PHOCIDAE GEN. & SP. INDET.
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publication ID |
https://doi.org/ 10.1093/zoolinnean/zlaa075 |
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DOI |
https://doi.org/10.5281/zenodo.10541485 |
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persistent identifier |
https://treatment.plazi.org/id/C15287FE-FFB2-7109-87C6-F9401A43F904 |
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treatment provided by |
Felipe |
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scientific name |
PHOCIDAE GEN. & SP. INDET. |
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PHOCIDAE GEN. & SP. INDET. View in CoL
Referred specimens: NMV P42523, metatarsal V, collected by J. Dixon; NMV P215759, metatarsal V, collected by D. Rawlings, 2002 ( Fig. 5 View Figure 5 ). NMV P240711, partial interorbital region of cranium, collected by B. S. J. Francischelli, 2013 ( Fig. 6 View Figure 6 ). NMV P41759 partial sacrum collected by C. Macrae, 1980 ( Fig. 7 View Figure 7 ). NMV P160433 eight articulated thoracic vertebrae and five ribs, collected by T. Flannery c. 1975 ( Figs 8–10 View Figure 8 View Figure 9 View Figure 10 ).
D e s c r i p t i o n: N M V P2 1 5 7 5 9 a n d N M V P 4 2 5 2 3 ( Fig. 5 View Figure 5 ) are both identified as fifth metatarsals due to the irregular, asymmetrical, transversely flattened proximal end. NMV P215759 is a left metatarsal V and NMV P42523 is a right metatarsal V, both lacking the distal articular surfaces ( Fig. 5 View Figure 5 ). The absence of the distal articular surface may represent an immature condition. However, the majority of postcrania of mature phocids (based on cranial fusion and dental eruption) is usually unfused (pers. obsv.). Both specimens are identified as pinnipeds, based on a dorsoventrally expanded proximal end [e.g. Monachus monachus (Hermann, 1779) NHMUK 1958.11.26.1, Phoca sp. NHMUK 1951.3.2.3 and Arctocephalus sp. NMV C 33579]. Both NMV P215759 and NMV P42523 are referred to Phocidae due to the shaft being more rounded (not dorsoventrally flattened) proximally approaching the base and having a plantar tubercle that (in dorsal view) is less than 90° proximal from the proximal– distal plane. The lateral surface of the proximal end is mostly orientated laterally (similar to phocids, e.g. Hydrurga leptonyx NMV C 23614 or Homiphoca capensis: Hendey 1972 ), thus differing from the otariid condition ( Arctocephalus sp. NMV C33579) where the lateral surface of the base is deflected to face proximally. A slight depression on the medial surface of the base, directly medial to the plantar tubercle, is present in both specimens. In addition, there is a shallow fossa present on the lateral surface of the proximal end on the ventral side for both specimens. NMV P42523 is larger than NMV P215759 (Supporting Information, Appendix S2) and has a more ventrally developed proximal end.
NMV P240711 ( Fig. 6 View Figure 6 ) is the interorbital region of a phocid cranium. The nasal bones are inserted medially between the frontal bones, and the lack of a supraorbital process is diagnostic for Phocidae ( King, 1983a) . The posterior extent of the nasal bone is preserved, along with an anterior section of the frontals. A small portion of cribriform plate and nasal turbinates of the ethmoid are preserved on the posteroventral surface; with a small section of the lateral interorbital region preserved on the dorsolateral surface of the frontal bone ( Fig. 6 View Figure 6 ). The interorbital region must have been narrow relative to most other phocids (excluding phocins), based on the posterior tapering of the frontal bones.
NMV P41759 ( Fig. 7 View Figure 7 ) represents the anterior portion of the body of a sacrum, with partially incomplete sacral wings. The cranial articular surface and sacral crests are missing. Identified as a phocid due to sacral wings that are orientated dorsoventrally and laterally flared. Referral to Phocini can be excluded as the sacral wings are not orientated anteriorly [e.g. Phoca vitulina Linnaeus, 1758 NMV P 27683 and Pagophilus groenlandicus (Erxleben, 1777) USNM 21532]. The dorsoventral orientation of the sacral wings is consistent across all other phocids. The promontory appears to be ovoid in shape (rather than spherical), but this may be due to the incomplete preservation of the dorsal surface. In dorsal view, the sacral foramina appear to be anteroposteriorly elongated.The auricular surface of the sacral wing appears to be concave and forms a fossa. This auricular fossa is present in most phocids and odobenids, but not in otariids.
NMV P160433 ( Figs 8–10 View Figure 8 View Figure 9 View Figure 10 ) represents an articulated thoracic vertebral column, with eight thoracic vertebrae, four right and two left ribs preserved. The preserved thoracic vertebrae represent T7–T14, based on the identification of the fifth vertebra from the anterior end of the column (T11) as the anticlinal vertebra.
Overall, the column is better preserved on the right lateral side, with the posterior vertebrae being the most complete. The column is eroded on the left posterolateral side. Most of T7 and T8 are missing. Both T9 and T12 are missing a large portion of the body on the left side. The spinous processes of all vertebrae, except T11 and T12, are not preserved, with T11 being the most complete. T11 (the anticlinal vertebrae) and T14 are the most complete vertebrae. While the entire column is articulated, it is contorted both mediolaterally and dorsoventrally relative to anatomical position. Descriptions and comparisons will be from the more complete right side and limited to pre-anticlinal (T7–T10, Fig. 10A–C View Figure 10 ), anticlinal (T11, Fig. 10D View Figure 10 ) and post-anticlinal (T12–T14, Fig. 10E–F View Figure 10 ).
The ribs of T9 and T10 are in articulation ( Fig. 10A View Figure 10 ), with the heads situated within the anterior costal fovea and the posterior costal fovea ( Fig. 10C View Figure 10 ). Due to dorsal displacement of the ribs, the tubercles are not articulated with the costal fovea of the transverse process. The tubercle is not preserved on rib 9. The transverse processes of T8–T10 are laterally separated from the anterior articular processes, supporting their identification as pre-anticlinal. On the transverse process, the mamillary process (preserved on T9) is clearly reduced, and the accessory process (preserved on T10) is underdeveloped, when contrasted to thoracic vertebrae later in the series. The posterior articular process on T7–T10 faces ventrally.
The anticlinal vertebra (T11) has an anterior articular process that contacts the anteromedial border of the mamillary process ( Fig. 10B View Figure 10 ). The mamillary process projects anteriorly ( Fig. 10D View Figure 10 ). As the section of the transverse process posterior to the transverse fovea is not preserved, the condition of the accessory process is unknown.A rib is articulated to the anterior costal fovea, and the body of T10 appears to be missing a posterior costal fovea ( Fig. 10C View Figure 10 ). The anterior and posterior borders of the spinous process are nearly vertical. The posterior articular process faces ventrolaterally.
The anterior articular process for the postanticlinal vertebrae (T12–T14) are dorsomedially facing. This results in the anterior portion being more open than the more anterior thoracic vertebrae. The mammillary process becomes more developed moving down the column, with little separation from the anterior articular process in T13 and T14. None of the post-anticlinal vertebrae have ribs articulated or preserved. While the transverse fovea is present on T13, it is completely absent on T14 ( Fig. 10E View Figure 10 ). The accessory process is complete on both T13 and T14, but is relatively larger on T13 ( Fig. 10F View Figure 10 ). The accessory processes of both these vertebrae appear to be bifurcated, with a lateral and posterior facing tubercle. In ventral view, the posterior end of the body appears to be narrower than the anterior end. The posterior articular processes of the post-anticlinal thoracic vertebrae are ventrolaterally facing.
Several differences between representatives of Otariidae ( Arctocephalus NMVC 33579and Callorhinus USNM 49439) and Phocidae ( Phoca NMV C 27683 and Neomonachus USNM 22543) support referral of NMV P160433 to Phocidae . The accessory process of the post-anticlinal thoracic vertebrae is elongate, ‘pronged’ and well separated from the transverse process, similar to Phoca . This contrasts with the thin and reduced accessory process seen in otariids, such as Arctocephalus Cuvier, 1826 and Callorhinus Gray, 1859 . Lastly, the vertical condition of the spinous process on the anticlinal vertebrae of NMV P160433 appears to be most similar to phocids (NMV C27683, USNM 22543), which have a much steeper angle than otariids (NMV C33579, USNM49439) and odobenids (USNM396932), which have a shallower angle.
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.