Ginglymostoma maroccanum Noubhani & Cappetta, 1997

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 : 20-22

Ginglymostoma maroccanum Noubhani & Cappetta, 1997

Fig. 7 A–D

Ginglymostoma maroccanum Noubhani & Cappetta, 1997: 34 , pl. 10, fig. 2.

Ginglymostoma serra – Woodward 1889: 348 , pl. 16, fig. 9.

Material examined

UNITED STATES OF AMERICA – Alabama • 8 isolated teeth; Claiborne Group; MSC 34407.2, MSC 35752.1–7.

Description

Teeth with symmetrical crown and prominent median cusp. Median cusp tall, erect, and triangular, flanked by three pairs of lateral cusplets. Lateral cusplets decrease in size laterally. Labial crown face generally flat and smooth; a pair of low ridges is at times present that extends to the crown base. Labial face distally oriented with a shallow basal apron. Basal edge of the apron generally flat or slightly concave. Lingual crown face convex with a strong medial protuberance. Crown T-shaped in oral view. Lateral edges of the root extend beyond the base of the crown. Root base heart-shaped in basal view. Wide nutritive groove on root base that opens labially. Nutritive foramen is positioned within the lingual half of the nutritive groove. Prominent marginolingual foramen present on lingual root protuberance.

Remarks

Noubhani & Cappetta (1997) and Cappetta (2012) recognized five species of Eocene Ginglymostoma including G. angolense Dartevelle & Casier, 1943 ; G. maghrebianum Casier, 1947 ; G. maroccanum Noubhani & Cappetta, 1997 ; G. serra Leidy, 1877 ; and G. sokotoense White, 1934 . The Ginglymostoma teeth described above are all assigned to G. maroccanum because they have no more than three pairs of lateral cusplets ( G. angolense = six or more; G. serra =five to nine; G. sokotoense =five or more; G. maghrebianum =two to six). Additionally, the Tallahatta Formation specimens have a pronounced apron that is either flat or slightly concave, as opposed to the shallow and rounded apron on G. angolense . These teeth are similar to the Thanetian G. chenanei Noubhani & Cappetta, 1997 and Ypresian G. maghrebianum , but differ by never having more than three pairs of lateral cusplets (as opposed to up to four pairs on G. chenanei and five on G. maghrebianum ). These teeth also differ from the Thanetian G. khourbgaense Noubhani & Cappetta, 1997 by having a shorter, and less triangular, median cusp and can be distinguished from the Danian G. subafricanum Arambourg, 1952 by having shorter and wider lateral cusplets. Because there appears to be a lack of variability regarding the number of cusplets on the teeth in our sample (only three pairs), these specimens are most appropriately assigned to G. maroccanum .

It should also be noted that although G. serra has been reported within the Paleogene by Dartevelle & Casier (1943) and Arambourg (1952), the species was originally erected by Leidy (1877) for teeth collected from South Carolina and is currently considered to be restricted to the Neogene (see Cappetta 2012). Woodward (1889), however, reported two G. serra teeth from Alabama that were derived from upper Eocene Jackson Group deposits in Choctaw County. Upon reexamining these teeth, Leriche (1942), and later White (1956), reassigned them to Ginglymostoma obliquum ( Leidy, 1877) based on the distal inclination of their crowns. Later, Case & West (1991) placed G. obliquum within the genus Nebrius because it has a crown morphology that is more typical of this latter genus. Thurmond & Jones (1981) compared the tooth illustrated by Woodward (1889: pl. 16: 9) to a suite of Ginglymostoma teeth they collected from the Gosport Sand at site ACl- 4 in Clarke County, AL. Their analysis concluded with the designation of G. obliquum as a junior synonym of G. serra , and they stated that crown inclination is not a taxonomically viable characteristic but is instead related to heterodonty. Unfortunately, the identity of the Thurmond & Jones (1981) specimens remain a mystery as the teeth they discussed could not be located and the figures they provided (fig. 10) are reproductions of the original G. serra type material illustrated by Leidy (1877), not their specimens from the Gosport Sand.

The Ginglymostoma specimens in our sample were collected from the Ypresian portion of the lower Tallahatta Formation at site ADl-1. Ginglymostoma maroccanum was originally described from Thanetian and Ypresian deposits in Morocco ( Noubhani & Cappetta 1997) and the stratigraphic overlap with our Tallahatta Formation specimens ( Fig. 7 A–D) supports that they do indeed belong to this species. These specimens differ from a sample of Ginglymostoma teeth collected from the Bartonian Gosport Sand at site ACl-4 ( Fig. 7 E–H), the latter of which has up to four pairs of triangular lateral cusplets. The Bartonian teeth, assigned here to Ginglymostoma sp., appear to represent a different species and are discussed in detail below.

Stratigraphic and geographic range in Alabama

Ginglymostoma maroccanum specimens have been recovered only from the lower Tallahatta Formation at site ADl-1. Upper Ypresian, zones NP13 and NP14.

Figures

Fig. 7. Ginglymostomatidae Gill, 1862, teeth. A–D. Ginglymostoma maroccanum Noubhani & Cappetta, 1997, MSC 34407.2, lower Tallahatta Formation. A. Labial view. B. Lingual view. C. Mesial view. D. Basal view. — E–H. Ginglymostoma sp., MSC 37548.1, basal Gosport Sand. E. Labial view. F. Lingual view. G. Mesial view. H. Basal view. — I–T. Nebrius thielensi (Winkler, 1874). I–L. MSC 35755.6, lower Tallahatta Formation. I. Labial view. J. Lingual view. K. Mesial view. L. Basal view. M–P. MSC 37266.1, basal Lisbon Formation. M. Labial view. N. Lingual view. O. Distal view. P. Basal view. Q–T. MSC 37496.1, basal Gosport Sand. Q. Labial view. R. Lingual view. S. Profile view. T. Basal view. Labial at bottom in basal views. Scale bars = 3 mm.