Jorge o. CALVO y Gerardo V. MAZZETIA, Nuevos hallazgos de huellas de dinosaurios en la Formación Candeleros (Albiano-Cenomaniano), Picún Leufú, Neuquén, Argentina, AMEGHINIANA (Rev. Asoe. Paleontol. Argent.) - 41 (4): 545-554. Buenos Aires, 30-12-2004.

Abstract. NEW FINDINGS OF DINOSAUR TRACKS lN THE CANDELEROS FORMATION (ALBlAN-CENOMANIAN), PICÚN LEUFÚ, NEUQUÉN, ARGENTINA. A new dinosaur tracksite is described from the lower section of the Candeleros Formation, Rio Umay Subgroup (Albian-Çenomanian). The footprints were found on greyish, coarse to thin sandstones from the Cerrito dei Bote islet, located at the south-west end of Ezequiel Ramos Mexia artificiallake, 15 km East .from Pietin Leuru., Neuquén, Argentina. The relatively good preservation of the ichnosite allows to recognise three footprint mor­photypes, corresponding to a middle-sized titanosaurian sauropod, a large camosaurian theropod, and a small coelurosaurian theropods. The titanosaur footprints were referred to the ichnospecies Sauropodichnus giganteus Calvo. The presence of Abelichnus astigarrae Calvo was also documented through two footprints belonging to a camosaur, and a non previously registered footprint morphotype was ascribed to coelurosaurs. The dinosaur speeds were estimated from stride and footprint lengths of the trackmakers. Footprint measurements were also used to estimate the body masses of the trackmakers. The ichnofauna studied shows, in ail cases, low speeds that range from a maximum of 1.8 m S-1 for a coelurosaur to a minimum of 0.9 m S-1 for the titanosaur. The. analyses show that the dinosaurs responsible for these trackways were either walking (the titanosaur and the camosaur) or using a slow trot gait (the coelurosaurs). Whichever the case, these dinosaurs were progressing with gaits weil below their potentiallocomotory capabilities. The overall correspondence in direction and speed observed in the tracks of the coelurosaurs is compatible with a social pack-moving hypothesis.

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