"Beautiful" Squirrel-Tail Dinosaur Fossil Upends Feather Theory

A newfound squirrel-tailed specimen is the most primitive meat-eating dinosaur with feathers, according to a new study. The late-Jurassic discovery, study authors say, challenges the image of dinosaurs as "overgrown lizards."

Unearthed recently from a Bavarian limestone quarry, the "exquisitely preserved" 150-million-year-old fossil has been dubbed Sciurumimus albersdoerferi—"Scirius" being the scientific name for tree squirrels.

Sciurumimus was likely a young megalosaur, a group of large, two-legged meat-eating dinosaurs. The hatchling had a large skull, short hind limbs, and long, hairlike plumage on its midsection, back, and tail.

"I was overwhelmed when I first saw it. Even apart from the preservation of feathers, this is certainly one of the most beautiful dinosaur fossils ever found," said study leader Oliver Rauhut, a paleontologist at the Bavarian State Collections of Palaeontology and Geology in Germany.

(See "One-Ton Feathered Dinosaur Found: Fluffy and Fierce.")

Goodbye, Overgrown Lizards?

Previously, paleontologists have found feathers only on coelurosaurs—birdlike dinosaurs that evolved later than so-called megalosaurs such as Sciurumimus.

Because Sciurumimus is not closely related to coelurosaurs, the new fossil suggests feathered dinosaurs were the norm, not the exception, Rauhut said.

"Probably all dinosaurs were feathered," he added, "and we should say good bye to the familiar image of the overgrown lizards."

Previous research had already suggested that feathers were widespread in the Cretaceous and late Jurassic periods (prehistoric time line), noted Corwin Sullivan, a paleontologist at the Chinese Academy of Sciences in Beijing—even if few specimens have been found.

Feathered-dinosaur remains are sparse because "we only find them in places where conditions were just right for their bodies to be buried and preserved in a way that kept the feathers as well as the bones intact," Sullivan, who was not involved in the research, noted by email.

(See "Dinosaur True Colors Revealed for First Time by Feather Study.")

Dinosaur-Feather Evolution Still Up in the Air

More interesting, according to Sullivan, is what Sciurumimus means for how dinosaurs evolved feathers.

Scientists weren't sure if dinosaurs other than coelurosaurs had feathers. But Sciurumimus is "the first clear evidence" that feathers predated those birdlike dinosaurs, Sullivan said.

Other than meat-eating dinosaurs, hair-like feathers are also known in two bird-hipped dinosaurs, a completely different branch of the dinosaur family tree.

According to the study authors, this "obviously" suggests that dinosaurs' common ancestor had feathers, which passed the trait on to each branch of the dinosaur family tree. (See pictures of big, bad, bizarre dinosaurs in National Geographic magazine.)

"I would say that this is an obvious possibility, rather than an obvious conclusion," Sullivan said.

Although the feathers of bird-hipped dinosaurs look similar to those of Sciurumimus and primitive coelurosaurs, it's still possible the trait evolved independently, and not in a common ancestor.

"We paleontologists are going to need to find more fossils—of things even less closely related to birds than Sciurumimus—to be sure."

Squirrel-tailed dinosaur study published this week in the journal Proceedings of the National Academy of Sciences.