安徽巢湖早三叠世短腿巢湖龙的牙齿替换研究OA北大核心CSTPCD

A specimen of Chaohusaurus brevifemoralis (GMPKU-P-3086) from the Lower Triassic in Chaohu City, Anhui Province is examined by using high-resolution CT scan data to create a 3D reconstruction. The reconstructed models include models of teeth, premaxilla, maxilla, and dentary. Through observation and measurement of the model, and comparison with the specimen, the following new features of this basal ichthyosauriformes were found. 1) the implantation is subthecodont based on the presence of a dental groove with shallow sockets at the bottom. 2) the sizes and shapes of the teeth vary periodically and appear as an odd-even alternate pattern. 3) the anterior teeth form a single row, with the replacement tooth setting on the distal position of the functional tooth. 4) Two rows of teeth at the distal parts of the dentary and maxilla are firstly found in Chaohusaurus. The lingual row comprises replacement teeth for the labial row, and each replacement tooth lies disto-lingual of its predecessor. These dental features found in Chaohusaurus brevifemoralis are consistent to that of the Early Triassic ichthyosauriformes, such as Grippia and Utatsusaurus, which might represent a primitive condition of the dental character of ichthyosauri-formes and reflect a broad geographical distribution of crunch feeding guild.