Abdounia beaugei ( Arambourg, 1935 )

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 : 82-84

Abdounia beaugei ( Arambourg, 1935)

Fig. 30

Eugaleus beaugei Arambourg, 1935: 430 , pl. 14, figs 28–35.

Galeus doncieuxi Leriche, 1936: 391 , pl. 27, fig. 9.

Galeorhinus beaugei – Dartevelle & Casier 1943: 154 , pl. 12, figs 40–46.

Scyliorhinus beaugei – Arambourg 1952: 123 , pl. 23, figs 20–47.

Abdounia beaugei – Cappetta 1980a: 35 , fig. 4.

Abdounia biauriculata – Cappetta & Case 2016: 56 , pl. 7, fig. 5.

Material examined

UNITED STATES OF AMERICA – Alabama • 50 isolated teeth; Claiborne Group ; MSC 35754.1 – 13 , MSC 37133, MSC 37318.2 , MSC 37318.4 , MSC 37570.3 – 5 , MSC 37571.1 – 21 , MSC 37572, MSC 37695.2 , SC 2012.47.167, SC 2012.47.177 (4 specimens), WSU CC 510 (2 specimens) .

Description

Anterior teeth with tall erect main cusp; cusp of lateral and lateroposterior teeth becoming shorter, more distally inclined. Anterior teeth with single pair of short, triangular cusplets; cusplets divergent and largely united to main cusp. Lateral teeth with two pairs of lateral cusplets; second pair smaller, vestigial on more distally located teeth. Lingual face of main cusp of anterior teeth strongly convex; less convex on lateral teeth. Labial cusp face flat; all enameloid smooth. Cutting edges of main cusp and lateral cusplets smooth, continuous. Root bilobate with short, diverging lobes. Lingual attachment surface flat; wide and deep nutritive groove.

Remarks

Three species of Abdounia have been identified within our sample of Claiborne Group teeth, including A. beaugei ( Arambourg, 1935) , A. enniskilleni ( White, 1956) , and A. minutissima (Winkler, 1874) . Two additional species previously assigned to Abdounia are placed within a new genus and are described in detail below. The A. beaugei anterior teeth in our sample have a single pair of lateral cusplets, easily separating them from the latter two species, which have three-to-eight pairs. Anterior teeth of A. minutissima have taller triangular cusplets that are less united to the main cusp. Teeth of A. enniskilleni are much larger in overall size and generally have fine longitudinal ridges on the lingual cusp face. The lateral teeth of A. beaugei have two pairs of lateral cusplets, whereas A. enniskilleni and A. minutissima have a single pair.

Cappetta & Case (2016) described and figured a single tooth from site ACov-11 that they assigned to Abdounia biauriculata ( Casier, 1946) . Teeth of to this species are very similar in size to those of A. beaugei , and anterior teeth of both species have a single pair of cusplets and the lateral teeth two pairs (see Arambourg 1935: text fig. 23, pl., 19, figs 28–35; Casier 1946: pl. 1, 6; Arambourg 1952: pl. 23, figs 20–47; Casier 1966: pl. 3, figs 23–25). Although Casier (1966: fig. 65) stated that the two taxa were “analogous”, he reported that his Ypresian A. biauriculata from Belgium differed from Arambourg’s (1952) A. beaugei from the Ypresian London Clay and Thanetian to Ypresian strata of Morocco in that the teeth have a less robust root, and the lateral cusplets that are taller, straighter, more pointed, and more separated from the main cusp.

When compared to the teeth in our sample, the Abdounia biauriculata specimen figured by Cappetta & Case (2016: pl. 7, fig. 5) appears anomalous as it has two pairs of tall, pointed cusplets that are separated from the main cusp. Although this single tooth could be identified as A. biauriculata , the absence of any other specimens in our sample leads us to believe that it may represent an aberrant A. minutissima . A few teeth from our sample of Gosport Sand Abdounia teeth have similar tall and pointed cusplets. However, in our opinion these teeth still fall within the morphological range of A. beaugei . Furthermore, as eluded to by Casier (1966: fig. 65), A. beaugei and A. biauriculata may be conspecific, with any observed differences being the product of heterodonty and/or intraspecific or geographic variation. Support for this stems from the difficulty, at times, in distinguishing these two morphologies, and the fact that the morphologies appear to be coeval within the same deposits in Belgium (see Noubhani & Cappetta 1997). Based on samples from both Alabama (see below) and Georgia (also Parmley & Cicimurri 2003), the variation we observed in A. enniskilleni leads us to believe that Cappetta & Case’s (2016) A. biauriculata is synonymous with A. beaugei .

Numerous teeth in our sample are assigned to Abdounia sp. (see Appendix 1 ) because of their incomplete preservation, making their specific assignments unclear.

Stratigraphic and geographic range in Alabama

Abdounia beaugei specimens have been recovered from the lower Tallahatta Formation at site ADl-1, the contact of the Tallahatta and Lisbon formations and the “lower” Lisbon Formation at site ACov- 11, the lower Gosport Sand at site ACl-4, and the Gosport Sand at ACl-15. Upper Ypresian to middle Bartonian, zones NP14 to NP17.

Figures

Appendix 1 (continued on next four pages) Number of non-otolith taxa identified to lowest taxonomic ranking within each Claiborne Group unit. Shaded areas represent the stratigraphic range of taxa within Claiborne Group units in Alabama, USA.

Fig. 30. Abdounia beaugei (Arambourg, 1935), teeth. A–C. MSC 35754.1, anterolateral tooth, lower Tallahatta Formation. A. Labial view. B. Mesial view. C. Lingual view. D–F. MSC 37571.1, lateral tooth, Gosport Sand. D. Labial view. E. Mesial view. F. Lingual view. G–I. MSC 37571.2, anterior tooth, Gosport Sand. G. Labial view. H. Mesial view. I. Lingual view. J–L. MSC 35754.9, lateral tooth, lower Tallahatta Formation. J. Labial view. K. Mesial view. L. Lingual view. Scale bars for A–L=2 mm.