The Aptian-Cenomanian ostracod "Conchoecia?"/Neorichterina: Taxonomic review and its paleoecological, paleobiogeographic, and biostratigraphic significance

Abstract

Though primarily a recent genus, Conchoecia Dana 1853 has had a number of Cretaceous forms dubiously attributed to it since the description of Conchoecia cretacea Pokorný, 1964. Recently, most of these species were reassigned to the genus Neorichterina Tóth and Cséfán, 2018, considered a Cretaceous representative of Family Entomozoidae. However, there are still taxonomic uncertainties regarding this assignment, and much is still unknown about the paleoecology, paleobiogeography, and biostratigraphic significance of these taxa. This paper provides a revision of the taxon based on available literature on Neorichterina and the Cretaceous forms attributed to “Conchoecia”. Considering several problems with the taxonomic description of Neorichterina, we propose the removal of the genus from Family Entomozoidae, and identify two potential new species, which are left in open nomenclature. The earliest occurrence of the genus is the late Hauterivian–early Barremian of the Haha Basin, Morocco. After that, Neorichterina spread to the South Atlantic and Tethys oceans during the late Aptian–late Albian, and became extinct in the lower Cenomanian. Neorichterina was likely a planktonic genus with a preference for warm neritic environments, and was able to tolerate fluctuating oxygenation levels. It frequently occurred in association with blooms of Favusellid foraminifera, and was particularly abundant in the South Atlantic Ocean. Although Neorichterina has a broad stratigraphic range, it occurred only for a small time interval during the late Aptian of the Santos Basin, Brazil, suggesting that it could be a useful regional biostratigraphic marker in the southeastern Brazilian margin.