Near the end of the age of dinosaurs, hulking lizards such as Tyrannosaurus rex ruled the Earth, while immense flying reptiles known as pterosaurs held dominion over the skies. But to the surprise of paleontologists, it seems one winged beast of the Late Cretaceous was thinking small.

A pterosaur that lived roughly 70 to 85 million years ago stood only as tall as a cat and had a wingspan just slightly wider than that of a great horned owl, according to the team that found the newly described fossil. (By contrast, the biggest known flying seabird had a 21-foot wingspan.)

Every other known pterosaur of the day was super-sized, leading to the proposal that birds pushed aside smaller aerial reptiles during the waning days of the Cretaceous. The itty-bitty pterosaur now calls that idea into question, the authors say.

“We’ve got a small pterosaur when everyone said they shouldn’t be there,” says study co-author Elizabeth Martin-Silverstone of Britain’s University of Southampton and University of Bristol. “But we have one, and that’s really cool.”

Small Wonder

Tiny pterosaurs, including at least one that could’ve nestled in the palm of your hand, thrived during the Jurassic and Triassic. But by the time the Cretaceous was winding down 80 million years ago, pterosaur options ranged from extra large to ginormous.

Some Late Cretaceous pterosaurs had wingspans of nearly 10 feet, making them about as big as a California condor. Many more were far larger, and several were in the range of 30 feet and up, rivaling the size of light aircraft. (Also see “Giant Pterosaurs Could Fly 10,000 Miles Nonstop.”)

The absence of pint-sized pterosaurs dating back to this era led to the proposal that “the niche for smaller animals was filled by birds,” Martin-Silverstone says. The reasoning went that “in order to survive, pterosaurs had to be big.”

A lucky encounter between human and fossil may change that thinking. In 2008, then-amateur paleontologist Sandy McLachlan was patrolling the coast of Canada’s Hornby Island, a fossil-rich locale, when he spotted a softball-sized rock nodule.

Fossil hunters there normally break apart such nodules to see what's inside. But McLachlan, who is now studying paleontology at Canada’s University of Victoria, saw bits of vertebrae in the rock, not just the usual mollusk shells. “Right then and there,” he says, “I knew this is not something you hit on the beach and destroy.”

His initial work on the fossil revealed what he calls a “flying something.” After the specimen reached Martin-Silverstone, she and her colleagues decided it wasn’t a bird and that, despite its size, it was nearing the end of its growing days.

According to their analysis, appearing in this week’s Royal Society Open Science, the animal had a wingspan around five feet. And despite its diminutive frame, it was probably closely related to other pterosaurs that were as tall as giraffes and boasted wingspans three times longer than anything alive today.

“Maybe small pterosaurs weren’t outcompeted,” Martin-Silverstone says. “Maybe they’re just not being preserved” in the fossil record.

Bone to Pick

Because the researchers have only vertebrae, a forelimb bone, and a few other fossil scraps to examine, they didn’t designate the animal as a new species. Nor do they know how it made a living. Its humongous relatives probably preyed on small dinosaurs, while slightly smaller kin may have eaten fish. (Read “Toothy Texas Pterosaur Discovered; Soared Over Dallas.”)

The sparse fossil evidence has other scientists reserving judgment about this bizarre beast and its meaning for pterosaur evolution.

“The authors have done a good job given the limited data,” Richard Butler of Britain’s University of Birmingham says via email. “A pterosaur identity is probable … but they cannot be completely certain that it is not a bird.” He’s also not yet convinced that the animal was close to full size.

Martin-Silverstone responds that the fossil bones looks more like a pterosaur than a bird. For example, the remains include one flight adaptation Cretaceous birds didn’t have: a redesign of some of the vertebrae to provide extra support for wing muscles. She also argues that the bones show changes that, in other pterosaurs, signal that the animal is nearly as big as it will get.