Bird-like footprints from the Late Triassic

RICARDO NESTOR MELCHOR; SILVINA DE VALAIS,; F GENISE, JORGE

NATURE

Nature Publishing

Lugar: Oxford; Año: 2002 vol. 417 p. 936 - 938

0028-0836

Vertebrate ichnology has provided insight into the origin, evolution and extinction of several major groups and their behaviour, it has also been an important complement to their body fossil record1-4. The known history of birds starts in the Late Jurassic (ca. 150 Ma) with the record of Archaeopteryx5, whereas the coelurosaurian ancestors of the birds date back to the Early Jurassic6. The hind limbs of Late Triassic theropods lack osteological evidence for an avian reversed hallux and also display other functional differences from birds7. Previous references to purported Late Triassic to Early Jurassic bird-like footprints have been reinterpreted as produced by non-avian dinosaurs having a high angle between digits II and IV8,9 and; in all cases, their avian affinities have been challenged10. Here we describe well-preserved and abundant footprints with clearly avian characters from a Late Triassic redbed sequence of Argentina11,12, at least 55 Ma before the first known skeletal record of birds. These footprints document the activities, in an environment interpreted as small ponds associated with ephemeral fluvial channels, of an unknown group of Late Triassic theropods having some avian characters.