Sphyraena undetermined

Sphyraena sp. Fig. 25A–F Material examined UNITED STATES OF AMERICA – Mississippi • 609 isolated teeth; Catahoula Formation; MMNS VP-9048, SC 2013.28.531 to 28.536, SC 2013.28.537 (50 teeth), SC 2013.28.538 (8 teeth), SC 2013.28.539 (15 teeth), SC 2013.28.540 (7 teeth), SC 2013.28.541 to 28.544, SC 2013.28.545 (Fig. 25A–C), SC 2013.28.546 (20teeth), SC 2013.28.547 (5teeth), SC 2013.28.548 (2 teeth), SC 2013.28.549 (109 teeth), SC 2013.28.550 to 28.557, SC 2013.28.558 (Fig. 25D–F), SC 2013.28.559 (79 teeth), SC 2013.28.560 (35 teeth), SC 2013.28.561 (10 teeth), SC 2013.28.562 (12 teeth), SC 2013.28.563 (10 teeth), SC 2013.28.564 (226 teeth). Description Two tooth morphologies are represented in our sample. The first includes tall teeth measuring up to 12 mm in height. These teeth have a sinuous profile, with the labial margin formed into a sharp, smooth carina that extends from the tooth base to the crown apex (Fig. 25A). This carina is more convex along the basal one-half, after which it is posteriorly directed and may or may not have a slight vertical rise to the apex. The posterior margin is convex and thickest basally, but it thins apically. In profile this margin is straight to concave along the lower two-thirds, but apically it can be straight to weakly convex. The apex bears a diminutive posterior barb, and on some teeth this barb is represented only by a short anterior carina. Relatively pristine specimens exhibit vertical striations or wrinkling at the postero-basal surface. In anterior/posterior view, the tooth is straight to slightly medially curved (Fig. 25B). The basal attachment surface is weakly concave, and its outline is generally teardrop-shaped on smaller specimens and oval on larger specimens (Fig. 25C). Teeth of the second morphology are lanceolate and highly labio-lingually compressed (Fig. 25D). In anterior/posterior view, the crown is straight to weakly medially curved (Fig. 25E). The anterior and posterior margins are formed into sharp and smooth carinae that extend from the base to the apex. Well-preserved teeth show that the crown is covered with thin enameloid that can be striated basally, but enameloid largely remains only at the anterior and posterior carinae. The labial and lingual crown faces are weakly convex, but the basal portion of the lingual face is somewhat more convex. In basal view, the attachment surface is concave, and the outline is elliptical (Fig. 25F). There are two slightly differing morphotypes, with one being taller and antero-posteriorly narrower than the other. The taller teeth are more often medially curved, whereas the shorter teeth are rather straight. Additionally, the cutting edges of taller teeth are proportionally longer and the apex more pointed compared to the shorter and wider teeth. Remarks Based on extant specimens of Sphyraena barracuda (Walbaum, 1792) that we examined (SC 2018.3.1; MSC 43215), the tall teeth with an anterior carina and posterior apical barb are laniary teeth that were located at the anterior end of the premaxilla or dentary. The lanceolate specimens occurred within the cheek regions of the palatine or dentary. Ebersole et al. (2019) and Ballen (2020) have indicated that tooth morphologies among extant Sphyraenidae are taxonomically distinctive, but intraspecific variation is not well documented. There is no evidence contradicting our conclusion that various Catahoula Formation Sphyraena morphologies are conspecific. Regarding the laniary teeth, all the well-preserved specimens, from the smallest (3 mm in height) to the largest (12 mm) exhibit a smooth anterior cutting edge, diminutive postero-apical barb, and postero-basal vertical striations. Specimen SC 2018.3.1 also indicates that somewhat taller and narrower lanceolate specimens from the Catahoula Formation were from the anterior dentary, whereas the slightly shorter and wider teeth were located on the palatine. The Catahoula Formation sample includes teeth with and without striations and ridges, and we observed this phenomenon in the jaws of the extant Sphyraena spp. that we examined. Crown ornamentation therefore does not appear to be taxonomically significant. Santini et al. (2015) demonstrated the existence of three Sphyraena lineages by the late Eocene, and the age of the Catahoula Formation specimens is close to the timing of radiation of the S. obtusata Cuvier, 1829 and S. sphyraena (Linnaeus, 1758) species groups (with each group containing several species). Extant representatives of both species groups currently inhabit the Gulf of Mexico (Hoese & Moore 1998). Ballen (2020) presented a listing of fossil Sphyraena species, including several from the Oligocene. Sphyraena intermedia Bassani, 1889 and S. pannonica Weiler, 1938 were based on skeletal material that included crania, but neither author provided tooth descriptions. Sphyraena tyrolensis von Meyer, 1863 is known from a dentary and various isolated teeth. Although von Meyer (1863) mentioned the occurrence of basal striations on laniary teeth (“Fangzahn” therein), he did not mention the presence of an apical barb, and the laniary tooth of the figured specimen (pl. 50 figs 7–8) is broken apically. The remainder of the teeth along the ramus of this specimen are otherwise comparable to any species of Sphyraena. Ebersole et al. (2021) documented similar Sphyraena sp. dentary teeth from the Rupelian Byram Formation in Alabama, and Ebersole et al. (2024a) identified both laniary and dentary teeth from the Rupelian Red Bluff Clay in the same state. Leidy (1855) named S. major based on specimens recovered from the Ashley River of South Carolina. He did not provide a description of the teeth and only mentioned that the material was collected from the Ashley River. The fossils in question may have been derived from the Ashley Formation (Rupelian), but the source unit could be older or younger (see Albright et al. 2018). We refrain from making a species determination, because we cannot accurately compare the Catahoula Formation material to all the other named species due to the lack of described morphological features.