Range, proportionate representation, and demise of brachiopod families through Permian Period

Publisher Website
Google Scholar
Abstract
Summary: The time range and proportional distributions of Permian brachiopod families are summarized for the Permian Period. The ‘imperfection’ of the record is calculated from the apparent absences of families known to have survived. It is shown that the phylum changed in composition during the late Middle and Late Permian, with increased importance of Orthida, Strophalosiacea, and Oldhaminida at the expense of the Productacea. Changes were over-printed by loss of families, markedly later than the extensive contraction of shelf-seas, concurrent probably with significant changes in geo chemistry and trophic resources. A number of highly significant families survived into the time of renewed transgression during the Otoceras and Ophiceras ammonoid zones, usually classed at the base of the Triassic Period. The demise of most Permian families proceeded in concert with climatic changes, but the initial deaths of families appear to have been caused by some other unknown factor, which may have severely disrupted Permian communities and biomes, and caused them to respond more than usual to climatic oscillations.