Sauropodian tracks from the Yacoraite Formation (Maastrichtian-Danian) - Valle del Tonco tracksite (Salta, northwestern Argentina)

ALFREDO ZELAYA; SILVINA DE VALAIS; SERGIO GORUSTOVICH; CARLOS A. CONSOLE GONELLA

Alpuente, Valencia

Encuentro; 1st International Meeting of Early-stage Researchers in Palaeontology 1st IMERP 1XIV Encuentro de Jóvenes Investigadores en Paleontología XIV EJIP. Valencia, España.; 2016

Universidad de Valencia

The Valle del Tonco tracksite is located in theSalta province, owned by the Argentinean atomiccommission (Comisión Nacional de Energía Atómicaor CNEA). This is a well-known ichnosite, regardinga diverse avian and dinosaur track fossilsdescribed since the 80?s (e.g., Alonso and Marquillas,1986). The tracks come from the Yacoraite Formation(Upper Maastrichtian), which at the studyarea represents a carbonate lagoon shoreline, withprogradacional/agradacional architecture. In theValle del Tonco, three members are recognized,from base to top: Caliza Amblayo, Complejo DonOtto and Arenisca Pedro Nicolás. In the Quebradade El Candado (25º34´54.96´´S; 65º54´36.12´´W),that is located in the middle of the Caliza AmblayoMember, there is a quadrupedal trackway, with heteropodialtwelve manus-pes set impressions, preservedas positive hypichnial on a wackestonesurface. The tracks are represented by pes trackswith subtriangular posterior edge, located posteriorlyto the manus tracks. Both manus and pestracks lack clear digital or claw impressions, maybedue to taphonomy bias. The pes tracks are longerthan wide (averages of length and width: 67 cmand 42.6 cm respectively). The manus tracks haveno clear morphological details and display about ahalf of the size of the pes tracks, are kidney-shapedwith the major axis rotated outwards relative to thetrackways midline (averages of length and width:19.8 cm and 30.8 cm respectively). The trackwaydisplays an average of stride length and pace angulationof the footprints of 220 cm and 122º, respectively.On the basis of the spatial-temporaldistribution and the general morphology of thetracks, they are assigned to titanosaur sauropod dinosaurs.Until now, this specimen represents themore detailed and clearest sauropodian tracks fromthe Yacoraite Formation. This trackway differs fromthose from the Cretaceous Bolivia (Toro Toro, CalOrck´o, Humaca and Fumanya localities), mainly becauseof the smaller internal trackway width andsize of the manus imprint of the former (Lockley etal., 2002). This finding extends the record of sauropodiantracks in Gondwana and provides new informationto the understanding the palaeobiologyof Upper Cretaceous sauropods.