Meeting Abstract

P3.101  Sunday, Jan. 6  Bringing Order to Taxonomic Chaos: Using Geometric Morphometrics and Elliptical Fourier Analysis to Distinguish Morphologically Equivocal Lirophora Species TATARIAN, A.F.F.*; ROOPNARINE, P.D.; Wesleyan University; California Academy of Sciences atatarian@wesleyan.edu

Lirophora (Family: Veneridae) is a diverse bivalve genus which originated in the western Atlantic 35 mya. Since its first appearance in the southeast United States, the genus has spread throughout the tropical western Atlantic and eastern Pacific. It is well represented in the fossil record and by at least 4 Recent species, but species are generally difficult to distinguish using qualitative morphological characters. Lirophora latilirata, as originally described, is a Miocene species from the Calvert Formation of Maryland; however, a widespread Recent species bears the same name. Because the western Atlantic experienced significant oceanographic changes and high extinction after the Miocene, it is unlikely that the Recent and Miocene species are the same. Our goal is to determine how many species are represented in the sub-tropical western Atlantic from the Miocene to the Recent. To do this, we applied geometric morphometrics and elliptical Fourier analysis to specimens from the Miocene, Pliocene, Pleistocene, and Recent. Our results indicate that the Recent group is a distinct species. Our results also support the separation of two Miocene species, L. alveata and L. vredenburgi, from each other and from the Plio-Pleistocene species L. athleta. We found that all Pliocene and Plio-Pleistocene specimens belong to L. athleta, though whether some groups deserve further separation requires additional study. These results indicate a need for taxonomic revision of the genus Lirophora, and continued scrutiny of Neogene tropical American taxa in general. Such corrections will increase the accuracy of origination and extinction rate estimates.