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A new plesiosaur specimen of Archeonectrus rostratus (Sauropsida: Sauropterygia) from the Lias (Lower Jurassic) of Normandy (France).





Complete plesiosaur skeletons are abundant in the Lower Jurassic of England and Germany, but are exceptional in France. In the 1980’s, a new Pliensbachian plesiosaur was discovered by amateur palaeontologists near Caen (Calvados Department, France). This specimen includes an incomplete skull, palate and mandible with several associated vertebrae. It is described here and its affinities are discussed. It is the second well preserved Liassic plesiosaur specimen discovered in France. Moreover, it comes from the Pliensbachian stage during which plesiosaur remains are scarcely found. The comparison of this new specimen with other plesiosaurs indicates that it belongs to the species Archeonectrus rostratus Owen, 1865 from the Sinemurian of England. The specimen studied here is thus the only referred specimen to this species, which extends significantly the stratigraphical range of this taxon. Its description provides important new data on the cranial anatomy, especially palatal aspects, which were not preserved on BMNH 38525, the holotype of Archeonectrus rostratus . A cladistic analysis, including 14 species and 45 cranial, dental and postcranial characters, was performed in order to understand the phylogenetic affinities of this species among Plesiosauria. It confirms the Pliosauroidea affinities of Archeonectrus rostratus .

Owen, R. 1865. A monograph on the fossil Reptilia of the Liassic formations. Part 1. Order Sauropterygia. Monograph of the Palaeontographical Society , 17 (75), 1-40,pls 1-16.

Vincent, P. 2004. Etude d’un spécimen de plésiosaure (Sauropsida, Sauropterygia) du Jurassique de Normandie: anatomie, systématique, phylogénie et paléobiogéographie. DEA de Systématique, Paris, Muséum National d’Histoire Naturelle de Paris, 45 pp. (unpublished).


YUAN WANG1, SUSAN E. EVANS2 & GUILIN ZHANG1

1Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China [wangyuan@ivpp.ac.cn]; 2Department of Anatomy & Developmental Biology, University College London, Gower Street, London, WC1E 6BT, England [ucgasue@ucl.ac.uk]


Mesozoic frogs and salamanders from China.





From 1986 to 1998, no new lissamphibian fossils were reported from China, and all known material was collected from Cenozoic deposits. The past eight years have witnessed an acceleration in the study of Mesozoic frogs and salamanders in China. This has been based on good new material (including a large number of articulated skeletons and exquisite soft tissue impressions) from the tuff-interbedded lacustrine deposits of northeastern China (Liaoning, Hebei and Inner Mongolia). Five frogs (Callobatrachus sanyanensis , Dalianbatrachus mengi, Liaobatrachus grabaui , Mesophryne beipiaoensis , Yizhoubatrachus macilentus ) and seven salamanders (Chunerpeton tianyiensis , Jeholotriton paradoxus , Laccotriton subsolanus , Liaoxitriton daohugouensis, L. zhongjiani, Pangerpeton sinensis, Sinerpeton fengshanensis) have been named. Most of them are from the Lower Cretaceous Jehol Group (i.e., Dabeigou, Yixian and Jiufotang formations in ascending sequence), whereas four salamanders (Chunerpeton, Jeholotriton, Liaoxitriton daohugouensis, Pangerpeton ) come from a lower horizon, the Daohugou fossil bed, argued as Middle Jurassic to Lower Cretaceous by different workers. Among the recent amphibian discoveries have been frog skeletons with three-dimensional preservation and salamander specimens representing different stages of ontogenetic development (larva to adult). Phylogenetic analyses suggest that the frogs are advanced over typical Jurassic frogs worldwide, and the salamanders advanced over Middle–Late Jurassic early caudates from England and Central Asia. Together with the findings from the Lower Cretaceous Tetori Group (Japan), these may represent one or two early adaptive radiations of East Asian lissamphibians, which were characterized by high taxonomic diversity and the first records of living amphibian families (e.g., Discoglossidae, Hynobiidae and Cryptobranchidae).

JOANNA WRIGHT



Dept of Geology & Environmental Sciences, University of Colorado - Denver Campus Box 172, PO Box 173364, Denver 80217-3364, USA (Joanna.Wright@cudenver.edu)

Bird and Dinosaur Tracks from the Cedar Mountain Formation (Barremian) of Utah.





In recent years the Cedar Mountain Formation of Utah has become famous for vertebrate remains. Only a few tracksites have been reported, probably due, in large part, to the fact that the unit is made up largely of mudstones. Most tracks have mainly been the usual iguanodontid-dominated assemblage typical of the early Cretaceous. However, in recent years, a more diverse track assemblage was reported from Arches National Park, which included the tracks of sauropods, and possibly didactyl theropods, e.g. dromaeosaurids. These tracks are very deeply impressed in what was evidently a wet muddy cohesive substrate. In addition to these, at a lower stratigraphic level, some enigmatic traces are also preserved, on a ripple-marked sandstone layer. These traces consist of sets of elongate scratch marks radiating out from a central area and forming ovals or paired crescents 8-10cm in maximum dimension. These have been variously interpreted as tool marks, invertebrate traces or pterosaur feeding traces.

Outside the park, bird tracks were discovered in the Poison Strip Sandstone in summer 2005. The tracks are preserved on three fallen blocks, although distinctive lithology allowed identification of the track horizon. All the tracks are preserved in concave epirelief on a thin fine-grained sandstone layer at the top of a metre thick erosional based coarser sandstone with a rippled top surface, which may be of crevasse splay origin. The tracks are approximately 30-40mm in length with no traces of interdigital webbing. These are the earliest known bird tracks in North America.


These tracksites provide a more complete view of the early Cretaceous vertebrate assemblages in western North America during the Early Cretaceous. This part of the Cedar Mountain Formation is thought to have been deposited on the margins of a large lake as channels, crevasse splays and lakeshore/floodplain sediments.


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