Neogene (Plio-Pleistocene) Fresh-Water Ostracodes from the Central High Plains

Abstract

Pleistocene deposits in southwestern and central Kansas, western Oklahoma, and northern Texas have yielded eleven species of fresh-water ostracodes. Pliocene and Recent deposits have each yielded one species. Genera represented are Cypricercus, Eucypris, Cypridopsis, Potamocypris, Candona, Ilyocypris, Cyprideis, and Limnocythere. Four species are new: Eucypris meadensis, Candona nyensis, C. renoensis, and Limnocythere staplini. Nine species described previously from living forms were found as fossils: Cypricercus tuberculatus (Sharpe), Cypridopsis vidua (O. F. Müller), Potamocypris smaragdina (Vávra), Candona caudata Kaufmann, C. crogmaniana Turner, C. fluviatilis Hoff, Ilyocypris bradyi Sars, I. gibba (Ramdohr), and Cyprideis littoralis Brady.

All genera represented and two of the new species (Eucypris meadensis and Candona nyensis) are living today. The existing classification of living ostracodes, based on appendages, is used for the Pleistocene forms, although the fossil ostracodes were necessarily described on the basis of their carapace features.

Candona nyensis n. sp. seems to be restricted to deposits of Pleistocene age, and can be used locally in southwestern Kansas to distinguish Pleistocene from Pliocene sediments.

Cyprideis littoralis Brady, which normally lives in brackish water, seems to have become adapted to the fresh-water environment of Pleistocene sinkholes.