Eutrichiurides plicidens ( Arambourg, 1952 ) Ebersole & Cicimurri & Stringer, 2019

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 : 169-170

Eutrichiurides plicidens ( Arambourg, 1952) comb. nov.

Fig. 62 M–X

Trichiurus (?) plicidens Arambourg, 1952: 265 , pl. 35, figs 39–42.

Trichiurus sp. – Clayton et al. 2013: fig. 6f.

Trichiurides cf. T. sagittidens – Maisch et al. 2016 : fig. 2, 17–18.

Material examined

UNITED STATES OF AMERICA – Alabama • 11 isolated teeth; Claiborne Group; MSC 188.2, MSC 37127, MSC 37148, MSC 37153, MSC 37460, MSC 37484, MSC 37908, MSC 38435, MSC 38482, NJSM 24322, WSU 5020.

Description

Largest tooth measuring 1.2 cm in height. Teeth elongated, conical, posteriorly curving. Upper one-third of tooth also with medial bend; some specimens slightly sigmoidal in profile. Anterior and posterior carinae absent. Medial and/or lateral carinae developed; medial carina more pronounced. Posterior face with fine striations extending nearly two-thirds height of the crown; anterior face smooth. Tooth base flat, with wide conical pulp cavity.

Remarks

The teeth in our sample are superficially similar to those of Trichiurides sagittidens and Trichiurus oshosunensis , but differ from both taxa by having one to two lateral carinae as opposed to anterior and/ or posterior carinae. The specimens in our sample appear to be conspecific with Arambourg’s (1952) Trichiurus plicidens , from the Ypresian of Morocco, as they are slightly sigmoidal, have one-to-two lateral carinae, lack an apical barb, and have striated ornamentation ( Arambourg 1952: 265, pl. 35, figs 39–42). Arambourg (1952) tentatively placed this species within Trichiurus because of the striations occurring on the tooth crown.

Herein we argue for a new combination for the plicidens morphology, placing it within the genus Eutrichiurides . This stems from the fact that the plicidens morphology has one-to-two lateral carinae (as opposed to anterior or posterior carinae), which is a characteristic of Eutrichiurides as seen on the type specimen of E. winkleri ( Casier 1946: pl. 4, fig. 19b), on White’s (1931: fig. 2) figured specimen of E. orpiensis (Leriche, 1906) , and on specimens illustrated by Casier (1944) when he redescribed E. delheidi (Leriche, 1908) . Although Gago (1997) observed that apical barbs are present on adult teeth but absent on juvenile teeth of extant Trichiurus species, Casier (1944) noted that barbs are completely lacking on teeth of all Eutrichiurides (see White 1931: fig. 2; Casier 1944: pl. 1 figs 5–9, 12–18, 1946: pl. 4, fig. 19b; Arambourg 1952: 265, pl. 35, figs 39–42). The combination of having lateral carinae, striations on the tooth crown, and the lack of an apical barb on all the observed specimens suggests these teeth are more closely aligned with Eutrichiurides , rather than Trichiurides or Trichiurus , and serves as the basis for this new combination. An “indeterminate fish tooth” figured by Otero et al. (2015: 14, fig. 11) from the Bartonian of Libya may be conspecific with E. plicidens comb. nov.

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, the basal Lisbon Formation at site ACov-11, and the basal Gosport Sand at site ACl-4. Lower Lutetian to middle Bartonian, zones NP14 to NP17.

Figures

Fig. 62. Sphyraena sp. and Eutrichiurides plicidens (Arambourg, 1952) comb. nov., teeth. A–L. Sphyraena sp. A–C. MSC 37142, laniary tooth, Tallahatta/Lisbon formation contact zone, courtesy of James Lowery. A. Lingual view. B. Anterior view. C. Basal view. D–F. MSC 35779, lower Tallahatta Formation. D. Lingual view. E. Carinal view. F. Basal view. G–H. MSC 37434.1, Gosport Sand. G. Lingual view. H. Carinal view. I. Basal view. J–L. MSC 37434.2, laniary tooth, basal Gosport Sand. J. Lingual view. K. Anterior view. L. Basal view. — M–X. Eutrichiurides plicidens comb. nov. M–O. MSC 188.2, Gosport Sand. M. Lingual view. N. Mesial view. O. Basal view. P–R. MSC 37908, basal Lisbon Formation. P. Lingual view. Q. Mesial view. R. Basal view. S–U. MSC 38482, basal Lisbon Formation. S. Lingual view. T. Mesial view. U. Basal view. V–X. MSC 37460, basal Gosport Sand. V. Lingual view. W. Mesial view. X. Basal view. Scale bars: A–C, G–X =5 mm; D–F =2 mm.