CONICET | Buscador de Institutos y Recursos Humanos

In the present work we report new ichnites corresponding to a trackway composed of three tetradactyl pedal footprints in stratigraphically close association with plant remains, at 8 kilometers Southeastern Guatacondo, Tarapacá Region, within the transition of Majala and Chacarilla formations (Late Jurassic-Early Cretaceous). The fossils were found during the construction of a road at PK23 site for the Copper Mine called Quebrada Blanca Phase 2 project, by the Teck Mining Company Quebrada Blanca S.A.We performed stratigraphical, paleobotanical, and paleoichnological studies, a long with the footprint characterization and comparisons by Principal Component Analysis, and Discriminant Analysis of I-II, II-III and III-IV interdigital angles, using a large tetradactyl footprint morphological database (96) of potential producers (dinosaurs, crocodiles, lepidosaurs, and pterosaurs), we conducted a pedal computer modeling kinematic analysis of the Chilesaurus diegosuarezis 3D modeled tetradactyl foot in two types of sedimentary conditions (hard soil with superficial impression, and soft sediment with a penetrative impression), to test it as a potential trackmaker.The stratigraphic section reveals an association of silicoclastic facies, formed by the intercalation of fine-grained sandstones and wackes, with ripple marks, cross and horizontal lamination, evidencing intermittent moderate to low sedimentation energy.Among the plant material, several organs of the family Cheirolepidiaceae were identified. Leaves and leafy branches of Brachyphyllum type, Classostrobus pollen cone, ovuliferous scales, and wood fragments related to Cupressinoxylon. The monodominance of Cheirolepidiaceae among the preserved macroflora allows inferring the characteristics of the environment in which the plants lived, highlighting halophytic, and temporarily arid conditions. The evidence as a whole, permits to interpret the depositional environment as an arid deltaic-littoral plain, temporarily covered with an ephemeral water layer associated with a stunted woody vegetation, in which terrestrial vertebrates walked by.Despite the fact of its low predictive power of the multivaried analysis, due to the various sources of morphological variability innherent to footprint formation, the PK23 footprints seemes to better correspond to Dinosauria or Avialae as the most likely producer, rather than to Lepidosauria or Crocodylia, discarding the dinosaur Chilesaurus due to very low interdigital medio lateral rotation capabilities.

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