Validity of Pitar Römer, 1857 species (Bivalvia: Veneridae) from the Cenozoic of Patagonia: a geometric morphometric approach

MAXIMILIANO ALVAREZ; PEREZ, DAMIÁN EDUARDO

Mar del Plata

Jornada; Reunión de Comunicaciones de la Asociación Paleontológica Argentina; 2015

Asociación Paleontológica Argentina

During the last 100 years some Patagonian Cenozoic species of the genus Pitar were described and discussed by several authors. Pitar lahillei var. ortmanni (Early Pleistocene; Santa Cruz) was synonymized to P. patagonicus (d?Orbigny) (Pliocene to Recent; Southwest Atlantic Ocean, Brazil to Chile), and del Río and Martinez Chiappara erected the fossil subspecies Pitar patagonicus mutabile (Miocene; Puerto Madryn Formation). To test the validity of these systematic proposals, two geometric morphometric analyses were performed. The first one using 13 landmarks of the hinge plate and the second one with an Elliptic Fourier Analysis (EFA) of the outline. The sample consist of 98 left valves, nine of P. patagonicus mutabile, three of P. patagonicus var. ortmanni, four of Pitar tumens (Gmelin) (Recent, Senegal, type species of Pitar; included as a clear distinct species) and 82 of Pitar patagonicus. With the results of both analyses two between-groups Principal Component Analysis were performed. The results of the landmark approach showed that P. patagonicus mutabile has a different hinge plate configuration, while P. ortmanni has a hinge plate similar to P. patagonicus. In the case of the EFA, the outline of P. patagonicus has a high variability, with subtriangular to suboval shapes, and the others species were placed in the same morphospace. P. patagonicus mutabile has a subtriangular outline and P. ortmanni has a suboval shape with the posterior-ventral margin projected. As a conclusion, we proposed that P. ortmanni is not a valid taxon, but P. patagonicus mutabile is separable from P. patagonicus.