New Cenozoic Deep-Sea Genus, <i>Abyssocythere</i> (Crustacea: Ostracoda: Trachyleberididae), with Descriptions of Five New Species

Abstract

The new genus <i>Abyssocythere</i> Benson has been erected to receive five new species and one described species of psychrospheric ostracode ranging in age from the Paleocene to the Recent. These species include <i>Abyssocythere casca</i> Benson, new species (Indian Ocean), herein designated the type species, <i>A. pannucea</i> Benson, new species (eastern Pacific), <i>A. japonica</i> Benson, new species (western Pacific), <i>A. atlantica</i> Benson, new species (Atlantic), <i>A. australis</i> (Southern Ocean), and <i>A. trinidadensis</i> (van den Bold) from the Caribbean region. Modern species are typical of the deep-sea floor and are common to depths below 2,000 meters. Fossils have been found in deep-water Paleocene and Miocene strata in Trinidad and in deep-sea cores in Pleistocene sediments. These species are thought to have descended from a yet unknown form of the complex of species assigned to the Cretaceous genus <i>Cythereis</i> (sensu lato). There seems to be an evolution of finer surface features of the carapace and an increase in size throughout the Cenozoic.