NEW ISOLATED TEETH OF MANIDENS CONDORENSIS FROM THE CAÑADÓN ASFALTO FORMATION: EXPLORING NEW METHODS OF MORPHOLOGYCAL ANALYSIS

BECERRA, M.; POL, D.; MARSICANO, C.A.

San Juan

Congreso; IV Congreso Latinoamericano de Paleontología de Vertebrados; 2011

The recently published ornithischian Manidens condorensis Pol et al. 2011 is one of the most complete records of the family Heterodontosauridae in southern landmasses. The holotype—a partial skeleton with most skull elements, lower jaws, precaudal vertebrae, the left scapula and coracoid, and almost complete pelvic girdles (Pol et al., 2011) —as well as other specimens represented by isolated teeth were recovered from outcrops of the Cañadón Asfalto Formation at the Queso Rallado locality (Middle Jurassic, Chubut Province, Argentina). The aforementioned additional material includes ten isolated leaf-shaped tooth crowns, laterally compressed and mesiodistally asymmetrical. The presence of a mesial concavity for dental interlocking, enameloid crenulations, and denticles asymmetrically disposed allow us to assign these isolated dental material to M. condorensis. An hypothetical position for these teeth is proposed on the basis of comparison with the teeth in place on the jaw of the type specimen. In this context, the tooth row was divided in three regions (anterior, medial and posterior) and the isolated teeth were assigned to a specific region considering morphologycal features and proportions of the lingual face of the crown. In order to test our hypotheses on tooth position we included the dental data available in a morphometrical analysis. With this analysis we evaluate if the isolated crowns occupy the same region in the morphospace as the teeth in place on the dentary, following the positional characterization based on the morphological and proportional analysis. The results obtained are in accordance with the positional determinations made on a morphological basis. Finally, the validity of the proposed positional groups was verified by means of a discriminant analysis of canonical factors based on the morphometric information. The study of the isolated crowns assigned to M. condorensis allowed us to explore new working methodologies that have proved to be of good use when a limited amount of information is available, a case much frequent when studying fossil material. Moreover, in this particular case, this methodology made it possible to improve our knowledge on the morphology of some dental elements of approximately known position on the taxon under study as, unlike the type specimen of Manidens, the isolated teeth are completely free of matrix and better preserved.