Sauropod dinosaur tracks from South America: perspectives and paleontological aspects

GONZÁLEZ RIGA, BERNARDO J.

La Plata

Congreso; X Congreso Argentino de Paleontología y Bioestratigrafía, VII Congreso Latinoamericano de Paleontología; 2010

Comision de la Universidad Nacional de La Plata

The ichnology gives relevant information to understand the paleobiology of sauropod dinosaurs, particularly in relation with two main aspects: locomotion (stance, gait, speed, centers of mass) and behavior (gregarious behavior, ‘herd structure’, habitats and sedimentary environments). Up to now, these studies have been applied to best known types of tracks and these conclusions have been extended to other sauropods, regardless of the extraordinary diversity of this clade. In South America, some titanosaur track sites from Bolivia and Argentina (Humaca, and Agua del Choique, respectively) exhibit sets of parallel trackways suggesting that the trackmakers traveled in social groups. In South America only two ichnotaxa have been described: Sauropodichnus giganteus Calvo (Candeleros Formation, early Cenomanian of Neuquén) and Titanopodus mendozensis González Riga and Calvo (Loncoche Formation, late Campanian-early Maastrichtian of Mendoza). The Titanopodus tracks represent an excellent case study of the wide-gauge style of locomotion produced by Aeolosaurini or Saltasaurinae titanosaurs. In this case, the speeds of the trackmakers were calculated throughout accurate estimations of hip height and gleno-acetabular distance, using for comparisons, an articulated titanosaurian specimen collected in strata that are correlative to those that have yielded Titanopodus tracks (Allen Formation, Neuquén Basin). Traditionally, in titanosaur tracks, the presence of wide-gauge trackways was associated to a low heteropody (e.g. manus:pes ratio between 1:1 to 1:2). However, Titanopodus tracks show a moderate heteropody (~1:2.6) associated with very wide trackways indicating that this general interpretation must be revised. It is probable that both the heteropody and the trackway ratio (ratio of the track width relative to the total trackway width) show variations during ontogenetic stages. Moreover, in an evolutionary perspective, the variations of these parameters are related with the amazing diversity of the titanosaurs (represented by around 48 genera), fact certainly no considered in most of the ichnological analyses.