New species of Fossocytheridea Swain & Brown, 1964 (Ostracoda, Crustacea) in the Upper Cretaceous of Santos Basin, Brazil

Abstract

-Eleven wells (1,765 cutting samples) from the Senonian of Santos Basin were examined, with the record of both marine and mixohaline ostracode faunas. The latter are composed mainly by Fossocytheridea and characterized by medium specific richness and high abundance. Four new species are here described: F. posterodentata, F. ventrotuberculata, F. santosensis and F. anfisulcata and another one is left in open nomenclature. Besides the conspicuous variability, F. ventrotuberculata sp. nov. is the first species described for the genus with valve reversal. The significance of these new species described and their potential for applied approaches are discussed.Key words: Fossocytheridea, Ostracoda, taxonomy, Brazil, Santos Basin.RESUMO -Onze poços (1.765 amostras de calha) do Senoniano da bacia de Santos foram estudados, registrando faunas de ostracodes marinhas e mixoalinas. Estas são compostas basicamente por Fossocytheridea e caracterizadas pela riqueza específica baixa e alta abundância. Quatro novas espécies são aqui descritas: F. posterodentata, F. ventrotuberculata, F. santosensis e F. anfisulcata, e outra é deixada em nomenclatura aberta. Além da notável variabilidade, F. ventrotuberculata sp. nov. é a primeira espécie descrita para o gênero com reversão de valvas. A importância destas novas espécies descritas e seu potencial para estudos aplicados são discutidos. Palavras INTRODUCTIONThe first researches on Cretaceous ostracodes from Santos Basin were done by Benson (1977) and Miller et al. (2002). More detailed taxonomic work began with the description and ecological characterization of the species Afrocytheridea? cretacea and Pelecocythere dinglei by Piovesan et al. (2010).One of the most remarkable consequences of the scarcity of taxonomic knowledge is the limitation it imposes on paleoceanographical and biostratigraphical uses. Ostracodes are the most abundant calcareous microfossil in the Upper Cretaceous paralic deposits of Santos Basin. Considering that this basin was strongly affected by sea-level changes, ostracode populations were influenced accordingly, under conditions favorable for speciation. These faunas are dominated by cytherideids, Fossocytheridea Swain & Brown being the most common genus.The first record of Fossocytheridea in Brazil was by Viviers et al. (2000) in the Campanian of Potiguar Basin, as Sarlatina Babinot & Colin, which is now considered its junior synonym (Tibert et al., 2003). In the latter article, some species of Fabanella Martin, Ovocytheridea Grekoff, Dolocytheridea Triebel, Antibythocypris Jennings and Cytheridea Bosquet, were also reassigned to Fossocytheridea. In other Cretaceous deposits (e.g. Western Interior Basin, USA: Swain & Brown, 1964, Tibert et al., 2003, 2009 West Africa, Mali: Colin et al., 1996) assemblages with Fossocytheridea are interpreted as indicators for marginal-marine environments. The ecological classification of brackish-water environments into oligohaline, mesoahaline and polyhaline used herein follows Belt et al. (2005).The main obje...

Fossocytheridea Swain & Brown and Perissocytheridea Stephenson (Ostracoda): insights into paleosalinity gradients of Late Cretaceous deposits from Brazil and Portugal

“…A similar pattern has been observed in Perissocytheridea cretacea (Piovesan et al, 2010) in the Santonian-Campanian of the Santos Basin, Brazil. P. cretacea occurs associated with Fossocytheridea spp., when it is most abundant, but it is also found associated with typically marine species (Piovesan et al, 2010;Bergue et al, 2011). These data demonstrate the euryhaline character of the Perissocytheridea species which occurs in the Brazilian Santonian-Campanian.…”

“…REVISTA BRASILEIRA DE PALEONTOLOGIA, 18(1), 2015 Fossocytheridea is a genus widely distributed in marginal marine facies from the Aptian to the Maastrichtian of America, Europe, China, Africa and Middle East (Swain & Brown, 1964;Babinot & Colin, 1976;Tibert et al, 2003;Bergue et al, 2011). Previous works have already highlighted its application in the characterization of marginal marine environments (e.g.…”

New genera and species of Ostracoda from the Maastrichtian and Danian of the Neuquén Basin, Argentina

“…nov. resembles none of the Fossocytheridea species described by Bergue et al . () species from the Senonian of the Santos Basin in SE Brazil.…”

The late Albian-early Cenomanian ostracodes from Naur Formation, Jordan

“…The occurrence of intraspecific variability is not uncommon in Cretaceous cytherideids (e.g. Fossocytheridea ventrotuberculata Bergue et al, 2011) and is, probably, environmentally induced.…”