New records of Mawsoniidae (Actinistia) from the Romualdo Formation, Aptian-Albian of the Araripe Basin in Pernambuco state, Brazil

This work presents the osteological description and taxonomic position of new mawsoniid fossils from the Early Cretaceous Romualdo Formation (Aptian-Albian) of the Araripe Basin, in Pernmabuco, Brazil. The fossils were collected in the municipalities of Araripina, Exu, Ipubi and a new occurrence is registered in the municipality of Ouricuri. In total, nine specimens were identified, eight of which were assigned to the species Axelrodichthys araripensis and one to the genus Mawsonia, (Mawsonia sp.). Although the accurate analysis of these fossils determines the presence of Axelrodichthys araripensis and Mawsonia sp., the first is more abundant in the region. The fossils studied include skull, postcranial, elements dissociated from the skull, an entire specimen, some being three-dimensionally articulated as well as meristical information on the number of fin rays. Remains of the ossified lung are preserved, showing morphological similarities to the Axelrodichthys araripensis. The morphological analysis of the lung covered by bony plaques, as well as the greater predominance of A. araripensis and an associated fauna composed of vertebrates, invertebrates and typically marine microfossils, is interpreted here as a eurialine character for this species. These new records help to understand the Mawsoniid Family during the Lower Cretaceous, in the Sedimentary Basin of Araripe.