ABSTRACT Newly discovered lizard fossils from the Upper Cretaceous Djadochta Formation in the Gobi Desert of Inner Mongolia, China, include early iguanids and agamids that are taxonomically and biogeographically important. Two iguanids reported here, Anchaurosaurus gilmorei, gen. et sp. nov. and Xihaina aquilonia, gen. et sp. nov., document the geologically earliest record of the family from Asia, and extend the fossil record of the group by 11–13 Myr. The geological age and primitive structure of these Cretaceous iguanids, coupled with other material of the same group from the slightly younger Barun Goyot Formation, suggest that the group had a long evolutionary history on the northern continents, and hence, challenge the widely accepted South American origin hypothesis of the Iguanidae (sensu lato). Three taxa of agamids are documented in the new collection: Mimeosaurus crassus Gilmore, 1943, Priscagama gobiensis Borsuk-Bialynicka and Moody, 1984, and Pleurodontagama aenigmatodes Borsuk-Bialynicka and Moody, 1984. Several well-preserved skulls of M. crassus show a structure that requires a taxonomic revision of this genus. Priscagama and Pleurodontagama are poorly documented. It has been long held that the iguanids and agamids have different centers of origin, and that the two groups have been separated geographically from one another since the beginning of their evolution. With the discoveries of new iguanids and agamids together from the Gobi, it is now clear that the two families were sympatric during their early evolution on the northern continents.
Late Jurassic and Early Cretaceous birds from northeastern China, including many complete skeletons of Confuciusornis, provide evidence for a fundamental dichotomy in the class Aves that may antedate the temporal occurrence of the Late Jurassic Archaeopteryx. The abundance of Confuciusornis may provide evidence of avian social behavior. Jurassic skeletal remains of an ornithurine bird lend further support to the idea of an early separation of the line that gave rise to modern birds. Chaoyangia, an ornithurine bird from the Early Cretaceous of China, has premaxillary teeth.
ABSTRACT Two new fossil crania of Old World vultures (Accipitridae, Aegypiinae), from the middle Pleistocene Jinniushan site of Liaoning Province, northeastern China, were studied. A new species of Aegypius, A. jinniushanensis, is erected and characterized by possessing a less developed processus zygomaticus and processus suprameaticus, as well as a relatively larger condylus occipitalis, compared with A. monachus. Another specimen, assigned to Torgos, is the first record of this genus from outside Africa. The presence of two large vultures, apparently in the same feeding group, in the Jinniushan faunal assemblage suggests that there were more opportunities for interspecific competition among scavengers in the middle Pleistocene of northeastern China than at present. By analogy with phylogenetically related modern vultures, we suggest that niche differentiation between the two extinct species may have reduced the degree of competition between them. The disappearance of the genus Torgos from northeast China might be the result of the Pleistocene extinction of a suite of large mammalian herbivores, and the loss of grassland and savannah from this region.
Flexible, or soft-shelled, eggs are almost unknown in the fossil record, leaving large gaps in our knowledge of the reproductive biology of many tetrapod clades. Here, we report two flexible-shelled eggs of the hyphalosaurid choristodere Hyphalosaurus baitaigouensis from the Early Cretaceous of China, one containing an embryo and the second associated with a neonate. Choristoderes are an enigmatic group of aquatic reptiles that survived the K–T extinction but died out in the Miocene. Hyphalosaurids, a specialized clade of Choristodera, resemble miniature plesiosaurs and are considered to be primarily aquatic in habit. Scanning electron microscopy of samples from the eggs reveals a thin, non-columnar external mineralized layer characterized by rounded nodes and tentatively identified poorly structured irregular pores, with an underlying amorphous layer presumably representing decomposed protein fibrils. While the relationships of Choristodera remain controversial, eggshell microstructure more closely resembles that of Lepidosauromorpha (the lineage including lizards) as opposed to that of Archosauromorpha (the lineage including birds and crocodiles).
Squamate fossils collected for the Sino-Canadian dinosaur expeditions (1986–1990) include some 70 specimens from the Upper Cretaceous (Campanian) Djadochta Formation, exposed at the vicinity of Bayan Mandahu, Inner Mongolia, China. Well-preserved skulls, jaws, postcranial skeletons, and even osteodermal armor document a fossil assemblage composed of at least 18 genera in 8 families. Besides showing considerable taxonomic diversity, several families recorded in the assemblage are of importance in understanding the geologic and biogeographic distribution of the relevant groups, and the paleoenvironment in which these lizards lived. Comparison of the Gobi lizard assemblage with North American and Central Asian assemblages is briefly discussed. Taxonomic differences in the assemblage from that of the Upper Cretaceous in the North American Western Interior reflect endemism and suggest a low frequency of interchange of small terrestrial vertebrates between the two regions during Campanian time. The taphonomic setting of the squamate fossils indicates quick burial in arid to semiarid environments in the Gobi Desert, differing importantly from the Western Interior of North America, where the accumulation of disarticulated jaw fragments reflects postmortem decomposition and fluvial transportation under subtropical to warm temperate conditions.
We describe a new enantiornithine bird, Huoshanornis huji gen. et sp. nov., from the Early Cretaceous Jiufotang Formation in Chaoyang, western Liaoning Province, China. This new bird is distinguished from other known enantiornithines in possessing a considerably reduced alular digit, a broad intermetacarpal space, a relatively long phalanx of the minor digit of the manus, and a remarkable triangular expansion at the distal end of the lateral trabecula of the sternum. The morphology of the manus may also suggest that at low flight speeds the new bird's maneuverability was exceptional.
We describe a new species of shorebird, tentatively referred to the family Charadriidae, from the Huadian Formation (Middle Eocene) in Jilin Province, China. In general morphology the specimen closely matches that of an extant charadriid, and corresponds in size to the Killdeer (Charadrius vociferus). If correctly identified this is the oldest record of the Charadriidae. The Middle Eocene paleoenvironment of the Huadian region is thought to have resembled a subtropical swamp.
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