Phylogeny and Biogeography of Spinicaudata (Crustacea: Branchiopoda).

Spinicaudata (spiny clam shrimp) is a taxon of Branchiopoda occurring since the Devonian and today it occurs nearly globally in temporary water bodies. We present the most species-rich phylogenetic analyses of this taxon based on four molecular loci: , , and . Our results support previous findings that Cyzicidae is paraphyletic. To render Cyzicidae monophyletic we establish a fourth extant spinicaudatan family to accommodate . Within Cyzicidae, none of the genera , or are monophyletic, and the morphological characters used to define these genera (condyle length and rostrum shape) are not associated with well-delimited clades within Cyzicidae. There is insufficient resolution to elucidate the relationships within Leptestheriidae. However, there is sufficient evidence to show that the leptestheriid genera and are non-monophyletic, and there is no support for the genus . Molecular clock analyses suggest that the wide geographic distribution of many spinicaudatan taxa across multiple continents is largely based on vicariance associated with the break-up of Pangea and Gondwana. Trans-oceanic dispersal has occurred in some taxa (, and within Leptestheriidae) but has been relatively rare. Our results highlight the need to revise the taxonomy of Cyzicidae and Leptestheriidae and provide evidence that the global spinicaudatan diversity may be underestimated due to the presence of numerous cryptic species. We establish Eocyzicidae fam. nov. to accommodate the genus . Consequently, Cyzicidae comprises only two genera - and . occurs also in Africa and Asia and new comb. is assigned to this genus.