Researchers have described a new dinosaur from fossils found in southwestern China. The dinosaur has been named Archaeocursor asiaticus. It is the oldest ornithischian (bird-hipped) dinosaur from Asia described to date. Phylogenetic analysis suggests Archaeocursor also represents the earliest-diverging ornithischian known from Asia. This discovery extends the known presence of ornithischian dinosaurs in East Asia to the Pliensbachian or even late Sinemurian stages of the Early Jurassic.
Archaeocursor asiaticus the oldest ornithischian dinosaur from Asia described to date. A silhouette of the dinosaur providing a basic body shape and highlighting the position of the fossil femur (top left). Top right, close-up view of bone histology confirming a subadult specimen. Proposed phylogeny (bottom) and the close relationship with Eocursor parvus from South Africa. Image credit: Yao et al.
Picture credit: Yao et al
Archaeocursor asiaticus
The Early Jurassic ornithischian dinosaurs in Laurasia are dominated by armoured dinosaurs. Other types of ornithischian are rare. Scientists from Yunnan University, the Chinese Academy of Sciences, the Southeast Sichuan Geological Team and the Chongqing Institute of Palaeontology examined a nearly complete left femur. The fossil, specimen number L01-HY999, was found approximately two kilometres north of Chongqing Central Park in Yubei District, Chongqing Municipality. The leg bone fossil comes from the Lower Jurassic Dongyuemiao Member of the Ziliujing Formation.
Osteohistological analysis of the bone indicates that it came from a young adult. The animal would have been less than a metre in length. The genus name is derived from the Latin words “archaeo”, “cursor” and “asiaticus” which translate as “old runner from Asia”. The team conducted an in-depth phylogenetic analysis that placed A. asiaticus as the earliest-diverging ornithischian dinosaur yet discovered in Asia, albeit with weak support. Archaeocursor asiaticus is identified as an ornithischian dinosaur based on distinctive morphological features, namely a broad, wing-like anterior trochanter and a well-developed flange-like fourth trochanter, which differentiate it within Ornithischia.
Related to Eocursor parvus from South Africa
Ornithischian fossils are scarce in Early Jurassic deposits of Asia, primarily reported from the contemporaneous Lower Jurassic Lufeng and Fengjiahe formations in Yunnan province, also in
southwestern China. The phylogenetic analysis indicated that Archaeocursor asiaticus was closely related to Eocursor parvus. Eocursor is a genus of basal ornithischian dinosaur that lived in South Africa in the Early Jurassic. Its fossils had been thought to be much older dating from the Late Triassic (Norian). However, it is not possible at this time to determine the age of this fossil material with confidence. Many palaeontologists consider Eocursor to have lived during the Sinemurian (Early Jurassic).
To read an article from 2007 about the discovery of E. parvus: The Ancestor of Stegosaurus, Triceratops etc.
Ornithischian dinosaurs originated from Gondwana and migrated to the North Hemisphere in the Early Jurassic. However, the timing of their arrival in East Asia is obscure. The close relationship between Archaeocursor asiaticus and Eocursor parvus, despite their distance (China and South Africa respectively), suggests a probable ornithischian origin in Gondwana. At some point there followed a northward migration to Laurasia and eventually to East Asia during the Pliensbachian. This timing might precede the arrival of armoured dinosaurs in the region.
Everything Dinosaur acknowledges the assistance of the corresponding author of the scientific paper Xi Yao in the compilation of this article.
The scientific paper: “New evidence for the earliest ornithischian dinosaurs from Asia” by Xi Yao, Qi Zhao, Tingcong Ren, Guangbiao Wei and Xing Xu published in iScience.
The award-winning Everything Dinosaur website: Dinosaur Toys and Models.
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