Middle-to-Late Jurassic terrestrial vertebrates of China: Systematics and geochronology

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Middle-to-Late Jurassic terrestrial vertebrates of China: Systematicsand geochronologyPI: James M Clark, George Washington University Co-PIs: Catherine A. Forster, GWU; Xu Xing, Chinese Academy of Sciences Land-living vertebrate fossils from the Middle and early Late Jurassic (176-156 million years ago) are very poorly known worldwide, but the Shishugou Formation of NW China preserves abundant articulated skeletons from this age. This is an important time in the history of modern land vertebrates, because the oldest occurrences of modern mammals, lizards, turtles, and salamanders are this age or slightly older, and the presence of the oldest bird Archaeopteryx later in the Jurassic indicates that birds evolved at about this time. The major lineages of dinosaurs that flourished in the Cretaceous (ceratopsians, ankylosaurs, ornithopods, neosauropods, and coelurosaurs) also appear at this time. From 2001-2006 joint expeditions by GWU and the Chinese Academy of Sciences to the Shishugou Formation, funded in 2004-2006 by the NSF, collected over 450 vertebrate fossils and documented the geology of the formation. We radiometrically dated rocks indicating the formation spans the Middle-Upper Jurassic boundary. Among our discoveries are the oldest and most primitive tyrannosauroid (Guanlong wucaii) and ceratopsian (Yinlong downsi) dinosaurs, the first ceratosaurian theropod dinosaur from Asia (Limusaurus inextricabilis), and the oldest and most primitive member of the bizarre alvarezsaurid theropods. Fossils in this collection bear important evidence on the origin of birds, generating a new hypothesis for the identity of the fingers present in theropods and documenting the diversification of the closest relatives of birds 10 million years prior to Archaeopteryx. Two extraordinary sites preserve evidence of miring, a highly unusual preservational milieu. Here we request support for 1) studies of undescribed fossils, including nearly complete skeletons of a basal lizard, a primitive mammal, an unusual new turtle, and a new maniraptoran theropod dinosaur, 2) preparation of detailed descriptions of several important dinosaur species, 3) radiometric dating (ID-TIMS) of rocks at the base of the Shishugou Formation, in contemporary rocks elsewhere in the Junggar Basin, and in the Middle Jurassic Shaximiao formations of Sichuan, China, and 4) continued exploration for fossils in the Shishugou Formation, especially in the lower part of the formation. Participants in this project include underrepresented groups in Earth Sciences (two females and a native American).