Beneziphius cetariensis, Miján & Louwye & Lambert, 2017
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publication ID |
https://doi.org/ 10.4202/app.00309.2016 |
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persistent identifier |
https://treatment.plazi.org/id/038D87D7-C67A-FF9A-417A-FC49FA7EFBC0 |
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treatment provided by |
Felipe |
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scientific name |
Beneziphius cetariensis |
| status |
sp. nov. |
Beneziphius cetariensis sp. nov.
Figs. 1–4 View Fig View Fig View Fig View Fig .
Etymology: From Latin cetarius, fishmonger; in reference to the Galician city Cedeira (Latin Cetaria), where many fishermen involved in the discovery of offshore fossil ziphiids come from.
Holotype: SGHNMF MA0953, a partial skull including rostrum, facial area (without the supraorbital regions) and part of the vertex.
Type locality: A Selva fishing ground, depth of approximately 500 m, off the Galician coast; approximate geographic coordinates: 44°10’ N, 8°40’ W.
Type horizon: Poorly constrained, middle Miocene to early Pliocene (see remarks below).
Diagnosis.— Beneziphius cetariensis differs from B. brevirostris in: the larger size; the rostrum being proportionally longer; the premaxillae being longer than the maxillae at the apex of the rostrum; the left premaxillary sac fossa being transversely concave; and the ascending process of the premaxilla reaching the vertical, with the posterodorsal portion of the ascending process slightly overhanging the bony nares.
Description.—The nearly complete rostrum of this mediumsize ziphiid is relatively short, less than 60% of the estimated condylobasal length (see Table 1 for cranial dimensions), but proportionally longer than in Beneziphius brevirostris (ratio between width of premaxillary sac fossae and length of maxilla on rostrum estimated to 0.33 and 0.38 in the holotypes of B. cetariensis and B. brevirostris , respectively). Transverse sections of the rostrum are higher than wide for the anterior half of rostrum length. The vertex of the skull is proportionally elevated and somewhat anterodorsally projected.
Premaxilla: Anteriorly, the premaxilla is longer than the maxilla, forming alone the tip of the rostrum for more than 50 mm ( Figs. 1 View Fig , 2 View Fig ), a difference with Beneziphius brevirostris and Choneziphius planirostris (both latter taxa having the maxilla reaching the end of the rostrum). In this anterior region, the lateral surface of the bone is pierced by a large foramen opening forwards. The thickened premaxillae are sutured to each other above a large part of the mesorostral groove; their suture is ankylosed for most of its extent ( Fig. 1A View Fig ). In lateral view, the maximum elevation of the premaxillae is approximately at half the rostrum length. The premaxillae are separated anteriorly for 120 mm, revealing an open mesorostral groove (transverse diameter 12 mm) as observed in B. brevirostris , Choneziphius leidyi , Messapicetus , and Ziphirostrum . Backwards, the premaxillae diverge abruptly 30 mm anterior to the premaxillary foramina, forming the U-shaped anterior limit of the moderately excavated prenarial basin. The prenarial basin is shallower than in Ziphirostrum marginatum , with a dorsoventral extent closer to Z. turniense and B. brevirostris .
The large premaxillary foramen is distinctly anterior to the level of the lost antorbital notch, at the bottom of the thick maxillary lateral wall of the prenarial basin; the foramen is followed posteriorly by a wide and deep groove probably partly homologous to the posterolateral sulcus), which widens progressively backwards towards the anterior part of the corresponding premaxillary sac fossa. The right groove widens more than the left, leading to a wider right premaxillary sac fossa (ratio between maximum widths of left and right fossae 0.69). In addition to asymmetric dimensions, the left fossa is transversely concave (but not as much as in Choneziphius spp. ), whereas the right fossa is barely excavated. As in B. brevirostris , the lateral margin of the left premaxillary sac fossa overhangs somewhat the adjoining maxilla, a condition not as developed as in Choneziphius , Globicetus , Imocetus , Izikoziphius , and Ziphius . The two premaxillary sac fossae are widely separated medially, a major difference with Choneziphius spp.
In anterior view, the right ascending process of the premaxilla is markedly transversely constricted ( Fig. 3 View Fig ). The better-preserved right premaxillary crest is thin and nearly rectilinear in dorsal view ( Figs. 1A View Fig , 4 View Fig ); it is directed anterolaterally and slightly laterally in its outer portion. This outer portion of the crest overhangs the ascending process, a condition related to the vertex being projected anterodorsally, more so than in B. brevirostris and Z. marginatum . Due to some degree of wear in the vertex region, the presence/ absence of a contact between the posterior projection of the premaxilla and the frontal is difficult to assess.
Maxilla: The maxilla is visible in dorsal view for most of the length of the rostrum ( Fig. 1A View Fig ). This dorsal exposure increases progressively along the posterior two thirds of the rostrum. The oblique dorsolateral surface is slightly transversely concave. Although partly worn, multiple excrescences cover this surface, probably for the origin of rostral muscles in a way similar to Beneziphius brevirostris and Choneziphius spp. (though with a high intraspecific variation in C. planirostris ; Lambert 2005; Bianucci et al. 2013). From a level shortly anterior to the premaxillary foramen, the lateral margin of the rostrum raises posterodorsolaterally, increasing the depth of the prenarial basin. At this level, the dorsomedial surface of the maxilla is barely transversely convex, much less than in Z. marginatum .
A posterior dorsal infraorbital foramen is preserved on the left side, partly overhung by the lateral margin of the left premaxillary sac fossa. Posterior to the ascending process of the premaxilla, the maxilla raises towards the vertex as a high wall; in dorsal view, this wall is much longer anteroposteriorly than in some species with a less anterodorsally projected vertex (e.g., C. planirostris and Z. marginatum ). The minimum distance between the maxillae across the elevated vertex is lower than the maximum width of the nasals ( Fig. 4 View Fig ).
The ventrolaterally facing alveolar groove is distinct and continuous in the maxilla until a level about 55 mm anterior to the premaxillary foramen ( Figs. 1B View Fig , 2 View Fig ). Although the surface of the alveolar groove is lightly worn, undulations correspond to highly reduced alveoli. It is nevertheless not possible to determine the upper tooth count. Shallow alveoli are similarly observed in B. brevirostris , likely corresponding to small, non-functional teeth. At half the rostrum length, a foramen pierces the maxilla just dorsal to the alveolar groove; it is followed anteriorly by a deep sulcus.
Ventrally, a large foramen is present in the maxilla at the anterior end of the ventral exposure of the vomer ( Fig. 2B View Fig ). Additionally, a major palatine foramen is anteromedial to each pterygoid sinus fossa.
Vomer: On the ventral surface of the rostrum, the vomer is exposed as a thin stripe (maximum breadth 4.5 mm) for a length of 88 mm between the maxillae. At the level of the pterygoid sinus fossae, the exposure of the vomer between the palatines is artificially increased due to heavy wear of the palate region.
Nasal: In dorsal view, the joined nasals form a large, roughly triangular area of the vertex ( Figs. 1A View Fig , 4 View Fig ). Each nasal is anteromedially pointed and longer than transversely wide. The anterior tip of the nasal nearly reaches the same anteroposterior level as the right premaxillary crest, only being slightly posterior. The left nasal is longitudinally shorter than the right; the suture with the corresponding frontal is shifted forwards compared to the right side. In addition, the suture between nasals is shifted to the left and directed anterolaterally towards the left side. The dorsal surface of the nasals is depressed medially and the top of the right nasal is markedly higher than the top of the left nasal (both features best seen in anterior view; Fig. 3 View Fig ). The posterolateral margin of the nasal displays a broad contact with the corresponding premaxillary crest.
Frontal: On the vertex, only the anteriormost portion of the frontals, along the nasals, is preserved. Therefore, we cannot assess the longitudinal extent of the frontals and the location of the frontal-supraoccipital suture. Considering the preserved maxillae along the lateral walls of the vertex, the minimum width of each frontal was much smaller than the maximum width of each nasal ( Fig. 4 View Fig ).
Pterygoid/palatine: The palatine-maxilla suture could not be observed on the partly worn palate, and the palatine is only detected as a slightly thickened region anterior to the pterygoid. Part of the pterygoid-palatine suture is visible, turning along the anterolateral margin of the pterygoid sinus fossa in an anteromedial and then posteromedial direction
Fig. 1B View Fig , 2 View Fig ). The maximum longitudinal distance between the anterior margin of the pterygoid sinus fossa and the pterygoid-palatine suture is 15 mm. The wide pterygoid sinus fossa extends anteriorly to the level of the premaxillary foramen (distinctly anterior to the level of the antorbital notch).
Remarks.—Unfortunately no sediment was preserved with the specimen SGHNMF MA0953 (recovered by trawling); no micropalaeontological analysis could thus be performed. This specimen was found in the same locality as part of the ziphiids described by Bianucci et al. (2013), in the area of Ortegal Spur; specimens of Choneziphius leidyi and Tusciziphius atlanticus originate from the same area and possibly from the same layers. The stratigraphic context of this deep submarine region is unfortunately poorly known, with Oligo-Miocene marl and conglomerate irregularly covered with Plio-Pleistocene deposits. Associated with phosphorite pebbles, the skulls may correspond to a late early to middle Miocene phosphogenesis episode Bianucci et al. 2013). However, specimens from a deep-sea locality off Portugal sharing several ziphiid species with the Galician assemblage were recently biostratigraphically dated from the latest Messinian to early Pliocene Antunes et al. 2015). Furthermore, though the type species of Beneziphius is dated from the late middle Miocene (early to mid-Serravallian, Antwerp area, Belgium; this study), other species of the genera Choneziphius and Tusciziphius are reported from younger, late Miocene and early Pliocene deposits from Belgium and Italy ( Bianucci 1997; Lambert 2005). Therefore, it seems more careful to provisionally retain a broad, middle Miocene to early Pliocene stratigraphic range for the Galician ziphiids of Ortegal Spur, pending a much-needed biostratigraphical or radiometric dating of specimens.
Stratigraphic and geographic range.— Type locality only.
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