New insights into the taxonomy, ontogeny and ecology of the coelacanth Axelrodichthys araripensis from the Romualdo Formation in the Araripe basin of northeastern Brazil

The present study describes a new specimen of a juvenile coelacanth from the Romualdo Formation, in the Lower Cretaceous (Aptian/Albian) of the Araripe Basin in Pernambuco, northeastern Brazil. At 187 mm in length, this is one of the smallest complete specimens of the species Axelrodichthys araripensis known from the Romualdo Formation. The comparative analysis of the specimen provides important insights into the ontogeny, taxonomy and ecology of the species, as well as the associated fauna and paleoenvironment of the study area. The analysis of the associated fauna and the local lithology indicates that Axelrodichthys araripensis was likely a marine species that settled in calm, shallow waters to breed and develop. Based on the ornamentation patterns observed in the cranial bones, it was possible to contribute to the diagnosis of the species, while the environments that were likely to have been most favourable to its reproduction and development are described and discussed.