Large theropod dinosaur footprint associations in western Gondwana: Behavioural and palaeogeographic implications

MORENO, K.; DE VALAIS, S.; BLANCO, N.; TOMLINSON, A. J.; JACAY, J.; CALVO, J. O.

ACTA PALAEONTOLOGICA POLONICA

INST PALEOBIOLOGII PAN

Lugar: Varsovia; Año: 2012 vol. 57 p. 73 - 83

0567-7920

In modern terrestrial ecosystems, the population size of large predators is low, and a similar pattern has usually been as− sumed for dinosaurs. However, fossil finds of monospecific, large theropod accumulations suggest that population dynam− ics were more complex. Here, we report two Early Cretaceous tracksites dominated by large theropod footprints, in Querulpa Chico (Peru) and Chacarilla (Chile). The two sites correspond to distinct depositional environments?tidal ba− sin/delta (Querulpa Chico) and meandering river (Chacarilla)?with both subject to extensive arid or semiarid palaeo− climatic conditions. Although most trackways show no preferred orientation, a clear relationship between two trackmakers is observed in one instance. This observation, coupled with the high abundance of trackways belonging to distinct large theropods, and the exclusion of tracks of other animals, suggests some degree of grouping behaviour. The presence of fresh− water sources in a dry climate and perhaps social behaviour such as pair bonding may have promoted interactions between large carnivores. Further, the occurrence of these two tracksites confirms that large theropod dinosaurs, possibly spino− saurids and/or carcharodontosaurids, existed on the western margin of Gondwana as early as the earliest Cretaceous.