Izikoziphius angustus, Bianucci & Lambert & Post, 2007

Bianucci, Giovanni, Lambert, Olivier & Post, Klaas, 2007, A high diversity in fossil beaked whales (Mammalia, Odontoceti, Ziphiidae) recovered by trawling from the sea floor off South Africa, Geodiversitas 29 (4), pp. 561-618 : 573-576

Izikoziphius angustus n. sp.

HOLOTYPE. — SAM PQ 3004 , a partial skull including the rostrum and most of the dorsal surface of the cranium with the vertex.

ETYMOLOGY. — From Latin “angustus”, narrow, for the transversely compressed rostrum, narrower than in the

type species I. rossi n. gen., n. sp.

TYPE LOCALITY. —Trawled at 34°39’82”S, 18°03’31”E, southwest of Cape Town, Atlantic Ocean, depth of 450 m.

DIAGNOSIS. — Izikoziphius angustus n. gen., n. sp. differs from I. rossi n. gen., n. sp. in: longer rostrum higher than wide; narrower rostrum base; more elevated maxillary crest, not extending on to the rostrum; mesethmoid distinctly keeled under the nasals; nasals much longer than wide and right side of vertex less elevated.

DESCRIPTION ( FIGS 10 ; 11 ; TABLE 2)

The only known specimen is a well preserved skull including the complete rostrum, most of the dorsal surface of the cranium, and the vertex.

The moderately elongated rostrum is higher than wide at mid-length and the dorsal surface of the maxilla is narrow. The rostrum base is narrower than in Izikoziphius rossi n. gen., n. sp.; the widening toward the antorbital notch is abrupt. The thickened vomer completely fills the mesorostral groove and is slightly higher than the premaxilla for its entire length. Only the apical premaxillary portion of the rostrum shows a concave dorsal surface. No alveolar groove could be detected.

The premaxillary foramen is posterior to the antorbital notch, roughly in line with the large, but transversely compressed, maxillary foramen. The slightly concave premaxillary sac fossa, as in Izikoziphius rossi n. gen., n. sp., overhangs the maxilla along its posterior part. The vertical anterior surface of the ascending process of the right premaxilla is excavated by a fossa less developed medially than in Izikoziphius rossi n. gen., n. sp., only contacting the nasal for a short distance. The left premaxilla is too damaged to determine the presence of a fossa. The keeled mesethmoid nearly completely covers the anterior surface of the nasals.

At the level of the preorbital process, the domelike maxillary crest is more elevated than in Izikoziphius rossi n. gen., n. sp. and does not extend into the rostrum base.

On the elevated vertex the premaxillary crests are anterolaterally directed, similar to Izikoziphius rossi n. gen., n. sp. The nasals are longer compared to their width than in the latter species and their dorsal surface is flat.

Figures

FIG. 10. — Skull of Izikoziphius angustus n. gen., n. sp. (SAM PQ 3004, holotype): A, dorsal view; B, lateral view; C, ventral view.Scale bar: 10 cm.

FIG. 11. — Skull of Izikoziphius angustus n. gen., n. sp. (SAM PQ 3004, holotype): A, detail of the vertex in dorsal view; B, corresponding line drawing; C, anterior view; D, corresponding line drawing. Scale bars: A, B, 5 cm; C, D, 10 cm.