Description and ecology of a new Middle Ordovician (Llanvirn) odontopleurid trilobite from the Builth Inlier of Mid-Wales, with a review of the genusMeadowtownella

Abstract

AbstractA new odontopleurid trilobite,Meadowtownella serrata, is described from a new Llanvirnian (Darriwilian;Didymograptus murchisoniBiozone) locality in the Builth Inlier, Mid-Wales. This unusually spinose species displays a remarkable array of pygidial spines and extends the stratigraphic range of the genus back into the Abereiddian. Benthic faunas are rare in the predominantly ‘anoxic’D. murchisoniBiozone of the Welsh Basin, and these beds are an unusual habitat for odontopleurids. Environmental analyses (framboidal pyrite and associated total organic carbon) in this study, together with the distribution of benthic faunas (described and figured) in the section, indicate a likely oxic water column and episodically oxic bottom waters. A new diagnosis forMeadowtownellais presented with a review of the genus, as a clarification of previous work. The greater spinosity of earlier members of the lineage may reflect either changing environmental preferences, or the derivation ofMeadowtownellafrom an original more spinose lineage.