Ziphius sp.

Lambert, Olivier, Muizon, Christian de, Duhamel, Guy & Plicht, Johannes Van Der, 2018, Neogene and Quaternary fossil remains of beaked whales (Cetacea, Odontoceti, Ziphiidae) from deep-sea deposits off Crozet and Kerguelen islands, Southern Ocean, Geodiversitas 40 (6), pp. 135-160 : 151-153

Ziphius sp.

(probably new species)

Ziphius sp. – Bianucci et al. 2007: 576; 2008: 141.

REFERRED SPECIMEN AND LOCALITY. — Fragment of the facial region of the cranium MNHN.F.COI9 including right premaxillary sac fossa and most of the vertex (premaxillary crests and nasals) ( Fig. 11 ). This specimen was collected before the involvement of procedures to record localities; no indication about the precise locality is thus available. It was most likely found off Kerguelen Islands.

BRIEF DESCRIPTION AND COMPARISON

Only preserved on the right side, the premaxillary sac fossa is transversely and longitudinally concave. In anterior view the

lateral margin of the ascending process of the premaxilla does not display a conspicuous constriction. The right ascending process is much wider than the left process (preserved in its upper region), and the anterior surface of each process is transversely concave. On the elevated vertex, the anterolaterally directed right premaxillary crest is much wider than the left crest, the latter being even more anteriorly directed. A vertical foramen pierces the posterior flank of each crest at the boundary between premaxilla and maxilla. In dorsal view the nasals are anteroposteriorly elongated, much longer than wide. Their anteromedial apex projects farther anteriorly than the premaxillary crests. The minimum distance between maxillae across the vertex is lower than the maximum width of nasals.

All the features listed above are shared with the extant Ziphius cavirostris Cuvier, 1823 , more specifically adult males who display markedly transversely concave premaxillary sac fossae in the deep prenarial basin (e.g. True 1910; Heyning 1989). The latter only differs in being considerably smaller in general dimensions. Interestingly, this fossil specimen shares morphological characters and dimensions with the South African specimen of Ziphius sp. SAM PQ 2826 ( Table 8). Furthermore, these two fossils nearly exactly preserve the same cranial regions, which may be an indication of a similar distribution of compact bone in the cranium (see a CT scan of the cranium of Z. cavirostris in Lambert et al. 2011: fig. 8). Although these two specimens represent a very large, new ziphiine species closely related to Ziphius cavirostris , their fragmentary state does not allow for a detailed differential diagnosis. Pending the discovery of more complete specimens, we therefore prefer not to define and name the new species.

Figures

FIG. 11. — Fragment of facial region of the cranium of Ziphius sp. (probably new species) (MNHN.F.COI9): A, right lateral view; B, anterior view; C, dorsal view; D, same view with interpretive line drawing. Scale bar: 100 mm.