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 : 116-122

Tusciziphius atlanticus n. sp.

( Figs 6-9 ; Table 2)

HOLOTYPE. — SGHN MA0926, a partial skull including rostrum, facial area, and vertex.

PARATYPE. — NMR 9991-3020, a partial skull including rostrum, facial area, and vertex, originally referred to Tusciziphius crispus (see Post et al. 2008). Morgan River, Beaufort County, South Carolina, USA, between 32°26’50”N, 80°35’57”W and 32°27’09”N, 80°28’44”W. Found reworked on the bottom of a river, it has been proposed to originate from late Miocene-Pliocene layers ( Post et al. 2008).

REFERRED SPECIMENS. — SGHN MA0632, a partial skull including rostrum, facial area, and vertex, As Paredes fishing ground, depth of approximately 470 m, off the Galician coast, 44°07’N, 08°07’W ; SGHN MA0644, a partial skull including rostrum, facial area, and vertex, A Selva fishing ground, depth of approximately 500 m, off the Galician coast, 44°10’N, 08°40’W ; SGHN MA0914, a partial skull including rostrum, facial area, and vertex, A Selva fishing ground, depth of approximately 500 m, off the Galician coast, 44°10’N, 08°40’W ; ML1365, a right facial area including right side of the vertex, south of Nazaré Canyon off the Portuguese coast, exact locality unknown, but likely around 39°18’N, 9°47’W .

ETYMOLOGY. — From the Atlantic Ocean distribution of the species (South Carolina, east coast USA and Iberian Atlantic coast, western Europe).

TYPE LOCALITY. — Cortada fishing ground, depth of approximately 600 m, off the Galician coast, 43°30’N, 09°25’W.

DIAGNOSIS. — Tusciziphius atlanticus n. sp. differs from all other ziphiids in the prominent medial rostral bulge formed by the fused premaxillae, which elevation varies individually and is probably related to sexual dimorphism (this feature cannot be observed in T. crispus , of which the rostrum is unknown; in Aporotus the elevated premaxillae are not fused in a single bulge).

It differs from T. crispus in having the right premaxillary sac fossa almost completely (except the posterior portion) filled by compact bone forming a semicircular shelf and in having the excavation for the premaxillary sacs restricted to the posterior portion of both right and left premaxillary sac fossae.

DESCRIPTION ffle holotype, the paratype, and the referred specimens of Tusciziphius atlanticus n. sp., share with T.crispus the similar size, the large and asymmetrical premaxilary sac fossae, and the vertex architecture with the extreme widening and anterior projection of the right premaxillary crest. All the Iberian specimens referred to this species exhibit, when preserved, a moderately elongated rostrum, suggesting that the apparently short rostrum of the paratype may be an artefact due to restoration of the broken apex with plaster ( Post et al. 2008).

A prominent medial elevation on the rostrum, formed by the fusion of premaxillae over the mesorostral groove, is visible in three of the four specimens with a preserved rostrum. In the paratype NMR 9991-3020 and in SGHN MA0914, the rostral bulge is present but less developed. fflis character cannot be observed in T. crispus because the rostrum is not preserved on the holotype and only preserved specimen.

Premaxilla

Due to the apical erosion of the rostrum, more or less pronounced in all specimens, it is not possible to evaluate the length of the portion of the rostrum formed by the premaxillae alone. In fact, this region is partly preserved (5 mm) only in SGHN MA0914. In all the specimens, the preserved portion of the rostrum exhibits thick premaxillae with a medial suture, dorsally closing the mesorostral groove. fflis closure starts from the preserved apical portion of the rostrum in all specimens except in the holotype, where the first 65 mm of the groove are still dorsally open. ffle fused premaxillae are massive and protuberant on the rostrum; they form a bulge, with a varying position and height, on which the medial premaxillary suture is completely obliterated.

ffle development of the medial premaxillary bulge extends from the apex of the rostrum to the level of the antorbital notch in the holotype, SGHN MA0632 and SGHN MA0914, and to the level of the anterior palatine suture in SGHN MA0644. ffle elevation of the bulge increases anteroposteriorly progressively in the holotype, and more abruptly in SGHN MA0644 and SGHN MA0632. ffle maximum height of the bulge above the maxilla is 90 mm in SGHN MA0632, 67 mm in SGHN MA0644, and 58 mm in the holotype. In the paratype and in SGHN M0914, only a small dome, respectively 27 and 33 mm above the maxilla, is present in the posterior part of the rostrum, just anterior to the antorbital notches. Macroscopic observation of transverse sections along the medial bulge of SGHN MA0632 reveal a high compacity of the bone tissue and the presence of a series of growth layers, a feature already noted in the pachyosteosclerotic rostrum of several other ziphiid taxa ( Lambert 2005; Buffrénil & Lambert 2011; Lambert et al. 2011). Posterior to the premaxillary bulge, there is a low medial shelf laterally delimited by two shallow depressions and posteriorly margined by the premaxillae sac fossae. ffle premaxillary sac fossae are strongly asymmetric in all the specimens of T. atlanticus n. sp. (ratio between the left and right width ranging from 0.43 to 0.57) and in T. crispus (0.44). However, in all the specimens of T. atlanticus n. sp. the anterior part of the right premaxillary sac fossa is completely filled by compact bone, forming a thick semicircular shelf. ffle filling is absent in the left premaxillary fossa, which is deeply concave in all specimens. Instead, in T. cripsus both premaxillary sac fossae are excavated. ffle deep concavity of the premaxillary sac fossae is likely a derived condition shared with Caviziphius , Choneziphius , Globicetus n. gen., and Imocetus n. gen., whereas the semicircular shelf that partially fills the right premaxillary fossa in T. atlanticus n. sp. may be homologous with the rectangular premaxillary shelf of Globicetus n. gen. (see below). Due to the presence of the anterior shelf, the posterior portion of the right premaxillary sac fossa displays an abrupt anterior slope. Interestingly, a similar step is present at the same level in the fully concave left premaxillary sac fossa. No premaxillary foramen is observed at the anterior end of the premaxillary sac fossae. Only one foramen is visible near the medial margin of the left fossa in the holotype, in the paratype, and SGHN MA0914, absent in SGHN MA0632 and SGHN MA0644. Similar to T. crispus , the ascending process of the premaxilla of T. atlanticus n. sp. exhibits a strong transverse constriction. Its posterior portion is anteriorly curved, overhanging the premaxillary sac fossa and bony nares. ffle right premaxillary crest of T. atlanticus n. sp. shows the extreme transverse widening typical for Tusciziphius . Moreover, as in T. crispus , the right premaxillary crest is more anteriorly projected than the left. For this character, Tusciziphius clearly differs from the closely related Globicetus n. gen., in which both crests have approximately the same anterior extent. fflis difference may be related to the different direction of the right premaxillary crest (anterolateral in Tusciziphius and more transversal in Globicetus n. gen.). Finally, as in Globicetus n. gen., Imocetus n. gen., and especially Caviziphius , the right premaxillary crest is considerably larger and especially higher than the left, a feature best seen in anterior view. Moreover, due to the fact that the right premaxillary crest is considerably higher than the left one, the dorsal surface of the right nasal is more medially inclined than that of the left nasal.

Maxilla ffle distal half part of the rostrum is narrow and strongly transversally compressed. Consequently the dorsal surface of the maxilla is nearly vertical and almost invisible in dorsal view. In the proximal half portion, the lateral inclination of the maxilla decreases progressively, with a wider portion visible in dorsal view.

At the rostrum base, just medial to the right antorbital notch, the holotype and SGHN MA0644 develop a high and voluminous rostral maxillary eminence, slightly medially curved.SGHN MA0632 lacks a portion of the right maxilla that probably included, judging from the shape and the position of the broken surface, a similar eminence. On the left side of the holotype, SGHN MA0644, and SGHN MA0632, the maxilla exhibits a similar but lower rostral maxillary eminence. In the paratype and SGHN MA0914, no prominent rostral maxillary eminence is present, only some irregular excrescences. On both sides of skulls bearing rostral maxillary eminences, a shallow longitudinal depression is margined laterally by the eminence, slightly overhanging the depression, and medially by the low medial premaxillary shelf. One to three dorsal infraobital foramina pierce the maxilla near the rostrum base, medial and/or posterior to the rostral maxillary eminence (when the eminence is present). From these foramina, several sulci run anteriorly and posteriorly. ffle vestigial alveolar groove is a narrow sulcus, with no visible alveoli.

Nasal ffle shape of the nasals, as the general architecture of the vertex, is rather stable in T. atlanticus n. sp. and T. crispus . ffle sutures of the nasals are generally hard to detect due to the extreme ossification and fusion of the vertex bones. ffle nasals are anteroposteriorly elongated, with lateral margins parallel or faintly convergent (but not as much as in Globicetus n. gen.). As in Globicetus n. gen. and Imocetus n. gen., the lateral margin of the nasal is in contact with the premaxillary crest for all its extent and the dorsal surface of the joined nasals forms a shallow depression between the premaxillary crests.

Frontal ffle frontals are visible on the vertex of several specimens. ffley are wider than in Globicetus n. gen. and Imocetus n. gen., related to the lesser transverse constriction of the posterior part of the vertex.

Vomer ffle vomer is not visible dorsally due to the complete closure of the mesorostral groove. It is visible only ventrally between the premaxillae and the maxillae along the mid-line of the rostrum, and anterior to the choanae due to the non-preservation of the palatine in that area.

Palatine ffle palatine is partially preserved only in SGHN MA0914.ffle maxilla-palatine suture extends about 150 mm anterior to the antorbital notch, the level of the abrupt widening of the rostrum.

REMARKS ffle previous assignation of the South Carolina paratype of Tusciziphius atlanticus n. sp. to the Italian species T. crispus was made at a time when only one skull was known ( Post et al. 2008), preventing any evaluation of the intraspecific or interspecific character for the variation at the level of the premaxillary sac fossae. ffle observation of the same filling of the right premaxillary sac fossa in all the examined skulls from the Atlantic Ocean floor off the Iberian Peninsula suggests that this character is valid for the definition of a new species, grouping the South Carolina specimen with the Iberian specimens. Additional specimens of T. crispus from Italy could confirm this interpretation in the future.

Figures

FIG. 6. — Skull of Tusciziphius atlanticus, n. sp. (SGHN MA0926, holotype): A, dorsal view; B, corresponding line drawing; C, lateral view; D, detail of the vertex and premaxillary sac fossae in anterior view. Parallel lines indicate a break surface. Scale bar: 10 cm.

FIG. 7. — Skull of Tusciziphius atlanticus, n. sp. (SGHN MA0632): A, dorsal view; B, corresponding line drawing. Cross-hatching indicates the presence of a concretion; tight parallel lines indicate a break surface. Scale bar: 10 cm.

FIG. 8.— Skull of Tusciziphius atlanticus n. sp.(SGHN MA0632):A, lateral view;B, corresponding line drawing (the arrows indicate the level of the transverse section); C, transverse section through the rostrum;D, detail of C showing the growth layers;E, anterior view; F, corresponding line drawing.Cross-hatching indicates the presence of a concretion;tight parallel lines indicate a break surface.Scale bar:10 cm.

FIG. 9. — A-C, skull of Tusciziphius atlanticus, n. sp. (SGHN MA0644); A, dorsal view; B, lateral view; C, anterior view. D, E, skull of T. atlanticus, n. sp. (SGHN MA0914); D, dorsal view; E, lateral view. Parallel lines indicate superficial wear. Scale bar: 10 cm.