Hermit Crab Phylogeny: A Reappraisal and Its “Fall-Out”

Abstract The hypothesis of monophyly in Paguroidea and the relationship of this superfamily to the other three superfamilies of Anomura have been reassessed using current cladistic methods and computer generated analysis. In the analysis, 79 external morphological characters were examined for an in-group consisting of the seven paguroid families, Pylochelidae, Coenobitidae, Diogenidae, Pylojacquesidae, Paguridae, Parapaguridae, and Lithodidae (divided into the subfamilies Lithodinae and Hapalogastrinae), three hippoid families, Blepharipodidae, Albuneidae, and Hippidae, five galatheoid families, Galatheidae, Chirostylidae, Kiwaidae, Aeglidae, and Porcellanidae, and the Lomisoidea's monotypic Lomisidae. The out-group was comprised of Neoglyphea inopinata, representing Fractosternalia, and the families Dromiidae and Dynomenidae representing Brachyura. This analysis has shown that Anomura indeed is a monophyletic infraorder, as is Hippoidea a monophyletic superfamily. However, while six of the paguroid families form a cohesive clade, the two subfamilies of Lithodidae form a distinct clade more closely related to the superfamily Hippoidea than to the other paguroids. Galatheoidea, as presently constituted, is polyphyletic. Aeglidae, like Lithodidae, is more closely related to Hippoidea than to the galatheoid clade formed by the families Galatheidae, Chirostylidae, and Porcellanidae. Kiwaidae is also distinct from Galatheoidea sensu stricto, but its relationship, and that of Lomisoidea, to the remainder of the anomuran taxa are unresolved in the present analysis. As a result of this reappraisal, we propose that Lithodidae be removed from Paguroidea sensu lato and elevated to superfamily rank with families Lithodidae and Hapalogastridae. Similarly, we propose that Galatheoidea be restricted to the families Galatheidae, Chirostylidae, and Porcellanidae, whereas Kiwaidae and Aeglidae are each to be elevated to superfamily rank. Anomura will then consist of seven superfamilies, Hippoidea, Lithodoidea, Aegloidea, Lomisoidea, Kiwaoidea, Galatheoidea sensu stricto, and Paguroidea sensu stricto.