Animals with bird-like feet were roaming the planet more than 200 million years ago, scientists say.
Analysis of ancient footprints, which experts were calling Trisauropodiscus, suggest these creatures were likely to have been three-toed.
It is unclear who made the track marks, but experts speculate they may have come from a dinosaur or a reptile.
But they said the findings, published in the journal Plos One, showed 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.
The authors wrote: “Birds are one of the most diverse groups of animals on Earth with 10,000 extant species, yet their early evolutionary history is still shrouded in mystery.”
The four sets of footprints uncovered in Lesotho, southern Africa, were analysed by a team of experts from the University of Cape Town, which also included an 80-metre-long tracksite found in the village of Maphutseng.
The team identified two distinct characteristics among the sets of footprints, the first of which was similar to non-bird dinosaur tracks while the second resembled modern-day bird footprints in size and proportion.
The researchers say it is possible that these tracks were produced by dinosaurs but note they could also have come from other reptiles that evolved to have bird-like feet.
At over 210 million-years-old, the footprints are 60 million years older than the earliest known fossils of true birds, they said.
The authors wrote: “Trisauropodiscus tracks are known from numerous southern African sites dating back to approximately 215 million years ago.
“The shape of the tracks is consistent with modern and more recent fossil bird tracks, but it is likely a dinosaur with a bird-like foot produced Trisauropodiscus.”