Análisis de huellas avianas del Cretácico Superior del Cañadón del Laberinto (Valle de la Luna Amarillo, Paso Córdoba, Río Negro, Argentina)

Abstract

Seven slabs bearing avian footprint s, collected from a new ichnosite in the Upper Cretaceous Allen Formation, are here analyzed and discussed. The new ichnosite is ubicated close to Valle de la Luna Amarillo (Paso Córdoba Protected Natural Municipal Area), few kilometers south from the city of General Roca, Río Negro province Argentina. The material was collected both in situ (three slabs) and as loose material (four slabs). Close range, high resolution d igital photogrammetry technique was adopted in order to digitalize specimens and obtain an objective representation of tracks three dimensional morphology. Different softwares were used to take measurements and elaborat e the stratigraphic section within which the ichnosite was found. Five trackways seven pa rtial trackways and 41 isolated tr acks were recognized, giving a total of 74 footprints preserved as concave epirelief Some slabs are characterized on their surfaces by desiccation cracks, ripples marks and different densities of trampling. F ootprints are didactyl, tridactyl or tetradactyl, and some of them retain impressions of digital pads and claw s Based on morphological features, assigned them to two previously reco gnized ichnogenera in the Cretaceous of Argentina, namely cf. Barrosopus isp. and Gruipeda isp. and undetermined avian footprint On the whole, studied avian footprints are related to shorebird producers D ifferent depths of footprints allow inferring dif ferent degrees of sediment moisture at the time of trampling. In addition, behavioral patterns compatible with both walking and foraging have been identified. Based on the sedimentological and paleontological data, it can be inferred that the birds walked over an area subject emersion and desiccation in a floodplain palaeoenvironment.