Scomberomorus, DE LACEPEDE, 1801

Cicimurri, David J., Knight, James L. & Ebersole, Jun A., 2022, Early Oligocene (Rupelian) fishes (Chondrichthyes, Osteichthyes) from the Ashley Formation (Cooper Group) of South Carolina, USA, PaleoBios 39 (1), pp. 1-38 : 23-24

SCOMBEROMORUS DE LACEPÈDE, 1801 SCOMBEROMORUS SP.

FIG. 9S–U

Type species — Scomber regalis, Bloch, 1793 ; Recent.

Referred specimens (n=5) —SC2007.36.135, SC2007.36.216, SC2015.29.214, SC2015.29.221 ( Fig. 9S–U ).

Description —The teeth are lanceolate and higher than wide. The anterior and posterior margins are formed into smooth, continuous cutting edges that are straight basally but become convex apically, culminating in a pointed apex. These carinae asymmetrically divide the crown such that the lingual face is much larger than the labial face, a characteristic that is particularly visible in basal view. The enameloid is smooth and typically only preserved at the carinae. The labial face is flat to weakly convex, and the lingual face is very convex, and the crown may be medially curved. A basal pulp cavity is large but shallow.

Remarks —These teeth differ from those of Palaeocybium sp. and non-laniary teeth of Sphyraena spp. from the Ashley Formation (see above) by being taller and narrower antero-posteriorly, and they have labial and lingual faces of conspicuously unequal thickness. In contrast, both Sphyraena spp. non-laniary teeth and Palaeocybium sp. teeth are very wide labio-lingually,

with equally convex labial and lingual faces ( Ebersole et al. 2019). Additionally, Sphyraena spp. non-laniary teeth typically lack medial curvature as observed on these Scomberomorus sp. teeth.

The Ashley Formation specimens are reminiscent of teeth of Scomberomorus bleekeri ( Storms, 1892) , a taxon known from the Claibornian (Ypresian to Bartonian) and into the Jacksonian (Priabonian) of Alabama ( Ebersole et al. 2019, JAE unpublished data). The teeth differ from those of Eocene Scomberomorus stormsi ( Leriche, 1905) by being wider antero-posteriorly and having convex carinae (as opposed to nearly parallel on the lower half). One specimen in our sample, SC2007.36.216, measures less than 1 mm in overall height. However, because it is morphologically similar to the other Scomberomorus teeth in our sample, we interpret this specimen as belonging to an immature individual. Although the Ashley Formation specimens compare favorably to Eocene S. bleekeri , they are herein not speciated because it is unclear if S. bleekeri persisted into the Oligocene. Nevertheless, the Ashley Formation specimens represent the first record of Scomberomorus from the Oligocene of South Carolina.

Figures

Figure 9. Teleost teeth from the Givhans Ferry Member, Ashley Formation (Rupelian), Dorchester County, South Carolina. A, B. Albula sp. tooth, SC2015.29.204 in profile (A) and basal (B) views. C, D. Osteoglossidae indet. tooth, SC2015.29.218 in profile (C) and basal (D) views. E–H. Sphyraena sp. cheek tooth, SC2007.36.120 in close-up showing serrations (E), labial (F), carinal (G), and basal (H) views. I–K. Sphyraena sp. laniary tooth, SC2007.36.190 in labial (I), basal (J), and anterior (K) views. L, M. Paralichthyidae indet. tooth, SC2007.36.259 in labial (L) and distal (M) views. N. Trichiurides cf. T. sagittidens laniary tooth, SC2015.29.185 in profile view. O. Trichiurides cf. T. sagittidens laniary tooth, SC2007.36.210 in profile view. P–R. Palaeocybium sp. tooth, SC2007.36.122 in labial (P), carinal (Q), and basal (R) views. S–U. Scomberomorus sp. tooth, SC2015.29.221 in lingual (S), carinal (T), and basal (U) views. Scale bar=0.4 mm in O; 0.5 mm in C, D, L–N, S–U; 1 mm in A, B, I–K; 3 mm in E–H, P–R.