A new actinolepid arthrodire (Class Placodermi) from the Lower Devonian Sevy Dolomite, East-Central Nevada

Abstract

A new genus and species of actinolepid, Aleosteus eganensis, is descried from the Lower Devonian (Late Emsian) Sevy Dolomite in the Egan Range of east-central Nevada. A cladistic analysis of the family Actinolepidae is presented for the first time and shows the Baltic Actinolepis species form the primitive sister-group of all other actinolepids. Rapid evolution of the Actinolepidae during the Lochkovian is reflected in the dispersal of the family around the Old Red Sandstone Continent at this time followed by the development of endemic faunas through the Lower Devonian and into the Middle Devonian.