GEOGRAPHY

3 meters long, China’s largest triassic ichthyosaur reappears in the sky


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Baise Ichthyosaurus (top) and Chaohu Ichthyosaurus (bottom) Restoration figure Shi Shunyi, Nobu Tamura painting

Han Fenglu, associate professor at the School of Earth Sciences of China University of Geosciences (Wuhan), and collaborators recently reported a fossil of a Pre-Triassic ichthyosaur from the Elastospheric region of Longlin County, Baise City, Guangxi Province, China. The world’s new genus is named “Stout Ichthyosaurus”. The ichthyosaur is 3 meters long, cute in appearance, has stronger swimming ability, and is currently the largest early Triassic ichthyosaur fossil found in China, and the research results were recently published in the journal PeerJ in the field of biology and medicine.

In 2017, the Guizhou Provincial Geological Survey found the vertebral bodies and ribs of suspected vertebrates during a field survey in Longlin, Guangxi. Upon invitation, Jiang Haishui, Han Fenglu and Chen Gong of the Department of Geobiology of the School of Earth Sciences of China University of Geosciences went to investigate and excavate, which was further confirmed to be vertebral and rib fossils of vertebrates.

The research team used excavation tools such as chainsaws to retrieve the surrounding rock containing fossils and carried out a three-month restoration at the Wuhan Geological Survey Center of the China Geological Survey. Studies have shown that the fossil mainly contains the front half of the trunk, including the anterior dorsal vertebrae (vertebral body and arch), ribs, peritoneal ribs, and a limb bone. The fossils are found in marine formations and have typical features of marine reptiles such as biconcave vertebrae. However, due to the fact that the fossils did not preserve the characteristics of key parts such as skulls and most of the limb bones, it brought certain difficulties to identification.

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Field expeditions using tools such as chainsaws to process fossils and their surrounding rocks

After a multi-faceted comparative study, they finally identified some key features, such as the ribs are relatively slender and not thickened at the proximal end, and the middle of the peritoneal ribs has long, thin protrusions. “Although this specimen is incompletely preserved, it has some characteristics unique to ichthyosaurs, unlike other marine reptiles such as finnosaurs.” Han Fenglu told China Science Daily.

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Stout Bose Ichthyosaurus Outcrops Courtesy of the Interviewee

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Han Fenglu repairing fossils photographed by Pang Weihong

It is reported that ichthyosaurs are marine reptiles that flourished in the Triassic and Jurassic periods, first appeared about 250 million years ago, and became extinct 90 million years ago, about the same period as dinosaurs. They are highly specialized, with a streamlined, fish-like body shape as well as large eyes and strong caudal fins.

Ichthyosaurs may have evolved from terrestrial reptiles, but their origins and early evolution remain unsolved mysteries. At present, the earliest discovery of ichthyosaurs appeared in the Early Triassic, and have been officially reported in Japan, Canada, Northern Europe and Hubei, Anhui and other places in China, mostly small individuals with a length of no more than 1.5 meters, and their fossil materials and distribution ranges are relatively limited.

The early Triassic ichthyosaurs previously discovered in China are mainly represented by Chaohu dragons, these early ichthyosaurs are small, most of them are under 1 meter, and the distribution of animals is more regional, and their swimming and migration ability is considered to be weak.

The specimens found this time are larger, estimated to be up to 3 meters long, far larger than the early Triassic ichthyosaurs previously found in China. At the same time, one of the limb bones (identified as radius) preserved in this specimen is long and stout, and the morphology is very regular, with high symmetry in all directions, the proximal joint surface is slightly protruding, and the distal end has 2 flat joint surfaces of similar size, and the restored appearance is similar to that of modern dolphins.

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Restored fossils photographed by Pang Weihong

In recent decades, Chinese fossils of early Triassic ichthyosaurs have only been found in Anhui and Hubei provinces. Ichthyosaur is the first discovery of early Triassic ichthyosaur fossils in Guangxi, which broadens the geographical distribution of Early Triassic ichthyosaurs in China and increases the morphological diversity of Early Triassic ichthyosaurs.

“Compared to other early ichthyosaurs, Ichthyosaurs had longer, stronger forelimb bones, suggesting that Ichthyosaurs may have had greater swimming abilities and may have been able to travel longer distances in the Guttis Ocean, while Ichthyosaurs were also the largest in China, the Early Triassic Ichthyosaurs, and may have played a role as a high-level predator in the oceans of the time.” Han Fenglu said. (Source: China Science Daily, Feng Lifei, Pang Weihong, Ren Jicheng)

Related paper information:https://doi.org/10.7717/peerj.13209



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