THE CAMBRIAN 'BASEMENT' OF GASTROPOD EVOLUTION

Abstract

The oldest gastropods are known from the uppermost Nemakit-Daldynian to lowermost Tommotian deposits. However, to trace ancestry before this time, when most metazoans did not possess shells, is difficult. Study of the oldest gastropods, diagnosed and discussed here, sheds some light on the earliest stages of evolution of major gastropod branches. It appears that the subclass Archaeobranchia served as the base for this early radiation.