Lamniform vertebrae from the Aptian-Albian Marne a Fucoidi of Umbria-Marche Domain (central Italy)

Abstract

The elasmobranch fossil record is essentially represented by isolated teeth due to high fossilization potential of hard dental components. Conversely, the cartilaginous skeletal elements, even though mineralized, are less prone to survive to the biostratinomic and diagenetic processes with negative implications in our understanding of the evolution of the elasmobranch skeletal anatomy. Even if fossil shark taxonomy is almost based on tooth characters, fossil vertebrae can provide useful information concerning the age, ontogenetic stage, and total length of the individual, along with crucial taphonomical and paleoecological information. In the present contribution we report and describe the first occurrence of lamniform vertebrae from the Cretaceous of the Umbria-Marche Domain (Central Italy), from the Aptian–Albian Marne a Fucoidi cropping out at Mt Nerone (Umbria-Marche Ridge, Northern Apennines, Italy). Although the material is solely represented by ten vertebrae (four found semi-articulated), the presence of well-calcified, amphicoelous, and slightly dorso-ventrally compressed centra having notochordal spaces constricted and reduced to intervertebral lenses confidently support their attribution to the group of lamniform sharks. In addition to taphonomic considerations, we have tried to provide a possible age for the individual and to estimate the minimum total length for the entire body. Based on the general morphology of the centra, size and annual growth bands, the preserved material can be referred to a small-medium sized fusiform and pelagic lamniform shark, with a body length reaching not less than 1.59 m, and being characterized by an approximately sub-circular trunk area, and a moderately fast swimming and consistent maneuverability. Considering the relative scarcity of shark vertebral remains in the fossil record, the material described herein represents an important source of information for the paleobiology of the Umbria-Marche Domain of Central Italy during the Cretaceous period.