- GeoRef, Copyright 2004, American Geological Institute.
Geological mapping in the Ellsworth Mountains of west Antarctica have established the existence of extensive Middle and Late Cambrian strata. Forms tentatively referred to Archaeocyatha have been examined by F.D. and A.R., who concluded that, despite the commonly held opinion that the phylum became extinct at the boundary of the Lower and Middle Cambrian, the Ellsworth Mountains forms represented Irregularian Archaeocyatha which survived in protected niches into the Late Cambrian. The age of the fauna containing the archaeocyaths is firmly dated by abundant trilobites including species of Homagnostus, Pseudagnostus, Kormagnostella, Erixanium and Onchopeltis.--Modified journal abstract.