Rebuilding the foundation of late Paleozoic pinnid bivalve study (family Pinnidae)

The early geologic history of family Pinnidae, a diverse and abundant component of mud-dominated shallow marine environments of the late Paleozoic, is obscured by ill-defined genus and species concepts. Mistakes in descriptions and reconstructions have provided a basis for suggestions that older taxa in the family differ from younger taxa and may not belong in family Pinnidae. This report provides improved documentation that removes the basis for the concept of divergence. Late Paleozoic genera and species have definite pinnid bivalve characters, including a dorsomarginal fold that holds the ligament, a thick outer columnar prismatic shell layer, and an equivalved, triangular shell, all of which provide evidence for confident assignment of the genus to family Pinnidae. The suggested synonymy of Aviculopinna with Pteronites is invalid, and genus Aviculopinna is limited to occurrence in Permian strata. The two genera belong in different families. A neotype is designated for genus Aviculopinna type species Aviculopinna pinnaeformis Geinitz from Gera, Germany, and a lectotype for Aviculopinna neukirchensis Langenhan from Nowy Kościół, Poland. Inferences on the life habits of Aviculopinna based on its occurrence in Poland are presented. An evaluation of the subterminal beak versus terminal beak concept in pinnids is presented and conclusion presented that there are few data available to support the concept or to test it. In its present form, the concept has no utility in the study of pinnid bivalves.