Dasyatidae

Cicimurri, David J., Ebersole, Jun A., Stringer, Gary L., Starnes, James E. & Phillips, George E., 2025, Late Oligocene fishes (Chondrichthyes and Osteichthyes) from the Catahoula Formation in Wayne County, Mississippi, USA, European Journal of Taxonomy 984 (1), pp. 1-131 : 63-64

Dasyatidae gen. et sp. indet.

18K–T

Material examined

UNITED STATES OF AMERICA – Mississippi • 3 isolated teeth; Catahoula Formation ; SC 2013.28.429 ( Fig. 18K–O ), SC 2013.28.430 ( Fig. 18P–T ), SC 2013.28.479 .

Description

The large dasyatid teeth are wider (mesio-distally) than long (labio-lingually). Specimen SC 2013.28.429 measures 4 mm wide and 3 mm long, and SC 2013.28.430 measures 3 mm and 2.5 mm, respectively, in these dimensions. In occlusal view, the crown is divided into labial and lingual parts by a sharp transverse crest ( Fig. 18K, P ) that does not reach the mesial and distal base of the crown ( Fig. 18N, S ). The lingual side of the crown is more expansive, and its margin is strongly convex but may be somewhat squared. The labial margin is weakly to moderately convex. The labial face of S2013.28.429 is concave medially but otherwise weakly convex mesio-distally, whereas SC 2013.28.430 has a more uniformly convex labial face. In profile view, the labial crown foot is highly convex, but apically the surface is relatively flat. Both specimens have a broad but low, medially located, and rounded ridge that divides the lingual face into concave mesial and distal parts ( Fig. 18M, R ). This ridge intersects with the cusp apex, which is flat on both specimens due to in vivo wear. The worn occlusal surface of both specimens exhibits an elliptical to D-shaped outline and the internal dentine is visible ( Fig. 18K, P ). In labial view, the cusp on SC 2013.28.429 is more clearly distinguished ( Fig. 18L ), and in profile view it appears to be distally curved ( Fig. 18N ). The crown of SC 2013.28.430 is more extensively worn and the nature of the cusp is unknown. The crown enameloid is smooth, although SC 2013.28.430 exhibits two unusual, indistinct node-like features on the labial face. The crown extends well beyond the root labially and laterally ( Fig. 18R–S ). The root of both specimens is ablated, but that on SC 2013.28.430 is low and completely divided into two lobes by a nutritive groove ( Fig. 18T ). In basal view, a foramen is located within the groove, and root lobes have a crescent-shaped outline. The basal view also makes evident how small the root is compared to the size of the crown, that enameloid extends onto the underside of the crown (especially labially), and the root lobes extend beyond the lingual crown margin ( Fig. 18O, T ).

Remarks

Specimens SC 2013.28.429 and SC 2013.28.430 are of large size and have unornamented enameloid, which clearly distinguishes them from the teeth of Hypanus ? heterodontus sp. nov. that also occur in the Catahoula Formation (see above). Specimen SC 2013.28.429 is highly ablated but is comparable to, although smaller than, SC 2013.28.430. Cicimurri & Knight (2009) reported a similarly large and smooth-crowned dasyatoid tooth morphology from the Chattian Chandler Bridge Formation of South Carolina, which Reinecke et al. (2014) proposed as a possible representative of Taeniurops . However, teeth of extant Taeniurops grabatus exhibit a conspicuous labial depression not observed on the U.S. Oligocene specimens. Additionally, teeth of extant Dasyatis pastinaca ( Linnaeus, 1758) and Neotrygon orientalis Last, White & Séret, 2016 have smooth crowns and superficially similar tooth shapes, further complicating our ability to accurately identify the Catahoula Formation specimens (see Reinecke et al. 2023). Specimens SC 2013.28.429 and SC 2013.28.430 are reminiscent of Middle Miocene specimens from France that Cappetta named Dasyatis serralheiroi ( Cappetta 1970: 92–95, pl. 20 figs 1–16. However, we hesitate to identify the material beyond the family level due to the limited comparative material available to us.

Figures

Fig. 18. Hypanus? heterodontus sp. nov. (A–J) and Dasyatidae gen. et sp. indet. (K–T), teeth. A–E. SC2013.28.475, Hypanus? heterodontus, tooth. A. Occlusal view. B. Labial view. C. Lingual view. D. Profile view. E. Basal view. F–J. SC2013.28.470, Hypanus? heterodontus, tooth. F. Occlusal view. G. Labial view. H. Lingual view. I. Profile view. J. Basal view. K–O. SC2013.28.429, Dasyatidae gen. et sp. indet., tooth. K. Occlusal view. L. Labial view. M. Lingual view. N. Profile view. O. Basal view. P–T. SC2013.28.430, Dasyatidae gen. et sp. indet., tooth. P. Occlusal view. Q. Labial view. R. Oro-lingual view. S. Profile view. T. Basal view. Scale bars = 2 mm.