Ihlengesi saldanhae, 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 : 580-583

Ihlengesi saldanhae n. sp.

HOLOTYPE. — SAM PQ 2792 , partial skull including the rostrum base, anterior part of the cranium, and the vertex.

PARATYPE. — SAM PQ 69673, rostrum with anterior part of the cranium trawled off Cape Columbine, west coast of South Africa, Atlantic Ocean. This specimen was previously referred to “cf. Mesoplodon densirostris , M. grayi , M. australis ” by Haughton (1956) on the basis of the location of the premaxillary foramina. This well preserved rostrum provides additional information for the species description.

ETYMOLOGY. — The holotype was found offshore from Saldanha Bay, a locality on the west coast of South Africa.

TYPE LOCALITY. — No exact locality.Trawled off Saldanha Bay, west coast of South Africa, Atlantic Ocean.

DIAGNOSIS. — Ihlengesi saldanhae n. gen., n. sp. differs from all other Hyperoodontinae in the shortened premaxillary sac fossa (ratio between measurements 15 and 16 lower than 0.30). It shares with Africanacetus n. gen., Hyperoodon , and Mesoplodon : the inclusion of the nasal into the premaxillary crest over at least half the length of the median margin of the crest and a deep anteromedian excavation of the nasals. Both characters are absent in Khoikhoicetus n. gen. and Indopacetus . It further differs from Africanacetus n. gen. in: smaller size; maxillary foramen close to the prominental notch at the rostrum base; roughly flat dorsal surface of the preorbital process and premaxillary sac fossa not laterally sloping. The space between the premaxillary crests is wider than in Hyperoodon and Mesoplodon .

DESCRIPTION ( FIGS 15 ; 16 ; TABLE 4)

A large part of the elongated and transversely compressed rostrum, higher than wide, is preserved in SAM PQ 69673. The maxilla is roughly hidden from the dorsal view for the anterior half of the rostrum. A slight constriction is seen in dorsal view at c. 120 mm from the preserved apex. The vomer fills the mesorostral groove over its whole length.

A maxilla

premaxilla

maxillary foramen

In the holotype, the maximum height and width of the vomer is reached at the rostrum base; a second hump at one third of the length of the rostrum is observed in SAM PQ 69673 (not preserved in the holotype). A median suture marks the dorsal surface of the vomer at the rostrum base. In the holotype, the two premaxillae nearly contact each other above the mesorostral groove 70 mm anterior to the antorbital notches, a condition sometimes observed in Recent Mesoplodon densirostris . The ventrolateral surface of the rostrum of both specimens is worn .

The prominental notch is wide and roughly as deep as in Mesoplodon layardii . A reduced maxillary foramen opens anterolaterally as a triangular fissure towards the prominental notch. At the level of the well developed maxillary tubercle, the preorbital process is barely convex, lacking a distinct maxillary crest.

The distinctly asymmetric premaxillary sac fossae are short; the distance between the anterior margin of the bony nares and the premaxillary foramen is small. The premaxillary foramen is located in a shallow depression behind the level of the antorbital notch. The ascending process of the premaxilla is strongly constricted in anterior view.

The vertex is moderately elevated. The premaxillary crest is thick and wide, posterolaterally directed. An oblique transverse groove limits ventrally the anterior surface of each premaxillary crest. The thicker right crest overhangs the ascending process. The lateral margins of the longitudinally elongated nasals are anteriorly diverging; the anterolateral corner is distinctly thrust into the medial part of the premaxillary crest. The anteromedial surface of the nasals is strongly excavated; it forms a deep vertical groove between the premaxillary crests. The naso-frontal suture is convex posteriorly.

Figures

FIG. 15. — Skull of Ihlengesi saldanhae n. gen., n. sp. (SAM PQ 2792, holotype): A, dorsal view; B, lateral view; C, detail of the anterior view; D, corresponding line drawing. Scale bar: 10 cm.

FIG. 16. — Ihlengesi saldanhae n. gen., n. sp.: A, B, vertex of skull (SAM PQ 2792, holotype); A, dorsal view; B, corresponding line drawing; C-E, incomplete skull (SAM PQ 69673, paratype); C, dorsal view; D, anterior view; E, lateral view. Scale bars: A, B, 2 cm; C-E, 10 cm.