International Cooperation

Mystery of Enigmatic Saurosphargids Revealed

Since a fragment of Saurosphargis was unearthed one hundred years ago, no fossil of such an animal has been found until 2011. In that year, Sinosaurosphargis, a new saurosphargid, was described on the basis of adequately preserved specimens collected from the Triassic marine strata of Yunnan-Guizhou area, southwestern China. Sinosaurosphargis is most characteristic in that its upper temporal opening is nearly closed while its lower temporal opening is widely open, which is unusual and rare among the Triassic aquatic reptiles except for certain species of the placodonts of Sauropterygia. In addition, the trunk of Sinosaurosphargis is covered dorsally by a carapace formed by small bony plates, as it is in certain placodonts, which is also more or less similar to that of the living Dermochelys. Saurosphargids are not turtles and their relationships with other reptiles have been still uncertain. Recently, an article on a new saurosphargid has been published in Geological Magazine of England (web-version), which is one of achievements derived from an international collaboration of the Chinese scientists with their colleagues from abroad. The new saurosphargid has an elongate body, like a common reptile, but its back is not covered by a carapace. It was named Largocephalosaurus and referred to Sauropterygia in a primary study. New specimens discovered by the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP), CAS and the School of Earth and Space Sciences, Peking University not only illustrated the entire morphology of Largocephalosaurus but also provided further information for establishing the phylogenetic relationships of Saurosphargidae. As the sister-group of Sauropterygia, Saurosphargidae, like the former, can be divided into two subgroups: one with a complete carapace to cover the back, represented by Sinosaurosphargis and the other lacking such a carapace, represented by Largocephalosaurus. They co-lived in the paleo-sea of Yunnan-Guizhou area about two hundred and forty million years ago. It is learned from Prof. Li Chun of IVPP, this scientific achievement totally relied on a sincere collaboration and selfless devotion of the scientists and their institutions. With great effort and time and the support of institutions involved, the mystery of the enigmatic saurosphargids has been finally uncovered.