Phylogenetic relationships of the family Carditidae (Bivalvia: Archiheterodonta)

Abstract

Carditidae is a highly speciose group of bivalves but is one of the more neglected and poorly studied families. This work presents the first phylogenetic study of the entire family, using 77 species-level taxa (including fossil and recent terminals) and 144 new morphological characters. Multiple searches were conducted, including comparisons of discrete and continuous characters and equal and implied weighting. Morphological disparity analysis, phylomorphospace construction and phylogenetic signal analysis were performed using the character matrix. A new systematic scheme is suggested on the basis of these results, including the already proposed subfamily Palaeocarditinae, the re-defined Carditinae, Thecaliinae (included within Carditinae in some searches), Carditamerinae (with reduced diversity) and Venericardiinae (with extended diversity). The new subfamily Scalaricarditinae and the new clades Eucarditidae (all carditids excluding Palaeocarditinae), Carditida (Carditinae + Thecaliinae + Carditamerinae) and Cyclocardida (Cyclocardia + Pleuromeris + Scalaricarditinae + Miodomeridinae) are proposed. The monophyly of the planicostate and alticostate lineages are confirmed within the Venericardiinae (now formally named Venericorini and Venericardiini, respectively). The relationships of Palaeocarditinae with other carditids and the origin of the family are discussed, as well as the phylogenetic placement of other carditid genera not included in the analyses. Homoplasy and the phylogenetic signals of different morphological characters are also explored and discussed.