Ichthyosaurs are a team of profitable Mesozoic marine reptiles that have a throughout the world distribution, but their evolutionary origin is nonetheless unclear. In modern several years, numerous new maritime reptiles related to ichthyosaurs, and identified as early ichthyosauromorphs, have been identified in rocks of Early Triassic age and shed light on the origin of ichthyosaurs. These early ichthyosauromorphs have been learned in quite a few international locations, but most of them are from China, like Cartorhynchus, Chaohusaurus, and quite a few customers of an ichthyosauromorph subgroup called the Hupehsuchia. They are usually small (about 1m very long) and are from the japanese and central areas of China.
In a new paper printed in the journal PeerJ, scientists from China and Canada report a new massive early ichthyosauromorph, named Baisesaurus robustus, from the southwest of China, extending the acknowledged geographic distribution of this group.
In 2017, Guizhou Geological Study discipline crews identified some vertebrate bones exposed in limestone in the Zhebao region of Guangxi Province, southwest China, and they invited scientists (Haishui Jiang and Fenglu Han) from China College of Geosciences (Wuhan) to be part of them in studying the specimen. Jiang and Han confirmed that the fossil was that of a marine reptile, possibly a relative of ichthyosaurs. The specimen was gathered by the joint study staff in 2018, and was ready in the Wuhan Centre of the China Geological Study.
The specimen contains only the front element of the trunk skeleton, together with some vertebrae and ribs, a limb bone, and stomach bones referred to as gastralia. This made classification tricky, but the scientists when compared the fossil comprehensively with other marine reptiles from the Early Triassic and eventually discovered it as an ichthyosauromorph. “The dorsal ribs and gastralia are additional equivalent to individuals of other early ichthyosauromorphs, this kind of as Chaohusaurus, than to sauropterygians,” explained Long Cheng, a coauthor on the study.
In standard, Baisesaurus robustus shares extra similarities with Utatsusaurus from Japan, a different early ichthyosauromorph, than with other maritime reptiles. The scientists also discovered some strange features that have been mysterious in other early ichthyosauromorphs, this sort of as deep depressions on the sides of the vertebrae, and a strong radius with two distinctive joint facets for speak to with wrist bones. These new characteristics reveal that the fossil belongs to a earlier unidentified species, which the scientists named Baisesaurus robustus. In addition, Baisesaurus is estimated to have been about 3m extensive, earning this freshly identified marine reptile noticeably more substantial than any other Early Triassic ichthyosauromorph from China. Last but not least, Baisesaurus has a more robust radius than numerous other early ichthyosauromorphs, suggesting sturdy swimming capabilities that may possibly have been made use of for extended-distance migrations alongside the jap margin of an historic ocean regarded as the Paleo-Tethys.
“I am inclined to just take Baisesaurus as a reminder that you can find even now a ton to be found out about the incredible evolutionary explosion of vertebrate variety that took put in the Triassic,” reported Corwin Sullivan, a coauthor on the study. Sullivan is an associate professor at the University of Alberta in Edmonton, Canada, and curator of the Philip J. Currie Dinosaur Museum in nearby Wembley.