Western Gondwana non-marine ostracods from Early Cretaceous low-latitude ephemeral lake, Northeastern Brazil

In the beginning of Gondwana's break up, small rift lakes were formed in the area that is nowadays located in Northeastern Brazil. These lakes captured the drainage systems and were subjected to hot and arid climatic conditions in a low-latitude area. These conditions are evidenced by the Lower Cretaceous fluvio-lacustrine deposits that filled the Sousa Basin, which integrates a complex of basins along the Rio do Peixe (State of Paraiba). The Sousa Formation is the most representative unit in the Sousa Basin, being predominantly composed of siltstones and shales deposited in shallow lacustrine environments with fluvial influence. The sedimentation occurred under a semi-arid climate with alternating rainy and dry seasons, indicating the presence of ephemeral lakes. This is also supported by the lithology, the sedimentary structures (mud cracks) and the evaporites (gypsum). The lacustrine environment is favorable to the proliferation of non-marine ostracods, which are microcrustaceans of great importance for the study of current and paleolake deposits. Non-marine ostracod assemblages recovered from the Sousa Formation, sampled from core 2-FC-1-PB, revealed undescribed species. In this work, these ostracods were studied taxonomically, with the new species Cypridea paraibensis sp. nov., Cypridea vianai sp. nov. and Alicenula sousaensis sp. nov., as well as the already described Alicenula leguminella (Forbes, 1855) Martens, Rossetti and Horne 2003, Brasacypris ovum Krommelbein 1965, Cypridea ambigua Krommelbein 1962, and Reconcavona swami Krommelbein 1962 being identified. Another set of taxa remained in open nomenclature, since the morphological descriptions did not fit existing species. Thus, the descriptions referring to the described groups take into consideration criteria such as similarity and variability of morphological factors (Alicenula ex gr. legurninella and Alicenula sp. 1), degree of preservation, and quantity of recovered carapaces.