Internal anatomy of the polybranchiaspids (Agnatha, Galeaspida)

Abstract

A number of polybranchiaspids (Agnatha) from the Devonian of China have parts of their soft anatomy, including the central nervous and vascular systems, extremely well preserved as mineral replicas. This has made possible direct comparisons with the internal anatomy of the living agnathans, the hagfish and lampreys, as well as the fossil heterostracans and cephalaspids. The polybranchiaspids do not seem to be related to either the hagfish or the heterostracans, but instead represent a separate grouping, the Galeaspida, allied to the lampreys and cephalaspids.