Meyer (1974: 199, fig. 63) included Squatirhina sp. cf S. lonzeensis CASIER, 1947 from the Santonian and Upper Campanian of the Gulf Coast; however, he noted that the teeth had thicker crowns than the syntypes and a clear carina. The illustrated specimen from the Eutaw Formation appears to represent the same tooth-design as included later by Case et al. Case et al (2001:89-90, plate 2, fig. 32-36 and text-fig. 3) erected Columbusia fragilis for small orectolobiform teeth from the Eutaw Fm. (Santonian) of Georgia, USA; in doing so, Case noted that the tooth-design was previously viewed by him as Squatirhina. The description was less than detailed, however Bourdon at al (2011:11, fig. 6f-i) noted that the Pt. Lookout Fm. (Santonian) of New Mexico included what appeared to be identical teeth.
The Columbusia fragilis tooth design is characterized by its small size (~2 mm), high narrow cusp, elongate and mesiodistally compressed apron, elongate shoulders, complete cutting edge and a low root with a strong nutrient groove (holaulacorhizous).
|1||Case et al (2001) included Family as Orectolobidae; however, there were no arguments to support that ascertian.|
Bourdon, J., Wright, K., Lucas, S.G., Spielmann, J.A. and Pence, R., 2011. Selachians from the Upper Cretaceous (Santonian) Hosta Tongue of the Point Lookout Sandstone, central New Mexico. New Mex. Mus. Nat. His. and Sc., Bulletin 52; 54pp.
Case, G.R., Schwimmer, D.R., Borodin, P.D. and Leggett, J.J., 2001. A new selachian fauna from the Eutaw Formation (Upper Cretaceous/Early to Middle Santonian) of Chattahoochee County, Georgia: Palaeontographica A, v. 261, p. 83-102.
Casier, E., 1947. Constitution et evolution de la racine dentaire des Euselachii, II. Etude comparative des types: Bulletin du Muse´e Royal d’Histoire Naturelle de Belgique, v. 23, p. 1–32.
Meyer, R., 1974. Late Cretaceous elasmobranchs from the Mississippi and East Texas embayments of the Gulf Coastal Plain. Unpubl. PhD dissertation, Southern Methodist Univ., Dallas, xiv+419 p.