PRELIMINARY STUDY OF THE FIRST RECORD OF TETRAPODOSAURUS STERNBERG 1932 FROM SOUTH AMERICA

RIGUETTI, FACUNDO; APESTEGUÍA, SEBASTIÁN; PAOLO CITTÓN; GERARDO ZACARÍAS

La Plata

Congreso; II Reunión de Comunicaciones de la Asociación Paleontológica Argentina; 2019

Tetrapodosaurus Sternberg, 1932 is a typically cretaceous ichnogenus from the North Hemisphere traditionally related to ankylosaur producers. Five new trackways attributed to this ichnogenus were found at Niñu Mayu, 60km west of Sucre, Bolivia. The trackway-bearing surface preserves not only ankylosaurian trackways but also some tracks probably related to sauropods and bipedal tridactyl producers. This is a typical cretaceous ichnological assemblage. The track-bearing layer is composed by sandy limestones that belong to the basal member of El Molino Formation (lower Maastrichthian). The depositional environment is discussed between transitional and lacustrine. Footprints are well detailed and inform on the producers pedal anatomy. Extra-morphologies showa wide variability, probably as a consequence of different degrees of substrate plasticity during the trampling. Manus prints are pentadactyl and symmetric with short digit traces disposed in arc. Digit traces I and V are respectively directed posteromedially and posterolaterally, while the central digits are anteriorly directed. Pes prints are tetradactyl and symmetrical with short digit traces and a subcircular proximal impression compatible with metatarsal support. The trackways are wide for both manus and pes. The prints are small compared with other Tetrapodosaurus records. However, the South American osteological record of ankylosaurs consists also of adult specimens of small overall dimension that could be compatible with the dimension of the new ichnological record. These are the first trackways assigned to Tetrapodosaurus found in South America, increasing the regional record of ichnogenus attributed to ankylosaur producers (Ligabueichnium Leonardi, 1984 from Bolivia and Metatetrapous Nopcsa, 1923 reported in Brazil).