Late Ordovician (Ashgill) Foliomena fauna brachiopods from northeastern Maine

Abstract

Foliomena folium (Barrande) and other very small, thin-shelled brachiopods from the Pyle Mountain Argillite in Aroostook County, Maine, provide the only record of the presence of the Foliomena fauna in North America. Associated fossils include numerous small trilobites and a few specimens of other groups. An Ashgill age is established by the presence of graptolites of the Climacograptus spiniferous Zone in the underlying Winterville Formation.Most of the 190 specimens are small strophomenaceans and plectambonitaceans. One of the most numerous is the christianiid Nubialba forbesi n. gen. and sp. that has ribs and elaborately developed internal features. In the absence of evidence to contradict previous interpretations that the Foliomena fauna records cold-water environments, the presence of one or more deep basins along the southeastern margin of the trans-equatorial North American paleoplate occupied by cool peri-Gondwanan waters during a short segment of Ashgill time is implied.