The Boothiaspidinae, a new agnathan subfamily (Heterostraci, Cyathaspididae) from the late Silurian and Early Devonian of the western United States and the Canadian Arctic

Abstract

AbstractThree new species of the new genusPhyllonaspisare described from Early Devonian localities in the western United States.Phyllonaspis laevis,P.serratus, andP.taphensisare broad, flattened cyathaspids with lateral brims and fine dermal ornament, that show a close relationship to the cyathaspidsBoothiaspisandAlainaspisfrom the late Silurian and Early Devonian of the Canadian Arctic. These taxa are here accommodated within the new subfamily Boothiaspidinae within the family Cyathaspididae. This relationship supports previous evidence of faunal connection between these two areas and indicates dispersal around the Old Red Sandstone Continent from a center in the Canadian Arctic. Isolated oral plates allow a reconstruction of the oral cover and increase our knowledge of the range of oral structures in this family.