Carcharhinus spp.

Jirapatrasilp, Parin, Cuny, Gilles, Kocsis, László, Sutcharit, Chirasak, Ngamnisai, Nom, Charoentitirat, Thasinee, Kumpitak, Satapat & Suraprasit, Kantapon, 2024, Mid-Holocene marine faunas from the Bangkok Clay deposits in Nakhon Nayok, the Central Plain of Thailand, ZooKeys 1202, pp. 1-110 : 1-110

Carcharhinus spp.

Figs 21 , 22

Referred material.

CUF - NKNY - 16.1 (Fig. 21 A – G ), CUF - NKNY - S 2 (Fig. 21 H – L ), CUF - NKNY - S 3 - 4, CUF - NKNY - S 3 - 8, CUF - NKNY - S 4 - 7 (5 lower teeth), CUF - NKNY - S 1 (Fig. 22 A – H ), CUF - NKNY - S 3 - 7 (two upper teeth).

Description.

The specimens CUF - NKNY - 16.1, CUF - NKNY - S 3 - 4, CUF - NKNY - S 3 - 8, and CUF - NKNY - S 4 - 7 display a narrow main cusp that is inclined lingually. Their labial face is flatter than the lingual one. The serrations are well-developed in the upper two-third of the cusp. The serrations appear to be very fine on the mesial and distal heels in CUF - NKNY - 16.1, CUF - NKNY - S 3 - 4, and CUF - NKNY - S 3 - 8, but the serrations are damaged in CUF - NKNY - S 4 - 7. The root is well preserved only in CUF - NKNY - S 3 - 4 and CUF - NKNY - S 3 - 8, both of which display a slightly arched base, a moderately bulged lingual face with a nutritive foramen in its centre in CUF - NKNY - S 3 - 4 and a faint nutritive groove in CUF - NKNY - S 3 - 4. The specimen CUF - NKNY - S 2 is asymmetric, with a mesial heel almost twice as elongated as the distal one and displays a sigmoid main cusp in labial or lingual view as well as in mesial or distal view, separated from the distal heel by a notch. The heels are serrated, but the main cusp is smooth. This tooth appears quite bulbous in mesial or distal view, being less compressed labio-lingually than the specimens described above. There is a well-developed nutritive groove on the root in lingual view, forming a basal notch in labial view.

A heavily worn tooth (CUF - NKNY - S 3 - 7) is better attributed to an upper tooth. The lingual and distal faces of the crown are strongly damaged and a part of the distal end of the root is missing. The serration is only preserved in the middle part of the mesial cutting edge and appears to be quite regular. The root has a basal face slightly arched with a well-developed nutritive groove on its lingual face, forming a notch at the base of the root in labial view.

Another upper tooth, CUF - NKNY - S 1, displays a crown with a quite coarse, irregular serration pattern nearly reaching the apex of the main cusp. The latter is bent lingually and slightly inclined distally. Its root shows a well-developed nutritive groove in lingual view, forming a notch at the base of the root in labial view. Apart from this notch, the base is almost straight.

Taxonomic remarks and comparisons.

Lower teeth of C. amblyrhynchos ( C. wheeleri in Garrick (1982): fig 51) display features similar to the specimen CUF - NKNY - 16.1. They are characterised by a narrow main cusp that displays serrations ending at mid-height. Some of the lower teeth of C. longimanus also have these morphological patterns, though their crown is often more robust and wider at their base ( Bass et al. 1973: pl. 17; Garrick 1982: fig. 70). Nevertheless, teeth very similar to the specimens CUF - NKNY - 16.1, CUF - NKNY - S 3 - 4, CUF - NKNY - S 3 - 8, and CUF - NKNY - S 4 - 7 from the Pliocene of Italy were attributed to C. longimanus ( Marsili 2007) .

The sigmoid crown of the specimen CUF - NKNY - S 2 is reminiscent of the posterior lower teeth of C. borneensis and C. tjutjot ( Voigt and Weber 2011) . The dentition attributed to C. dussumieri by Voigt and Weber (2011) belongs in fact to C. tjutjot ( White 2012) . A sigmoid cusp, when present, is less developed in C. sealei and C. sorrah ( Voigt and Weber 2011) , and the distal heel is coarsely serrated in C. coatesi ( White 2012) . The morphology of the crown recalls that of Rhizoprionodon , but in the latter genus, the distal heel is often more convex than in the specimen CUF - NKNY - S 2 ( Cappetta 2012: fig. 283; Carrillo-Briceño et al. 2015). This set of lower teeth is therefore attributed to the genus Carcharhinus but represents more than a single species, whereas the specimen CUF - NKNY - S 3 - 7 is poorly preserved. Moreover, the posterior part is only preserved in the specimen CUF - NKNY - S 1 and this does not allow us to reach the species-level identification.

There are 27 species of the genus Carcharhinus reported from the Southeast Asian region ( Froese and Pauly 2024), and at least 20 taxa were recorded in Thai waters ( Krajangdara et al. 2022) including all the ones mentioned above.

Glyphis Agassiz, 1843

Figures

Figure 21. Carcharhinid shark teeth - Carcharhinus spp. A – G specimen CUF - NKNY - 16.1 in A lingual B labial C mesial D distal and E, F apical views G close-ups of the serration on the upper part of the cusp mesial cutting edge in lingual view H – L specimen CUF - NKNY - S 2 in H labial I apical J lingual K mesial and L distal views.

Figure 22. Carcharhinid shark teeth - Carcharhinus sp. A – H specimen CUF - NKNY - S 1 in A lingual B labial C mesial D distal and E, F apical views G, H close-ups on the serration G at mid-height of the cusp mesial cutting-edge and H at the level of the distal heel and base of the cusp.