HYPEROODONTINAE

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 : 145-146

HYPEROODONTINAE indet. aff. Africanacetus

REFERRED SPECIMENS AND LOCALITIES. — Partial rostrum MNHN.F.COI3. Partial rostrum MNHN.F.COI4 ( Fig. 7 ). These

specimens were collected before the involvement of procedures to record localities; no indication about the precise locality is thus available. They were most likely found off Kerguelen Islands.

BRIEF DESCRIPTION AND COMPARISON

In dorsal view these two robust rostra display a minor constriction slightly posterior to mid-length, followed anteriorly by a distinct widening. The acute lateral margin of the rostrum forms a plate diverging abruptly posterolaterally. The vomer is widely exposed dorsally in the mesorostral groove, and is margined by longitudinal sulci along its anterior portion. Posterior to the vomer, the presphenoid is similarly thickened in the mesorostral groove, raising posteriorly until the level of the premaxillary foramen. The premaxillary foramen is at the same anteroposterior level as the large dorsal infraorbital foramen, posterior to the anterior tip of the presphenoid.

A lateral expansion of the rostrum, as seen in dorsal view of these two specimens, is absent in Africanacetus ceratopsis , but present in Pterocetus benguelae (holotype and SAM PQ 69684) and Africanacetus gracilis ( Ichishima et al. 2017) . Specimens of P. benguelae similarly display a wide exposure of the vomer in the mesorostral groove, with a pointed anterior portion margined by sulci (e.g. SAM PQ 1770 and 69684). However, in P. benguelae the premaxillary foramen is much more anteriorly located, anterior to the large dorsal infraorbital foramen. The absence of this key character in MNHN.F.COI3 and MNHN.F.COI4 makes these two rostra slightly more similar to A. ceratopsis than to P. benguelae . The rostrum of A. gracilis is considerably more slender. More robust than currently known specimens of A. ceratopsis these two rostra are too incomplete for a more precise taxonomic assignation.

Figures

FIG. 7. — Partial rostra of Hyperoodontinae indet. aff. Africanacetus: A, B, MNHN.F.COI3; C, D, MNHN.F.COI4; A, C, dorsal views; B, D, right lateral views. Scale bar: 100 mm.