Microberardius africanus, 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 : 565-568

Microberardius africanus n. sp.

HOLOTYPE. — SAM PQ 3003 , a partial skull including the anteriorly worn rostrum, most of the dorsal surface of the cranium and the nearly complete vertex.

ETYMOLOGY. — “africanus” for the African origin of the holotype.

frontal

FIG. 2. — Skull of Microberardius africanus n. gen., n. sp. ( SAM PQ 3003 , holotype): A, dorsal view ; B, lateral view; C, ventral view. Scale bar: 10 cm.

TYPE LOCALITY. — No data. Trawled off the South African coast.

DIAGNOSIS. — Microberardius africanus n. gen., n. sp. differs from Berardius in: smaller size; thickening of the vomer in the anterior portion of the mesorostral groove; rostrum higher than wide along most of its length; narrower rostrum base and maxillary crest not extended on the rostrum base. It differs from Archaeoziphius in: slightly concave premaxillary sac fossa; higher maxillary crest; more anteriorly pointed nasals; larger distance between the maxillae across the vertex and the nodular bone in the posterior vertex being the interparietal instead of the frontals.

DESCRIPTION (FIGS 2; 3; TABLE 1)

Considering the height of the preserved apex of the rostrum, a significant part of the anterior portion is probably missing. Where preserved, the rostrum

height is larger than the width at the same level, except along the base. The dense vomer fills the anterior part of the mesorostral groove, leaving a widely open space posteriorly for the presumed anterior extension of the ossified mesethmoid. Among Recent ziphiids, a lengthened ossified portion of the mesethmoid is only observed in Berardius spp. (e.g., B. arnuxii, SAM ZM 39296; B. bairdii in True 1910: pl. 26). A marked sulcus laterally separates the thickened vomer from the premaxilla.

The premaxillary sac fossa is slightly concave. The ascending process of the premaxilla lacks a constriction under the premaxillary crest in anterior view. The moderate elevation towards the vertex does not reach vertical. The premaxillary crest is transversely oriented without a distinct dorsal thickening or widening, similar to Archaeoziphius and Berardius . The right crest is somewhat wider than the left. The large maxillary foramen just posterior to the level of the antorbital notch is anteriorly followed by a wide and short groove. Both right premaxillary and maxillary foramina are located more posteriorly than their left side counterparts. A high maxillary crest culminating on the preorbital process adjoins the maxillary foramen laterally. Unlike in Berardius , the crest does not extent onto the rostrum base.

The dorsal surface of the nasals is damaged. Their outline is pentagon-shaped, their anterior point reaches the level of the premaxillary crest and the anterolateral corner does not thrust into the premaxillary crest. The anteromedian groove between the nasals seen in dorsal view is probably caused by erosion. The naso-frontal suture is irregular with a posteriorly longer right nasal. The frontals are more transversely compressed and lower than the nasals on the vertex. Posterior to the frontals, lower and slightly shifted to the right, is a nodular uneven bone interpreted as an interparietal. Its low position relative to the vertex in lateral view suggests that the supraoccipital did not reach the vertex dorsally. Such a bone is at least occasionally observed in a similar position in Berardius arnuxii (e.g., SAM ZM 39296, Fig. 4 ; Moore 1968: figs 19, 23). In other specimens of Berardius spp. and in Archaeoziphius , the frontals themselves form a nodular eminence between the lower supraoccipital and the nasals.

Figures

FIG. 4. — Vertex of skull of Berardius arnuxii (SAM ZM 39296): A, dorsal view; B, posterior view; C, lateral view. Note the nodular interparietal between the frontals and the supraoccipital that does not reach the vertex dorsally. Scale bar: 10 cm.