See more from this Division: Topical Sessions
See more from this Session: Integrative Systematic Paleontology for a New Century: Advancing Evolutionary, Phylogenetic, Biogeographic, and Ecologic Theory with Specimen-Based Studies
Abstract:
In spite of this widespread morphologic convergence with the morphology of other bivalve families, a cladistic analysis of this Miocene corbulid fauna (with congeneric species of Pachydon, Anticorbula, and Ostomya from the Paleocene Tongue River Formation of the northern Great Plains of the USA incorporated) firmly place Ostomya and Anticorbula (previously asssigned to either Corbulidae or Lyonsiidae) and newly described highly divergent taxa (e.g., Concentricavalva) within the Corbulidae. Further, phylogenetic analysis reveals that the Pebas fauna represents radiation(s) within a limited number of subclades, three of which have evolutionary histories dating back at least to the Paleocene. Pachydon species form two derived sublclades within the ingroup, one of which has a less chordate shape and typical chondrophore morphology (Paleocene Pachydon mactriformis falls within this subclade). Also included in the larger Pachydon clade is Exallocorbula and a well-supported subclade of Anticorbula spp. The monophyly of Ostomya (in which species have a more or less pronounced myiform shape) is less well supported, with members falling basally within the ingroup. Clearly, although several of these lineages have evolutionary histories spanning the Cenozoic, species radiations within the Miocene Pebas Formation can be considered endemic to that basin.
See more from this Division: Topical Sessions
See more from this Session: Integrative Systematic Paleontology for a New Century: Advancing Evolutionary, Phylogenetic, Biogeographic, and Ecologic Theory with Specimen-Based Studies