A new physeteroid cetacean from the Lower Miocene of southern Italy: CT imaging, retrodeformation, systematics and palaeobiology of a sperm whale from the Pietra leccese

Herein we describe a new finding of a medium-sized sperm whale from the Burdigalian (Lower Miocene) of the Pietra leccese formation (southern Italy) on the basis of a partly prepared specimen that includes a partial cranium, seven detached teeth, the fragmentary right mandible and two partial vertebral bodies. Because of the overall compression of the specimen, we carried out a retro deformation of a 3D model of the cranium obtained via CT-scanning. The combined analysis of the original specimen and the retrodeformed model has allowed us to recognise that the studied specimen constitutes a new physeteroid taxon: Angelocetus cursiensis n. gen. n. sp., a longirostrine sperm whale characterised by a sideward projected supracranial basin, as evidenced by the overall displacement of its posteriormost margin. Based on a phylogenetic analysis, A. cursiensis n. gen. n. sp. is determined to be a crown physeteroid that does not belong to either the Physeteridae or the Kogiidae. The wide temporal fossa, elongated rostrum and slender teeth, as well as the skull dimensions (estimated bizygomatic width c. 550 mm) suggest a diet based on medium to large-sized bony fish that were likely captured by a raptorial pierce feeding strategy (as for most of the coeval Burdigalian physeteroids). Despite a seemingly low ecomorphological disparity, the high degree of taxonomic diversity of the Burdigalian physeteroids suggests that this time span represents a crucial phase for the evolutionary history of sperm whales.