New evidence and analyses indicate that Tursiops osennae is a Globicephaline (Odontoceti, Delphinidae) from the Pliocene of Siena Basin (Tuscany, Italy)

Tursiops osennae is a species of Delphinidae first described by Simonelli in 1911. It was found in Pliocene sediments (5.33.35 Ma) from the sedimentary basin of Siena- Radicofani in Tuscany, Italy. The holotype consists of an incomplete skull including the ear bones (right periotic and right and left tympanic bulla), a small portion of the left mandible, the atlas articulated with the axis, and the third and fourth cervical vertebrae. The objective of this study was to redescribe this fossil specimen and evaluate its phylogenetic position using both molecular and morphological data. The morphology of Tursiops oseannae significantly differs from extant Tursiops spp. and from all other extant and fossil delphinids, indicating that it belongs to a new genus. Key diagnostic characters that identify this new taxon are: (1) broad rostrum; (2) very wide anterior angle between nasals; (3) very short orbit compared to skull length; (4) deep and narrow antorbital notches; (5) tilted posterior process of periodic; (6) tall atlas, with a long neural spine; and (7) little sloping neural spine of atlas. The phylogenetic position of Tursiops oseannae was evaluated using a supermatrix of 19630 characters coded for 45 taxa. The molecular partition is previously published, whereas the morphological partition was developed for the present study. It includes 63 morphological characters, of which 13 are new. The entire supermatrix was analyzed with implied weighting, with the constant k = 3. The single tree from the combined dataset shows T. osennae as nested in the Globicephalinae rather than in Delphininae, where Tursiops is situated. Tursiops osennae is the sister-taxon of Peponocephala electra and its closest fossil relative is Hemisyntrachelus cortesii, which is the sister-group of the clade of Globicephalinae + Steno bredanensis. Thus T. ossenae represents the oldest fossil genus of Globicephalinae, confirming the great diversification of Delphinidae in the Pliocene.