The shared history of birds and dinosaurs is well-established, but exactly how true birds evolved during the Mesozoic is a bit of a mystery.
Adding to this conundrum are fossilized footprints of bird-like tracks that are 210 million years old—a good 60 million years before the arrival of the genus Archaeopteryx, one of the oldest true birds ever discovered.
While scientists can’t ascertain what produced these tracks, it definitely establishes that bird feet evolved millions of years earlier than we previously thought.
The age of the dinosaurs never really ended—it only evolved. Birds (and their more reptilian cousins, the Crocodilia) are the modern-day legacy of dinosaur’s 165-million-year-long stint on Earth. While our avian friends’ Mesozoic origin story isn’t up for debate, the timing of when birds first arrived on Earth isn’t as clear cut.
Exhibit A in this prehistoric mystery is a series of bird-like footprints at the Maphutseng paleontological site in Lesotho. Drawing data from four sites—along with a detailed 262-foot-long set of fossil prints—scientists at the University of Cape Town (UCT) identified two types of footprints belonging to the Trisauropodiscus, a kind of three-toed dinosaur from the Late Triassic/Early Jurassic whose fossils are common across Africa.
One set of tracks resembles footprints found at other sites. But a second set is surprisingly similar to bird tracks, which were half the size of the other tracks, wider than they were taller, and contained slender toes. While these are all common attributes of bird tracks, there’s just one problem—true birds don’t arrive in the fossil record until some 60 million years later, in the Late Jurassic. UCT scientists published the results of their study last week in the journal PLOS ONE.
“Fossil tracks of early birds and theropods, the co-existing dinosaurian ancestors of birds, co-occur in the rock record since the Early Cretaceous. However, the evolutionary transition from dinosaur to bird and the timing of the birds’ origin are still contested,” the paper reads. “That these tracks of southern Africa, dating to the Late Triassic, so strongly resemble Cenozoic and modern bird tracks substantiates the converging pedal morphology of Late Mesozoic archosaurs and firmly shows that the origin of bird-like foot morphology is at least ~210 million years old.”
Although scientists now have these early, bird-like footprints, they’re not certain exactly who made them. The researchers say that they could belong to the earliest known ancestor of the modern birds, or to a dinosaur that belongs to the near-bird lineage. However, it’s also possible that this is a case of convergent evolution—another, unrelated species could have independently evolved the same type of foot. What can be confirmed is that the evolution of bird-like feet is officially many millions of years older than we originally thought.
It wasn’t until 1861 that the discovery of Archaeopteryx—a Jurassica-era proto-bird—revealed the dino ancestory of the modern bird. In the 160 years since, paleotonlogists have only drawn more connection between the class Aves and their reptilian forebears. T. rexes might now be displayed in their more resplendent plumage, but mysteries like these tracks found in Lesotho prove that there is still a lot more to learn about early creatures.
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