Cretaceous–Lower Paleogene ostracods from the Pelotas Basin, Brazil

Abstract

A total of 479 samples from five drill-holes of the Pelotas Basin were analysed. Despite the huge number of samples, only 98 specimens were recovered, belonging to nine families, 21 genera and 34 species (most in open nomenclature). Due to the paucity and poor preservation of this material, just seven taxa were identified or tentatively identified at the species level: Cytherella cf. C. araucana Bertels, Cytherelloidea spirocostata Bertels, Bairdoppilata triangulata Edwards, Actinocythereis indigena Bertels, Brachycythere gr. sapucariensis Krommelbein, Wichmannella araucana Bertels and Wichmannella meridionalis Bertels. Four taxa could not even be identified at the generic level and are referred as “gen. et sp. indet.”. Trachyleberididae and Cytherellidae were the most diversified and abundant families while Cytherella and Paracypris were the most diversified genera, with seven and four species, respectively. The K–Pg boundary in the Pelotas Basin is marked by a faunal change with the local disappearance of the genera Cytherelloidea, Argilloecia, Cythereis, Brachycythere, Pondoina and Rostrocytheridea, and the first local occurrence of Neonesidea?, Bairdoppilata, Ambocythere, Buntonia, Langiella?, Trachyleberis and Krithe. The genera Cytherella, Paracypris, Wichmannella and Actinocythereis are recorded in the Cretaceous as well as the Paleogene. This faunal study suggests a neritic marine environment for the analysed interval.