This one’s a headscratcher.
More than 200 million years ago, a mystery animal left bird-like footprints across what is now South Africa – 60 million years before birds evolved.
For many years, researchers have puzzled over what may have left these three-toed tracks, and whether it was a dinosaur, one of their lizard cousins, or something else. The tracks do not match those for any known species in that place, at that time.
Scientists have provisionally named the creature Trisauropodiscus, but have no other information about what may have left the footprints, discovered in the middle of last century.
Now, a new study investigating the tracks has discovered two distinct types of print, the first of which is similar to certain non-bird dinosaur tracks, and the second of which is very similar in size and proportions to the footprints of birds.
The fossilised imprints date back to the Late Triassic and Early Jurassic periods, 237 to 175 million years ago, while evidence of what many consider to be the first bird, Archaeopteryx, appeared in the Middle to Late Jurassic periods, 175 to 145 million years ago. Modern birds evolved in the Cretaceous period.
Writing in the journal PLOS ONE, authors Miengah Abrahams and Emese Bordy from the University of Cape Town highlight the still fuzzy origins of the first birds.
‘Birds are one of the most diverse groups of animals on Earth, with around 10,000 extant [existing] species, yet their early evolutionary history is still shrouded in mystery,’ they said.
‘The dinosaur origin of modern birds (Neornithes) unequivocally points to Maniraptora, a group of therapos, but the timing of the origin of birds is contested.
‘The oldest body fossil record of basal [early] birds comprises Middle to Late Jurassic, while dinosaurian footprints with bird-like morphologies are known since the Late Triassic.’
However, debate still continues over the earliest bird-like fossil, that of Protoavis, which is not widely accepted to be a bird. This means the leap from pterosaurs to birds is still yet to be explained.
The authors say the findings show bird-like feet evolved much earlier than thought, possibly by 60 million years, and could help shed new light on how birds came into existence.
They add that the second type of tracks, more similar to those of birds, were likely made by a yet-to-be-discovered tridactyl archosaur – ancestors of modern birds.
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