Galeorhinus ypresiensis ( Casier, 1946 )

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 : 64-65

Galeorhinus ypresiensis ( Casier, 1946)

Fig. 23 N–P

Eugaleus ypresiensis Casier, 1946: 86–89 , pl.1, fig. 11a–t.

Galeorhinus ypresiensis – Kemp 1982 : pl. 9, fig. 4.

Material examined

UNITED STATES OF AMERICA – Alabama • 3 isolated teeth; Claiborne Group ; MSC 37693.1 – 2 , MSC 37898 .

Description

Teeth do not exceed 4.5 mm in mesiodistal width. Main cusp thin, triangular, and distally inclined. Mesial edge of main cusp ranges from straight to slightly concave. Distal edge of main cusp slightly convex. Large distal heel with four-to-five triangular distal cusplets, which decrease in size distally. A series of weak serrations present on mesial cutting edge, most prominent on the lower third. Labial crown face flat, bulbous basally and overhanging root, with faint wrinkling at the mesial half of the labial crown foot. Lingual crown face strongly convex. Root lobes are divergent and rounded. Interlobe area shallow. Root high and thick lingually and covers much of the crown face. Nutritive grooves deep and wide; forms a basal notch on the root base.

Remarks

The specimens in our sample are similar in overall morphology to those of Galeorhinus duchaussoisi , G. louisi , and G. mesetaensis , but are easily differentiated by having prominent mesial denticulations. Furthermore, the teeth of G. ypresiensis lack heavy crenulations across the labial crown base as seen on the teeth of G. louisi (see above). The teeth of G. ypresiensis are further differentiated from those of G. mesetaensis by the complete absence of ornamentation on the lingual crown face, and teeth of G. duchaussoisi (see above) can attain larger overall sizes (up to 6.7 mm in mesiodistal width as opposed to 4.5 mm for G. ypresiensis ). The teeth of G. ypresiensis are similar to some tooth positions of Physogaleus (see below) but can be differentiated by having a more convex labial crown face and a more bulbous labial crown base that overhangs the root.

Stratigraphic and geographic range in Alabama

The specimens in our sample were collected from the Gosport Sand at site ACl-15. Middle Bartonian, Zone NP17.

Figures

Fig. 23. Galeorhinus de Blainville, 1816 and Pachygaleus Cappetta, 1992, teeth. A–F. Galeorhinus aff. G. duchaussoisi Adnet & Cappetta, 2008. A–C. MSC 35756.1, lower Tallahatta Formation. A. Labial view. B. Lingual view. C. Mesial view. D–F. MSC 37691, basal Lisbon Formation. D. Labial view. E. Lingual view. F. Mesial view. — G–J. G. louisi Adnet & Cappetta, 2008, MSC 37353.2, lower Tallahatta Formation. G. Labial view. H. Lingual view. I. Mesial view. J. Close–up of labial wrinkling. — K–M. G. aff. G. duchaussoisi, MSC 37353.4, Tallahatta Formation. K. Labial view. L. Lingual view. M. Mesial view. — N–P. Galeorhinus ypresiensis (Casier, 1946), MSC 37693.1, Gosport Sand. N. Labial view. O. Lingual view. P. Mesial view. — Q–V. Pachygaleus lefevrei (Diameries, 1891). Q–S. MSC 37688, basal Lisbon Formation. Q. Labial view. R. Lingual view. S. Mesial view. T–V. MSC 35763, lower Tallahatta Formation. T. Labial view. U. Lingual view. V. Mesial view. Scale bars = 2 mm.