A new delphinid record (Odontoceti, Cetacea) from the Early Pliocene of Tuscany (Central Italy): systematics and biostratigraphic considerations

摘要

A new partial delphinid skeleton (Cetacea, Odontoceti), from Pliocene sediments of Tuscany (Italy) consists of a fragmentary skull, ear bones, mandible, some vertebrae and rib fragments. The specimen is related to the Pliocene "Stenella" giulii, a species known from four specimens collected in the Pisa hills in the second half of 19~(th) Century. "Stenella" giulii is here referred to the new genus Etruridelphis. Differences between Etruridelphis and all the extant Stenella spp. include: i) larger size of skull ii) wider and flatter premaxillae on the rostrum iii) narrower superior process of the periotic and iv) lower processus muscularis of the malleus. The dolphin is from a 25 m thick section for which foraminifera indicate an Early Pliocene outer shelf or upper slope environment (slightly before 3.98 Ma). The dolphin horizon, 13 meters above the base of the section produces Globorotalia margaritae and G. puncticulata, indicating the MP1 3 zone (Zanclean). Previous biostratigraphic analyses on other Etruridelphis specimens confirm that E. giulii is Early and Middle Pliocene in age.