Four-Winged Dinosaur May Have Hunted Early Birds 120 Million Years Ago

One fossil arm may solve a 120-million-year-old predator mystery.

At a Cretaceous lake in what is now northwestern China, paleontologists have found the fossilized remains of ancient birds piled up in the mud by the hundreds. Some of their bones were smashed into tight, pellet-like clumps—the kind of remains a predator might cough up after a meal—but the hunter itself left no trace in the fossil record.

Now researchers say a lone 120-million-year-old shoulder and arm may reveal the culprit: Jian changmaensis, a newly named, feathered microraptor that likely glided through the trees on four winglike limbs.

So these early birds were likely being hunted by a feathered dinosaur that still trying to figure out powered flight, a stunning predator-prey dynamic that is rarely spoken about among conversations dominated by more charismatic predator dinosaurs like T.rex.

One Wing

The Changma Basin, in Gansu Province, has yielded more than 100 partial bird skeletons from the Lower Cretaceous Xiagou Formation. Many preserve traces of feathers, skin, and other soft tissues. The site is especially known for yielding Gansus yumenensis, one of the earliest fossil birds found in China.

Until now, that picture was strangely one-sided. Changma had birds in abundance, but almost no sign of the larger animals that lived beside them. Then researchers reexamined a fossil first noted years ago: part of a left shoulder and forelimb, including the scapulocoracoid, humerus, radius, and ulna.

The arm bones did not match Changma’s birds. Instead, they pointed to a microraptor, a feathered carnivore from the same dinosaur family as Velociraptor.

In the new study, researchers describe that fossil as a new genus and species, Jian changmaensis—from Jiān, the one-winged bird from Chinese mythology, a nod to the animal’s birdlike body and the lone preserved forelimb and changmaensis from the place where it was found.

“Scientists have found these weird, broken-up clusters of bird bones at this site, and we didn’t know what made them,” said Jingmai O’Connor, a paleontologist at the Field Museum and senior author of the study. “This new microraptor dinosaur, Jian changmaensis, is our best guess,”

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The fossil is fragmentary, but the context in which it was found carries weight. At a site dominated by early birds, Jian gives researchers their first clear non-bird dinosaur body fossil from the Changma Basin—and it belonged to a larger carnivore.

“It’s the only dinosaur found at this site that wasn’t a bird, it was a carnivore, and it was much bigger than everything else that we’ve found there,” O’Connor noted.

Four Wings

Jian changmaensis was a dromaeosaur, a.k.a. a raptor. Unlike the exaggerated movie adaptations, these animals looked more birdlike and were far smaller.

The holotype consists of only the shoulder and arm—the one wing. The upper arm and the shoulder matched the anatomy of microraptors, which carried long feathers on both the forelimbs and hind limbs. In life, Jian probably had four winglike surfaces: two on its arms and two on its legs.

That does not mean it flew like a crow. Microraptor anatomy suggests they could not sustain flapping flight. Instead, this creature was likely a good climber that probably glided between trees and ambushed prey.

“Jian and the other microraptors probably weren’t capable of true, powered flight, but they could probably glide like a flying squirrel,” O’Connor explained.

It likely had a toothed snout, a long bony tail and the trademark curved claws on its feet.

The preserved upper arm measures about 10 centimeters (4 inches). By comparing it with related microraptors, researchers estimate that Jian may have had a wingspan of roughly 1.2 meters (4 feet), about the span of a barn owl. That made it large for a microraptor, though still smaller than some of the group’s biggest known relatives.

A Predator at the Lake’s Edge

The Changma Basin was not a dinosaur graveyard—although, technically birds are dinosaurs. It was an ancient lake, and lakes tend to preserve the animals that lived in or near the water. That preservation bias may explain the imbalance: the lake sediments captured birds such as Gansus, which had webbed feet, far more often than they captured a tree-dwelling predator like Jian.

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“If you could take a time machine back 120 million years ago, you’d be on the shore of a vast lake with vegetation surrounding it,” Matt Lamanna, a paleontologist at the Carnegie Museum of Natural History and a coauthor of the study, told CNN. “It stands to reason that maybe if you’re looking in a lake, you might find the animals that are living there more than you would find the animals that are living around the margins.”

The researchers cannot prove Jian ate Changma’s birds. No stomach contents preserve its last meal. But the evidence now lines up: abundant small birds, pellet-like bone masses and one unusually large microraptor in the same deposits.

The find sharpens the picture of Changma from a bird-rich lake into a habitat with predators, prey, and close dinosaur relatives experimenting with aerial movement long before modern birds.

The study was published in the journal Annals of Carnegie Museum.