Ichthyosaurs are a group of thriving Mesozoic marine reptiles that are distributed throughout the world, but their evolutionary origins are still unclear. In recent years, many new marine reptiles related to ichthyosaurs and called early ichthyosauromorphs have been discovered in early Triassic rocks, shedding light on the origin of ichthyosaurs. These early ichthyosauromorphs have been found in many countries, but most originated in China, including Carthorhynchus, haohusaurus, and several members of a subgroup of ichthyosauromorphs called Hupehsuchia. As a rule, they are small in size (about 1 m in length) and come from the eastern and central regions of China.
In a new article published in the journal PeerJresearchers from China and Canada report a new large early ichthyosauromorph named Kissesaurus Robustfrom southwestern China, expanding the known geographic distribution of this group.
In 2017, Guizhou Geological Survey field teams discovered exposed vertebrate bones in limestone in the Zhebao region of Guangxi province in southwest China and invited researchers (Haishui Jiang and Fenglu Han) from the China University of Geosciences (Wuhan) to join them to study. sample. Jiang and Han confirmed that the fossil belonged to a marine reptile, possibly related to ichthyosaurs. The sample was collected by a joint research team in 2018 and prepared at the China Geological Survey’s Wuhan Center.
The specimen includes only the anterior torso skeleton, including vertebrae and ribs, limb bones, and abdominal bones called gastralia. This made classification difficult, but researchers carefully compared the fossil to other early Triassic marine reptiles and eventually identified it as an ichthyosauromorph. “The dorsal ribs and abdomen more closely resemble those of other early ichthyosauromorphs such as haohusaurusthan sauropterygians,” said Long Cheng, co-author of the study.
Generally, Kissesaurus Robust has more resemblance to Utatsavr from Japan, another early ichthyosauromorph than other marine reptiles. The researchers also found unusual features not found in other early ichthyosauromorphs, such as deep depressions along the sides of the vertebrae and a strong radius with two separate articular facets for contact with the carpal bones. These new features indicate that the fossil belongs to a previously unknown species, which the researchers have named Kissesaurus Robust. Except, Kissesaurus It is estimated to have been around 3 m long, making this newly discovered marine reptile much larger than any other early Triassic ichthyosauromorph from China. End, Kissesaurus has a larger radius than many other early ichthyosauromorphs, indicating a strong swimming ability that could have been used for long-distance migrations along the eastern margin of the ancient ocean known as the Paleo-Tethys.
“I tend to accept Kissesaurus as a reminder that much remains to be learned about the huge evolutionary explosion of vertebrate diversity that occurred during the Triassic period,” said study co-author Corwin Sullivan. Sullivan is an adjunct professor at the University of Alberta in Edmonton, Canada and curator of the Philip J. Curry Dinosaur Museum at Wembley.
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