Khoikhoicetus agulhasis, 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 : 578

Khoikhoicetus agulhasis n. sp.

HOLOTYPE. — SAM PQ 2678 , partial skull including most of the rostrum, the anterior part of the cranium, and the vertex.

ETYMOLOGY. — The holotype was found offshore from Cape Agulhas, a locality on the south coast of South Africa. The oceanic current running along the south-east coast of South Africa is also named Agulhas Current.

TYPE LOCALITY. — No exact locality.Trawled west of Cape Agulhas, south coast of South Africa, Indian Ocean.

DIAGNOSIS. — Khoikhoicetus agulhasis n. gen., n. sp. differs from all the other Hyperoodontinae in lacking the posterolaterally directed premaxillary crest. It differs from Indopacetus in: smaller size; narrow rostrum base; narrower premaxillary crests and nasals longer than the frontals on the vertex. It differs from Africanacetus n. gen., Hyperoodon , Ihlengesi n. gen., and Mesoplodon in: shorter intrusion of the nasal in the premaxillary crest; premaxillary crest not overhanging the premaxillary sac fossa. The space between the premaxillary crests is wider than in Hyperoodon and Mesoplodon .

DESCRIPTION ( FIGS 13 ; 14; TABLE 4)

On the only known skull, the rostrum was probably relatively short, not much longer than the preserved length. It is somewhat wider than high along its anterior half and as wide as high posteriorly. The mesorostral groove is filled by the vomer, with a median suture on the posterior half. The ventral margin of the alveolar groove, lacking marks of alveoli, extends to the antorbital notch; contrary to Mesoplodon grayi , M. hectori , M. layardii , and M. slangkopi n. sp. (see below) this feature is not visible in dorsal view.

The rostrum base lacks a prominental notch; the antorbital notch is wide and probably shallow, at the level of the premaxillary foramen and slightly anterior to the small maxillary foramen lying along the premaxilla-maxilla suture. Posterior to the antorbital notch, a low maxillary crest thickens the preorbital process, with a lateral slope similar to Africanacetus n. gen.

The weakly asymmetric premaxillary sac fossae are anteromedially tilted. The ascending process is moderately constricted in anterior view. The foramina for the terminal nerve in the mesethmoid are strongly asymmetric; the left foramen is much smaller than the right.

The premaxillary crest is thin and laterally elongated, with a vertical anterior surface. The posterior projection of the premaxilla along the nasal reaches the frontal. The anterolateral corner of the roughly pentagon-shaped nasals forms only a small part of the premaxillary crest; the dorsal surface is anteromedially depressed. The naso-frontal suture is anteriorly pointed; the left nasal extends longer posteriorly than the right nasal.

Figures

FIG. 13. — Skull of Khoikhoicetus agulhasis n. gen., n. sp. (SAM PQ 2678, holotype): A, dorsal view; B, lateral view; C, ventral view. Scale bar: 10 cm.