Nature 417, 936-938 (2002)
Bird-like fossil footprints from the Late Triassic
RICARDO N. MELCHOR*+, SILVINA DE VALAIS++ & JORGE F. GENISE*++
* CONICET, Av. Uruguay 151, 6300 Santa Rosa, La Pampa, Argentina
+ Universidad Nacional de La Pampa, Av. Uruguay 151, 6300 Santa Rosa, La Pampa,
Argentina
++ Museo Paleontolo'gico "Egidio Feruglio", Av. Fontana 140, 9100 Trelew,
Chubut, Argentina
The study of fossilized footprints and tracks of dinosaurs and other
vertebrates 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 record. The known history of birds
starts in the Late Jurassic epoch (around 150 Myr ago) with the record
of Archaeopteryx, whereas the coelurosaurian ancestors of the birds
date back to the Early Jurassic. The hind limbs of Late Triassic epoch
theropods lack osteological evidence for an avian reversed hallux and also
display other functional differences from birds. Previous references to
suggested 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 IV and in all cases their avian affinities have
been challenged. Here we describe well-preserved and abundant footprints
with clearly avian characters from a Late Triassic redbed sequence of
Argentina, at least 55 Myr before the first known skeletal record of
birds. These footprints document the activities, in an environment
interpreted as small ponds associated with ephemeral rivers, of an
unknown group of Late Triassic theropods having some avian characters.
Andrew Taylor
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