New ornithischian remains of the Cañadon Asfalto Formation: body length estimations using linear regresions and hindlimb proportions.

BECERRA, MARCOS G.

La Rioja

Congreso; XXVII Jornadas Argentinas de Paleontología de Vertebrados; 2013

Asociación Paleontológica Argentina

The MPEF-PV3826 remains represent a small ornithischian dinosaur from the Lower Jurassic (Toarcian) of the Cañadon Asfalto Formation (Queso Rayado Locality) with tentative heterodontosaurid affinities, from Cerro Condor, Chubut. The former specimen includes two complete metatarsus with preserved medial distal tarsals, several caudal vertebrae and scattered phalanges. The size of MPEF-PV3826 seems to be lower than all known ornithischians, including also the small heterodontosaurids (eg. Fruitadens, Tianyulong). Also, is generally accepted that the hindlimb bones features can be used for body length and body mass estimations, and that the length proportion of long bones within the hindlimb also dependends of the gait (cursorial, graviportal, etc.). In this work we use linear regresions to estimate an hypothetical length of the absent hindlimb bones of MPEF-PV3826, to finally estimate an hypothetical body length. To accomplish these objectives, we relate the length of the preserved limb bones of several measured species within Ornithischia, with the estimated body length. The linear function that explains the resulting regresions allows to estimate the length of absent bones on MPEF-PV3826 and an hypothetical body length. Furthermore, the body length estimations obtained for MPEF-PV 3826 were also compared with the supposed body length on Manidens condorensis (an heterodontosurid dinosaur from the same locality). The obtained results not only allows to conclude in both the size of Manidens and the former specimen, also allows to conclude on the posture and gait on MPEF-PV3826 and that this approach can be used to estimate body length in other bipedal dinosaurs.