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

A new genus and species of actinolepid arthrodire, Aleosteus eganensis, is described from the Lower Devonian (Late Emsian) Sevy Dolomite in the Egan R ange of east-central Nevada. A cladistic analysis of the family Actinolepid ae 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 o f the family around the Old Red Sandstone Continent at this time followed b y the development of endemic faunas through the Lower Devonian and into the Middle Devonian. (C) 2000 The Linnean Society of London.