The affinities of the ostracod genus Cypridea Bosquet, 1852, and its allies, with consideration of implications for the phylogeny of nonmarine cypridoidean ostracods

The nonmarine ostracod genus Cypridea s.l., characterized by an antero-ventral “beak” (rostrum and alveolus) in both valves, achieved high diversity and global distribution in the Early Cretaceous but declined in the Late Cretaceous and became extinct during the Paleogene. Although it clearly belongs to the Superfamily Cypridoidea (Order Podocopida, Suborder Cypridocopina), the precise affinities of Cypridea s.l. have been controversial, different authors variously suggesting it to be most closely related to the cypridoidean families Ilyocyprididae, Cyprididae or Notodromadidae. Since Cypridea s.l. was responsible for much of the explosive radiation of nonmarine cypridoidean taxa during the Mesozoic, a clear understanding of its affinities is crucial to the elucidation of nonmarine ostracod phylogeny. We evaluate some of the key morphological features of cypridoidean carapaces as indicators of phylogenetic affinity, paying special attention to adductor muscle scar patterns and the structure of the anterior marginal zone. The morphology of Cypridea s.l. is compared with certain cypridoideans that bear similar beak-like or lip-like antero-ventral marginal structures, notably genera of the Family Cyprididae such as Bennelongia, Chlamydotheca, Cypris and Talicypridea, and consider whether these similarities represent close phylogenetic relationships or homeomorphy.