Trichiurus oshosunensis White, 1926

Ebersole, Jun A., Cicimurri, David J. & Stringer, Gary L., 2019, Taxonomy and biostratigraphy of the elasmobranchs and bony fishes (Chondrichthyes and Osteichthyes) of the lower-to-middle Eocene (Ypresian to Bartonian) Claiborne Group in Alabama, USA, including an analysis of otoliths, European Journal of Taxonomy 585, pp. 1-274 : 172-173

Trichiurus oshosunensis White, 1926

Fig. 63 J–R

Trichiurus oshosunensis White, 1926: 65–66 , pl. 16, figs 14–20.

Sphyraena sp. – Maisch et al. 2016: 8, fig. 2, 19–22.

Trichiurides oshoshunensis – Arambourg 1952: 264 , pl. 35, figs 47–52.

Trichiurides sp. – Thurmond & Jones 1981: 106, fig. 50.

Material examined

UNITED STATES OF AMERICA – Alabama • 33 isolated teeth; Claiborne Group ; ALMNH PV1985.87.2, ALMNH PV1985.87.3, MSC 37146, MSC 37173.1 – 2 , MSC 37308.1 – 7 , MSC 37657, MSC 37666.1 – 2 , MSC 38437, MSC 38438, MSC 38489.1 – 7 , NJSM 24042 , NJSM 24319 , SC 2012.47.97, SC 2012.47.98 (5 specimens), WSU CC 548 .

Description

Teeth measuring over 1.0 cm in height. In profile, basal one-third of tooth vertical, but then sharply curved posteriorly; apical portion anteriorly directed. Anterior margin formed into sharp carina, whereas posterior margin uniformly convex. Enameloid generally not preserved, but small apical posterior barb sometimes present. Tooth base with teardrop-shaped outline, shallow pulp cavity may be present.

Remarks

The teeth described above appear to be conspecific with White’s (1926) Trichiurus oshosunensis from the early-to-middle Eocene of Nigeria. Although similar to the Sphyraena laniary teeth we examined, they can be distinguished by being much more sinuous in profile. In contrast, laniary teeth of Sphyraena have an oblique, slightly sinuous anterior margin but nearly vertical posterior margin. Arambourg (1952: pl. 35, figs 43–45, 53–56) figured several teeth he assigned to T. oshosunensis that better fit our definition of Sphyraena sp. in that they have anterior and posterior carinae and are lanceolate in form. Unfortunately, White (1926) only illustrated laniary teeth, and the morphology of other T. oshosunensis teeth is uncertain. Until more complete specimens are known, we restrict the usage of T. oshosunensis to teeth that match White’s (1926) type description.

Trichiurus oshosunensis differs from Eutrichiurides plicidens comb. nov. in having a single anterior carina and by lacking posterior crown ornament. It differs from Trichiurides sagittidens in being laterally compressed along the entire crown height (not just apically), by having a smaller posterior barb (if present), and by having a teardrop-shaped basal outline (not circular). A laniary tooth identified as Sphyraena sp. by Maisch et al. (2016) is herein considered to be T. oshosunensis . Also, our examination of a specimen that Thurmond & Jones (1981: fig. 50) referred to Trichiurides sp. (specimen ALMNH PV2005.6.432) is also referred to T. oshosunensis .

Several of the teeth in our sample lack a posterior barb, a feature that Gago (1997) noted as being absent on juveniles of extant Trichiurus and could reflect ontogeny as opposed to jaw heterodonty.

Stratigraphic and geographic range in Alabama

The specimens in our sample were collected from the contact of the Tallahatta and Lisbon formations at sites ACh-14 and ACov-11, and the basal Lisbon Formation at site ACov-11. Lower Lutetian, zones NP14 and NP15.

Figures

Fig. 63. Trichiurides sagittidens Winkler, 1874 and Trichiurus oshosunensis White, 1926, teeth. A–I. Trichiurides sagittidens. A–C. MSC 12800,, basal Gosport Sand. A. Lingual view. B. Anterior view. C. Basal view. D–F. MSC 2405.1, Gosport Sand. D. Lingual view. E. Anterior view. F. Basal view. G–I. MSC 37486, basal Gosport Sand. G. Lingual view. H. Anterior view. I. Basal view. — J–R. Trichiurus oshosunensis. J–L. MSC 38489.1, basal Lisbon Formation. J. Profile view. K. Anterior view. L. Basal view. M–O. MSC 37657, Tallahatta/Lisbon formation contact zone, courtesy of Bruce Relihan. M. Profile view. N. Anterior view. O. Basal view. P–R. MSC 37146, Tallahatta/Lisbon formation contact zone, courtesy of James Lowery. P. Profile view. Q. Anterior view. R. Basal view. Scale bars = 5 mm.