DIGITAL INVESTIGATION OF LAMNIFORM SHARK VERTEBRAE FROM THE SCAGLIA CINEREA - BISCIARO BOUNDARY (MIOCENE, UMBRIA-MARCHE BASIN)

During the sampling of a stratigraphic section along the shore of the Fiastra Lake (Carg Project - sheet 313 Camerino of the Geological Map of Italy 1:50000), a rock boulder with partially exposed skeletal materials has been discovered at the base of a small cliff at the northern termination of the Sibillini Mts. Ridge. In this area the Umbria-Marche Basin stratigraphic succession is extensively exposed. The Oligo-Miocene portion of the succession is well-exposed is the examined section, represented by the ~200 m-thick Scaglia Cinerea Formation passing upwards to the ~100 m-thick Bisciaro Formation. The studied specimen was found erratic in close proximity to the boundary between the two formations, in a stratigraphic interval attributable to the Aquitanian p.p. To better investigate the nature of the exposed skeletal structures, the block has been examined using a CT scan. From the acquired digital data, the elements appeared to be articulated fish vertebrae affected by a certain degree of lithostatic compression. Through computed tomography investigations, the vertebrae have been digitally isolated and extracted from the block, and the digital model has been 3D printed. Thanks to the identification of diagnostic characters, the vertebral material has been attributed to a lamniform shark (order Lamniformes). The vertebrae were also digitally retro-deformed, and a body length estimate has been proposed, suggesting in an individual not shorter than four meters of total length. The effectiveness of these non-invasive methods has been demonstrated for the intended purpose. The obtained data also allowed a taxonomic identification of the specimen and to report the first occurrence of a large vertebrate remains discovered to date at the Scaglia Cinerea - Bisciaro boundary.