Jaekelotodus robustus ( Leriche, 1921 )

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 : 48-49

Jaekelotodus robustus ( Leriche, 1921)

Fig. 16

Odontaspis robusta Leriche, 1921: 117 .

Odontaspis (Synodontaspis) robusta – White 1931: 62 , figs 75–79.

Hypotodus robustus – Nolf 1986 : pl. 28, figs 1–6.

Carcharias robustus – Case 1994a: 111 , text-fig. 4.

Jaekelotodus robustus – Cappetta & Nolf 2005: 264 , pl. 5.

Material examined

UNITED STATES OF AMERICA – Alabama • 157 isolated teeth; Claiborne Group ; ALMNH PV1992.28.18b, ALMNH PV1992.28.34b, ALMNH PV1992.28.53, ALMNH PV2000.1.43.1a (5 specimens), ALMNH PV2000.1.43.5c (4 specimens), ALMNH PV2013.3.136a, ALMNH PV 2016.4.30 (2 specimens), ALMNH PV 2016.4.31 (4 specimens), GSA-V698 (3 specimens), GSA-V716 (3 specimens), MMNS VP-7495, MMNS VP-8215 (2 specimens), MMNS VP-8230 (61 specimens), MSC 1424.26 , MSC 2372.11 , MSC 2372.21 , MSC 2383 , MSC 33371, MSC 33374, MSC 33483, MSC 33656, MSC 33875, MSC 33900, MSC 33926, MSC 33932, MSC 33950, MSC 35738.1 – 4 , MSC 35740.1 – 2 , MSC 35783.1 – 3 , MSC 37061, MSC 37064.1 – 2 , MSC 37108.1 – 2 , MSC 37149, MSC 37171.1 – 3 , MSC 37529, MSC 38282.1 – 2 , SC 2012.47.179, SC 2012.47.251 (3 specimens), SC 2012.47.70, SC 2012.47.71 (2 specimens), SC 2012.47.72, SC 2012.47.73 (11 specimens), SC 2012.47.74, SC 2012.47.75 (16 specimens), SC 2012.47.91, SC 2012.47.159 .

Description

Anterior teeth with tall triangular main cusp; crown base wide. Main cusp of anterior teeth biconvex in labial/lingual views, sigmoidal in profile view. Lingual face of main cusp very convex; labial face flat to slightly convex; enameloid on both faces smooth. Single pair of very narrow and medially curved lateral cusplets present that are small compared to main cusp size. Lateral teeth with lower, broader, conspicuously distally curved main cusp. Apex on upper lateral teeth with slight labial bend. Generally, a single pair of small, pointed lateral cusplets, that are broader than those of anteriors; some lateral teeth with a secondary pair of vestigial cusplets. Cutting edges of all teeth complete and extend to the base of main cusp, reaching cusplets. Weak lingual dental band occasionally observed at base of the main cusp. All teeth bilobate with rounded, divergent root lobes and U-shaped interlobe area. Interlobe area on anterior teeth deeper than on lateral files, and root lobes less divergent. Prominent lingual boss bears shallow nutritive groove.

Remarks

The teeth of Jaekelotodus robustus were separated from those of taxa with similar teeth in our sample by the following combination of features: the main cusp cutting edges extend to the lateral cusplets on all teeth (separating them from Hypotodus ); the lack of crown ornamentation (separating them from Striatolamia and Brachycarcharias lerichei and B. atlasi ); and the anterior teeth have a single pair of lateral cusplets (separating them from Anomotodon ). Tethylamna anterior teeth are similar to those of Jaekelotodus , but the cutting edges reach the crown foot and the cusplets are larger and more sharply curved medially. Lateral teeth of Jaekelotodus have much smaller lateral cusplets, and a central cusp that is more sharply apically tapered and distally curved than Tethylamna. Teeth of Otodus (Otodus) are robust like those of Jaekelotodus , but the lateral cusplets of Otodus (Otodus) are very broadly triangular and diverging, the lateral teeth are not as sharply tapered and distally curved, and roots lack a lingual nutritive groove.

Stratigraphic and geographic range in Alabama

The specimens in our sample were collected from the Meridian Sand Member of the Tallahatta Formation and the lower Tallahatta Formation at site ADl-1, the contact of the Tallahatta and Lisbon formations and basal Lisbon Formation at site ACov-11, the “upper” Lisbon Formation at site ACl-3, the contact of the Lisbon Formation and Gosport Sand at site AMo-4, the basal Gosport Sand at site ACl-4, and the Gosport Sand at site ACh-21. Upper Ypresian to middle Bartonian, zones NP12 to NP17.

Figures

Fig. 16. Jaekelotodus robustus (Leriche, 1921), teeth. A–C. MSC 35740.1, anterior tooth, Meridian Sand Member of the Tallahatta Formation. A. Labial view. B. Lingual view. C. Mesial view. D–F. MSC 33371, anterior tooth (lower Tallahatta Formation). D. Labial view. E. Lingual view. F. Mesial view. G–I. MSC 2372.11, anterior tooth, Gosport Sand. G. Labial view. H. Lingual view. I. Mesial view. J–L. MSC 37149, upper lateral tooth, Tallahatta/Lisbon formation contact zone, courtesy of James Lowery. J. Labial view. K. Lingual view. L. Mesial view. M–O. MSC 33932, upper lateral tooth, lower Tallahatta Formation. M. Labial view. N. Lingual view. O. Mesial view. P–R. MSC 35783.1, upper lateral tooth, lower Tallahatta Formation. P. Labial view. Q. Lingual view. R. Mesial view. Scale bars = 1 cm.