MEANING: Yuxi lizard
PERIOD: Early Jurassic
CONTINENT: Asia
Yuxisaurus is a basal thyreophoran dinosaur from the Early Jurassic, and the earliest known in Asia. Its discovery definitively proves the rapid geographic spread and diversification of thyreophorans across the continent, as previous evidence was too fragmentary to be of any significance. Yuxisaurus had a heavy build, and distinctive spiked armor. It seems to have been facultatively bipedal, meaning it would mainly walk on four legs, but was able to walk on two.
Yuxisaurus is from the Jurassic. The Jurassic is a geologic period that spanned from the end of the Triassic, 201 million y ears ago, to the beginning of the Cretaceous, 145 million years ago. It is the middle period of the Mesozoic Era. The start of the Jurassic was marked by the major Triassic-Jurassic extinction event. The end, however, has no clear boundary with the Cretaceous. By the beginning of the Jurassic, Pangea had begun rifting into two landmasses: Laurasia and Gondwana, and the climate was warm with no ice caps. Life on land was dominated by dinosaurs, and the first birds appeared, evolving from a branch of theropods. The oceans were inhabited by marine reptiles, while pterosaurs were the dominant flying vertebrates.
Yuxisaurus is a thyreophoran. Thyreophora is a group of armored ornithischian dinosaurs that lived from the Early Jurassic until the end of the Cretaceous. They are characterized by the presence of body armor lined up in longitudinal rows along the body. Early forms had simple, low, keeled scutes or osteoderms, whereas more derived forms developed more elaborate structures including spikes and plates. Most thyreophorans were herbivorous and had relatively small brains for their body size. In the Jurassic, Thyreophora diverged into two main groups: Ankylosauria and Stegosauria. In both the suborders, the forelimbs were much shorter than the hindlimbs, particularly in stegosaurs.
Basal thyreophorans were small to medium size dinosaurs with small, primitive plates. Many of them walked bipedally, or were facultatively quadrupedal. The majority of these are known from the Northern Hemisphere.