A new genus of the 'Pitar' group (Bivalvia: Veneridae) from the Western Atlantic Ocean revealed by geometric morphometric analysis.

Understanding shell morphology is central to taxonomic and evolutionary studies of bivalves. When traditional systematic studies find limitations in the recognition and classification of taxa, geometric morphometrics methods become a tool to tackle these uncertainties. Taxonomic difficulties are frequently found in systematics studies of the generally homoplastic Pitarinae (Venereidae). Recent contributions have proposed that Neogene-Recent South American species traditionally assigned to Pitar sensu stricto showed a distinguishable morphology that allowed separating them from that genus, including them in Proteopitar. In this contribution, we perform two morphometric analyses: elliptic Fourier analysis (EFA) and 2D landmark analysis with the aim of evaluating the intra- and interspecific variation of these taxa from the Western Atlantic Ocean included in Pitar s.s. to evaluate its doubtful generic assignments. EFA results show a highly variable outline in Proteopitar patagonicus, superimposed in the morphospace of all other taxa. The three analyzed groups, Pitar, Proteopitar, and extant Western Atlantic Ocean species, are statistically differentiable in hinge morphologies (landmark analysis), as corroborated by the Discriminant Function Analysis. The latter taxa are also distributed in a restricted portion of morphospace in EFA and along with the recognition of additional morphological differences allow us to define the new genus Jasypitar.