Mysterious bird-like tracks in Africa: The oldest birds?

Fossil tracks found in southern Africa, push the potential evolution of the first birds back to 210 million years ago – during the Triassic (252–201 million years ago), the first epoch of the “Age of Dinosaurs.”

Birds are all around us today, with more than 10,000 species around the world. But when did birds evolve?

It is now pretty well understood that birds are dinosaurs. Specifically, they are the branch of the dinosaur lineage that survived the mass extinction caused by an asteroid that crashed into Earth 66 million years ago.

But what is less well understood is when birds first emerged.

Archaeopteryx (meaning “old wing”) lived 150 million years ago. The fossils, discovered in the late 19th century in Germany, were believed to represent the oldest bird.

However, in the last 15 years, older potential avians have since been identified, including Anchiornis, Xiaotingia and Aurornis. These dinosaurs all lived about 160 million years ago.

Research published in PLOS ONE might push the first birds back in time by 50 to 60 million years.

The study analysed fossil footprints known by the ichnospecies (a taxon based on the fossilised impressions made by an organism, not the body of the organism itself) Trisauropodiscus.

Numerous Trisauropodiscus sites have been found throughout southern Africa. For decades, palaeontologists have debated what kind of animal could have left the distinctive three-toed prints, and how many different species of Trisauropodiscus exist.

Examining Trisauropodiscus traces at four sites in Lesotho, the team identified two distinct morphologies. One is similar to non-avian dinosaur tracks. The other is very close in size and proportions to the footprints of birds.

So, who made the footprints if the earliest known birds didn’t emerge until at least 50 million years later?

“The only Late Triassic body fossil specimen posited to be bird-like is Protoavis, but this assessment is based on ambiguous material and is not widely accepted to be a basal [archaic] bird,” write authors Dr Miengah Abrahams and Professor Emese Bordy, both from the University of Cape Town.

It’s possible the tracks were made by some other early dinosaur – even one that is an early member of a near-bird lineage. But there could also have been another reptile species that also evolved feet that resemble those of modern birds.

“Trisauropodiscus tracks are known from numerous southern African sites dating back to approximately 215 million years ago,” they write. “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.”

Until the fossil of an animal that lived at the right time, in the right place, and with the right proportions is found, the mystery of who created the Trisauropodiscus tracks remains.