Evolutionary relationships among American mud crabs (Crustacea: Decapoda: Brachyura: Xanthoidea) inferred from nuclear and mitochondrial markers,with comments on adult morphology

Members of the brachyuran crab superfamily Xanthoidea sensu Ng, Guinot & Davie (2008) are a morphologically and ecologically diverse assemblage encompassing more than 780 nominal species. On the basis of morphology, Xanthoidea is presently regarded to represent three families: Xanthidae, Pseudorhombilidae, and Panopeidae. However, few studies have examined this superfamily using modern phylogenetic methods, despite the ecological and economic importance of this large, poorly understood group. In this study we examine phylogenetic relationships within the superfamily Xanthoidea using three mitochondrial markers, 12S rRNA, 16S rRNA, and cytochrome oxidase I (COI), and three nuclear markers, 18S rRNA, enolase (ENO) and histone H3 (H3). Bayesian and maximum‐likelihood analyses indicate that the superfamily Xanthoidea is monophyletic; however, the families Xanthidae, Panopeidae, and Pseudorhombilidae, as defined by Ng et al., are not, and their representative memberships must be redefined. To this end, some relevant morphological characters are discussed. © 2013 The Linnean Society of London