Phylogeny of the Brachyura with particular reference to the Podotremata: evidence from a review of spermatozoal ultrastructure (Crustacea, Decapoda)

Parsimony analysis, whether using only spermatozoal characters or spermatozoal and non-spermatozoal characters, suggests that: (i) the Brachyura is a monophyletic taxon relative to the outgroup, three paguroids; (ii) the Podotremata is a monophyletic taxon and the sister-group of the heterotreme-thoracotreme assemblage; (iii) within the Podotremata, the Dromiidae appears paraphyletic as its clade includes Paradynomene; (iv) the Homolidae is a monophyletic family; (v) the Raninoidea and Cyclodorippoidea are sister groups within a monophyletic (unnamed) clade; (vi) Latreillia sp. forms a polytomy with Homolidae + Raninoidea-Cyclodorippoidea; and (vii) within the heterotreme-thoracotreme assemblage, the Thoracotremata is a monophyletic taxon but the Heterotremata s. strict, is a paraphyletic grouping. Analyses based on sperm data alone differ from the combined data in not including the Homolidae in the Archaeobrachyura (Homolidae + Raninoidea-Cyclodorippoidea), thus the Dromiidae-Paradynomene + Homolidae + Latreillia form a polytomous clade which is the sister-group of the Raninoidea + Cyclodorippoidea. Spermatozoal data also give majids the most basal position in the Heterotremata whereas for the combined data Neodorippe (a shell carrier) appears the least modified member of the heterotreme-thoracotreme assemblage. These findings are viewed in the perspective of other, notably molecular, studies. Spermatozoal synapomorphies are listed and illustrated.