; class Reptilia)
A subclass of reptiles that have a single, upper temporal opening behind the eye. The subclass includes the Plesiosauroidea, Nothosauria, and Placodontidae. The Ichthyosauria had a similarly placed opening but there were key differences in the arrangement of the bones forming its margins. For this and other reasons the ichthyosaurs are placed in the subclass Ichthyopterygia. Euryapsids were typically aquatic especially from the mid-Triassic onwards. They first appeared in the Permian and became extinct at the end of the Mesozoic.
Subjects: Earth Sciences and Geography — Zoology and Animal Sciences.