Tusciziphius atlanticus, Bianucci & Miján & Lambert & Post & Mateus, 2013

Bianucci, Giovanni, Miján, Ismael, Lambert, Olivier, Post, Klaas & Mateus, Octávio, 2013, Bizarre fossil beaked whales (Odontoceti, Ziphiidae) fished from the Atlantic Ocean floor off the Iberian Peninsula, Geodiversitas 35 (1), pp. 105-153 : 137-138

aff. Caviziphius sp.

( Fig. 18 )

REFERRED SPECIMEN. — SGHN MA0920, partial skull including rostrum and right part of facial area, Cortada fishing ground, off the Galician coast, depth of approximately 400-800 m, 43°36’N, 9°0’W.

DESCRIPTION ffle original shape of this badly preserved fragmentary skull might have been partially modified by an intense wear. ffle sutures between the bones are also almost completely obliterated. Nevertheless some typical features of the premaxilla and maxilla (medial rostral premaxillary bulge, strongly asymmetric premaxillary sac fossae, and prominent right rostral maxillary eminence) are conspicuous and allow a relevant comparison with other ziphiids.

Premaxilla

In dorsal view, the premaxillae are medially sutured for all their rostral length except for the apical 55 mm portion, where the premaxillae abruptly diverge and leave the mesorostral groove dorsally open. From the anteriormost point of their junction, the height of the premaxillae increases progressively, reaching an elevation of 78 mm above the maxilla at 186 mm from the anterior margin of the right premaxillary sac fossa, forming a protuberant bulge. Posteriorly, the height of the premaxillae decreases abruptly, generating a clear step on the dorsal outline of the rostrum seen in lateral view. On the whole, this premaxillary bulge is similar to the bulge observed in some skulls of Tusciziphius atlanticus n. sp. (holotype, SGHN MA0632, and SGHN MA0644) even if its posterior margin is distinctly more anterior. In fact, the distance from the posterior margin of the bulge and the anterior margin of the premaxillary sac fossa is 186 mm in SGHN MA0920, whereas it varies from 81 to 128 mm in T. atlanticus n. sp. A similar anterior premaxillary bulge is present in a partial skull from the Neogene of Antwerp, Belgium (NMB 002), referred by Lambert (2005: fig. 27A-C) to Ziphiidae aff. Eboroziphius .

Between the bulge and the premaxillary sac fossae, the premaxillae form a shallow medial elevation laterally delimited by two longitudinal depressions. A similar architecture is present in T. atlanticus n. sp. (even if this area is anteroposteriorly shorter), NMB 002, Eboroziphius coelops Leidy, 1876 , and Caviziphius altirostris . ffle incompletely preserved premaxillary sac fossae are strongly asymmetric (ratio between maximum width of left and right fossae approximately 0.5) and deeply excavated, even more than in T. crispus . ffle fossae are separated by a narrow septum corresponding to the medial overlap of the premaxillae. For these characters, the premaxillary sac fossae are similar to those of NMB 002, Caviziphius , E. coelops , and Pelycorhamphus pertortus Cope, 1895 (see Lambert 2005: fig. 28). It is important to outline that the holotypes and only referred specimens of E. coelops and P. pertortus are fragmentary and considerably worn; consequently we restrict the genera to their type-species and the typespecies to their holotypes, and consider them as incertae sedis.

Only the incomplete ascending portion of the right premaxilla is preserved. It abruptly rises from the level of the premaxillary sac fossa; consequently, in lateral view, the outline of the anterior margin of the vertex displays a deep concavity, followed ventrally by a semicircular deep excavation corresponding to the premaxillary sac fossa. A similar lateral profile is observed in Caviziphius .

Although no premaxillary crest is preserved, the thin broken surface at the posterior end of the right ascending process suggests that the right crest was not massive and wide as seen in Globicetus n. gen. and Tusciziphius . Nevertheless, the right premaxillary crest of Caviziphius , even if not completely preserved, seems to have been more robust than in SGHN MA0920, judging from the wider break surface on the ascending process of the right premaxilla of the holotype and only referred specimen.

Maxilla

Due to the incompleteness and the strong erosion, the maxilla does not show any significant features, with the exception of a prominent right rostral maxillary eminence. Roughly located at the rostrum base, this semicircular crest is tilted medially. A similar crest is present in several skulls of T. atlanticus n. sp. and in NMB 002.

REMARKS

SGHN MA0920 shares with some skulls of Tusciziphius atlanticus n. sp. and the fragmentary skull NMB 002 the medial bulge on the fused premaxillae, the strongly asymmetric premaxillary sac fossae, and the prominent right rostral maxillary eminence. Considering the deep excavation of both premaxillary sac fossae, the anterior location of the premaxillary bulge, and the diverging premaxillae near the anterior end of the bulge, SGHN MA0920 is more similar to NMB 002 than to T. atlanticus n. sp. SGHN MA0920 also shares with Caviziphius the deeply excavated asymmetric premaxillary sac fossae, the longitudinal depressions that laterally margin the shallow medial elevation of the sutured premaxillae at the rostrum base, and the abrupt elevation of the ascending process of the right premaxilla. Unfortunately the anterior part of the rostrum and the antorbital area of the maxillae are not preserved in the holotype and only referred specimen of Caviziphius altirostris (see Bianucci & Post 2005); consequently it is not possible to establish if the premaxillary bulge and the prominent right rostral maxillary eminence are also present in the latter. Nevertheless, considering that the holotype of C. altirostris and NMB 002 are nearly identical for the parts preserved in both specimens and show similar dimensions, it is likely that both these incomplete skulls belong to the same species. Furthermore they were collected in the same area (Antwerp). If this hypothesis is confirmed with future discoveries, C. altirostris will be redefined with the combination of the characters of the holotype and NMB 002. ffle only significant differences between SGHN MA0920 and these two skulls from Antwerp are the smaller size and probably the thinner right premaxillary crest.

Figures

FIG. 18. — Skull of aff. Caviziphius sp. (SGHN MA0920): A, dorsal view; B, lateral view. Parallel lines indicate a break surface. Scale bar: 10 cm.