Tagicetus joneti, Lambert & Estevens & Smith, 2005

Lambert, Olivier, Estevens, Mário & Smith, Richard, 2005, A new kentriodontine dolphin from the middle Miocene of Portugal, Acta Palaeontologica Polonica 50 (2), pp. 239-248 : 240-241

Tagicetus joneti gen. et sp. nov.

Figs. 2–7 , Tables 1, 2.

Holotype and only known specimen: IRSNB M.1892, a nearly complete skull missing the apex of the rostrum, all teeth, the left supraorbital process, the left lambdoidal crest, the left squamosal, the lateral laminae and hamular processes of the pterygoids, some other thin fragments of the basicranium, and the earbones. The anterior part of the rostrum is transversely crushed, precluding width measurements from a level 100 mm anterior to the antorbital notches. The skull is associated to five lumbar vertebrae (four of which still attached to the right posterolateral region of the skull), two fragments of ribs, and a partial left scapula.

Type locality: Known as Penedo Norte in recent literature, corresponds to the northern section of the coastal cliffs at Bicas beach (38°27’N, 9°11’W), located some 30 km SW of Lisbon in southwestern Setúbal Peninsula , Lower Tagus Basin , Portugal ( Fig. 1 ) .

Type horizon: Judging from the adhering matrix, this specimen probably came from bed 8 or 9 of the section published by Antunes et al. (1997) for the type locality. According to these authors, these beds were 87 Sr/ 86 Sr dated at 13–11.5 Ma and consequently correlated with the N12–N13 planktonic foraminifera zones of Blow; they may thus correspond to the depositional sequence S2 of Antunes et al. (2000), which ranges from 12.7 to 11.6 Ma, late Serravallian, middle Miocene. The same beds constitute a condensed section that accumulated abundant vertebrate remains ranging in age from the late Burdigalian–Langhian to the Serravallian (N9–N13 of Blow), among which are included several odontocetes, but also some mysticetes and even scarce sirenians and phocids ( Estevens 2003a).

Taphonomy: The skull was extracted from the outcrop with five lumbar vertebrae and several fragments of ribs piled up against the right posterolaterodorsal side of the cranium. All vertebral apophyses and neural spines were still connected to the centra, except for one apophysis, slightly shifted from its original position. The left scapula was wedged between the paroccipital process of the right exoccipital and the corresponding basioccipital crest.

Etymology: Dedicated to the late Simon Jonet (13.11.1902 – 29.01.1987), a Belgian palaeontologist who lived in Portugal during the 1960s–1980s, having then published mostly on the Miocene fish faunas of that country (but likewise on fossil cetaceans), and who introduced RS to the outcrops of the Penedo area.

Generic and specific diagnosis.— Tagicetus joneti gen. et sp. nov. is a moderate−sized kentriodontine with a cranium length close to Rudicetus , differing from Delphinodon , Kampholophos , Kentriodon , Macrokentriodon , and Rudicetus by the long and wide posterolateral projection of the nasal on the vertex; from Delphinodon , Kampholophos , Kentriodon , and Rudicetus by the premaxilla distinctly wider than the maxilla in the rostrum (anterior to a constriction at the level of the antorbital notch) and the elevated vertex (with anterior surface of the premaxilla reaching a slope of 65 degrees); from Delphinodon , Kampholophos , Macrokentriodon , and Rudicetus by the shortened zygomatic process of the squamosal (in which the dorsoventrally thick apex ends abruptly); from Delphinodon , Kentriodon , and Rudicetus in that the rostrum is more than twice as long as the neurocranium; and by the elongated fossa for the hamular lobe of the pterygoid sinus reaching significantly beyond the antorbital notches anteriorly; from Delphinodon and Kentriodon by the lower number of alveoli by length unit; and from Macrokentriodon by the considerably smaller size and the less prominent and more laterally located lambdoidal crests.

Figures

Fig. 2. Tagicetus joneti gen. et sp. nov., IRSNB M.1892, holotype, Middle Miocene of Portugal. A. Dorsal view of the skull. B. The explanatory drawing of the same; not to scale. C. Detail of the vertex in dorsal view.

Fig. 3. Tagicetus joneti gen. et sp. nov., IRSNB M.1892, holotype, middle Miocene of Portugal. A. Right lateral view of the skull. B. The explanatory drawing of the same; not to scale.

Fig. 1. Geographic location of the type locality Penedo Norte, Setúbal Peninsula, Lower Tagus Basin, Portugal (modified from Antunes et al. 1997).