Preliminary phylogeny of the Venericardiinae Chavan, 1969 (Bivalvia: Carditidae)

DAMIÁN PÉREZ; MAXIMILIANO ALVAREZ

Mendoza

Congreso; 4º International Palaeontological Congress; 2014

International Palaeontological Association

Carditidae Férussac is a big family of bivalves with an explosive diversification during the early Cenozoic. At the present time, this family has more than 140 species and six subfamilies. The boundaries among some subfamilies are not clear, and the limits among different genera and subgenera are argued and used with dissimilar criteria by previous authors. For example, in some revisions, the genus Venericardia Lamarck includes the subgenera Claibornicardia Stenzel and Krause, Venericor Stewart or Megacardita Sacco, while in other ones, these subgenera have genus status. Venericardia is the genus-type of the subfamily Venericardiinae. This subfamily includes from three to more than ten genera according to different authors, and many others subgenera were considered subgenera of Venericardia. Two lineages were recognized in the subfamily Venericardiinae: the large ?planicostae? (Venericor-like), with elevated hinge plates with highly developed, subtrigonal-shaped shells and smooth flattened radial ribs; and the ?alticostae? (Venericardia-like), with lower hinge plates, subelliptical-shaped shells and noded and tripartite radial ribs. The monophyly of each of these lineages is debated. In this contribution, to test the relationships among these carditids, a phylogenetic analysis of the Venericardiinae was carried out. The cladistic analysis based on 103 shell-characters scored for 40 fossil and recent species (including the type species for 25 genera) was performed with TNT 1.1. The ingroup comprises the planicostate Venericor (3 spp.), Leuroactis Stewart and Pacificor Verastegui, the alticostate Venericardia (4 species), Arcturellina Chavan, Purpurocardia Maxwell, Fasciculicardia Maxwell (2 spp.), Baluchicardia Rutsch and Schenck, Rotundicardia Heaslip (2 spp.), Claibornicardia (2 spp.), and Glyptoactis Stewart. Additionally, we considered 16 other species of 11 genera. Our results show that the ?planicostae? and the ?alticostae? are clearly separated. Megacardita and Bathycardita Iredale are sister-groups of the planicostate clade. Cardiocardita Anton and Paraglans Chavan are included into the alticostate clade. Cyclocardia Conrad, Pleuromeris Conrad, Pteromeris Conrad, Vimentum Iredale and Scalaricardita Sacco resulted into a completely-resolved clade, closely related to alticostates venericardids. Cardites Link is closer to the Cyclocardia-group and alticostates than to other taxa. Glans Megerle and Centrocardita Sacco form a group outside de venericardids. This preliminary exploration of the phylogenetic relationships of this group is a key step to a better understanding of the relationships of the subfamily, which we intend to improve by including more species, fossil and recent.