Dinosaur Footprints From Yanguoxia Yongjing County Gansu Province And Implications For Paleaenvironment And Paleaecology

Dinosaur is the extinct creature who rose in the later Triassic, bloomed during the Jurassic and Cretaceous, and then extincted in the end of Cretaceous. As the dominator of the Mesozoic, it is the focus of the science. Especially in the last 20 years, with the discovery of the dinosaur fossil from Sichuan, Liaoning, Xingjiang Provinces and others sites and the implement of the project of the international cooperation including projects of Sino-Canada, Sino-Belgium, Sino-Japan Silk Road expedition and a joint Sino-Japan-America expedition, the dinosaur study has got another climax. Footprint study, which is one of the branches of dinosaur research, has got the breakthrough of the history of the tracks studies with the upsurge of dinosaur study nationally and abroad and the spectacular discoveries of the footprints. And it comes to be field of the intercrossing subject, which focus on the study of paleoecology and paleontology.The study of dinosaur footprints is still weak for the limitation of the subject development though dinosaur remains are abundance in China. By far most of the documents are only about the news reports and identification of these tracks. The tracks applications in paleoenvironment and paleoecology are scare. Here we describe the dinosaur tracks from Yanguoxia County, Gansu Province, which enrich the data of dinosaur tracks in china, provide the evidence in dinosaur activity in the northwest of China during the Mesozoic. What is more, it is important in exploring the dinosaur behavior, palaeoecology and renewing the paleoenvironment and paleoclimate at that time.There are 10 tracks sites found around Yanguoxia since the first discovery in 1999, in which the site 1 is the largest one including sauropod, theropod, ornithopod and pterosaur tracks. A bird track-bearing horizon also occurs 2m above this level. The dissertation deal with many fields as following:1. Paleontology A. The footprints fauna from Yanguoxia is the most spectacular one, where preserved the largest footprints in the world. Sauropod tracks from Yanguoxia are different from those in America and Korea. These footprints are identified as three new ichnospecies including Brontopus megaensis, Brontopus gansuensis and Brontopodus yongjingensis.B. We consider the tridactyl footprints as theropod and ornithopod impressions, and assign them as theropod and ornithopod. Theropod footprints hold the characters of Coelurosauria. Different from the dinosaur impressions, theropod tracks here are 5 new ichnospecies of Ichnofamily Anchisauripodidae including Grallator leei, Grallator curvensis, Grallator laohukouensis, Grallator monax. Ornithopod footprints are the typical Iguanodon tracks, which is considered a new ichnospecies Iguandontipus yanguoxiaensis by theirs sizes and character of digits.C. After the report of bidactyl footprints from Sichuan Province, we can find another one bidactyl impression in Yanguoxia, which is Velociraptorichnus huanghensis, a new species of Ichnofamily Dromaeosauridae.D. The first pterosaur tracks in China were discovered associated with abundant dinosaur footprints in this level. Similar with other pterosaur footprints, this track, which is pteraichnus yanguoxiaensis, is quadrupedal, with strong asymmetric tridactyl manus and sub-rectangle pes with no well separated digit impressions.2. Sedimentology There are many typical lacustrine structure including intercrossing bedding, ripple marks, mud cracks, convolute laminations and burrow structure. Combining with the character of the sedimentary structure, we can arrive at the conclusion that the dinosaurs have being trampling lacustrine margin after waning flood, with matrix saturated. Following trampling, the substrate dried and were exposed for a long periods. The repeated track-bearing depositions indicate that the climate is in periodic and cyclic episodes. 3. Paleoecology A. The size of footprints indicates that the trackmakers are huge, largest of which is up to 32m length. All the sauropod footprints tend to be w...