PARALICHTHYIDAE REGAN, 1910

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 : 22-23

PARALICHTHYIDAE REGAN, 1910

GEN. ET SP. INDET.

FIG. 9L, M

Referred specimen (n=1) —SC2015.36.259.

Description —This tooth is thin, needle-like, and measures approximately 1.0 mm in total height. In labial view, the margins of the tooth are relatively straight but gradually taper to a sharp point. In mesial and distal views, the tooth has a conspicuous lingual curvature, with a uniformly convex labial margin and a concave lingual margin. The main body of the tooth lacks carinae, but short labial and lingual cutting edges occur at the apex. The apex is slightly upturned and labiolingually flared. The tooth lacks ornamentation, and the enameloid at the crown apex is flared, semi-translucent, and lighter in color than that of the remainder of the tooth. The tooth has a conical cross section, and the base has a circular outline, is thin-walled and bears a shallow pulpcavity.

Remarks —The combination of features occurring on SC2015.36.259 has also been observed by us on the teeth of Recent members of the Lepisosteidae (gars) and Paralichthyidae (large-tooth flounders). However, specimen SC2015.36.259 lacks finely striated enameloid ornamentation and has a more evenly convex labial edge when compared to any of the Recent gar teeth we examined. Our specimen, however, compares very well to the dentary incisors of a Recent Paralichthys lethostigma Jordan and Gilbert in Jordan and Meek, 1884 specimen we studied (MSC 42999), indicating that this tooth belongs to an Oligocene member of the Paralichthyidae . Extant Paralichthyidae is an extremely diverse family consisting of at least 14 genera and approximately 111 species ( Nelson et al. 2016). Unfortunately, the diversity within this family and our lack of Recent comparative material does not allow us to identify this tooth beyond the familial level. Nevertheless, Ebersole et al. (2021) recently confirmed two unspeciated, otolith-based paralichthyid genera ( Citharichthys and Syacium ) from the Rupelian Glendon Limestone Member of the Byram Formation in Washington County, Alabama. These occurrences show that members of the family were well-established in the nearby Gulf Coastal Plain of the USA during the Oligocene.

SCOMBRIFORMES RAFINESQUE, 1810b SCOMBROIDEI BLEEKER, 1859

TRICHIURIDAE RAFINESQUE, 1810b

TRICHIURINAE RAFINESQUE, 1810b

TRICHIURIDES WINKLER, 1874

TRICHIURIDES CF. T. SAGITTIDENS WINKLER, 1874 FIG. 9N, O

Type species — Trichiurides sagittidens, Winkler, 1874 ; Belgium, Eocene.

Referred specimens (n=2)—SC2007.36.210 ( Fig. 9O ), SC2015.29.185 ( Fig. 9N ).

Description —Our sample consists of two ablated laniary teeth. As preserved, specimen SC2015.29.185 consists of a laterally compressed crown and some of the peduncle. In labial view the crown apex has a low, subtriangular outline, and in posterior view the enameloid-covered labial and lingual faces are weakly convex. The enameloid is smooth at the apex but is not preserved on the remainder of the specimen. The anterior and posterior margins are formed into a smooth, continuous and bi-convex cutting edge, and a small barb is located towards the apex on the posterior edge. The peduncle consists of dentine and is cylindrical and slightly curved medio-posteriorly. In basal view the tooth has a circular outline and a medially located pulp cavity is visible. Specimen SC2007.36.210 consists of a minute but well preserved crown apex. The crown of this specimen is triangular but taller than that of SC 2015.29.185, and the cutting edges are straight to weakly concave. The enameloid is smooth and a posterior barb is conspicuous.

Remarks —The teeth in our sample clearly differ from the Ashley Formation Sphyraena spp. laniary teeth by having a highly laterally compressed enameloid apex and narrow, cylindrical neck. The overall morphology of these teeth, especially the size and shape of the posterior barb, is morphologically similar to Recent Trichiurus lepturus Linnaeus, 1758 (MSC 42592) laniary teeth, as well as to those of the Eocene Trichiurides sagittidens Winkler, 1874 (see Ebersole et al. 2019). Although the Ashley Formation teeth could belong to the latter taxon,we only tentatively refer them to this species due to their incomplete preservation. Nevertheless, these teeth represent the first Oligocene records of cutlassfish in 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.