The Families Veneridae, Trochidae, Akeridae and Acteonidae (Mollusca), in the Romualdo Formation: Paleoecological and Paleobiogeographic Aspects in the Lower Cretaceous of the Araripe Basin, NE of Brazil

Abstract

Fossil mollusks in the Araripe Sedimentary Basin have been reported since the 1960s, with bivalves present in the Crato and Romualdo formations and gastropods restricted to the latter. The identification and description of those mollusks have assisted in the paleoenvironmental reconstruction of the Romualdo Formation (Aptian-Albian) and in the interpretation of the marine incursion route that indicates the influence of the Tethy Sea on the basin. This paper describes and illustrates fossils collected in the locations of Zé Gomes, Cedro-Tabuleiro and Santo Antônio, municipality of Exu, Pernambuco, highlighting the paleoecology and geographic distribution of the genera, as well as observing the faunal affinities between the Romualdo and Riachuelo formations. This analysis resulted in the identification of bivalves of the Veneridae family - Eocallista sp. and Eocallista sp. 2., and gastropods of the Trochidae - Calliostoma sp., Akeridae - Akera sp. and Acteonidae – Acteon sp. families. The paleogeographic distribution of the genera demonstrated congruence with the Tethyan corridor, the specimens being within the limits of the Tethys Sea, confirming the presence of this sea in the Araripe Basin. The paleoecological association of the fauna has demonstrated affinity with a restricted marine lagoon environment already identified for the Romualdo formation. The presence of these genera of mollusks extends the faunal affinity between the Araripe (Romualdo Formation) and Sergipe (Riachuelo Formation) basins, demonstrating that probably due to the eustatic characteristics present in the Albian, there was a connection between those basins, allowing for the interchange not only of Thetyan elements, but also of species related to the South Atlantic already dominant in the Sergipe Basin