Wellerodus priscus Eastman, 1899
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publication ID |
https://doi.org/ 10.4202/app.2012.0101 |
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persistent identifier |
https://treatment.plazi.org/id/6B2D1521-EF6F-1224-FCED-14EAB7C55A03 |
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treatment provided by |
Felipe |
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scientific name |
Wellerodus priscus Eastman, 1899 |
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Wellerodus priscus Eastman, 1899
Fig. 7 View Fig ; SOM 3.
Material.— NYSM 17773–17779 About NYSM , juvenile teeth from Plattekill Formation , Cairo quarry, Greene County, New York, USA .
Description.—The teeth are diplodont with one intermediate cusp. When compared to the main cusps, the intermediate cusp appears to be bigger than observed in previously described specimens of W. priscus ( Turner 1997: figs. 1, 5; Ginter et al. 2010: fig. 25C–H). Absence of the intermediate cusp in certain specimens appears to be the result of abrasion ( Fig. 7B View Fig ). The teeth are small and of approximately similar size. The base ranges in width from 1.0 to 2.3 mm and in length from 0.4 to 1.3 mm. The cusps are round in cross-section, but the minor cusps are occasionally compressed front to back. Only the main cusps have a cutting edge on the mesial and external side. A notch is seen in the cutting edge at the junction between the principal and the intermediate cusps.A comparison of cusp shapes is not easy because many specimens are damaged. In NYSM 17775 ( Fig. 7A View Fig ), the minor cusp is sigmoid, and the major cusp is straighter. The minor cusp diverges more strongly from the occlusal axis. The cusps are characterized by few cristae on the labial side. They originate at the level of the base of the intermediate cusp and begin to curve mesially at the mid-height of the principal cusps, then curve again towards the apex of the cusp. The cristae are straight on the labial side of the right cusp of NYSM 17775. The intermediate cusp shows two straight cristae that start at the cutting edge level and join at the cusp’s apex. The lingual side of the cusps is smooth.
The tooth base is oval, lingually oriented, and has a well-developed oval button ( Fig. 7B View Fig 2, C 2 View Fig ). A single notch is found on the lingual margin, except in NYSM 17778 where two are present. The base is arched in lingual view and expands laterally beyond the width of the principal cusp base. The base can narrow under the area of cusp insertion. The base can be asymmetrical, in which case it is more laterally extended in the direction opposite the apex of the minor cusp. In lateral view, the base has a labial concavity that would seem to fit into the articular button of the next tooth in the series. In some cases, a slight labial extension is present. Specimen NYSM 17779 differs from the other specimens in that the orientation of its base is not clearly defined ( Fig. 7D View Fig ).The orientation is inferred from the position of the marginal notch and the cristae which, based on NYSM 17775 ( Fig. 7A View Fig 3 View Fig ), should be labially orient- ed. The cusps are flattened and triangular, and the size of the intermediate one is similar to the main cusps.
Histology.—Based on the similarity of general morphology, Wellerodus priscus is expected to share the same histological structure as Antarctilamna prisca in possessing an internal layer of trabecular dentine with an outer layer of orthodentine at the crown level ( Hampe and Long 1999). Micro-tomodensitometry of W. priscus teeth did not provide histological detail, but a few canals are apparent within the base ( Fig. 7E View Fig 1 View Fig , F). The cusps are characterized by one main canal ( Fig. 7G View Fig 1 View Fig ) that connects to a more complex network located in the base underneath the articular button. In NYSM 17776, circulation at the level of the articular button is ensured by two main canals
Fig. 7E View Fig 2 View Fig , F 1 View Fig ) that open in the lingual side of the depression seen underneath the base. Only one such canal was noted in A. prisca ( Hampe and Long 1999) . In situ, the basal depression would have been connected to the articular button of the following tooth in a tooth family, thus putting in contact the internal canals of one tooth with the straight canals crossing underneath the articular button of the following tooth ( Fig. 7G View Fig 2 View Fig ; see also SOM 3). The lingual side of the base is crossed by smaller canals leading directly to the depression; there are no similar canals on the labial side of the base ( Fig. 7F View Fig 2 View Fig ).
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