A New Material of Chaohusaurus (Diapsida: Ichthyosauriformes) from the Early Triassic Nanzhang-Yuanan Fauna

The Nanzhang-Yuanan Fauna yielded the latest marine reptiles assemblages in the Early Triassic of the world. It is a little younger than the neighboring Chaohu Fauna. The diversity of marine reptiles is much higher than other fossil sites of the Early Triassic in the world. There are twelve genera and species in that fauna hitherto, including Hupehsuchia, Ichthyosauriformes, and Sauropterygiformes. However, there just is ichthyosaur Chaohusaurus zhangjiawanensis in Nanzhang-Yuanan Fauna. In these years, we got dozens of new complete materials based on several excavation in the same quarry. One of them could represent a new species of Chaohusaurus. The specimen shares typical characters with other Chaohusaurus. But it is distinctly different from other species. The specimen is slender, about 1 miter. The trunk is tubulous, because of almost same height in trunk region. The counts of cervical region, dorsal region and sacral region are 5, 37, and 2, respectively. The rostrum is more slender than Chaohusaurus zhangjiawanensis. The tip of upper jaw exceeds the tip of lower jaw. The dentition is distinctly different from other species of Chaohusaurus. There are only 5 small conical teeth in the premaxilla. The teeth in the posterior snout are discoid. The manus is fin-like, with phalange formula 3-4-4-3-2. The pes is paddle-like, with phalange formula 3-5-5-4-1. The most striking thing is that there are abundant conodonts in the abdomen. This is the direct evidence that ichthyosaur can catch and feed on tiny animals.