Zuo-Yu Sun

First record of Placodontoidea (Reptilia, Sauropterygia, Placodontia) from the Eastern Tethys

DA-YONG JIANG, RYOSUKE MOTANI, WEI-CHENG HAO, OLIVIER RIEPPEL, YUAN-LIN SUN, LARS SCHMITZ, and ZUO-YU SUN Department of Geology and Geological Museum, Peking University, Beijing 100871, P. R. China, djiang@pku.edu.cn; Department of Geology, University of California, Davis, California 95616-8605, U.S.A; Department of Geology, The Field Museum, Chicago, Illinois 60605-2496, U.S.A., rieppel@fieldmuseum.org.

A New Middle Triassic Eosauropterygian (Reptilia, Sauropterygia) from Southwestern China

Abstract A new eosauropterygian genus and species is described from the middle Anisian (Middle Triassic) of Panxian (Guizhou Province, southwestern China). The new taxon is characterized by an unique specialization of the jaws that form an elongate pointed rostrum furnished with numerous small, monocuspid and vertically oriented teeth with a basally expanded crown and pointed tip, which is quite unlike any other sauropterygian known. Other diagnostic characters include: frontals paired; parietal unpaired; pineal foramen located centrally in broad parietal skull table; two carpal ossification; ilium with distinct preacetabular process at the base of the dorsally extending iliac blade; pubis plate-like and of rounded contours; two tarsal ossifications. The curved and distally expanded humerus, the reversed topological relationship of the clavicle and scapula, and the presence of three sacral ribs indicate sauropterygian affinities of the new taxon, whereas the ‘butterfly-shaped’ or ‘cruciform’ facet for the neural arch on the dorsal centrum surface indicate its eosauropterygian status.

Tanystropheus cf. T. longobardicus from the Early Late Triassic of Guizhou Province, Southwestern China

ABSTRACT The protorosaur Tanystropheus longobardicus is well known from the Middle Triassic of alpine Europe. It has been described on the basis of a number of specimens that apparently range from juvenile to adult. The largest specimens have a total body length of approximately 3 m. Here we report on the first occurrence of a large tanystropheid from the Middle or early Late Triassic of southwestern China. The new specimen is indistinguishable from the largest specimens of T. longobardicus from Europe, although it lacks a skull. Both the Chinese specimen here described and the European specimens of T. longobardicus are characterized by 13 cervical vertebrae (not 12 as had previously been assumed). The new find, together with a recent specimen of Macrocnemus from Yunnan Province, highlight shared elements of the vertebrate fauna around the coastline of western and eastern Tethys during Middle to Late Triassic times.

Horizons and Assemblages of Middle Triassic Marine Reptiles from Panxian, Guizhou, China

RYOSUKE MOTANI, DA-YONG JIANG, ANDREA TINTORI, YUAN-LIN SUN, WEI-CHENG HAO, ALEC BOYD, SANJA HINIC-FRLOG, LARS SCHMITZ, JI-YEON SHIN, and ZUO-YU SUN; Department of Geology, University of California, Davis, California 95616, U.S.A., montani@geology.ucdavis.edu; Department of Geology and Geological Museum, Peking University, Beijing 100871, China; Dipartimento di Scienze della Terra, Università degli Studi di Milano, Via Mangiagalli 34 I-20133 Milano, Italy

The Early Triassic eosauropterygian Majiashanosaurus discocoracoidis, gen. et sp. nov. (Reptilia, Sauropterygia), from Chaohu, Anhui Province, People’s Republic of China

ABSTRACT Records of Early Triassic marine reptiles, when they first emerged after the end Permian mass extinction, are rare. During an excavation at Majiashan, Chaohu, Anhui Province, a new sauropterygian specimen was found co-occurring with the ichthyopterygian Chaohusaurus from the Upper Member of the Nanlinghu Formation, of Olenekian (Spathian, Early Triassic) age, for which a new taxon, Majiashanosaurus discocoracoidis, gen. et sp. nov., is erected. This skeleton is exposed in ventral view, with the last three cervical vertebrae together with 19 dorsal, three sacral, and more than 18 caudal vertebrae preserved. The cervical centra are keeled ventrally, and cervical ribs are double-headed, carrying a free anterior process. The transverse processes of the dorsal vertebrae are not distinctively elongated. The dorsal ribs are single-headed, and the clavicles articulate on the anteromedial aspect of the scapula. The humerus is curved. These features allow assignment to a new sauropterygian taxon. The interclavicle has no posterior process, and the scapula is of typical eosauropterygian shape, with a broad and ventrally expanded glenoidal portion that is separated from a narrow posterodorsal blade by a distinct constriction. The coracoid is round and plate-like without a waist. This feature is different from that of all other known eosauropterygians, but resembles that of placodonts.

Phylogeny of the Ichthyopterygia Incorporating Recent Discoveries from South China

ABSTRACT During the last decade, abundant ichthyopterygian material has been found from the Triassic of South China as well as the Upper Jurassic and Lower Cretaceous of Europe and South America, significantly expanding our knowledge of ichthyopterygian diversity through the Mesozoic. Previous phylogenetic hypotheses of the group no longer account for these extensive additions, necessitating a new phylogenetic framework for the entire Ichthyopterygia to enable evolutionary studies of the group. We present here a comprehensive phylogenetic hypothesis for Ichthyopterygia based on cladistic analysis of 163 characters coded for 59 ingroup and five outgroup taxa. The monophyly of Ichthyopterygia is strongly supported by a Bremer index value of 7. Five major groups of Ichthyopterygia during the Triassic, viz., Grippioidea, Cymbospondylidae, Mixosauridae, Shastasauridae, and Toretocnemidae, are well supported by Bremer index values between 3 and 5. Major clades that evolved in the Triassic, including Merriamosauria, Euichthyosauria, and Parvipelvia, are also robustly supported, whereas most post-Triassic clades are very weakly supported with a Bremer index value of 1, with a few exceptions, such as Thunnosauria and Ophthalmosauridae. The traditional Shastasauridae is expanded to comprise six genera but excludes Callawayia, which is more closely related to Parvipelvia than to Shastasauridae. ‘C.’ wolonggangensis is a shastasaurid but does not form a monophyletic clade with Callawayia neoscapularis or Guizhouichthyosaurus tangae as previously asserted. The new phylogenetic hypothesis is generally consistent with the stratigraphic occurrences of each taxon especially for the Triassic taxa.

A NEW BASAL NEOPTERYGIAN FROM THE MIDDLE TRIASSIC OF LUOPING COUNTY (SOUTH CHINA)

A new taxon belonging to Neopterygians is described, based on very nicely preserved specimens from the rich vertebrate levels recently discovered in Luoping County, Yunnan Province, South China. This new assemblage dates to Pelsonian (Anisian, Middle Triassic), about the same age of the Panxian Fauna from the nearby Guizhou Province. The Luoping Fauna, yielding this new taxon, is turning out to be one of the most important fish faunas of the whole Middle Triassic and the oldest evidence of the fish radiation of this time span. This new genus of basal neopterygian shows unique derived characters, especially for the almost naked body, with a single row of urodermals covering the body lobe in the tail and a row of very small and thin scales bearing the lateral line canal along the flank. Also in the axial skeleton the new taxon shows peculiar characters such as the neural spines perfectly aligned to each paired neural arches and abdominal ribs well developed. Concerning skull bones, no suborbitals have been detected.

OLDEST STEM TELEOSTEI FROM THE LATE LADINIAN (MIDDLE TRIASSIC) OF SOUTHERN CHINA

The origin of the largest modern vertebrate group, the Teleostei, saw major refinements in the last decades, thanks to newly discovered and stratigraphically closely spaced Triassic Lagerstatten. Here we report the oldest Pholidophoriformes (stem teleosts) that were collected during a large scale yet detailed excavation of Upper Ladinian (Middle Triassic) marine deposits in Xingyi City, Guizhou Province, China. Taxonomic comparisons support the erection of a new pholidophorid genus, Malingichthys gen. nov., with two species. The new genus shows a partially fused skull roof, a preopercular bone with a hockey-stick shape and, for the first time in Pholidophoridae, supraneural elements. Most Triassic marine vertebrate clades (fishes and reptiles, Malingichthys included) first emerged in the South China Block, with Late Ladinian most showing an important faunal transformation that was strengthened by our last findings. The material here described is about 2 million years older than the previous records for pholidophorids.

A new juvenile specimen of Guanlingsaurus (Ichthyosauria, Shastasauridae) from the Upper Triassic of southwestern China

ABSTRACT A new nearly complete skeleton from the Wayao Member of the Falang Formation (lower Carnian, Upper Triassic) of Guizhou, South China, is described and ascribed as a juvenile individual of Guanlingsaurus liangae. The new specimen supplies hitherto unknown information on this species: a complete pelvic girdle shows that the ilium was misidentified as the ischium by previous authors; complete hyoids show that their length was overestimated previously; unlike in other shastasaurids, the obturator foramen on the pubis is widely open as part of the obturator fossa; and the fibula has a posterior flange, similar to that of Shonisaurus. Guanlingsaurus liangae was reassigned to the genus Shastasaurus and was suggested to be a suction feeder due to its short snout, lack of teeth, and hyoid. However, the new specimen of Guanlingsaurus described here shows much smaller hyoids compared with Shonisaurus, which was thought to be a suction-feeding ichthyosaur. Suction feeding in ichthyopterygians as a whole requires scrutiny: the group lacks an ossified hyoid corpus that is typically expanded in suction-feeding cetaceans, which suggests that ichthyopterygian hyoids were insufficiently robust for suction feeding. A phylogenetic analysis of Ichthyopterygia based on a revised data matrix clarifies the shastasaurid affinity of G. liangae as a sister taxon of Shonisaurus, with Shastasaurus as their sister group, and Shonisaurus is reestablished as a genus containing Shonisaurus sikanniensis as traditionally held. It suggests that the assignment of Guanlingsaurus and Shonisaurus sikanniensis to Shastasaurus unnecessarily confuses existing taxonomy.

New information on the protorosaurian reptile Macrocnemus fuyuanensis Li et al., 2007, from the Middle/Upper Triassic of Yunnan, China

ABSTRACT A new specimen of the protorosaur Macrocnemus fuyuanensis, from the Zhuganpo Member of the Falang Formation at Fuyuan (Yunnan Province, southwestern China), is described and compared with Macrocnemus bassanii. The new specimen is the first in the genus Macrocnemus that clearly shows details of the preorbital region of the skull. A large, plate-like lacrimal is located in front of the tall, columnar prefrontal that defines the anterior margin of the orbit. A longitudinally oriented nasal groove extends along the anterior two-thirds of the snout, accommodating the external naris at its anterior part. A similar preorbital depression has previously been described for Dinocephalosaurus and it is also reported here for the first time in Tanystropheus. The new specimen confirms the status of Macrocnemus fuyuanensis as a species distinct from Macrocnemus bassanii on the basis of a humerus that significantly exceeds the radius in length. The occurrence of both Macrocnemus and Tanystropheus in southwestern China further underscores the close faunal affinities of the eastern and western Tethyan realms during the Middle and early Late Triassic.