaurus pumilio. The premaxilla from the Schaumkalk of Freyburg/Unstrut is again about twice the size of the premaxilla in the holotype of Anarosaurus pumilio: the distance from the tip of the snout to the anterior margin of the external naris is 25.7 mm in the first, 13.2 mm in the latter. In terms of size and morphology (five tooth po- sitions), the premaxilla from the Schaumkalk of Freyburg/Unstrut again compares closely to ma- FiG. 9. Anarosaurus heterodontus n. sp., left pre- maxilla (Institut fur Geowissenschaften, Martin-Luther- Universitat, Halle, M4/12). Scale bar = 10 mm. Abbre- viations: mf, maxillary facet; np, nasal process; vp, vo- merine process. terial from the lower Muschelkalk of Winterswijk, which includes a skull deposited in the Museum Freriks, as well as a large amount of undescribed material kept in private collections (Oosterink, 1986, Foto 38). The skull in the Museum Freriks (#20778; Fig. 10) shows a number of characters diagnostic of pachypleurosaurs, such as the rela- tively short and unconstricted snout, the large pre- frontal, the presence of a scleral ring, and the rel- atively short postorbital portion of the skull, and it shares with other pachypleurosaurs from the lower Muschelkalk the deep embayment of the cheek region and the relatively large upper tem- poral fossa (as compared to the Serpianosaurus- Neusticosaurus dade). Apart from relative size and the heterodont dentition (enlargement of the an- terior dentary and premaxillary teeth), the skull differs from the holotype of Anarosaurus pumilio by a close approximation of prefrontal and post- frontal, restricting the frontal to a very narrow entry into the dorsal margin of the orbit. Discussion— The material from the Schaum- RIEPPEL AND KEBANG: PACHYPLEUROSAURS Fig. 10. A narosaurus heterodontus n. sp. , skull in left lateral view, from the lower Muschelkalk of Winterswijk (Museum Freriks, #20778). Scale bar = 20 mm. kalk (upper lower Muschelkalk) of Freyburg/Un- strut and that from the lowermost Muschelkalk of Winterswijk represent a new species of Anarosau- rus that is geologically somewhat older than An- arosaurus pumilio from the lower middle Mus- chelkalk. Morphological differences include ab- solute size, the number of premaxillary teeth, the relative size of the anterior dentary and premax- illary teeth, and the configuration of the prefrontal and postfrontal bones. It may be noted that the lower Muschelkalk in the western part of the Ger- manic basin (Winterswijk) is geologically some- what younger that the lower Muschelkalk deposits in the eastern part of the basin (Freyburg/Unstrut), which brings the two localitites close in geological time. Using Captorhiniis (Heaton, 1979) Petrolaco- 5aMms (Reisz, 1981), C/aw^/osawms (Carroll, 1981), and Youngina (Gow, 1975) as successive out- groups (Storrs, 1991, 1993a), v4narc>5aMrus shows the following plesiomorphic characters: relatively large upper temporal fossae with both the post- frontal and the parietal broadly entering the an- terior and anteromedial margin of the fenestra; postorbital distinctly triradiate; humerus retaining an ectepicondylar groove in addition to an entepi- condylar foramen, and a well-developed delto- pectoral crest; dorsal ribs without pachyostosis; gastral ribs composed of five elements each. Apomorphic features of Anarosaurus include the spatulate expansion of the crown of the teeth, a character discussed and figured in detail by Dames (1890) but which is difficult to ascertain on the basis of the available casts of the holotype of An- arosaums pumilio. The distinction of cervical from dorsal vertebrae is difficult in reptiles in general, a problem aggravated by the fact that the transition is very poorly preserved in Anarosaurus. Never- theless, a count of 25-26 dorsal vertebrae is most probable, and it is distinctly higher than in all other pachypleurosaurs known. Both overall size and the position of the ente- picondylar foramen at some distance from the dis- tal articular surface of the humerus indicate a ma- ture individual, yet the obturator foramen in the pubis remains widely open. The pubis carries a distinct anteroventral spine resulting from a con- cavity of its ventral (medial) margin, otherwise known only in Serpianosaurus among other pachy- pleurosaurs (Rieppel, 1989). Isolated elements with an open obturator foramen and an anteroventral spine have also been reported from the base of the middle Muschelkalk (Hagdom 8l Simon, 1993), and a concave lower margin of the pubis is a gen- eral character for Simosaurus and Nothosaurus among eusauropterygians. Carroll and Gaskill (1985, p. 349; see also Kuhn- Schnyder, 1959; Rieppel, 1993) considered the elongated femur diagnostic of Anarosaurus. Mea- surements of the femur differ on different casts, but inspection of Table 2 indicates that 35.75 mm is an average estimate of the length of the femur. Using 23 mm as standard length, the ratio femur length/standard length is 1.55, an exceptionally high value among all other pachypleurosaurs known (Rieppel, 1993), corroborating relative fe- mur length as a diagnostic feature of Anarosaurus (Table 3). The corresponding values for other taxa are 0.86 for "Psilotrachelosaurus," 0.97-1.2 for Serpianosaurus (juveniles and adults, both sexes), 0.9 1-1 .5 for Neusticosaurus pusillus (juveniles and adults, both sexes), 0.79-1.06 for Neusticosaurus peyeri (juveniles and adults, both sexes), and 0.65- 0.96 for Neusticosaurus edwardsii (juveniles and adults, both sexes). The distinct striations on the surface of humerus and femur near the proximal and distal heads form another characteristic fea- ture of this genus (sometimes also observed on well-preserved humeri and femora of Neustico- saurus: H.-D. Sues, pers. comm.). If these stria- tions are taken as indicators of adult individual age, they document that differences in overall body size and degree of bone sculpturing are not merely ontogenetic variations in Anarosaurus pumilio and Anarosaurus heterodontus. Dactylosaurus Giirich, 1884 Type SvEdES— Dactylosaurus gracilis Giirich, 1884. 10 FIELDIANA: GEOLOGY Generic Diagnosis— A small pachypleurosaur with a narrow interorbital bridge formed by the frontals; a close approximation of the postfrontal and prefrontal along the dorsal margin of the orbit due to a long and slender anterior process of the postfrontal (leaving a narrow entry of the frontal in the dorsal margin of the orbit); long but narrow (kidney-shaped) upper temporal fenestrae; no con- striction of the dorsal vertebral centra; clavicles with an anterolateral expansion; preaxial margin of the radius with a distinctly concave margin. The humerus is plesiomorphic at the level of the Pachypleurosauroidea but unique within the group by the retention of an entepicondyle distinctly set off from the shaft (in sex y). Distribution— Lower Muschelkalk, central Europe. Dactylosaurus gracilis Giirich, 1884 1884 Dactylosaurus gracilis, Giirich, p. 125, PI. 2, Figs. 1, 2. 1886 Dactylosaurus gracilis, Giirich, pp. 457- 458, text fig. 1. 1886 Dactylosaurus gracilis, Deecke, p. 187. 1 899 Dactylosaurus gracilis, Schrammen, PI. 25, Fig. 10. 1924 Dactylosaurus gracilis, Arthaber, pp. 483- 484, text fig. 14. 1928 Dactylosaurus schroederi, Nopcsa, pp. 3 1- 37, PI. 3, Figs. 1-6. 1935 Dactylosaurus gracilis, Zangerl, p. 66. 1935 Dactylosaurus schroederi, Zangerl, p. 67. 1959 Dactylosaurus gracilis, Kuhn-Schnyder, p. 652. 1959 Dactylosaurus schroederi, Kuhn-Schnyder, p. 652. 1985 Dactylosaurus gracilis. Sues and Carroll, pp. 1602, 1608. 1985 Dactylosaurus schroederi. Sues and Carroll, pp. 1602-1608, text figs. 1-3. 1987 Dactylosaurus gracilis, Rieppel, pp. 1 109- 1110. 1987 Dactylosaurus schroederi, Rieppel, pp. 1 109-1 1 10. 1993 Dactylosaurus gracilis, Rieppel, p. 10. 1993 Dactylosaurus schroederi, Rieppel, p. 10. HoLOTYPE.— Dactylosaurus gracilis was de- scribed by Giirich (1884) on the basis of a cast made from a natural mold (Fig. 1 1) deposited at the Institute of Geological Sciences, University of Wroclaw (mgu Wr 3871s). A cast corresponding c -a S¥ 3 2 Ji Xi "3. *J >> c J3 V a > <£73 u V u ^ s c a "^ a u .2 J O t/> O. et O — ^^ o "* ^•s. .2 3 .-5 sill 2.» 11 II ill I 5 •Si g « o I *s3 ^1 •* o o o o o 00 •* *n Ov — < vo CTv vO ^ Tt 00 vO >n — vq 0 vo Q Tt CO «*% —<* Q —•' Q -^ I I I T I T I r<^ — r~- 00 Cn O -" 0 r<^ O O O ^ rt -^ r^ V) r^ ■^ n ov O — r^ (N O; r-_ —_ 00 P^ O; <*i d d d c> d O — ' — o > "O cj 3-0«333i;iJ RIEPPEL AND KEBANG: PACHYPLEUROSAURS 11 Fig. 1 1. Holotype of Dactylosaurus gracilis Giirich (mgu Wr 3871s). Scale bar = 20 mm. to the figure given by Giirich (1884, PI. II, Figs. 1 , 2) is kept at the Natural History Museum, Hum- boldt University, Berlin (mb R. 63). The holotype comes from Michalkowitz, Upper Silesia (now Michalowice, Poland), assigned to the lower Mus- chelkalk. The holotype of Dactylosaurus schroederi Nopcsa, 1928, was deposited in the collections of the Preussische Geologische Landesanstalt in Ber- lin (Kuhn, 1934), and now is in the collections of the Bundesanstalt fur Geowissenschaften und Rohstoffe, Berlin (uncatalogued) (Fig. 1 2). A rubber cast of the specimen, described by Sues and Carroll (1985), is kept at the Forschungsinstitut und Na- turmuseum Senckenberg, Frankfurt a.M. (smf R-4097 a, b). The holotype comes from deposits assigned to the lower Muschelkalk of Gross-Stein, Upper Silesia. The holotypes of Dactylosaurus gracilis as well as D. schroederi are both natural molds preserved in yellow matrix. The color of the matrix, as well as the preservation of vertebrate fossils as natural molds, is characteristic of the upper Buntsandstein (Rot) which underlies the lower Gogolin Beds (H. Hagdom, pers. comm.). Referred Material— Institut und Museum fur Geologic und Palaontologie, University of Tii- bingen, uncatalogued (Fig. 13), lowermost Mus- chelkalk of Gogolin (lower Gogolin beds). A poor- ly preserved specimen represented by barely vis- ible impressions of the skull, cervical and anterior dorsal region of the vertebral column preserved in dorsal view or as faint impression (of the ventral aspect), right humerus, and left forelimb. The specimen is slightly larger than the one described by Nopcsa (1928). Nopcsa ( 1 928) and Sues and Carroll ( 1 985) refer to Meyer (1847-1855) who figured humeri closely similar to those of Dactylosaurus gracilis from the Muschelkalk ("Saurier-Kalk") from Jena. Other humeri of this type are known from the lower Muschelkalk of Bobrek near Beuthen (Bundesan- stalt fur Geowissenschaften und Rohstoffe, Berlin, drawer S 45/5 right) (Fig. 14), and from the Mus- chelkalk of Gogolin (Museum fur Naturkunde, Berlin, mb R. 772. 1 ., MB R. 769, and uncatalogued; Institut und Museum fur Geologic und Palaon- tologie, University of Tubingen gpit 1744/1-10: Rieppel, 1993). Diagnosis— Same as for genus, of which this is the only known species. Locus Typicus— Upper Buntsandstein of Michalowice, Upper Silesia (Gomy Slask, Po- land). Distribution— Upper Buntsandstein and low- er Muschelkalk, Europe. CoMMEt^TS— Dactylosaurus gracilis is the type species of the genus (Giirich, 1 884). The cast avail- able in the Natural History Museum in Berlin is of rather poor quality, and shows little morpho- logical detail. The following description of the specimen is based on a new silicon cast made from 12 FIELDIANA: GEOLOGY Fig. 1 2. Holotype of Dactylosaurus schroederi Nopcsa (bor, uncatalogued). the holotype in 1 994. Preserved are the posterior part of the skull, the cervical vertebral column, the pectoral girdle, and the right forelimb, all ex- posed in dorsal view on the cast. The posterior part of the skull shows a deeply excavated cheek and relatively large, kidney-shaped upper temporal fossae. Sutures are difficult to identify except for the posterior end of the post- frontal, which defines the anteromedial margin of the upper temporal fossa. Sixteen cervical verte- brae (including the atlas) are preserved in articu- lation; an additional vertebra would have been positioned at the level of the clavicles. This count of 1 7 cervical vertebrae corresponds to the holo- RIEPPEL AND KEBANG: PACHYPLEUROSAURS 13 Fig. 13. Dactylosaurus gracilis Giirich from the lower Muschelkalk of Gogolin, Upper Silesia (Gomy Slask, Poland) (gpit, uncatalogued). Fig. 1 4 . Dactylosaurus gracilis Giirich, humerus, from the lower Muschelkalk of Bobrek near Beuthen (bgr, drawer S 45/5 right). Scale bar = 10 mm. type of Dactylosaurus schroederi Nopcsa, 1928. Cervical ribs can only be identified along the pos- terior part of the cervical vertebral column, and they are of typical structure with a free anterior process. The centra of four anterior dorsal verte- brae are preserved and exposed in ventral view on the actual specimen: they show no sign of con- striction, but slightly convex lateral margins in- stead. The proximal part of the dorsal ribs (as far as preserved) shows no pachyostosis. In the pectoral girdle, the distal end of the clav- icle is seen to overlap with the anterior and medial aspect of the scapula in a typical pachypleurosau- roid pattern. The interclavicula cannot be iden- tified. The clavicle shows expanded lateral comers that are not as pronounced as in the holotype of Dactylosaurus schroederi, possibly a juvenile char- acter. The coracoids are represented by impres- sions only. Their length is 7.4 (8) mm, their prox- imal width is 3.6 (3) mm, their minimal width is 3.4 (3.4) mm, and their distal width is 4.6 (5.3) mm (values in parentheses refer to the right ele- ment; all measurements were taken on the natural mold). The coracoids of both sides meet ventrally in a well-defined suture, but their proximal ex- pansion is relatively weak, and the proximal mar- gin shows no notch indicating the position of the 14 FIELDIANA: GEOLOGY mc hu Fig. 1 5. Dactylosaurus gracilis Gmich, holotype (mgu Wr 387 Is), right forelimb. Scale bar = 5 mm. Abbreviations: dc4, distal carpal 4; hu, humerus; in, intermedium; mc,, metacarpal 1; mcj, metacarpal 5; ra, radius; ul, ulna; uln, ulnare. coracoid foramen. This might indicate incomplete ossification of the coracoid in a juvenile si)ecimen. The right front limb is well preserved (Fig. 1 5). The right humerus is a slightly curved element that shows hardly any morphological differentiation, as is characteristic of juvenile pachypleurosaurs (Rieppel, 1989; Sander, 1989). The deltopectoral crest is hardly differentiated, and an entepicon- dylar foramen cannot be identified. In juvenile pachypleurosaurs, the entepicondylar foramen lies at the distal margin of the ossified part of the hu- merus or, in even earlier stages, beyond that (Riep- pel, 1989; Sander, 1989). The total length of the humerus is 11.9 mm, its proximal width is 2. 1 mm, its minimal width is 1.85 mm, and its distal width is 2 mm. The radius is incompletely exposed due to the overlapping ulna, but appears slightly longer than the ulna. Total length of the radius is 6.3 mm, that of the ulna is 5.8 mm. Some con- troversy surrounds the structure of the carpus (Giirich, 1886), but the new cast taken from the holotype corroborates Giirich's (1886) description of three ossified carpal elements. The intermedium is elongated and rectangular in shape; posterior to it lie the rounded ulnare and distal carpal 4. The phalanges are incompletely preserved, probably due to incomplete ossification. The cast shows a number of ossified elements that correspond to Giirich's (1886) illustration of 2-3-3-4-3. Un- guals are unequivocally identified on digits 1 and 2 only; the count for the remaining digits may therefore be incomplete. Sander (1989) docu- mented a proximo-distal sequence of ossification of the phalanges in Neusticosaurus pusillns. The overall size of Dactylosaurus gracilis, and details of morphology throughout the skeleton, in- dicate that the holotype of that siiecies is a juvenile specimen. The only character potentially contra- dicting this conclusion is the advanced degree of ossification in the carpus, but variation in the tim- ing of ossification can be extensive in extant rep- tiles (Rieppel, 1 994a). The relatively low count of cervical vertebrae (17) is shared with Dactylosau- rus schroederi Nopcsa, 1928, and is otherwise known only from lower Ladinian pachypleuro- saurs {Neusticosaurus peyeri: Sander, 1989; Neus- ticosaurus edwardsii: Carroll & Gaskill, 1 985). The latter taxa are characterized by a relatively smaller upper temporal fossa than is observed in Dacty- losaurus gracilis and D. schroederi. On the basis of the limited data available, we conclude that Dactylosaurus gracilis Giirich, 1884 and Dacty- losaurus schroederi Nopcsa, 1 928, are subjective synonyms (see also Sues & Carroll, 1 985); the first name has priority. Morphological Descrifhon— The morpho- logical description oi Dactylosaurus gracilis is based on new latex casts made from the original speci- men (natural mold) described by Nopcsa (1928, holotype of Dactylosaurus schroederi), as well as on the rubber casts kept at the Senckenberg Mu- seum, Frankfurt. The specimen is represented by natural molds of part and coimterpart. The total length of the fossil must remain unknown because of the incompletely preserved tail, but it must have exceeded 213 mm; snout-vent length is 158 mm. Skull length (the length of the left lower jaw ramus in ventral view) is 27 mm; glenoid-acetabulum length (measured on the right side of the body) is 68 mm; standard length (length of the last four dorsal vertebral centra) is 15.5 mm (the length of the last dorsal vertebral centrum is 3.5 mm). In the skull (Fig. 1 6), the snout complex is not well exposed. The nasal process of the premaxilla remains separated from the frontal by the broad nasals, which meet along a middorsal suture. The frontal forms a short anteromedial process enter- ing between the nasals, as well as short anterolat- eral processes that meet the maxilla and thereby separate the prefrontal from the nasal. The pre- frontal reaches high up along the anterodorsal margin of the orbit. The postfrontal forms a slen- RIEPPEL AND KEBANG: PACHYPLEUROSAURS 15 Fig. 16. Skull of Dactylosaunis gracilis Giirich (bgr, uncatalogued). A, Drawn after a new cast made from the original of Nopcsa (1928); B, reconstruction of the skull in dorsal view. Scale bar = 5 mm. Abbreviations: ar, articular, f, frontal; m, maxilla; n, nasal; p, parietal; pm, premaxilla; po, postorbital; pof, postfrontal; prf, prefrontal; q, quadrate; so, supraoccipital; sq, squamosal. der anterior process running along the postero- dorsal margin of the orbit. The prefrontal and postfrontal fail to meet, however, allowing the frontal to enter into the dorsal margin of the orbit for a short distance. The interorbital bridge formed by the paired frontals is narrow (2 mm in the latex cast taken from the original specimen). The fron- toparietal suture is in a rather forward position. The posterolateral processes of the frontals extend posteriorly between the parietal and postfrontal. The skull table is well exposed. The upper tem- poral fossae are relatively large and of an elongated kidney shape. The length of the upper temporal fossa is 4.3 mm (right) and 4.5 mm (left), respec- tively; the width of the upper temporal fossa is 1.5 mm (right) and 1.3 mm (left), respectively. The postfrontal, the triradiate postorbital, the parietal, and the squamosal all participate in the formation of the margin of the upper temporal fossa. The paired parietals enclose the pineal foramen, which is positioned halfway along the length of the pa- rietals. The occiput is difficult to analyze. In particular, the occipital exposure of the parietal, and its re- lation to the squamosal, remain unclear. The ventral view of the skull displays a dermal palate of typical pachypleurosauroid structure; lit- tle can be added to its description and illustration by Sues and Carroll (1985). The pterygoid shows a thickening (a rudimentary "transverse flange") 16 FIELDIANA: GEOLOGY along the anterior margin of the subtemporal fos- sa. There is no positive evidence for the presence or absence of an ectopterygoid. A ceratobranchial element is preserved, overlying the posterior part of the left pterygoid. Dactylosaunis gracilis shows a total of 36 pre- sacral vertebrae, of which 1 7 are counted as cer- vical elements (Sues & Carroll, 1985), character- ized by a keeled ventral surface of the centrum. The ventral surface of the dorsal centra is smooth, and the centra are not constricted. The neural arches are pachyostotic, and the neural spines are consistently low. Based on the Senckenberg casts. Sues and Carroll (1985) believed the neurocentral sutures to be closed in Dactylosaunis gracilis, but they are quite distinct in the cervical, posterior dorsal (where they pass below the transverse pro- cesses), sacral, and preserved caudal region (where they pass through the transverse processes). The material does not allow the presence of a neuro- central suture in the anterior dorsal region to be ascertained. Sues and Carroll (1985) describe atlantal ribs, which are difficult to identify, however. The cer- vical ribs bear a distinct free anterior process. The dorsal ribs are not pachyostotic, and the last three dorsal ("lumbar") ribs are distinctly reduced in length. Dactylosaunis gracilis shows three sacral ver- tebrae. The sacral ribs are broad, stout elements with a weak proximal expansion; they are not fused to the respective vertebrae. Caudal ribs (again not fused to caudal vertebrae) and chevron bones are not well exposed. Gastral ribs are likewise poorly preserved, but what little is present suggests that they are composed of five elements each, one me- dioventral and two lateral ones on either side. Little can be added to Sues and Carroll's (1985) description of the pectoral girdle. The right clav- icle shows a rounded and somewhat expanded an- terolateral edge (Fig. 17). This character is oth- erwise known from A narosaurtds only among other pachypleurosaurs (undescribed material from Winterswijk), but is distinctly developed in the eusauropterygian genera Nothosaurus and Simo- saurus (pers. obs.). The overlap of the clavicles with the anterior and medial surface of the scapula is well exposed in dorsal view on the right side of the specimen. The shape of the interclavicle re- mains unknown. The scapula is of the typical sau- ropterygian structure with a reduced and poste- riorly directed dorsal wing. The coracoid foramen is distinct and enclosed between the notched pos- teromedial margin of the scapula and the opposing Fig. 17. Pectoral girdle of Dactylosaunis gracilis Giirich (bgr, uncatalogued), drawn after a new cast made from the original of Nopcsa (1928). Scale bar = 5 mm. Abbreviations: cl, clavicle; co, coracoid; co.f., coracoid foramen; cr, cervical rib; icl, interclavicle; sc, scapula. posterolateral margin of the coracoid. The right coracoid measures 12.5 mm in length. In the pel- vic girdle, the pubis shows a complete enclosure of the obturator foramen by bone (Fig. 1 8); the bone is completely fused between the obturator foramen and the posterior edge of the pubis. The pubis is a relatively broad element with a length of 1 1 mm, a proximal width of 6.8 mm, a minimal width of 5 mm, and a distal width of 7.8 mm. The right ischium is well exposed, and shows a mark- edly thickened proximal (acetabular) portion. The bone is 1 2 mm long, its proximal width is 4.5 mm, its minimal width is 3.5 mm, its distal width is 1 3 mm. Sues and Carroll (1985) describe a well-de- veloped supra-acetabular buttress, but in ventral view the ilium does not display its acetabular por- tion; in dorsal view; the left ilium is concealed by sacral ribs. RIEPPEL AND KEBANG: PACHYPLEUROSAURS 17 obt.f. Fig. 18. Right pubis of Z)ac/>'/o5aMrus^rac/7wGurich (bgr, uncatalogued), drawn after smns R-4907a. Scale bar = 5 mm. Abbreviations: il.f., facet for ilium; is.f., facet for ischium; obt.f, obturator foramen. The humerus of Dactylosaurus gracilis is very distinctive (Fig. 1 9), at least in sex y {sensu Riep- pel, 1989, and Sander, 1989; see also the discus- sion in Rieppel, 1993). The element bears a well- developed deltopectoral crest distinctly set off from the waisted diaphysis. The distal head is broadly expanded, with the entepicondyle forming a me- dial process distinctly set off from the articular head. The entepicondylar foramen lies at some distance from the distal articulation. The distal articular heads are level. A deep ectepicondylar ridge is present. The radius of Dactylosaurus gracilis appears to be characterized by a distinct notch in the medial (preaxial) margin of the shaft (Fig. 20 A). Sues and Carroll (1985, p. 1607) attribute this feature to a preservational artifact. Latex casts taken from the original specimen show the concavity on the pre- axial margin of the radius in both limbs, more distinctly in their ventral exposure (and a similar concavity is also observed in the radius of unde- scribed Anarosaurus material from Winterswijk). ec r ec.r. ent.f. B Fig. 1 9. Humerus of Dactylosaurus gracilis Giirich (bgr, uncatalogued). A, Right humerus in ventral view, drawn after smns R-4907a; B, left humerus in dorsal view, drawn after smns R-4907b. Scale bar = 5 mm. Abbreviations: ec.r., ectepicondylar ridge; ent, entepi- condyle; ent.f, entepicondylar foramen. The ulna is somewhat shorter than the radius and bears a weakly developed olecranon on its ex- panded proximal head. The carpus (Fig. 20A) comprises three undis- puted ossified elements, viz. the intermedium, the ulnare, and the fourth distal carpal. The inter- medium is of subcircular shape and lies distal to the spatium interosseum between radius and ulna. A pisiform is distinct in Nopcsa's ( 1 928) retouched photograph of the specimen, and its presence (or that of a neomorph in its position) was confirmed by Sues and Carroll (1985). Latex casts taken from the original sp)ecimen indicate the presence of a minute structure next to the ulnare in the left limb only. If that structure represents a carpal ossifi- cation, the pisiform (or a neomorph) would be extremely small and present in one limb only. In extant reptiles, the pisiform generally is the last of all carpal elements to ossify (Rieppel, 1992). Ev- idence that this bone (or a neomorph) is, indeed. Table 4. Measurements of the humerus in articulated specimens of Dactylosaurus gracilis Giirich. Length Proximal width Minimal width Distal width Left Right Left Right Left Right Left Right Specimen Giirich (1884) Specimen Nopcsa (1928) Specimen in Tiibingen 20.5 25.2 11.9 21 25.6 4 5.1 2.1 4 5 3 3 1.85 2.8 3 2 7 6.5 7 7.2 i 18 FIELDIANA: GEOLOGY mc B Fig. 20. Manus and pes of Dactylosaurus gracilis Giirich (bgr, uncatalogued). A, Left forelimb, dorsal view, drawn after smns R-4907b; B, right hindlimb, ventral view, drawn after smns R-4907a. Scale bar = 5 mm. Abbre- viations: as, astragalus; ca, calcaneum; dc4, distal carpal 4; dt4, distal tarsal 4; fi, fibula; in, intermedium; mci, metacarpal 1; mcj, metacarpal 5; mt,, metatarsal 1; mt,, metatarsal 5; pi, pisiform; ra, radius; ti, tibia; ul, ulna; uln, ulnare. present in Dactylosaurus gracilis is here consid- ered equivocal. The phalangeal count in the manus is 2-3—4-7-3. The presence of either four or five phalanges in the fourth digit cannot be ascertained unequivocally. Measurements of the humerus are given in Table 4. Only the proximal head of the left femur and the distal head of the right femur are exposed. These indicate a slender bone with tibial and fib- ular articular heads level. The right fibula is only partially exposed. The right tibia is a little sturdier than the fibula but it is still a rather slender bone Table 5. Measurements of the limb bones of Dactylosaurus gracilis (holotype of Dactylosaurus schroederi Nopcsa; BGR, uncatalogued). ] Length Proximal width Minimal width Distal width Left Right Left Right Left Right Left Right Humerus 20.5 21 4 4 3 2.8 7 6.5 Radius 11.1 11.1 2.5 2.2 1 1 1.8 1.6 Ulna 10.2 9.7 2.9 2.8 1.2 1.2 2.9 2.8 Metacarpal 3 4.5 4.7 — — — — — — Metacarpal 4 3.8 3.9 — — — — — — Femur — — — — — — — — Tibia — 9.8 — 3 — 2.0 _ 2.3 Fibula — _ — — — — — — Metatarsal 3 _ 6.5 — — — _ _ _ Metatarsal 4 - 6.8 - - - - - - RIEPPEL AND KEBANG: PACHYPLEUROSAURS 19 with a straight medial, and a slightly concave lat- eral, margin. Three ossified elements can be iden- tified in the tarsus (Fig. 20B), viz. the astragalus, calcaneum, and the fourth distal tarsal. The pha- langeal formula in the pes is 2-3-7-5—4, five pha- langes in the fourth digit representing the plesio- morphic condition. Measurements of the limb bones of the specimen described by Nopcsa are given in Table 5. Discussion— The body proportions of Dacty- losaurus gracilis fall squarely within the range of variability of the Monte San Giorgio pachypleu- rosaurs (Table 3). The upper temporal fenestrae are distinctly smaller than the orbit, yet distinctly larger than the upper temporal fenestrae in Ser- pianosaurus and Neusticosaurus. As in Anarosau- rus, the postfrontal, postorbital, and parietal broadly enter the margin of the upper temporal fossa (unlike in Serpianosaurus and Neusticosau- rus), but the upper temporal fenestrae in Dacty- losaurus gracilis are rather narrow and elongated as opposed to the subcircular contours of the upper temporal fenestra in Anarosaurus. As in Anaro- saurus, the upper temporal arch of Dactylosaurm is narrow and the cheek deeply excavated, unlike Serpianosaurus and Neusticosaurus, which show a broadened postorbital and squamosal. Like oth- er pachypleurosaurs, Dactylosaurus shows a rather anterior position of the frontoparietal suture, with distinct posterolateral processes of the frontals ex- tending backward between the parietal and post- frontal. Dactylosaurus gracilis differs from other pachypleurosaurs except Keichousaurus in the nar- row interorbital bridge formed by the frontals; the close approximation of the prefrontal and post- frontal bones along the dorsal margin of the orbit is shared with undescribed Anarosaurus material from Winterswijk. The latter character is associ- ated with the development of a long and slender anterior process of the postfrontal. The cervical vertebral count in Dactylosaurus gracilis is low compared to other pachypleuro- saurs, particularly those of the lower Muschelkalk {Anarosaurus: 19-20 [see above]; Keichousaurus: 26; Serpianosaurus: 714-18 [Rieppel, 1 989]; Neus- ticosaurus: 15-20 [Carroll &. Gaskill, 1985; Sand- er, 1989], but the significance of this character is difficult to assess because of the lack of data on intraspecific variability. Vertebrae are difficult to count in the Tubingen specimen of Dactylosaurus gracilis, but there may be as many as 1 9 cervicals (and 1 7 preserved dorsals). The morphology of the humerus of Dactylosau- rus is quite distinctive. Nopcsa ( 1 928; see also Sues & Carroll, 1985, p. 1607) found it similar to iso- lated humeri from the lower Muschelkalk referred to "Macrotracheli" by H.v. Meyer (1847-1855). Huene (1942, Fig. 11) figured a humerus from much younger deposits (lowermost Lettenkohle of Schwabisch Hall, southern Germany), which Sues and Carroll (1985, p. 1607) again found similar to that of Dactylosaurus, but the Lettenkohle speci- men appears more curved rather than angulated as in the humerus of Dactylosaurus, and the ent- epicondyle is set off" from the shaft by a crack rather than a notch. Indeed, the specimen figured by Huene (1942) closely resembles the humerus of Neusticosaurus pusillus (Sander, 1989, Fig. 15c), and does not indicate the extension of the strati- graphic occurrence of Dactylosaurus beyond the lower Muschelkalk. The humerus of Dactylosaurus gracilis (sex y sensu Rieppel, 1989; Sander, 1989) is plesio- morphic with respect to all other pachypleurosaurs in the retention of a well-differentiated entepicon- dyle and a distinct ectepicondylar groove. The ju- venile specimen described by Giirich (1884) in- dicates similar ontogenetic changes in the mor- phological differentiation as those known in other pachypleurosaurs (Rieppel, 1989; Sander, 1989), while a series of humeri from the lower Muschelk- alk of Goglin, Upper Silesia (GPIT 1744/1-10) indicates a similar sexual dimorphism in Dacty- losaurus gracilis as is known for other pachypleu- rosaurs (Rieppel, 1989; Sander, 1989). As in other pachypleurosaurs, the index of minimal width/ distal width is most informative with respect to ontogenetic changes and sexual dimorphism in the differentiation of the humerus. Plotting all avail- able material (see referred material above) results in an index of 0.53-0.67 for sex x and/or juveniles, and 0.40-0.57 for adult specimens of sex y. Over- lap of this ratio (in the range of 0.54-0.57) between sexes is restricted to three specimens (mb R. un- catalogued, gpit 1744/1-2), and may reflect nat- ural variability as well as wear of the ectepicondyle during postmortem transport. Sauropterygia incertae sedis Huene (1944) described an isolated humerus from the lowermost Muschelkalk (lower Gogolin beds) of Gogolin, Upper Silesia, which is housed in the Staatliches Museum fur Naturkunde, Stutt- gart (SMNS 16253). The humerus is noteworthy because of its well-developed deltopectoral crest. 20 FIELDIANA: GEOLOGY the presence of a rudimentary supinator ridge, a distinct ectepicondylar groove, and the absence of an entepicondylar foramen (Fig. 21). The total length of the humerus is 104.1 mm, its proximal width is 28.5 mm, minimal width at mid-diaph- ysis is 1 2.4 mm, and the distal width is 29 mm. The humerus is morphologically well differen- tiated and in one character (presence of the supi- nator ridge) more plesiomorphic than any other sauropterygian humerus known. It differs from the humerus of Dactylosaurus in the absence of an entepicondylar foramen and in the absence of an entepicondyle distinctly set off from the shaft of the bone. Humeri of Nothosaurus sp. from the lower Muschelkalk (Natural History Museum, Humboldt University, Berlin, MB R. 1 62.2; mb R. 162.4; MB R. 777; mb R. I. 007; Martin Luther Universitat, Institut fur Geowissenschaften, Hal- le, uncatalogued) differ from smns 16253 by the absence of the supinator ridge, by the presence of an entepicondylar foramen, and by a less distinctly developed ectepicondylar groove. Also, the hu- merus oi Nothosaurus is relatively broader at mid- diaphysis than is smns 16253. Indeed, the slender appearance of the humerus smns 16253 renders it comparable to two humeri of Cymatosaurus, one from the lower Muschelkalk of Winterswijk, Neth- erlands (smns 58463), the other from the upper- most lower Muschelkalk (Schaumkalk) of Frey- burg a.d. Unstrut (Institut fiir Geowissenschaften, Martin-Luther-Universitat, Halle, uncatalogued) (Rieppel, 1 994b). The ratio of humerus length to minimal width at mid-diaphysis is approximately 7.8 in Anarosaurus, and it ranges from 5.75 to 7.35 in Dactylosaurus gracilis sex x, 5.0 to 8.47 in Dactylosaurus gracilis sex y, 4.94 to 7.79 in A'^o- thosaurus sp. from the lower Muschelkalk, and 8.3 to 8.85 in Cymatosaurus; the ratio is 8.39 in smns 1 6253. The humerus oi Cymatosaurus approaches smns 1 6253 in overall size, but it differs from smns 16253 by the presence of an entepicondylar fo- ramen (Halle specimen) or groove (smns 58463), an even deeper ectepicondylar groove, and in par- ticular by separate articular condyles for radius and ulna, which are not level. In conclusion, the humerus smns 16253 cannot be referred to any known sauropterygian taxon from the lower Muschelkalk. Huene (1944) be- lieved the specimen to be of particular importance because of its "primitive" morphology, but the humerus of Cymatosaurus shows even more ple- siomorphic characters, such as the presence of an entepicondylar foramen, well-differentiated ect- and entepicondyles, a deep ectepicondylar groove. Fig. 21. Sauropterygia indet., an isolated humerus from the lower Muschelkalk of Gogolin, Upper Silesia (Gomy Slask, Poland) (original of Huene, 1 944, smns 16253). Scale bar = 20 mm. and separate articular condyles for the radius and ulna. Phylogenetic Analysis Reconstruction of the evolutionary and biogeo- graphical history of the Pachypleurosauroidea must be based on a well-corroborated hypothesis of phylogenetic relationships. This study of pachy- pleurosaurs from the lower Muschelkalk provides a much expanded data matrix for the analysis of pachypleurosaur interrelationships, resulting in a modification of phylogenetic hypotheses present- ed in earlier studies (Rieppel, 1987, 1993). The terminal taxa of pachypleurosaurs entered in this analysis are Anarosaurus, Keichousaurus (Young, 1 958, and pers. obs.), Dactylosaurus, the three spe- cies of Neusticosaurus {N. edwardsii: Carroll & Gaskill, 1985; A^. peyeri and A^. pusillus: Sander, 1989; A'^. staubi Kuhn-Schnyder, 1959, is a junior synonym of A^. pusillus: Sander, 1989, p. 580), ''"'Psilotrachelosaurus''' toeplitschi (Rieppel, 1993), and Serpianosaurus (Rieppel, 1989). The phylo- genetic analysis was performed using the software package PAUP version 3.1.1. developed by David RIEPPEL AND KEBANG: PACHYPLEUROSAURS 21 L. Swofford (SwofFord, 1990; Swofford & Begle, 1993). DELTRAN character optimization will be favored in the diagnosis of monophyletic taxa as it minimizes subsequent loss of diagnostic char- acters within the clade. In the listing of synapo- morphies, 'D' will refer to DELTRAN, 'A' to ACCTRAN character optimization. Monophyly of the Pachypleurosauroidea had generally been assumed, but evidence in its sup- port remained scanty. Sanz, Alafont, and Mora- talla (1993) recently published a phylogenetic analysis of Sauropterygia indicating paraphyly of the Pachypleurosauroidea: Anarosaurus was found to be more closely related to Eusauropterygia {sen- su Tschanz, 1 989) than to a clade comprising Dac- tylosaurus plus "^"^Pachypleurosaurus." Reanalysis of their data matrix did not duplicate their results. Rooting the branch-and-bound search on an all-0 ancestor generates six equally parsimonious trees (tree length [TL]: 46 steps; consistency index [CI]: 0.826; rescaled consistency index [RC]: 0.723), which all indicate paraphyly of pachypleurosaurs, but in all six trees the Dactylosaurns-^ Pachypleu- rosauriis" clade is closer to the Eusauropterygia than Anarosaurus. The character uniting the Dac- tylosaurus-^Pachypleurosaurus''^ clade with the Eusauropterygia is the relative length of the hu- merus exceeding that of the femur (in adults, and in sex y [Rieppel, 1989; Sander, 1989] if appli- cable; reversed in ''Psilotrachelosaurus'''' toeplit- schi). However, the relatively long femur is an autapomorphy of Anarosaurus among Saurop- terygia. Monophyly of the Pachypleurosauroidea re- mains an issue because Anarosaurus shares some characters with the Eusauropterygia that might in- dicate paraphyly, such as the sculpturing of dermal skull bones, the large and leaf-shaped nasals close- ly resembling those from the lower Muschelkalk Nothosaurus (undescribed material from Winter- swijk; see also Schroder, 1914), the enlarged an- terior teeth in the upper and lower jaws {Anaro- saurus heterodontus), the anterolateral expansion of the clavicles (undescribed material from Win- terswijk, also shared by Dactylosaurus), the high number of dorsal vertebrae, and the concave lower margin of the pubis (resulting in an anteroventral spine on the pubis). Keichousaurus, on the other hand, shares with Lariosaurus the broad ulna and hyperphalangy in the manus. However, Keichou- saurus could potentially be the sister-taxon to all other Sauropterygia, since it lacks some of the sau- ropterygian synapomorphies such as anterolateral processes of the frontal, three or more sacral ver- tebrae, lack of distal expansion of the sacral ribs, and a reduction of carpal ossifications to three or less in the adult (reversed in some specimens of Lariosaurus). Previous studies (Rieppel, 1989) supported the monophyly of pachypleurosaurs on the basis of the two characters, that is, absence of an ectoptery- goid, and presence of a trough on the dorsal surface of the retroarticular process to accommodate the mandibular condyle of the quadrate during jaw opening (Rieppel, 1989). Additional support for the monophyly of the Pachypleurosauroidea de- rives from additional character congruence, which hinges on the nesting of the clade within the Sau- ropterygia and relative to the position of Placodus. Storrs (1991, 1993a) hypothesized placodonts as the sister-group of the Eusauropterygia, the two clades constituting his Nothosauriformes. The monophyletic pachypleurosaurs were shown to be the sister-group of the Nothosauriformes. Rean- alysis of Storr's (1993a) data matrix showed his characters 10, 40, 50, 54, 55, 56, and 72 to be uninformative (56 only becomes informative rel- ative to an all-0 ancestor). The same strict con- sensus tree topology results for the unrooted net- work, rooting the tree on all-zero ancestor, or root- ing the tree on Captorhinus, Petrolacosaurus, Youngina, and Cladiosaurus. The latter procedure results in 1 2 equally parsimonious trees with a tree length of 182 steps, CI = 0.665, and RC = 0.524. The strict consensus tree is the same as in Storrs (1993a), except for the unresolved position of Sil- vestrosaurus; the latter genus groups with the No- thosaurus-Paranothosaurus clade in the 50% ma- jority rule consensus tree. The diagnosis of the monophyletic Pachypleurosauroidea is predicated on the position of Placodus as sister-taxon of the Eusauropterygia: neck length approximately equal to trunk length (D); suborbital fenestra absent (D, coded present in Placodus; for further discussion of this character, see Rieppel, 1994b); palatal den- tition absent (coded present in Placodus); sacral ribs distally reduced (A, D; Keichousaurus was not included in the analysis. The character was coded unknown for Placodus); small iliac blade (A, D); radius longer than ulna (D). Expansion of the database both in terms of taxa and characters (Rieppel, 1994b) resulted in a re- version of sauropterygian interrelationships. The Placodontia were shown to be the sister-taxon to all other Sauropterygia, the Eosauropterygia. Within the latter, Corosaurus turned out to be the sister-taxon to an unnamed clade comprising the monophyletic Pachypleurosauroidea and Eusau- 22 FIELDIANA: GEOLOGY 5 5 :s _o :2 "3 i E S 5 2 C u o c O o C^ 'c u5 ,c: u JS c^ o c u o (/a O a. o (J '5b c 3 o 3 o 2 as Q. U H < >^ U < Fig. 22. Strict consensus tree of sauropterygian interrelationships, generated from 54 MPRs (28 taxa, 108 char- acters, TL = 415, CI = 0.629, RC = 0.475). ropterygia. With Corosaurus and Placodus as suc- cessive outgroups, the characters diagnostic for the Pachypleurosauroidea changed dramatically, in- volving reversals (ACCTRAN) or convergences (DELTRAN), with important implications for the reconstruction of the evolutionary history of the group (Rieppel, 1 994b). The data matrix used in Rieppel (1994b) for the analysis of phylogenetic interrelationships of stem- group Sauropterygia (23 taxa, 94 characters) was expanded for the present study by the inclusion of all terminal taxa for pachypleurosaurs, and by the addition of new characters not already included in the previous analysis (Rieppel, 1 994b; charac- ters 8, 21, 23, 28, 29, 30, 31, 34, 40, 41, 43, 45, 46, 49, as defined below). These modifications re- sult in a data matrix for a total of 28 taxa and 108 characters. A heuristic search rooted on an all-0 ancestor treated all characters as unordered except for character 22 (Rieppel, 1994b). It resulted in 54 equally parsimonious trees with a tree length of 415 steps, CI = 0.629, and RC = 0.475. All trees show Placodus to be the sister-taxon to all other Sauropterygia (Eosauropterygia). All trees confirm monophyly of the Pachypleurosauroidea and their position as sister-group to the Eusau- ropterygia. Diagnostic characters of the Pachy- pleurosauroidea are: preorbital region of the skull longer than postorbital region (D, A); frontal with concave lateral edge (D), parietal skull table broad (A); mandibular articulation at the level of the occipital condyle (A); quadrate with concave pos- terior margin (A); ectopterygoid bone absent (D, A); trough on dorsal surface of retroarticular pro- cess present (D, A); anterior teeth not strongly precumbent (D, A); posterior process on inter- clavicle rudimentary or absent (D); radius longer than ulna, or both bones of equal length (D, A); iliac blade absent (D, A). The strict consensus tree (Fig. 22) remains highly unresolved within the pa- chypleurosaurs, which, however, may be an effect of the larger number of taxa and characters entered in the analysis. To resolve phylogenetic interre- lationships within the Pachypleurosauroidea, a new RIEPPEL AND KEBANG: PACHYPLEUROSAURS 23 Table 6. Data matrix for 14 taxa and 50 characters. 1 1 2 3 4 5 6 7 8 9 1 0 1 Anarosaurus 0 0 0 0 1 1 0&1 0 0 0 2 Dactylosaurus 1 0 0 0 0 1 1 0 0 0 3 Keichousaurus 1 0 7 2 1 0 0 0 0 0 4 N. pusillus 1 0 1 1&2 1 1 0 0 1 0 5 N. peyeri 1 0 1 1&2 1 1 0 0 1 0 6 N. edwardsii 0&1 0 1 1&2 1 1 0 0&1 1 0 7 Psilotrachelosaurus 7 ? 7 7 7 7 7 7 7 7 8 Serpianosaurus 1 0 1 1 1 1 0 0 1 0 9 Cymatosaurus 0 1 2 2 0 0&1 3 2 0&1 1 0 Lariosaurus 0 1 7 7 1 7 0 2 1 1 1 Nothosaurus 0 1 0 1&2 1 1 0 2 1&2 1 2 Pistosaurus 0 ? 2 2 1 1 2 2 2 1 3 Simosaurus 0 0 1 2 1 1 0 2 1 1 4 Placodus 0 1 0 0 0&1 1 3 2 0 1 5 outgroup 0 0 0 0 0 0 0 0 0 0 data matrix was therefore constructed, including a total of 50 characters defined below and 14 taxa plus an all-0 ancestor for an outgroup (Table 6). Definition of Characters 1. Bones in the dermatocranium distinctly sculptured (0) or rather smooth (1). The plesiomorphic condition within the Rep- tilia is sculpturing of the surface of dermatocranial bones. Sculpturing is present in the eusauropter- ygian genera Nothosaurus and Simosaurus; sculp- turing may be weak, but is present in some Lar- iosaurus, in Cymatosaurus, and in Pistosaurus. Among pachypleurosaurs, skull roof ornamenta- tion appears present but is poorly visible in the cast of Anarosaurus pumilio; ornamentation of the dermatocranial bones in Anarosaurus is confirmed by undescribed material from Winters wijk. Among Table 6. Continued. 2 1 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 9 20 1 Anarosaurus 0 0 0 0 0 7 0 1 7 2 Dactylosaurus 0 0 0 0 0 7 0 1 0 3 Keichousaurus 0 1 1 0 0 0 0 1 7 4 N. pusillus 0 0 0 0 0 0 0 1 0 5 N. peyeri 1 0 0 0 0 0 0 1 0 6 N. edwardsii 1 0 0 0 0 0 0 1 0 7 Psilotrachelosaurus 7 7 7 7 7 7 7 7 7 7 8 Serpianosaurus 0 0 0 0 0 0 0 1 0 1 9 Cymatosaurus 0 0 0&1 1 1 0 1 0 1 0 Lariosaurus 0 2 0 1 ? 1 7 0 1 1 Nothosaurus 0 2 0 1 1 1 1 0 1 2 Pistosaurus 0 1 1 0 1 0 7 0 1 3 Simosaurus 0 2 0 1 0 1 0 0 1 4 Placodus 1 0&1 0 0 0 1 0 1 0 1 5 outgroup 0 0 0 0 0 0 0 0 0 0 24 FIELDIANA: GEOLOGY Table 6. Continued. 3 2 1 22 23 24 25 26 27 28 29 30 1 Anarosaurus 0 0 1 0 0 0 0 0 1 2 Dactylosaurus 0 0 0 0 0 0 1 1 0 3 Keichousaurus 1 0 0 0 0 0 0 2 0 4 N. pusillus 0 0 0 0 0 0 0&1 1 5 N. peyeri 0 0 0 0 0 0 0 0 6 N. edwardsii 0 0 0 0 0 0 1 0 7 Psilotrachelosaurus ? ? 7 7 7 7 0 7 0 8 Serpianosaurus 0 0 1 0 0 0 0 0 1 9 Cymatosaurus 1 0 1 1 0 7 7 7 7 1 0 Lariosaurus 1 0 1 1 1 1 1 1 1 1 1 Nothosaurus 1 0 1 1 1 1 0 1 1 1 2 Pistosaurus 7 0 1 0 0 1 ? ? 7 1 3 Simosaurus 0 0 0 0 1 1 0 7 2 1 4 Placodus 1 0 0 1 0 0 0 0 0 1 5 outgroup 0 0 0 0 0 0 0 0 0 0 other pachypleurosaurs the skull roof bones are smooth except for very large specimens of Neus- ticosaums edwardsii, where a weakly expressed or- namentation may appear (Carroll & Gaskill, 1 985). 2. Snout unconstricted (0) or constricted (1). The unconstricted rounded snout observed in Dactylosaurus, Serpianosaurus, and Neusticosau- rus is the plesiomorphic condition. The snout is elongated and distinctly constricted in Cymato- saurus, Lariosaurus, and Nothosaurus. A very weak embayment of the snout at the maxilla-premax- illary suture can be observed in Anarosaurus (un- described material from Winterswijk), Keichou- saurus, and Simosaurus, all of which are coded (0), however. 3. Nasals broad and leaflike (0), slender (1), or much reduced (2). The nasals are broad elements defining most of the posterior margin of the external naris in An- arosaurus and Dactylosaurus. In Serpianosaurus Table 6. Continued. 4 3 1 32 33 34 35 36 37 38 39 40 1 Anarosaurus 0 1 0 1 2 1 1 0 0 2 Dactylosaurus 0 1 0 1 7 0 0 0 0 3 Keichousaurus 1 0 0 ? 0 1 1 1 1 4 N. pusillus 1 1 1 0 1&2 0&1 0&1 0 5 N. peyeri 1 1 1 0 1&2 0&1 0&1 0 6 N. edwardsii 1 1 1 0 1&2 0&1 0&1 0 7 Psilotrachelosaurus 1 1 7 0 7 1 1 0 8 Serpianosaurus 0 1 0 0 1&2 1 1 0 9 Cymatosaurus 7 7 7 7 ? 7 0 0 0&1 0 1 0 Lariosaurus 1 2 0 1 7 1 1 0 0 1 1 Nothosaurus 0 1 0 1 0&1 0&1 0&1 0 0 1 2 Pistosaurus 7 7 ? 7 7 7 1 1 1 0 1 3 Simosaurus 0 1 0 0 1 0 1 1 1 0 1 4 Placodus 0 1 0 0 0 0 1 0 1 0 1 5 outgroup 0 0 0 0 0 0 0 0 0 0 RIEPPEL AND KEBANG: PACHYPLEUROSAURS 25 Table 6. Continued. 5 4 1 4 2 43 44 45 4 6 47 48 49 50 1 Anarosaurus 0 7 1 ? 7 7 7 1 1 2 Dactylosaurus 0 1 0 1 0 0 0 0 3 Keichousaurus 1 0 0 0 1 0 0 0 4 N. pusillus 0 0 0&1 2 0 0 0 1 5 N. peyeri 0 0 0&1 2 0 1 0 0&1 6 N. edwardsii 0 0 0&1 1 0 1 0 1 7 Psilotrachelosaurus 0 0 1 1 0 7 0 1 8 Serpianosaurus 0 1&2 0 0 2 0 0 1 1 9 Cymatosaurus 0 ? 7 7 7 7 7 7 7 7 1 0 Lariosaurus 1 2 0 0 0&1 1 0 1 0 7 1 1 Nothosaurus 0 2 0 0 1 0 0 0 1 0&1 1 2 Pistosaurus 0 2 7 7 7 ? ? 0 7 7 1 3 Simosaurus 0 2 0 0 1 0 0 0 1 0 1 4 Placodus 0 7 0 0 1 0 0 0 0 0 1 5 outgroup 0 0 0 0 0 0 0 0 0 0 and Neusticosaurus, the nasals are slender and elongate elements, restricted to the posteromedial margin of the external naris. The exact contours of the nasals cannot be unequivocally identified in the Keichousaurus material available to us. The nasals are small in Simosaurus (1) but broad in Nothosaurus; the contours of the nasals remain poorly known in Lariosaurus. The strong reduc- tion of the nasals (2) in Cymatosaurus and Pis- tosaurus results in their exclusion from the exter- nal naris. 4. Nasals in broad contact at midline of skull (0), nasals meet in a short suture only (1), or nasals are separated by the contact of the nasal processes of the premaxillae with the frontal (2). This character is polymorphic in some taxa, where the nasals may come into narrow contact (1), or remain separate from each other (2) by a contact between premaxilla and frontal (Neusti- cosaurus: Sander, 1989; Nothosaurus, pers. obs.). However, a distinction can be made between taxa in which the nasals establish a broad contact (An- arosaurus, Dactylosaurus), a narrow contact (Ser- pianosaurus, Rieppel, 1 989), or in which the nasals always remain separated by the premaxilla, which extends backward to meet the frontal (Cymato- saurus, Simosaurus, Pistosaurus). The condition in Lariosaurus remains unknown due to poor pres- ervation of the available material. As far as is known, Keichousaurus always shows the premax- illa-frontal contact (Young, 1958; and per. obs.). 5. Frontals paired (0) or fused (1) in the adult. 6. Frontal(s) without (0) or with ( 1 ) distinct an- terolateral process(es) entering between the pre- frontal and the nasal. 7. Frontal broadly enters the dorsal margin of the orbit (0); participation of the frontal in the dorsal margin of the orbit is restricted due to an elongated anterior process of the postfrontal (1); participation of the frontal in the dorsal margin of the orbit is restricted due to an elongated pos- terior process of the prefrontal (2); the frontal re- mains excluded from the dorsal margin of the orbit due to a prefrontal-postfrontal contact (3). Dactylosaurus and some specimens of Anaro- saurus (undescribed material from Winterswijk) show a slender anterior process of the postfrontal extending along the dorsal margin of the orbit and narrowly approaching the prefrontal. A reduced participation of the frontal in the dorsal margin of the orbit is also observed in Pistosaurus, al- though in this taxon it is rather the prefrontal ex- tending backward than the postfrontal extending forward. This condition, and the complete exclu- sion of the frontal from the dorsal margin of the orbit in Cymatosaurus, are autapomorphic for the respective taxa in this analysis. 8. Lateral edge of frontal concave (0) or straight (1). In their analysis of sauropterygian interrelation- ships, Sanz, Alafont, and Moratalla (1993) listed a number of problematic characters such as the 26 FIELDIANA: GEOLOGY relative size of the upper temporal fossa (their character 1), the relative size of the external nares (their character 3), and the relative size of the or- bits (their character 4). All of these characters are subject to potential ontogenetic variation (allo- metric growth), and all may be interrelated, de- pending on how skull measurements are taken and how relative size is calculated. Among the taxa included in this analysis, the ratio (longitudinal diameter of orbit/width of bony bridge between orbits) is distinctly larger in small pachypleurosaurs (>3.5) than in large eusaurop- terygians (<2.5), indicating relatively larger orbits or a relatively narrower frontal bridge in pachy- pleurosaurs (frontal constriction is extreme in Kei- choiisaurus with an index of 7.2!). For most of the taxa entered in this analysis, very few specimens allow the size of the orbit (known to grow with negative allometry: Sander, 1989; Rieppel, 1994c) to be related to standard length defined as length of the last fovu" presacral centra. This relation in- dicates a slightly smaller size of the orbits in No- thosaurus (holotype of Nothosaurus "^raabi": Schroder, 1914) and Lariosaurus (neotype of Lar- iosaurus balsami: Kuhn-Schnyder, 1987), speci- mens of distinctly larger overall size than the small pachypleurosaurs. An overlap in the relative size of the orbit is observed in large specimens of Net4s- ticosaurus edwardsii (Carroll & Gaskill, 1985). The character may therefore be directly related to over- all body size. Nevertheless, the relatively narrower frontal bridge between the orbits in Anarosaurus, Dac- tylosaurus, Keichousaurus, and small specimens of Neusticosaurus translates into a concave lateral margin of the frontal, whereas in large Neustico- saurus and eusauropterygians, the lateral edge of the frontal is rather straight. 9. Longitudinal diameter of upper temporal fossa about 50-60% of longitudinal diameter of orbit (0), 25-30% of orbital diameter (1), or 150- 220% of orbital diameter (2). As discussed above, the orbit shows negative allometric growth, which may affect this character as defined above to a certain degree. However, the Eusauropterygia show a marked elongation of the postorbital region of the skull (to a somewhat less- er degree in Simosaurus than in the other taxa), if compared to pachypleurosaurs or the plesio- morphic reptile condition (Captorhinus, Araeos- celidia, Youngina, Claudiosaurus). Within the pa- chypleurosaurs, a relatively large upper temporal fossa is observed in Anarosaurus, Dactylosaums, and Keichousaurus. which compares to the lon- gitudinal diameter of the orbit in a way closely similar to Petrolacosaurus, Claudiosaurus, and Youngina. In Serpianosaurus and Neusticosaurus, however, the upper temporal fenestra is strongly reduced, small, and keyhole shaped. The small size of the upper temporal fenestra correlates with a widening of the upper temporal arch and the trans- formation of the postorbital from a triradiate bone to a broad, triangular plate. Serpianosaurus is aut- apomorphic in the (variable) exclusion of the pa- rietal from the medial margin of the upper tem- poral fossa. Exclusion of the postorbital from the reduced upper temporal fossa is polymorphic in Neusticosaurus and Serpianosaurus. 10. Posterior part of parietal skull table broad and flat (0), constricted (1), or forming a sagittal crest (2). Pachypleurosaurs show a broad parietal skull table, whereas the parietal skull table is constricted between the posterior parts of the upper temporal fossa in eusauropterygians. Cymatosaurus is cod- ed polymorphic for this character for reasons dis- cussed in Rieppel (1994b). A sagittal crest may develop in some Nothosaurus {Nothosaurus edin- gerae: Rieppel & Wild, 1994), as well as in Pis- tosaurus. 11. Width of upper temporal arch (i.e., tem- poral emargination) visible (0) or not visible (1) from above. 12. Parietal paired (0) or fused (1) in adult. 13. Pineal foramen located in center of skull table (0), or displaced anteriorly (1), or displaced posteriorly (2). In pachypleurosaurs the pineal foramen is lo- cated in the center of the skull table except in Keichousaurus, where it is displaced anteriorly. The pineal foramen is in a central position in Cyma- tosaurus, displaced anteriorly in Pistosaurus, and displaced posteriorly in Nothosaurus; Lariosaurus shows the pineal foramen either in a central (Re- nesto, 1993, and pers. obs.) or in a posterior po- sition. 1 4. Frontal excluded from upper temporal fos- sa (0) or narrowly enters the anteromedial edge of the upper temporal fossa (1). The derived character state is observed in some specimens of Cymatosaurus as well as in Pisto- saurus among the taxa considered in this analysis. 15. Jugal extends anteriorly along the ventral margin of the orbit (0) or remains restricted to a position behind the orbit (1). The plesiomorphic condition is known or as- sumed to exist in all pachypleurosaurs, as well as in Simosaurus. The jugal is restricted to a position RIEPPEL AND KEBANG: PACHYPLEUROSAURS 27 behind the orbit in Lariosaurns and Nothosaurus. For reasons discussed elsewhere, Cymatosaurus is coded (1), Pistosaurus (0) for this character (Riep- pel, 1994b). 16. Quadratojugal present (0) or absent (1). Presence of a quadratojugal is documented for Serpianosaurus, Keichousaurus, and Neusticosau- rus among pachypleurosaurs, as well as for Si- mosaurus among eusauropterygians. Its absence is documented for Cymatosaurus, Nothosaurus, and Pistosaurus. 1 7. Quadrate with straight posterior margin (0) or with concave posterior margin (1). 18. Pterygoid flanges well developed (0) or strongly reduced (1). Among the taxa here considered, pterygoid flanges are strongly reduced in all except Cyma- tosaurus and Pistosaurus. 19. Premaxillae enter internal nares (0) or re- main excluded therefrom (1). Because of poor preservation, this character is know for few taxa only. The premaxilla enters the internal naris in Serpianosaurus and Neusticosau- rus, probably also in Dactylosaurus (Sues & Car- roll, 1985— as in all other pachypleurosaurs), as well as in Simosaurus, but it remains excluded from the internal naris in Nothosaurus and Cy- matosaurus (coded unknown for Lariosaurus and Pistosaurus). 20. Ectopterygoid present (0) or absent (1). There continues to be no unequivocal evidence for the presence of an ectopterygoid bone in pa- chypleurosaurs {Dactylosaurus, Keichousaurus, Serpianosaurus, Neusticosaurus). 21. Scleral ossicles present (0) or absent (1). Scleral ossicles are present in all pachypleuro- saurs except, apparently, Keichousaurus. Scleral ossicles have never been reported for stem-group eusauropterygians, but are present in some plesi- osaurs. 22. Mandibular symphysis short (0) or elon- gated (1). The mandibular symphysis is short in all pa- chypleurosaurs (including Anarosaurus: unde- scribed material from Winterswijk), but is elon- gated in all eusauropterygians except Simosaurus (unknown in Pistosaurus). 23. Trough on dorsal surface or retroarticular process absent (0) or present (1). 24. Premaxillary and anterior dentary teeth smaU (0) or enlarged (1). The plesiomorphic character state is observed in all pachypleurosaurs except for Anarosaurus (undescribed material from Winterswijk; see also Oosterink, 1986, Foto 40). The derived character state is observed in all eusauropterygian taxa ex- cept Simosaurus. 25. One or two maxillary fangs present (0) or absent (1). Maxillary fangs are absent in all pachypleuro- saurs but present in all eusauropterygians here considered with the exception of Simosaurus and Pistosaurus (although that genus shows larger an- terior than posterior maxillary teeth). 26. Tooth row restricted to a level in front of the posterior margin of orbit (0) or extending back- ward to a position below the anterior part of upper temporal fossa. This character is discussed in detail in Rieppel (1994b). 27. Vertebrae amphicoelous (0) or platycoelous (1). The vertebrae of pachypleurosaurs are amphi- coelous; those of Lariosaurus, Nothosaurus, Pis- tosaurus (Sues, 1987), and Simosaurus are platy- coelous. The vertebrae of Cymatosaurus, are un- known except for Cymatosaurus muhidentatus, which shows amphicoelous vertebrae, possibly a juvenile feature (Rieppel, 1995). 28. Dorsal centra constricted (0) or unconstrict- ed (1) in ventral view. Nopcsa (1928) drew attention to the fact that the dorsal centra of Anarosaurus appear constrict- ed in ventral view, whereas those of Dactylosaurus do not. This character is not related to pachyos- tosis, which is absent in the dorsal ribs of Dacty- losaurus and Serpianosaurus, but present in the dorsal ribs of Neusticosaurus and '''' Psilotrachelo- saurus," all of which have unconstricted centra. The dorsal centra of Keichousaurus are slightly constricted. 29. Neck less than 80% of trunk length (0), 80- 100% of trunk length (1), or distinctly more than 100% of trunk length (2). These relations are calculated on the number of vertebrae in the cervical and dorsal region, al- though it must be admitted that the two regions are sometimes difficult to delineate from one an- other. In Dactylosaurus and Neusticosaurus ed- wardsii, the dorsal region comprises two more ver- tebrae than the neck (perhaps three in one poorly preserved specimen of the latter species). In An- arosaurus, Neusticosaurus pusillus, Neusticosaurus peyeri, and Serpinaosaurus, the difference between trunk and neck is generally larger, involving a min- imum of three and a maximum of nine more dor- sal vertebrae; a slight overlap between two or three vertebrae may exist between Neusticosaurus ed- 28 FIELDIANA: GEOLOGY wardsii and Neusticosaurus pusillus. Of all speci- mens of Serpianosaurus. one has been reported with 1 8 cervicals and 20 dorsals (T 1071 ; Rieppel, 1 989), compared to the average difference within the whole sample of four to nine more dorsals than cervicals, the count for T 1071 seems erroneous and could have been caused by a slight backward shift of the pectoral girdle during fossilization. A neck that is longer than the trunk is autapomorph- ic for Keichousaurus. 30. Number of dorsal vertebrae: 20 or below (0), 20 or more (1), 30 or more (3). The number of dorsal vertebrae is variable with- in taxa, and the ranges of variation overlap to some slight extent {Serpianosaurus, Anarosaurus). Nineteen to 20 dorsal vertebrae is considered the plesiomorphic condition (0), present in Dactylo- saurus, Keichousaurus, Neusticosaurus edwardsii, Neusticosaurus peyeri, and "Psilotrachelosaurus."' Twenty to 24 (26) dorsal vertebrae is the derived condition observed in Anarosaurus (25 or 26 dor- sals!), Neusticosaurus pusillus, Serpianosaurus, Lariosaurus, and Nothosaurus (holotype of No- thosaurus raabi: Schroder, 1914). Simosaurus is autapomorphic with a minimum of 32 dorsal ver- tebrae (Huene, 1959). The number of dorsal ver- tebrae is unknown for Cymatosaurus and Pisto- saurus. 31. Dorsal ribs without (0) or with (1) pach- yostosis. Pachyostosis is subject to ontogenetic variation, but it is present in adult Neusticosaurus and "/*5/- lotrachelosaurus.'''' It is absent, or only very weakly developed, in adult Anarosaurus, Dactylosaurus, and Serpianosaurus. Rib pachyostosis appears variable in Keichousaurus, which is coded as poly- morphic for that character. Among Eusauropter- ygia, only Lariosaurus shows pachyostotic ribs. 32. Number of sacral ribs: two (0), three (1), four (2). Two sacral ribs have been described for Kei- chousaurus (Lin Kebang, quoted in Sues, 1987), and this is the character state accepted here. It should be noted, however, that only one sacral rib shows a distinct distal expansion abutting the me- dial side of the ilium; a second sacral rib with no distal expansion extends toward the posterolateral aspect of the ilium. In some specimens, an anterior (i.e., last dorsal) rib converges toward the antero- lateral aspect of the ilium. Three sacral ribs is the typical condition observed in all other pachypleu- rosaurs, as well as in Simosaurus and Nothosaurus (Rieppel, 1994b). Four sacral ribs is autapo- morphic for Lariosaurus among the taxa included in this analysis. The sacrum of Cymatosaurus and Pistosaurus remains unknown. 33. Sacral ribs with (0) or without (1) distinct distal expansion. The one principal sacral rib in Keichousaurus shows a distal expansion, whereas the distal ex- pansion of the sacral ribs is not pronounced in other pachypleurosaurs, or in Lariosaurus or No- thosaurus. The sacral ribs are distally expanded in Simosaurus. 34. Gastral ribs composed of five (0) or three (1) segments. In an earlier analysis of pachypleurosaurian in- terrelationships (Rieppel, 1987), the number of segments included in each gastral rib was used as a character, with three segments being the derived condition. With Pachypleurosaurus a junior syn- onym of Neusticosaurus (Sander, 1989), this char- acter is autapomorphic for the latter genus (not known for "Psilotrachelosaurus"). 35. Clavicles without (0) or with (1) expanded comers. In Anarosaurus (undescribed material from Winterswijk) and Dactylosaurus, the clavicles are expanded into distinct anterolateral comers, as is also the case in Lariosaurus, Nothosaurus, and Si- mosaurus. These clavicular "comers" (Storrs, 1991, 1993a) are absent in all other pachypleurosaurs. 36. Posterior stem on interclavicle distinct (0), rudimentary (1), or absent (2). The interclavicle of Simosaurus retains a dis- tinct (yet short) posterior stem (Huene, 1952). In articulated specimens of Nothosaurus, the inter- clavicle carries no posterior process, but isolated interclaviculae most probably referable to Notho- saurus may retain a very rudimentary process (Rieppel, 1994b). A rudimentary process is also observed in Keichousaurus, and in some speci- mens of Neusticosaurus and Serpianosaurus. No trace of a posterior process is observed in Arui- rosaurus (undescribed material from Winter- swijk). The interclavicle of Dactylosaurus, ^'Psi- lotrachelosaunds" and Lariosaurus is poorly known; that of Cymatosaurus and Pistosaurus remains un- known. 3 7 . Ectepicondylar groove on humems notched anteriorly (0) or without notch (1). Humerus morphology has traditionally played an important role in sauropterygian systematics (see Storrs, 1991, 1993a, and Rieppel, 1994b, for a discussion). In the most recent analysis, Sanz, Alafont, and Moratalla (1993) defined yet different character states for humerus morphology, all of which are difficult to recognize. The major prob- RIEPPEL AND KEBANG: PACHYPLEUROSAURS 29 lem is that humeral morphology is subject to on- togenetic variation and sexual dimorphism. The shape of the humerus can also be quite variable, as in the genera Keichousaurus and Lariosaums. In an eariier analysis, a "curved" humerus was accepted as a sauropterygian synapomorphy (Rieppel, 1994b); the rather straight humerus of Cymatosaurus is autapomorphic among the gen- era included in this analysis. The ectepicondylar groove is generally present on sauropterygian humeri, and it is "notched" an- teriorly in Dactylosaurus (sex y), large individuals of Neusticosaurus edwardsii (sex y; Carroll & Gas- kill, 1985; Sander, 1989), in large Nothosaurm, and in Cymatosaurus. 38. Humerus with (0) or without (1) distinct entepicondyle. Sues and Carroll (1985) commented on the dis- tinct morphology of the humerus in Dactylosau- rus, with an entepicondyle distinctly set off from the humeral shaft by a notch (in sex y; see also Rieppel, 1993, Fig. 8). Similar humeri have been recorded for Neusticosaurus pusillus and other spe- cies of Neusticosaurus (Carroll & Gaskill, 1985; Sander, 1989). The entepicondyle is less distinct in Anarosaurus, Keichousaurus, "Psilotrachelo- saurus," and Serpianosaurus. 39. Entepicondylar foramen present (0) or ab- sent (1). Among the genera considered in this analysis, an entepicondylar foramen is absent in Keichou- saurus, some specimens of Cymatosaurus, Simo- saurus, and Pistosaurus. 40. Humerus without (0) or with (1) vermicu- late surface. Serpianosaurus, ''''Psilotrachelosaurus,^' and Neusticosaurus share a peculiar "orange-peel" or- namentation of endochondral bone surface, most conspicuously developed on the humerus (Sander, 1989; Rieppel, 1993). A similar ornamentation of the bone surface occurs in Keichousaurus. 41. Ulna with slender shaft (0) or distinctly broadened (1). Among the genera included in this analysis, the ulna is distinctly broadened in Keichousaurus and Lariosaurus. 42. Radius shorter than ulna (0), radius slightly longer than ulna (1), or bones of approximately equal length (2). The radius is slightly longer than the ulna in Dactylosaurus, Keichousaurus, Neusticosaurus, and "Psilotrachelosaurus"; in Serpianosaurus, the ra- dius may be slightly longer than the ulna, or the two bones may be of equal length (the elements are imkuown in the holotype of Anarosaurus pum- ilio). In Eusauropterygia, the radius and ulna are of equal length (the character is not known for Cymatosaurus). 43. Radius without (0) or with (1) distinct con- cavity in the medial (preaxial) margin of the shaft. 44. The intermedium is rounded (0) or a rect- angular elongate element located at the preaxial margin of the distal tip of the ulna (1). The derived condition is observed in some spec- imens of Neusticosaurus and in ''Psilotrachelosau- rus" (Rieppel, 1993) among the genera included in this analysis. 45. Number of ossified carpal bones in adult: five (0), three (1), or two (2). The carpus of Anarosaurus is imknown. Dac- tylosaurus shows three undisputed carpal ossifi- cations, with the possible occurrence of a pisiform (perhaps a neomorph: Sues & Carroll, 1985). In Serpianosaurus, Neusticosaurus pusillus, and Neusticosaurus peyeri, only two carpals ossify (Sander, 1989); large Neusticosaurus edwardsii show three carpal ossifications (Carroll & Gaskill, 1985). Adult Keichousaurus show five carpal os- sifications. Simosaurus and Nothosaurus (Notho- saurus "raabi": Schroder, 1914) show three ossi- fied carpals. In Lariosaurus, adults (of perhaps two different species) may show three (neotype of Lar- iosaurus balsami: Kunn-Schnyder, 1987) or up to five ossified carpals. The carpus of Cymatosaurus and Pistosaurus is unknown. 46. Phalangeal formula of manus 2-3-4-5-3 (0) or characterized by hyperphalangy (1). Hyperphalangy is observed in Keichousaurus and Lariosaurus among the genera included in this analysis. 47. Phalangeal formula in pes 2-3-4-5-3 (0) or less than 2-3-4-4-3 (1). The formula 2-3-4-4-3 itself is coded (0) because of incomplete or prob- lematic preservation (Keichousaurus: Young, 1958; Dactylosaurus: Sues & Carroll, 1985) or ontoge- netic variation (Neusticosaurus: Sander, 1989). The reduction of the phalangeal count in the pes (be- yond 2-3-4-4-3) is autapomorphic for Neustico- saurus edwardsii (Sander, 1 989). 48. Dorsal part of ilium forming an iliac blade (0) or a simple dorsal process (1). An iliac blade is absent in all pachypleurosaurs, as well as in Lariosaurus, among the genera in- cluded in this analysis. 49. Pubis without (0) or with (1) an tero ventral process. In Anarosaurus, the pubis forms a distinct an- teroventral process that is also observed in Ser- 30 FIELDIANA: GEOLOGY 2 a C •S 3 < N. edwardsU PsUotrachelo- saurus Fig. 23. Unrooted network for Placodus, Pachypleurosauroidea, and selected representatives of the Eusaurop- terygia. For further discussion see text. pianosaurus, among other pachypleurosaurs. This antero ventral process of the pubis results from a concavity of the medial (ventral) margin of the pubic plate, which is also observed in Simosaurus and Nothosaurus, but not in Lariosaurus among the Eusauropterygia. The pubis of Cymatosaurus and Pistosaurus is unknown. 50. Obturator foramen closed (0) or open ( 1 ) in adults. The obtiu^tor foramen is open or slitlike in An- arosaurus, Serpianosaurus, and ^^Psilotrachelosau- rus"; both conditions may occur in Neusticosau- rus. The foramen is closed in Dactylosaurus and Keichousaurus. The obturator foramen is closed in Simosaurus. but may be closed or open in A^o- thosaurus. The character is unknown in Cymato- saurus, Lariosaurus, and Pistosaurus. In a first analysis, an imrooted network was re- constructed for all taxa except Placodus and the all-0 ancestor. The branch-and-bound algorithm found one single most parsimonious reconstruc- tion (MPR) with TL = 123, CI = 0.756, and RC = 0.555. The addition oi Placodus to the analysis increased the lack of resolution within the Eusau- ropterygia, resulting in five MPRs with TL = 1 34, CI = 0.709, and RC = 0.506. The addition of Placodus did not alter the relative adjacency of pachypleurosaur taxa in the unrooted network, however. The unrooted network suggests the pos- sibility of grouping pachypleurosaurs into a nested hierarchy of monophyletic taxa (Fig. 23), which is exactly the pattern observed if pachypleurosaurs (assumed to be monophyletic) are rooted on the monophyletic Eusauropterygia, their sister-group (Rieppel, 1994b). When Placodus and the all-0 ancestor were excluded, the branch-and-bound al- gorithm found one single most parsimonious tree (Fig. 24) with TL = 123 steps, CI = 0.756, and RC = 0.555. The Serpianosaurus-Neusticosaurus clade shows the same substructure as in Sander (1989), but "Psilotrachelosaurus" no longer ap- pears as the sister-taxon to that clade (Rieppel, 1993) but rather is nested within that clade as the sister-taxon to Neusticosaurus edwardsii. Anaro- saurus is the sister-taxon to the Serpianosaurus- Neusticosaurus clade, Dactylosaurus is the next successive sister-taxon, and Keichousaurus is the sister-taxon to all other pachypleurosaurs. The rel- ative position of Anarosaurus is weakly supported and breaks in a tree one step longer (TL = 1 24), in which Anarosaurus and Dactylosaurus fall into an unresolved trichotomy with the Serpianosau- rus-Neusticosaurus clade. The position of Ana- rosaurus as sister-taxon to the Serpianosaurus- Neusticosaurus clade is accepted here, because it also appears in the strict consensus tree (Fig. 25) generated from four MPRs (heuristic search, tree bisection-reconnection [TBR] branch swapping, random stepwise addition, 10 replications; TL = 137, CI = 0.701; RC = 0.483), which result from rooting the 1 3 taxa included in the analysis (Table 6; Placodus excluded) on an all-0 ancestor as out- group. The position of Anarosaurus as the sister- group to the Serpianosaurus-Neusticosaurus clade is further supported by the stratigraphic position RIEPPEL AND KEBANG: PACHYPLEUROSAURS 31 Fig. 24. The single most parsimonious tree for pachypleurosaur interrelationships, with the monophyletic Pachy- pleurosauroidea rooted on the monophyletic Eusauropterygia (TL = 123 steps, CI = 0.756, RC = 0.555). of Anarosaurus, which is somewhat younger than Dactylosaurus. As pachypleurosaurs and eusauropterygians are rooted on an all-0 ancestor (Fig. 25), Dactylosau- rus and Keichousaurus fall into an unresolved position with respect to other pachypleurosaurs. The relative position of Dactylosaurus and Kei- chousaurus at the base of the pachypleurosaur cladogram is of major historical biogeographical importance, because Dactylosaurus is the first ge- nus to appear in Europe, whereas Keichousaurus is restricted to China. It is tempting to resolve the basal polytomy in the pachypleurosaur cladogram with reference to stratigraphy, but the stratigraphic control on the occurrence of Keichousaurus is rath- er poor. IfPlacodus is included in the analysis and all 14 taxa are rooted on an all-0 ancestor, reso- lution within the Eusauropterygia drops again, and the result is 10 MPRs (heuristic search, TBR branch swapping, random stepwise addition, 10 replications; TL = 147, CI = 0.667; RC = 0.455) with no improved resolution for Dactylosaurus and Keichousaurus in the strict consensus tree (Fig. 26). Previous work has shown Placodus to be the sister- taxon to all other Sauropterygia (Rieppel, 1 994b). Using this information to root pachypleurosaurs and the eusauropterygians considered in this anal- ysis on Placodus results in five MPRs (heuristic search, TBR branch swapping, random stepwise addition, 10 replications; TL = 134, CI = 709, RC = 506), which all confirm the position of Kei- chousaurus as sister-taxon to all other pachypleu- rosaurs. This is the position of Keichousaurus pro- visionally accepted in this analysis (Fig. 27). The cladogram of the Pachypleurosauroidea thus reads: {Keichousaurus {Dactylosaurus {Anarosau- rus {Serpianosaurus {N. pusillus {N. peyeri {N. ed- wardsii, '"'"Psilotrachelosaurus"))))))). The mono- phyly of the Pachypleurosauroidea was discussed above. With the restricted data set (Table 6), monophyly is supported by the following unequiv- ocal synapomorphies (CI = 1, ACCTRAN and DELTRAN optimization, rooting pachypleuro- saurs on Eusauropterygia [Fig. 24], or together with eusauropterygians on Placodus [Fig. 27]): 8— lat- eral edge of frontal concave; 9— longitudinal di- ameter of orbit 50-60% of diameter of orbit; 17 — quadrate with concave posterior margin; 20— ec- topterygoid absent; 23— trough on dorsal surface of retroarticular process present; 42— radius slightly longer than ulna. Continuing to root pachypleurosaurs on the Eu- sauropterygia (Fig. 24), or together with eusau- ropterygians on Placodus (Fig. 27), then Dactylo- saurus, Anarosaurus, and the Serpianosaurus- Neusticosaurus clade group to the exclusion of Kei- 32 FIELDIANA: GEOLOGY 2 3 ea 1/1 o 13 c < 3 •c T3 C/5 2 2 2 3 3 3 O 3 O 2 3 ">» s: rt (/3 o o e o C3 'S >^ to Q ^ u (X o o Z 3 O Fig. 25. Strict consensus tree for pachypleurosaurs and selected eusauropterygians, rooted on an all-0 ancestor (four MPRs, TL = 137, CI = 0.701, RC = 0.483). chousaurus on the basis of the following charac- ters: 4— nasals in broad contact (CI = 1; D, A); 12— parietals paired in adult (CI = 1; D, A); 21 — scleral ossicles present (D, A); 28— dorsal centra unconstricted (CI = 0.5; A); 33— sacral ribs with- out distal expansion (CI = 0.5; D, A); 36— pos- terior stem on interclavicle absent (CI = 1; A); 39— entepicondylar foramen present (CI = 0.667; D, A); and 43— radius with distinct concavity on preaxial margin (CI = 0.5; A). Anarosaums and 2 3 _ « — > % C < 3 Tt t/; M 5 3 s« O 2 « a 3 £ !/; n O O S5 2 .1 Fig. 26. Strict consensus tree for Placodus, pachypleurosaurs, and selected eusauropterygians, rooted on an all-0 ancestor (10 MPRs, TL = 147, CI = 0.667, RC = 0.455). RIEPPEL AND KEBANG: PACHYPLEUROSAURS 33 g -I s 3 O ">% 5 3 H 3 CO c« O 6 2 3 O s o •S 5 '5 >. o Q ^ u J Z Fig. 27. Strict consensus tree for pachypleurosaur interrelationships, with the pachypleurosaurs plus selected eusauropterygian taxa rooted on Placodus (five MPRs, TL = 134, CI = 709, RC = 506). the Serpianosaurus-Neusticosaurus clade group to the exclusion of Dactylosaurus on the basis of: 29— neck less than 80% of trunk length (CI = 0.75; D, A if rooted on Eusauropterygia; CI = 0.6; A, if rooted on Placodus); 30—20 or more dorsal ver- tebrae (CI = 0.5; D, A); 36— posterior stem on interclavicle absent (CI = 1; D); 45— carpal ossi- fications reduced to two (CI = 0.75; A); 49— pubis with anteroventral process (CI = 0.25; A); and 50— obturator foramen open in adults (CI = I; D, A). The Serpianosaurus-Neusticosaurus clade is united by the following synapomorphies: 3— na- sals slender (CI = 0.5-1; D, A); 4— nasals meet in short suture (CI = 0.857-1; D, A); 9 -longitudinal diameter of upper temporal fossa 25-30% of or- bital diameter (CI = 1; D, A); 28— dorsal centra unconstricted (CI = 0.333; D); 35— clavicles with- out expanded comers (CI = 0.33-0.5; D, A); 40— humerus with vermiculate surface (CI = 0.5; D, A); 43— radius without distinct concavity on pre- axial margin (CI = 0.5; A); and 45— carpal ossi- fications reduced to two (CI = 10.75; D). The ge- nus Neusticosaurus is diagnosed by: 31— dorsal ribs pachyostotic (CI = 0.333; D, A); 34-gastral ribs composed of three segments (CI = 1 ; D, A); 44— rectangular and elongated intermedium (CI = 1; A); and 49— pubis without anteroventral pro- cess (CI = 0.25; A). Neusticosaurus peyeri, N. ed- wardsii, and "Psilotrachelosaurus" are united by: 11— upper temporal arch broad (i.e., temporal emargination not visible from above) (CI = 0.5- 1; D, A— not known for ^'' Psilotrachelosaurus'''); 30-19-20 dorsal vertebrae (CI = 0.5; D, A); and 47— phalangeal reduction in manus (CI = 1; D, A— not known for ^''Psilotrachelosaurus'"). Neus- ticosaurus edwardsii and "Psilotrachelosaurus" are united by: 29 -neck 80-100% of trunk length (CI = 0.6-0.75; A); and 45— three carpal ossifications (CI = 0.75; D, A— this character was miscoded for Neusticosaurus edwardsii in Rieppel, 1993). Genera and Species of Pachypleurosauroidea in the Middle and Upper Triassic The morphological and phylogenetic analyses presented above show Anarosaurus, Dactylosau- rus, and Keichousaurus to represent well-diag- nosed genera from the lower Middle Triassic. The diagnoses of Anarosaurus and Dactylosaurus are 34 FIELDIANA: GEOLOGY given above. Characters diagnostic of Keichou- saurus Young, 1958, are the relative length of the neck (130-140% of trunk length as expressed by the number of vertebral elements), the narrow frontal with no anterolateral processes, the fused parietal with an anteriorly located pineal foramen, the gently curved humerus with no entepicondylar foramen but with a vermiculate surface, the broad ulna, and hyperphalangy in the manus. Upper Middle Triassic pachypleurosaurs form the Serpianosaurus-Neusticosaurus clade. ''Psi- lotrachelosaurus" is shown by the above analysis to be nested within species referred to the genus Neusticosaurus and hence must be included in that genus as a fourth species, A^. toeplitschi. The as- sociation with Neusticosaurus edwardsii is weak, however, based only on the presence of three car- pal bones (other synapomorphies are imknown for toeplitschi; see discussion above). In a tree one step longer (122 steps), A^. peyeri, N. edwardsii, and A^. toeplitschi fall into an unresolved trichotomy, with N. pusillus being the sister-taxon to those three. The systematics of Middle Triassic Pachypleuro- sauroidea may be formalized as follows. G«nns Neusticosaurus Seeley, 1882 Type Species— Neusticosaurus pusillus Seeley, 1882. Diagnosis— Small to medium-sized pachypleu- rosaurs with pachyostotic dorsal ribs; gastral ribs composed of three segments; pubis without an- teroventral process; intermedium may be rectan- gular and elongate, located at the postaxial margin of the distal tip of the radius. Distribution— Middle Triassic (Ladinian), western Europe (western Tethyan Province). Referred Species Neusticosaurus peyeri Sander, 1989 Diagnosis— A small pachypleurosaur (450-550 mm overall length, 90-1 30 mm trunk length) with a distinctly wedge-shap>ed skull (shared with A^. edwardsii); relatively large orbits; keyhole-shaped upper temporal fossae; 19-20 dorsal vertebrae (shared with A^. edwardsii and A^. toeplitschi); no accessory intervertebral articulations; relatively small pectoral fenestra; two carpal ossifications in adult; phalangeal reduction in manus (shared with A^. edwardsii). Locus Typicus— Cava Sujieriore horizon, low- er Meride Limestone (middle Ladinian), Monte San Giorgio, Switzerland. Neusticosaurus pusillus Seeley, 1882 Diagnosis— A small pachypleurosaur (400-520 mm overall length, 85-105 mm trunk length); skull table with parallel margins; orbits relatively small; oval upper temporal fossae; 22-24 dorsal verte- brae; no atlas rib; two carpal ossifications in adult (Sander, 1989). Locus Typicus— Lettenkeuper (lower Keuper, middle to lower upper Ladinian) of Hoheneck near Ludwigsburg, southwestern Germany. Distribution— Middle Triassic of southern Germany (Germanic Triassic), Switzerland, and northern Italy (northern and southern Alpine Tri- assic). Neusticosaurus edwardsii (Comalia, 1854) Diagnosis— A large pachypleurosaur (up to 1,200 mm overall length) with a wedge-shaped skull; upper temporal fossae oval; neck 80-100% of trunk length; 19-20 dorsal vertebrae; relatively short femur; three carpal ossifications in adult; phalangeal reduction in manus and pes. Locus Typicus— Uppermost part of upper Meridekalke (upper Ladinian; lower Camian ac- cording to Tintori et al., 1985), Ca' del Frate near Besano, Italy. Distribution— Middle and upper Ladinian (lower Camian?) of southern Switzerland and northern Italy (southern Alpine Triassic). Neusticosaurus toeplitschi (Nopcsa, 1928) Diagnosis— A small pachypleurosaur (56 mm tnmk length) with 19-20 dorsal vertebrae (shared with N edwardsii); relatively short humerus; rel- atively broad ventral elements in the pelvic girdle; three carpal ossifications (shared with A^. edward- sii); fourth distal tarsal ossified. Locus Typicus— Upper unit of the Partnach- Plattenkalk (middle Ladinian), Stadelbachgraben, Gailtaler Alps, Austria. Genus Serpianosaurus Rieppel, 1989 Type Species: Serpianosaurus mirigiolensis Rieppel, 1989. RIEPPEL AND KEBANG: PACHYPLEUROSAURS 35 Diagnosis: A medium-sized pachypleurosaur (up to 750 mm overall length; up to 1 87 mm trunk length); skull relatively long; lower jaw straight; upper temporal fenestra small and oval with pos- sible exclusion of parietal from its medial margin; 20-23 dorsal vertebrae; distinct striations on neu- ral spines; two carpal ossifications. Locus Typicus— Grenzbitumenzone (Anisian- Ladinian boundary), Monte San Giorgio, Swit- zerland. Referred Species— Serpianosaurus mirigiolen- sis is the only known species of its genus. Historical Biogeography of the Pachypleurosauroidea Stem-group Sauropterygia are known from the Lower and Middle Triassic of China, from the Middle to Upper Triassic of Europe, and from the upper Lower and Middle Triassic of the western United States. As presently known, the strati- graphic and geographic distribution of the Pachy- pleurosauroidea is restricted to the Middle Tri- assic (perhaps extending into the lower Upper Tri- assic) deposits of coastal stretches and epiconti- nental seas of the Tethyan Province. The only possible record of pachypleurosaurs from the western hemisphere is represented by as yet un- described material from the Wupatki Member of the Moenkopi Formation (Lower Triassic: Colbert & Gregory, 1957), in northeastern Arizona, but their resemblance to pachypleurosaurs is only su- perficial and their relationship with the group has not been established on the basis of shared derived characters (Storrs, 1991). With stem-group Sauropterygia in the Lower Triassic of China (Young, 1965), Europe, and the western United States (Storrs, 1991), a reasonable assumption would be to locate the origin of the clade in the eastern Tethyan Province, from where the group spread eastward (into the eastern Pacific Province, western United States) and westward (western Tethyan Province, Europe). Whereas the phylogenetic positions of Placodontia and Coro- saurus as currently understood continue to chal- lenge this broad scenario, an eastern Tethyan or- igin of the Pachypleurosauroidea is indicated by the phylogenetic position of Keichousaurus. It is relatively the most plesiomorphic genus within the clade, sister-taxon to all other Pachypleurosau- roidea, and its distribution is restricted to the Mid- dle Triassic epicontinental sea of China. The hy- pothesis of immigration of Sauropterygia into the Middle Triassic epicontinental sea of Europe (Muschelkalk Basin) from the East is supported by independent evidence derived from geology and invertebrate fossils. The history of the Muschelkalk Basin has re- cently been reviewed by Hagdom (1985, 1991; see also Ziegler, 1982). A relative rise in sea level in early Anisian time induced the Muschelkalk trans- gression. The base of the lower Muschelkalk is in the lower Anisian (Kozur, 1974; Hagdom, 1985). The analysis of invertebrate faunas indicates im- migration into the Muschelkalk Basin from the east, through the East Carpathian Gate (Kozur, 1974; Ziegler, 1982, 1988; Hagdom, 1985, 1991; Urlichs & Mundlos, 1985), but westward dispersal was stopped by a salinity barrier. With a second sea level rise during the lower Anisian, the inver- tebrate fauna expanded throughout the basin. During Pelsonian times, the main faunal exchange occurred through the Silesian-Moravian Gate, al- though the East Carpathian Gate persisted. Study of longshore transport directions in the area of the Silesian-Moravian Gate indicates a fan-shaped current diagram changing from a SE-NW direc- tion in westem Upper Silesia to a SW-NE direc- tion in eastern Upper Silesia (Szulc, 1 99 1). Marine faimas populating the Muschelkalk Basin may have dispersed into the intraplatform basins of the Al- pine Triassic (Mostler, 1 993). In late Anisian times (lower lUyrian, middle Muschelkalk), a southern connection from the Muschelkalk Basin to the Te- thys, the Burgandy Gate, opened. The earliest pachypleurosaur to appear in the Germanic Triassic is Dactylosaurus (Fig. 28), from the lower Muschelkalk (lower Gogolin beds, Dad- ocrinus biozone: Hagdom, 1991; corresponding to Kozur's [ 1 974] "assemblage zone" with Beneckeia buchi, Myophoria vulgaris, and Dadocrinus gracilis at the transition from the Rot to the lower Mus- chelkalk; see also Wysogorski, 1903-1908) of Up- per Silesia. Its early appearance in the Muschelk- alk Basin indicates immigration from the east, per- haps through the East Carpathian Gate, although crinoid data also support immigration through the Silesian-Moravian Gate at that time (Hagdom, 1985). Pachypleurosaurs, however, have not (yet) been reported from Transylvanian deposits east of the Silesian-Moravian Gate (Jurcsak, 1973, 1 976, 1 977, 1 982). Dactylosaurus is the sister-tax- on to Anarosaurus and the Serpianosaurus-Neus- ticosaurus clade. Early westward dispersal of pachypleurosaurs through the Muschelkalk Basin is documented by the genus Anarosaurus (Fig. 28). The undescribed 36 FIELDIANA: GEOLOGY ^ V w I RIEPPEL AND KEBANG: PACHYPLEUROSAURS 37 Anarosaurus material from the lower Muschelkalk of Winterswijk (Oosterink, 1986; here referred to Anarosarus heterodontus n. sp.) is geologically younger than the vertebrates from the Gogolin beds, since the deposition of marine sediments started earlier in the eastern part of the Muschelk- alk Basin than in the western part (Hagdom, 1991). The temporal occurrence of Anarosaurus may be closer to the Anarosaurus heterodontus material from the upper lower Muschelkalk in the eastern part of the Muschelkalk Basin (Schaumkalk, Frey- burg/Unstrut). The holotype of Anarosaurus pum- ilio comes from the orbicularis beds of Remker- sleben near Magdeburg, now referred to the basal part of the middle Muschelkalk (Hagdom & Simon, 1993), which renders Anarosaurus pumilio (upper Pelsonian or lower lUyrian) distinctly younger than Dactylosaurus (Bithynium), and also younger than Anarosaurus heterodontus. The genus Anarosau- rus is the sister-group to the Serpianosaurus-Neus- ticosaurus clade of the Alpine Triassic. The earliest pachypleurosaur from the Alpine Triassic is an isolated neural arch (not diagnostic) found in lower Anisian (Dadocrinus biozone) de- posits of the Vicentinian Alps, northeastern Italy (coll. H. Hagdom, mhi 1292). It is contempora- neous with, or only slightly younger than, the oc- currence of Dactylosaurus in Upper Silesia. The specimen might indicate a very early southward migration from the Germanic into the Alpine Tri- assic, or alternatively an independent migration of pachypleurosaurs with Asiatic affinities into the European epicontinental sea (Muschelkalk Basin) and into the intraplatform basin facies along the northwestern shores of the Tethys. This latter sce- nario would be supported by a position of Ana- rosaurus as sister-taxon to Dactylosaurus, that clade in turn forming the sister-group to the Serpiano- saurus-Neusticosaurus clade [((Anarosaurus, Dac- tylosaurus) (Serpianosaurus, Neusticosaurus))]. It has been pointed out that the phylogenetic posi- tion of Anarosaurus is weakly supported, since the genus falls into an unresolved trichotomy with Dactylosaurus and the Serpianosaurus-Neustico- saurus clade in a tree one step longer than the most parsimonious reconstruction. Also, Anarosaurus (undescribed material from Winterswijk) and Dac- tylosaurus share two potential synapomorphies, viz. the close approximation of postfrontal and prefrontal along the dorsal margin of the orbit (due to an anterior process of the postfrontal) and the notch on the preaxial side of the radius. However, on the basis of the currently available evidence (Table 6), no tree could be generated that shows Anarosaurus to be closer to Dactylosaurus than either is to the Serpianosaurus-Neusticosaurus clade. The earliest diagnosable pachypleurosaur from the Alpine Triassic is Serpianosaurus from the Grenzbitumenzone (Anisian-Ladinian boundary) of Monte San Giorgio, Switzerland (Rieppel, 1989). Stratigraphically, this occurrence corresponds to the transition from mo, to moj in the lower part of the upper Muschelkalk (i.e., to the boundary between lUyrian and Fassanian) (Kozur, 1974). It also corresponds to a time period when the Bur- gandy Gate had established a southern connection of the Muschelkalk Basin to the westem Tethys, although a migration of marine faunal elements from the Muschelkalk Basin southward into the southern Alpine carbonate platform facies was possible earlier (Mostler, 1993). The sister-group relationship of the geologically older Anarosaurus from the Germanic Triassic and the geologically younger Serpianosaurus-Neusticosaurus clade from the Alpine Triassic may indicate a southward dis- persal of pachypleurosaurs from the Muschelkalk into the southern Alpine intraplatform basins. Diagnostic remains of Serpianosaurus are re- stricted to the Grenzbitumenzone (Anisian-Lad- inian boundary) of Monte San Giorgio, Switzer- land (Rieppel, 1989). An incomplete pachypleu- rosaur from the Calcare di Perledo, recognized as the Perledo Member of the Perledo- Varenna For- mation (northem Italy) of upper Ladinian age (Gaetani et al., 1992), was referred to as Phygo- saurus by Arthaber (1924). The name is a nomen dubium (Rieppel, 1989), and the specimen is now lost, but early and informal comparison of pachy- pleurosaurs from the Grenzbitumenzone of Monte San Giorgio with Arthaber's (1924) genus Phy- gosaurus (Peyer, 1933-1934) indicates the possi- bility of the occurrence of Serpianosaurus outside the Monte San Giorgio Basin, and at a younger geological age. Isolated pachypleurosaur remains from the basal part of the middle Muschelkalk (lower Illyrian) of Eberstadt near Heilbronn (Ba- den-Wurttemberg) have been referred to Anaro- saurus pumilio of closely similar geological age (Hagdom & Simon, 1993), although they are typ- ically larger than the corresponding elements in the skeleton of Anarosaurus. The (disarticulated) material includes a slender femur, a pubis with a concave ventral (medial) margin, an open obtu- rator foramen, and a left clavicle. The clavicle lacks an expanded anterolateral comer, present in un- described material of Anarosaurus from Winter- swijk, unknown in the holotype of Anarosaurus 38 FIELDIANA: GEOLOGY pumilio, but absent in Serpianosaurus. The pubis morphology of the Eberstadt material is similar to that of Serpianosaurus, and isolated posterior dor- sal and anterior caudal vertebrae from Eberstadt show distinctly striated neural spines, a character known to occur within the Serpianosaurus-Neus- ticosaurus clade (particularly in Serpianosaurus: Rieppel, 1989), but unknown (for lack of ade- quately preserved and/or prepared material) in Anarosaurus. The fragmentary remains from Eberstadt might indicate the early occurrence of Serpianosaurus in the Germanic Triassic (Hag- dom & Simon, 1993), from where it might have spread southward into the intraplatform basin fa- cies of the southern Alpine region. Serpianosaurus is the sister-taxon of the genus Neusticosaurus. The genus Neusticosaurus occurs in the Monte San Giorgio deposits with three spe- cies, each relatively short-lived and following one another in stratigraphic succession within the low- er Meridekalke (Sander, 1989) of lower to middle Ladinian age: the earliest species, Neusticosaurus pusillus, comes from the Cava Inferiore beds, fol- lowed by Neusticosaurus peyeri from the Cava Su- periore beds, which in turn is followed by Neus- ticosaurus edwardsii from the Alia Cascina beds. The intrageneric cladistic structure fits the strati- graphic succession of Neusticosaurus species at Monte San Giorgio, but the pattern becomes com- plicated if the distribution of the species is con- sidered over a wider range. The most widespread species of Neusticosaurus is A^. pusillus, the first species of Neusticosaurus to occur in the Monte San Giorgio deposits and the sister-taxon to all other species of Neusticosaurus. Restricted to the Cava Inferiore beds (lower or middle Ladinian) at Monte San Giorgio, the spe- cies is abundant in the Lettenkeuper deposits of the Germanic Triassic (Hagdom «& Simon, 1993), considered to be of lower to middle Ladinian age by Brinkmann (1986). However, Kozur (1974, p. 62) identified the first Cordevolian faunal ele- ments in the Grenzdolomit, which he places at the very base of the middle Keuper. This indicates that the lower Keuper (Lettenkeuper) corresponds to the upper Longobardian, that is, to the middle to upper Ladinian. Neusticosaurus pusillus has also been reported from the middle Ladinian Prosanto formation of the eastern Alps (Biirgin et al., 1991), and it occurs in the Perledo Member of the Per- ledo-Varenna formation (northern Italy) of upper Ladinian age (Rieppel, in prep.). This pattern of geographic and temporal distribution suggests a faster faunal turnover rate at Monte San Giorgio compared to other localities. Diagnostic remains of Neusticosaurus peyeri are known only from the Monte San Giorgio deposits, which might indicate that the genus Neusticosaurus originated in the intraplatform basin facies of the southern Alps. Such a conclusion is difficult to support, however, because the identification of Neusticosaurus spe- cies is contingent on the availability of fairly com- plete skeletons. These are not available from the upper Muschelkalk, in which disarticulated pa- chypleurosaur remains are abundant. The holotype of Neusticosaurus edwardsii is from Ca' del Frate, a locality in northern Italy that has been correlated with the Kalkschieferzone (up- permost Meridekalke) and has been assigned a middle Camian age by Tintori et al. (1985). In southern Switzerland, the Meridekalke do not ex- tend into the Camian (Scheuring, 1978), and the Kalkschieferzone of Monte San Giorgio has yield- ed Lariosaurus (Kuhn-Schnyder, 1987), as have northern ItaUan outcrops (Tintori & Renesto, 1 990; Renesto, 1 993). A middle Camian age may be too young for the Ca' del Frate locality (which may be upper Ladinian), but the occurrence of Neustico- saurus edwardsii at Ca' del Frate indicates a longer persistence of this species in the latter locality than in Monte San Giorgio and hence again a faster faunal turnover rate in the Monte San Giorgio Basin than in other similar intraplatform basins of the southern Alps. Diagnostic remains of Neusticosaurus toeplitschi are restricted to middle Ladinian deposits of the Gailtaler Alps. Other, less complete pachypleu- rosaur specimens from the same deposits (Zapfe & Konig, 1980) cannot be identified to species level. For taphonomic reasons, articulated vertebrate skeletons are generally preserved in intraplatform basins of the southem Alps and allow species di- agnoses based on meristic data. The identification of disarticulated pachypleurosaur remains from the upper Muschelkalk to the species level is dif- ficult if not impossible. Furthermore, the delin- eation of genera and species within a fully resolved tree ("Hennigean comb": Panchen, 1992) of monophyletic taxa is a purely conventional one. Nevertheless, current knowledge of the Pachy- pleurosauroidea indicates an increase in taxic di- versity among crown-group pachypleurosaurs (Serpianosaurus-Neusticosaurus clade) from the Ladinian, as compared to the stem-group pachy- pleurosaurs from the Anisian. Based on the hy- pothesis that pachypleurosaurs invaded the west- em Tethyan Province from the east, it might be RIEPPEL AND KEBANG: PACHYPLEUROSAURS 39 argued that the increased taxic diversity of crown- group pachypleurosaurs is correlated with a great- er habitat fragmentation and habitat diversity in the intraplatform basin facies of the southern Alps, as compared to the more contiguous habitat in the Muschelkalk Basin. Pachypleurosaurs also docu- ment the fact, however, that faunal interchange did take place between the two environments throughout the Middle Triassic (Wild, 1 972). The Paleoecology of Pachypleurosaurs Using generalized reptiles such as Captorhinus, Petrolacosaurns, Claudiosaums, and Youngina as outgroups, and comparing pachypleurosaurs to Eusauropterygia (Storrs, 1991, 1993a), indicates a relatively plesiomorphic morphology for the Pa- chypleurosauroidea (Rieppel, 1989): retention of the posteriorly excavated quadrate, no distinct posterior displacement of the mandibular articu- lation, no constriction of the skull table and no posterior elongation of the tooth row beyond the posterior margin of the orbit. All of these char- acters indicate that pachypleurosaurs retained an impedance-matching middle ear and a simple jaw adductor system. The Eusauropterygia have reduced or lost the tympanum and the large, air-filled middle ear cav- ity to avoid problems generated by hydrostatic pressure during diving (Taylor, 1 992). Advanced stem-group Sauropterygia, as well as crown-group taxa, are also characterized by an elongation of the upper and lower jaws and dorsoventral depression of the skull, changes that reduce hydrostatic drag during lateral snapping bites. In association with these modifications there developed a specialized dual system of jaw adduction (Rieppel, 1 989; Tay- lor, 1992; Storrs, 1993b) in correlation with a rel- ative elongation of the postorbital region of the skull. The reorientation of the jaw adductor mus- cle groups is correlated with a posterior extension of the tooth row beyond the posterior margin of the orbit, and with changes in the morphology of the mandibular joint preventing disarticulation of the lower jaw. All of these morphological corre- lates suggest that Eusauropterygia became pro- gressively more adapted to an open marine en- vironment than is typical for pachypleurosaurs, which inhabit intraplatform basin and shallow epicontinental marine habitats (Sues, 1987). Currently available evidence supports the po- sition of Placodontia as sister-taxon to all other Sauropterygia (Eosauropterygia) and Corosaurus as sister-taxon to a clade comprising pachypleu- rosaurs plus Eusauropterygia (Rieppel, 1994b). Such changes in the relative relationships of sau- ropterygian taxa require the impedance-matching middle ear and the simple jaw adduction system to have re-evolved in pachypleurosaurs (on the basis of ACCTRAN optimization; DELTRAN optimization treats the loss of the impedance- matching middle ear and the evolution of the dual jaw adduction system in Corosaurus and Eusau- ropterygians as convergent) as an adaptation to a coastal environment. The correct interpretation of character evolu- tion within the Sauropterygia will depend on fur- ther tests of sauropterygian interrelationships. Several faunas have not yet been brought to bear on that problem, such as sauropterygians from the Triassic deposits in Transylvania (Jurcsak, 1982) and Israel (Brotzen, 1955; Peyer, 1955; Haas, 1963), the Eusauropterygia from the Lower and Middle Triassic of China, and new material from the Middle Triassic of northwestern Nevada. Nev- ertheless, the morphology of pachypleurosaurs, whether relatively plesiomorphic or apomorphic, as well as the geographic and geologic occurrence of the group, indicates that pachypleurosaurs were inhabitants of shallow epicontinental seas or in- traplatform basins along coastal stretches (Sues, 1987; Rieppel, 1989; Storrs, 1993b). In the upper Muschelkalk, the occurrence of pachypleurosaurs tends to be correlated with the beginning of a trans- gressive phase, or the waning of marine conditions during a regressive phase, and the frequency of their occurrence is increased in deposits close to the paleocoast (Hagdom & Simon, 1993). Intra- platform basins along the northwestern coast of the Tethys temporarily communicated with the open sea, but pachypleurosaurs have so far not been recorded outside coastal environments. Acknowledgments Access to the Anarosaurus and Dactylosaurus \ material was made possible by H. Haubold, In- stitut fiir Geowissenschaften, Martin-Luther- Universitat Halle; W.-D. Heinrich, Museum fiir Naturkunde, Berlin; H. Jahnke, Institut und Mu- seum fiir Geologic und Palaontologie, Gottingen; 1 A. C. Milner, The Natural History Museum, Lon- don: H. Oosterink and the Werkgroep Muschelk- 40 HELDIANA: GEOLOGY alk, Winterswijk; G. Plodowski, Forschungsinsti- tut und Naturmuseum Senckenberg, Frankfurt a.M.; H. U. Schliiter, Bundesanstalt fur Geowis- senschaften und Rohstoffe, Berlin; F. Westphal and A, Liebau, Geologisch-Palaontologisches Institut der Universitat, Tubingen; R. Wild, Staatliches Museum fiir Naturkunde, Stuttgart. A specimen of Keichousaurus was made accessible by K. Bart- lett. Children's Museum, Indianapolis. H. Hag- dom and R. Wild freely shared their knowledge on Muschelkalk fossils and stratigraphy. An earlier draft of this paper was kindly read by R. L. Carroll and H.-D. Sues. This study was supported by NSF grants DEB-9220540 and DEB-94 19675 (to O.R.). Literature Cited Arthaber, G. V. 1924. Die Phylogenie der Notho- saurier. Acta Zoologica, Stockholm, 5: 439-516. Brinkman, R. 1986. Brinkmans Abriss der Geologic. Zweiter Band. Historische Geologic, Erd- und Le- bensgcschichtc, 12th/ 13th ed. Ehnkc, Stuttgart. Brotzen, F. 1955. Occurrence of vertebrates in the Triassic of Israel. Nature, 176: 404—405. BiJRGIN, T., U. ElCHENfBERGER, H. FURRER, AND K. TscHANZ. 1991. Die Prosanto-Formalion — cine fischreichc Fossil-Lagerstatte in der Mittcltrias der Sivretta-Dccke (Kanton Gaubiinden, Schweiz). Eclo- gae gcologicac Hclvctiae, 84: 921-990. Carroix, R. L. 1981. Plesiosaur ancestors from the Upper Permian of Madagascar. 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Appendix: Material Included and Institutional Abbreviations Institutional Abbreviations Bundesanstalt fiir Geowissenschaften und RohstofFe, Berlin: bgr; The Natural History Mu- seum, London: BNora; Institut und Museum fiir Geologie und Palaontologie, Georg-August-Uni- versitat, Gottingen: Go; Institut und Museum fur Geologie und Palaontologie, University of Tu- bingen: gpit; Natural History Museum, Hum- boldt University, Berlin: mb; Institute of Geolog- ical Sciences, University of Wroclaw: mgu; For- schungsinstitut und Naturmuseum Senckenberg, Frankfurt a.M.: smf, Staatliches Museum fiir Na- turkunde, Stuttgart: smns. Anarosaurus heterodontus n. sp. Institut fur Geowissenschaften, Martin-Luther- Universitat, Halle; right dentary and left premax- illa (M4/12); Schaumkalk (upper lower Muschel- kalk), Freyburg/Unstrut. Museum Freriks, Win- terswijk (uncatalogued): skull; lower Muschelkalk, Winterswijk, Netherlands. Anarosaurus pumilio Institut und Museum fur Geologie und Palaon- tologie, Georg-August-Univeritat, Gottingen, Go 409-1; Museum fiir Naturkunde, Berlin (mb R. 57.1-3, dorsal view; mb R. 58, ventral view); In- stitut fur Geowissenschaften, Martin-Luther- RIEPPEL AND KEBANG: PACHYPLEUROSAURS 43 Universitat, Halle (uncatalogued, skull only, dor- sal view); The Natural History Museum, London (bmnh R-5691, dorsal view; mbnh R-5866, ven- tral view); Staatliches Museum fur Naturkunde, Stuttgart (SMNS 59073). Charitosaurus tschudii Humboldt Museum, Berlin (mb R. 61-62); Staatliches Museum fur Naturkunde, Stuttgart (SMNS 80082-83); lower middle Muschelkalk, Remkersleben. (brg, uncatalogued, original specimen of Nopcsa, 1928; MB R. 772.1., mb R. 769, and uncatalogued; humeri from lower Muschelkalk of Gogolin); For- schungsinstitut und Naturmuseum Senckenberg, Frankfurt a.M. (smf R-4097 a, b; original speci- men of Nopcsa, 1928, cast); Bundesanstalt fur Geowissenschaften und Rohstoffe, Berlin (bgr, drawer S 45/5 right; humerus from lower Muschel- kalk of Bobrek near Beuthen); Institut und Mu- seum fiir Geologic und Palaontologie, University of Tubingen (gpit 1744/1-10; humeri from lower Muschelkalk of Gogolin, Poland; and an uncata- logued articulated skeleton from the same depos- its). Dactylosaurus gracilis Sauropterygia incertae sedis Museum fiir Naturkunde, Berlin (mb R. 63, cast of original specimen of Giirich, 1884); Bundesan- stalt fiir Geowissenschaften und Rohstoffe, Berlin Staatliches Museum fur Naturkunde, Stuttgart (SMNS 16253, humerus, lower Muschelkalk, Go- golin, Upper Silesia [Poland]). 44 HELDIANA: GEOLOGY A Selected Listing of Other Fieldiana: Geology Titles Available A Preliminary Survey of Fossil Leaves and Well-Preserved Reproductive Structures from the Sentinel Butte Formation (Paleocene) near Almont, North Dakota. By Peter R. Crane, Steven R. Manchester, and David L. Dilcher. Fieldiana: Geology, n.s., no. 20, 1990. 63 pages, 36 illus. Publication 1418, $13.00 Comparative Microscopic Dental Anatomy in the Petalodontida (Chondrichthyes, Elasmobranchii). By Rainer Zangerl, H. Frank Winter, and Michael C. Hansen. Fieldiana: Geology, n.s., no. 26, 1993. 43 pages, 35 illus. Publication 1445, $16.00 Status of the Pachypleurosauroid Psilotrachelosaurus toeplitschi Nopcsa (Reptilia, Sauropterygia), from the Middle Triassic of Austria. By Olivier Rieppel. Fieldiana: Geology, n.s., no. 27, 1993. 17 pages, 9 illus. Publication 1448, $10.00 Osteology of Simosaurus gaillardoti and the Relationships of Stem-Group Sauropterygia. By Olivier Rieppel. Fieldiana: Geology, n.s., no. 28, 1994. 85 pages, 71 illus. Publication 1462, $18.00 Revised Phylogeny and Functional Interpretation of the Edrioasteroidea Based on New Taxa from the Early and Middle Ordovician of Western Utah. By Thomas E. Guensburg and James Sprinkle. Field- iana: Geology, n.s., no. 29, 1994. 43 pages, 37 illus. Publication 1463, $12.00 Giant Short-Faced Bear {Arctodus simiis yukonensis) Remains from Fulton County, Northern Indiana. By Ronald L. Richards and William D. TumbuU. Fieldiana: Geology, n.s., no. 30, 1995. 34 pages, 20 illus. Publication 1465, $10.00 Order by publication number and/or ask for a free copy of our price list. All orders must be prepaid. Illinois residents add current destination tax. All foreign orders are payable in U.S. dollar-checks drawn on any U.S. bank or the U.S. subsidiary of any foreign bank. Prices and terms subject to change without notice. Address all requests to: HELD MUSEUM OF NATURAL HISTORY Library— Publications Division Roosevelt Road at Lake Shore Drive Chicago, Illinois 60605-2498, U.S.A. Field Museum of Natural History Roosevelt Road at Lake Shore Drive Chicago, Illinois 60605-2496 Telephone: (312) 922-9410 HECKMAN IXI BINDERY INC. |s| AUG 96 Boumi -To-Plca^ N. 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