Revision of the ostracode genus Fossocytheridea Swain and Brown 1964: Mesozoic ancestral root for the modern eurytopic Cyprideis Jones.

The ostracode genus Fossocytheridea Swain and Brown 1964 is emended herein. A summary of the diagnostic characters include: (1) a median sulcus, (2) a tripartite antimerodont hinge with distinct heart-shaped terminal elements, (3) distinct sexual dimorphism; (4) a narrow inner margin that has 20-28 straight radial pore canals, and (5) variability in the external carapace (pore shape, pore density, and patterns of reticulation) that bears close resemblance to Cyprideis. Two new species are described from southwest Utah (U.S.A): Fossocytheridea mosbyense sp. nov. and Fossocytheridea kirklandi sp. nov. and 21 taxa previously assigned to Fabanella, Sarlatina, Ovocytheridea, Dolocytheridea, Antibythocypris, and Cytheridea are assigned to the emended genus. Fossocytheridea resembles Cyprideis with respect to both shell morphology and ecology since it occurs in association with euryhaline biota in coal-bearing strata. Expansion of marginal marine environments during the highest sea level of the Mesozoic saw Fossocytheridea successfully migrate and dominate restricted coastal environments. Since this expansion, the prominent characters of Fossocytheridea have been preserved in descendent genera belonging to the tribe Cyprideidini Kollmann 1960 that are preserved to this day in Cyprideis. [ABSTRACT FROM AUTHOR]