A new species of Neovenericor (Bivalvia: Carditidae) from Patagonia (Gaiman Formation, Argentina) and an evaluation of the presence of Neovenericor in the Early Miocene

Abstract

Among Patagonian Carditidae bivalves, the ‘planicostates’ or Venericorini are a group extensively studiedfrom several points of view. All species of this group were included in the genus Neovenericor. Newspecimens from the Gaiman Formation (Early Miocene) allow us to describe a new Neovenericor speciesand to analyse the presence of the group in the Early Miocene of Patagonia within a systematic,phylogenetic, morphometric, and stratigraphic framework. A phylogenetic analysis using 65 terminalsand 154 characters, adding to a detailed systematic description, allows us to describe the new speciesNeovenericor camachoi, based on the presence of large shells with 19–20 radial ribs and small nodulesaround the lunule, which is covered by the umbo. This species is distinguishable from other Neovenericor,such as N. austroplata and N. paranensis. The morphometric analysis shows a clear separation betweenN. camachoi and other species and confirms the assignment of the Gran Bajo del Gualicho specimens toN. austroplata. The temporal co-occurrence of two species of Neovenericor during the Early Miocene ofPatagonia is determined from stratigraphic data, and a complex evolutionary scenario for the Venericorinilineage is proposed.