When dinosaurs roamed the Earth, flying reptiles known as pterosaurs ruled the skies. These leathery-winged flyers reached enormous size, with some species unfurling wings that spanned 30 feet across or more.
The first pterosaurs appeared around 220 million years ago and disappeared from the planet along with the dinosaurs 66 million years ago during the Cretaceous-Paleogene mass extinction. For 200 years, researchers have been unable to trace the evolutionary path this group of reptiles took to get airborne.
Now, newly described fossils may clarify the evolutionary origins of the first vertebrates to develop powered flight, reports Riley Black for Scientific American. The new research, published last week in the journal Nature, analyzes fossils from North America, Brazil, Argentina and Madagascar and comes to the conclusion that pterosaurs evolved from a group of small Triassic reptiles called the lagerpetids, reports George Dvorsky for Gizmodo.
Lagerpetids were small, insectivorous and possibly bipedal reptiles that lived between 201 and 237 million years ago, reports Will Dunham for Reuters. Recent research has suggested these delicately built reptiles might also be ancestors of the first dinosaurs, which appeared around 233 million years ago.
Researchers studied existing lagerpetid fossils as well as newly unearthed specimens using high-resolution scans and 3-D modeling. The analyses yielded 33 skeletal features that made the case for an evolutionary through-line between lagerpetids and pterosaurs, per Reuters.
“Lagerpetids would have the basic body form and skull anatomy of what we think was the common ancestor of pterosaurs and lagerpetids,” Sterling Nesbitt, a paleontologist at Virginia Tech and co-author of the paper, tells Scientific American. “Llagerpetids are essentially flightless pterosaurs.”
As Laura Geggel of Live Science points out, this means the lagerpetids didn’t lead directly to the pterosaurs. Instead, their shared skeletal features, such as the shape of the inner ear, braincase, teeth, hand, leg, ankle and pelvic bones, suggest the two groups shared a relatively recent common ancestor.
In particular, the inner ear and braincase anatomy of lagerpetids hinted at adaptations that have been linked to the pterosaurs’ development of flight.
“The presence in lagerpetids of neuroanatomical features that were previously linked to the origin of flight in pterosaurs indicates that they instead appeared before the acquisition of flight and were exploited later by pterosaurs, allowing them to conquer the skies,” Martín Ezcurra, co-author of the paper and a paleontologist at the Bernardino Rivadavia Natural Sciences Argentine Museum and the University of Birmingham, tells Scientific American.
But, for all their similarities, the lagerpetdids show no anatomical signs of taking to the skies themselves.
“We are still missing lots of information about the earliest pterosaurs, and we still don’t know how their skeletons transformed into an animal that was capable of flight,” says Nesbitt in a statement.
Though the moment of transition between land-dwelling and flying vertebrates remains shrouded by the stone encasing fossils yet to be discovered, if the new findings are confirmed they shrink the gap between the oldest pterosaurs and their closest relatives.