Primitive broad-crowned titanosaurs

Primitive broad-crowned titanosaurs in the Uppermost Cretaceous?

P.A. Gallina, S. Apesteguía and F.A. Gianechini

Despite several tooth morphologies were recognized in sauropods, it is widely accepted that macronarians exhibit two main morphotypes: broad-crowned teeth and narrow-crowned teeth. The former, spoon-shaped and provided of a main axis and two lateral flanges, is present in basal forms like Camarasaurus Cope. Conversely, the latter, with reduced flanges, is considered as characteristical for derived titanosaurs, notwithstanding this ―narrow tooth concept actually masks a hidden diversity of morphologies (i.e., cylindrical, hexagonal prisms, and double-ridged). Otherwise, the diversity of Upper Cretaceous dental morphotypes includes also two broader forms. One is represented by broad, distally acuminated, labiolingually compressed, and spatulated crowns, similar but much lesser than that of Camarasaurus Cope, and present in undoubted titanosaurs like Ampelosaurus Le Loeuff from France. The other is represented by labiolingually compressed and distally acuminated teeth with a D-shaped crown slightly broader than the root, and both lingual and lateral high-angled wear facets that resembles those of basal titanosauriforms (e.g., Brachiosaurus Riggs). This type is well represented in Argentina, as show the teeth from the Arroyo Morterito (Salta, PVL 3670-12), some smaller teeth from Los Alamitos Formation (MACN 1133RN), isolated tooth from the Allen Formation (MMRM-PV 53). The presence of this kind of teeth in Campanian-Maastrichtian strata can be attributed both to the presence of surviving basal titanosaurian lineages and/or, the preservation of plesiomorphical traits in the dental morphology of late lineages like the Saltasaurinae.
Fuente: XXV Jornadas Argentinas de Paleontología de Vertebrados, San Luis, 2010.
Foto: solo a modo ilustrativo.

0 comentarios: