A preliminary report on a new dinosaur tracksite from the Candeleros Formation (Cenomanian, Upper Cretaceous) of southern Neuquén Basin, Patagonia, Argentina

HEREDIA, A.M.; BELLARDINI, F.; GARRIDO, C.A.; MANIEL, I.J.; WINDHOLZ, G.J.; GUEVARA LUCERO, J.E.; MESSINA, M.Y.; CIAFFI, A.; BAIANO, M.A.

Malargüe

Jornada; IV Jornadas de Paleontología de la Cuenca Neuquina; 2023

Universidad Nacional de Cuyo

The Upper Cretaceous Candeleros Formation comprises one of the richest dinosaur footprint records in terms of abundance and diversity for the Neuquén Basin. A new Cenomanian dinosaur tracksite from the El Sauce locality, Neuquén Province, northern Patagonia, Argentina, is reported here. Several tridactyl and subcircular footprints were recognized in medium‐ to coarse‐grained sandstones from alluvial deposits of the Candeleros Formation, the oldest geological unit of the Neuquén Group (Cenomanian–Campanian). The paleoenvironment would consist of a zone of distal alluvial fans converging in a depressed area where ephemeral water masses formed. We interpreted that the footprints would have been generated at the margins of these water bodies. Considering that no large plane surfaces are exposed in the studied outcrops, it is difficult to find trackways, and most of the footprints are isolated, especially the larger ones. Generally, the footprints are preserved as convex hyporelief, and in some cases only the infill of the footprint has been observed. The largest tridactyl footprint found is 27 cm long and 15 cm wide, is slightly asymmetrical, and the central digit impression is significantly longer than the lateral ones, preserving claw marks, typical of theropod footprints. On the same footprint‐bearing surface, small tridactyl footprints (10 cm long on average) of indeterminate bipedal dinosaurs have been recognized, associated with pterosaur manus impressions. These small dinosaur footprints have the impression of the central digit longer than the lateral ones and are found two pairs of footprints that could correspond to two different trackways with almost perpendicular directions. Large subcircular footprints about 100 cm in diameter have been documented in both plane and profile views. These footprints are preserved as undertracks since the deformed layers into the footprint can be recognized, and considering the morphology and size of the footprints, they are attributed to sauropod dinosaurs. Due to the poor preservation of these footprints and the lack of trackways, we could not assign them to a specific ichnotaxon. However, these new footprints from the El Sauce locality contribute to increasing the knowledge of the Cenomanian dinosaur ichnology of the Neuquén Basin, on both the preservational variability of the tracks in relation to their depositional environment and also their paleoecological implications, including the occurrence of theropod and sauropod dinosaurs and even pterosaurs for this type of alluvial environments.