Protanago nonsector Schwarzhans, Stringer & Takeuchi 2024

Protanago nonsector (Nolf & Stringer, 2003) Fig. 24A–D Ariosoma nonsector Nolf & Stringer, 2003: 7. Material examined UNITED STATES OF AMERICA – Mississippi • 2 sagittae; Catahoula Formation; MMNS VP-8200.3 (Fig. 24A–B), MMNS VP-8713 (Fig. 24C–D). Description The sagitta outline is primarily oval (sensu Smale et al. 1995; also Nolf & Stringer 2003) due to the presence of a prominent dorsal dome (Fig. 24A, C), which increases the height of the otolith relative to its length. Height/length ratios are commonly 0.85. The margins are smooth and a posterodorsal concavity is common. The inner face is generally smooth and evenly convex, although some irregular depressions occur within the upper portion of the dorsal area. The sulcus is wide, slightly incised, and undivided, with no clearly defined ostium and cauda (Fig. 24C). The sulcus begins very near the anterior margin and extends approximately 85% the length of the inner face (Fig. 24A). The sulcus is filled with colliculum except for the backward curving ostial channel. No ventral furrow is present. The outer face is relatively smooth and convex (Fig. 24B, D), with the exception of an area near the posterior end, where a shallow and dorsoventrally oriented depression occurs. Remarks Protanago nonsector otoliths from the Catahoula Formation have several characteristics in common with Ariosoma as illustrated in Schwarzhans (2019a), but it differs in the lack of an S-shaped sulcus, which is considered to be a diagnostic and autapomorphic characteristic of Ariosoma (Schwarzhans et al. 2024). Protanago nonsector (previously reported as Ariosoma nonsector) otoliths are widely distributed across Paleogene sediments in the Gulf Coastal Plain, from Louisiana eastward into Georgia (Breard & Stringer 1995; Nolf 2013; Ebersole et al. 2019; Stringer et al. 2022a). This species was abundant in the upper Eocene (primarily Priabonian) Yazoo Clay in Louisiana, where it constituted 10.9% of the 5599 specimens available (Nolf & Stringer 2003), and it has also been identified in small numbers in the Eocene and Oligocene of Alabama (Ebersole et al. 2019, 2021). Protanago nonsector appears to be the only species of this genus recorded outside of North America, as it has been documented in Italy (Schwarzhans et al. 2024). Schwarzhans’ work on extant species of the family Congridae (Schwarzhans 2019b) indicates that careful review of Paleogene congrid otoliths is warranted. One additional Catahoula Formation specimen (MMNS VP-8713) exhibits the salient features of Protanago sp., but we cannot make a more accurate determination due to its poor preservation and small size (juvenile). It is possible that the otolith represents P. nonsector, but we cannot rule out the possibility that it belongs to a different, but closely related, species. The otolith is mentioned here for completeness.