Estudio preliminar del primer registro de Tetrapodosaurus Sternberg 1932 para Sudamérica

Abstract

Tetrapodosaurus Sternberg, 1932 is a typically cretaceous ichnogenus from the North Hemispheretraditionally related to ankylosaur producers. Five new trackways attributed to this ichnogenuswere found at Niñu Mayu, 60 km west of Sucre, Bolivia. The trackway-bearing surface preservesnot only ankylosaurian trackways but also some tracks probably related to sauropods and bipedaltridactyl producers. This is a typical cretaceous ichnological assemblage. The track-bearing layer iscomposed by sandy limestones that belong to the basal member of Chaunaca Formation(Santonian-?lower Campanian). The depositional environment is discussed between transitionaland playa lake. Footprints are well detailed and inform on the producers pedal anatomy. Extramorphologiesshow a wide variability, probably as a consequence of different degrees of substrateplasticity during the trampling. Manus prints are pentadactyl and symmetric with short digit tracesdisposed in arc. Digit traces I and V are respectively directed posteromedially and posterolaterally,while the central digitsare anteriorly directed. Pes prints are tetradactyl and symmetrical with shortdigit traces and a sub-circular proximal impression compatible with metatarsal support. Thetrackways are wide for both manus and pes. The prints are small compared with otherTetrapodosaurus records. However, the South American osteological record of ankylosaursconsists also of adult specimens of small overall dimension that could be compatible with thedimension of the new ichnological record. These are the first trackways assigned to Tetrapodosaurusfound in South America, increasing the regional record of ichnogenus attributed to ankylosaurproducers (Ligabueichnium Leonardi, 1984 from Bolivia and Metatetrapous Nopcsa, 1923 from Brazil).