The Chengjiang fossil locality of China has become famous for the exceptional quality of preservation of its Lower Cambrian soft-bodied animals. Among these is a cephalochordate that appears similar to Pikaia from the Middle Cambrian Burgess Shale of Canada. The new fossil is named Cathaymyrus . Another Chengjiang fossil, Yunnanozoon , was originally described as a chordate, but has been re-evaluated as a probable hemichordate. Correlated progression and the origin of turtles.
Turtles have one of the most distinctive body plans among all vertebrates.
They appear abruptly in the fossil record, without any clear morphological intermediates. Lee advocates the pareiasaurs, a group of fossils found in Permian rocks of the Old World. Some pareiasaurs have a dorsal ridge of osteoderms, which provide anchorage for muscle attachment. Other pareiasaurs, such as Scutosaurus , have a dorsal covering of largely separated osteoderms. In the genus Anthodon , the osteoderms are united to form a rigid dorsal covering.