Reinforcing the idea of an early dispersal of Hippopotamus amphibius in Europe: Restoration and multidisciplinary study of the skull from the Middle Pleistocene of Cava Montanari (Rome, central Italy)

A skull of Hippopotamus recovered from the area of Tor di Quinto, within the urban area ofRome (central Italy) is here redescribed. Despite being one of the most complete specimensof hippopotamuses of the European Pleistocene, the Tor di Quinto skull did not attract muchresearch interest, due to long-standing uncertainties on its provenance. This work begun in2021, when the skull was restored, within a large renovation project on the vertebrateexposed at the Earth Science University Museum of Sapienza University of Rome. Originalsediments were found inside the cranial and mandible cavities during the restoration work,which were sampled for petrographic analyses. By combining a review of the old paleontological,archeological and geological literature published during the 19th and 20th century onthe Rome basin and the correlation of these new sedimentological and petrographic informationwith the lithostratigraphic and synthemic units of the national geological cartography,we clarify that the Hippopotamus skull was most likely to have been collected from a quarrycalled Cava Montanari, from a formation dated between 560 and 460 ka. Morphological andbiometric analyses clearly support an attribution of the Cava Montanari specimen to theextant species Hippopotamus amphibius. The reassessment of the stratigraphic and geologicaldata on Cava Montanari implies that the studied specimen is the earliest confirmedoccurrence of Hippopotamus amphibius in the European fossil record.