Dasyatis undetermined

Cicimurri, David J. & Knight, James L., 2019, Late Eocene (Priabonian) elasmobranchs from the Dry Branch Formation (Barnwell Group) of Aiken County, South Carolina, USA, PaleoBios 36, pp. 1-31 : 18

DASYATIS SP. CF. D. TRICUSPIDATUS CASIER 1946

( FIG. 6I–P )

Referred specimens —SC2013.38.41, tooth; SC2013.38.42, male tooth; SC2013.38.43, male tooth; SC2013.38.44, six teeth.

Remarks —Nine large Dasyatis teeth are characteristic in their lack of enameloid ornamentation, a feature that readily distinguishes them from most other species that have been reported from Eocene strata (Ward 1979b, Noubhani and Cappetta 1997). The intersection of the transverse crest with a sagittal lingual crest results in a tripartite division of the crown (i.e., Fig. 6M ). This species was originally reported from lower Eocene strata of Belgium ( Casier 1946), and the taxon has subsequently been documented in middle Eocene strata of Europe ( Kemp et al. 1990, Van den Eeckhaut and de Schutter 2009).

Dasyatis exhibits gynandric heterodonty (male teeth differ from those of females), but the identification of male and female teeth of a fossil species may not be as clear cut as previously thought. Kajiura and Tricas (1996) found that male and female teeth of Dasyatis sabina (= Hypanus sabinus ) (Lesueur, 1824) may be nearly indistinguishable from each other, with both sexes having low-crowned teeth. However, as mating season approaches, male teeth exhibit a transition ( Fig. 6K ) to taller, highly cuspidate crowns that are effective at grasping pectoral fins of females during copulation ( Kajiura et al. 2000). Assuming this phenomenon was developed in Eocene fossil species, isolated low-crowned teeth ( Fig. 6M–P ) in the Dry Branch sample could belong to males or females, whereas high-crowned cuspidate teeth belonged to males ( Fig. 6I–J ).

Figures

Figure 6. Batoid teeth from the Dry Branch Formation (Priabonian) of Aiken County, South Carolina. A–D. Rhinobatos sp. Tooth in occlusal (A), labial (B), profile (C), and basal (D) views, SC2013.38.45. E–H. Rhynchobatus sp. cf. Rhy. pristinus. Tooth in occlusal (E), labial (F), profile (G), and basal (H) views, SC2013.38.46. I–P. Dasyatis sp. cf. D. tricuspidatus. Male anterior tooth in labial (I) and distal (J) views, SC2013.38.42. Tooth in labial (K) and occlusal (L) views, SC2013.38.43. Tooth in occlusal (M), labial (N), profile (O), and basal (P) views, SC2013.38.41. Q–Y. Dasyatis sp. SC2013.38.49. Male anterior tooth in labial (Q) and distal (R) views. Tooth in occlusal (S) view, SC2013.38.55. Tooth in occlusal (T), labial (U), and profile (V) views, SC2013.38.52. Tooth in occlusal (W), labial (X), and profile (Y) views, SC2013.38.53. Labial at top in A, D, E, H, L, M, P, S–T, W; at left in C, G, J, O, R, V, Y. Scale bars=1 mm.