Paleoecological aspects of the Southwestern portion of the Araripe Basin (Ipubi Formation, lower Cretaceous), Northeastern Brazil

Abstract

The Araripe Basin in northeastern Brazil is known worldwide for the exceptionality of its fossils. Its Cretaceous sedimentary record (Santana Group), represented from the base to the top by the Barbalha, Crato, Ipubi, and Romualdo formations, has excellent paleontological content. The Ipubi Formation, previously described as devoid of fossils, has shown good paleontological potential in recent studies. This work presents the paleoecological aspects present in the shales immediately superimposed on the gypsum layer of this formation, aiming to recognize and identify changes over time that influenced the distribution and diversity. The taxonomic, morphometric, quantitative, and qualitative analyses presented here indicate a biota a with high probability of discovering of new taxa. The parameters of diversity, species richness, and evenness indicate a little diversified but abundant biota. Smaller total-length fish sizes were observed compared to specimens of the same species described for the other formations of the Santana Group. These data were visualized with box plots. This condition is possibly associated with variations in salinity and temperature, resulting in a high degree of environmental stress that limits the growth of organisms and could have caused mortality events in several species.