Beida researchers make progress on the origin of Mesozoic ichthyosaurs
Peking University, Nov. 15, 2014: On Nov. 5th, 2014, Nature published (online) a scientific paper titled A basal ichthyosauriform with a short snout from the Lower Triassic of China by the internationally collaborative team led by Professor Jiang Dayong from School of Earth and Space Sciences, Peking University. This is their one more significant research progress after the discovery reported by Sea Monsters, the special edition in National Geographic (Dec., 2005) and the scientific excavation in Chaohu, Anhui Province reported by Science (Nov. 26th, 2010) titled Excavation Yields Tantalizing Hints of Earliest Marine Reptiles.
The large-scale scientific excavations and research since 2008 on marine reptile fossils from Lower Triassic in Chaohu, Anhui have made big impact in the international academia.
Reptiles were the dominators on Earth in Mesozoic (from 252 million years ago to 65 million years ago) and got rapid diversified on land, in ocean and in sky after the end-Permian Mass Extinction that severely destroyed the ecosystem. Reptiles’ invasion to ocean in Early Triassic is one of the most important evolution events of reptiles and marine reptiles became the rulers in the ocean when dinosaurs ruled the land during Jurassic and Cretaceous.
However, the driving factors, the timing, the site, the environment of the origin of marine reptiles and how they adapted to life in water are still unknown and a key issue in international academia, especially ichthyosaurs, an important clade of Mesozoic marine reptiles, which was considered as a potential evidence against Darwin’s theory of evolution by Darwin himself. Two hundred years after the first report of Mesozoic ichthyosaur from UK in 1814, the discovery of Cartorhynchus from Chaohu, Anhui with the ancient and transitional characters filled the evolutional missing link from terrestrial to marine reptiles. In this case, the original place of ichthyosaurs probably is China and from here they swam to Europe and North America through ocean.
Cartorhynchus is the smallest ichthyosaur with ~40 cm body trunk so far and it lived at about 248 million years ago in Early Triassic, considered as the oldest ichthyosaur fossil record and a basal clade in phylogenetic analysis. With heavy skeleton, Cartorhynchus can feed from the bottom of the sea. Based on its short snout and absence of teeth, it is likely the only suction feeder among ichthyosaurs. Smaller body and larger flippers probably allowed limited terrestrial locomotion, indicating possible amphibious habit.
Figure 1 The basal ichthyosauriform Cartorhynchus from Chaohu
Paleontology in Peking University is one of the earliest science majors established in 1909 and makes great contribution to the establishment of Chinese paleontology and the personnel training of a large amount of paleotologists. ProfessorJiang from School of Earth and Space Sciences, Peking University and his collaborators with top expertise from University of California, Davis, (US), University of Milano (Italy), The Field Museum (US) etc. established an international research team and cooperated with relative institute, museums and geologic parks. Focusing on the recovery of ecosystem after end-Permian Mass Extinction, the team has conducted scientific field work on Triassic fossil sites in Anhui, Jiangsu, Hubei, Guizhou, Yunnan etc. in China and some other sites in Europe and U.S. and has obtained great amount of geochemical and paleontological samples from three large-scale excavations in Chaohu, Anhui Province, Panxian and Xingyi, Guizhou Province. A series of research results based on these has drawn widespread attention from all over the world.
Further work is still going on by them. As what was said by Olivier Rieppel, the Macarthur Professor from The Field Museum, “This is very exciting discovery and we are looking forward to more!”
The research team is supported by the Geology Museum of Peking University and funded by Peking University Project 985, the international cooperation key program and general program of the National Natural Science Fund and Geological Relics Protection Program of Anhui Province.
Edited by: Zhang Jiang