T. rex has another fine, feathered cousin

New dinosaur species was generously plumed

From 125-million-year-old rocks, scientists have unearthed the remains of a new species of extensively feathered dinosaurs that weighed up to about 1,400 kilograms and stretched 9 meters from nose to tail.

An artist’s impression of a group of Yutyrannus shows the newfound dinosaur’s feather-covered body. Brian Choo

The skull of Yutyrannus, along with other fossils from China, helped paleontologists unravel its relationship to Tyrannosaurus rex. Zhang Hailong

The fossils, from one adult and two younger dinos, were unearthed in northeast China, a region known for keeping soft tissues of ancient animals well-preserved. The discovery is described April 5 in Nature.

“It changes the way we really look at things — from these big, scaly, Jurassic Park animals to ones that were big and fluffy,” says Mark Norell, a paleontologist at the American Museum of Natural History in New York City.

Based on the shapes of the jaw and skull bones found in the fossils, the team concluded that the three animals belonged to the same species and were tyrannosaurs. Such dinosaurs fall under a broader classification of two-legged meat-eaters called theropods, which scientists believe gave rise to modern birds.

The biggest of the newly described creatures — the largest extensively feathered dino known to date — was about one-quarter the weight of its relative, Tyrannosaurus rex. The smaller dinosaur is named Yutyrannus huali, which translates to “beautiful feathered tyrant.”

The new species had feathers that were at least 15 centimeters long and look as if they covered the dinosaur’s skin. This might have given the dinosaur a shaggy appearance, says study author Corwin Sullivan, a paleontologist at the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences in Beijing.

But the full extent of this covering is difficult to confirm because the specimens aren’t complete.

Over the past decade, scientists have characterized many dinosaurs that thrived around this time but have been unable to describe them fully. “For the vast majority of dinosaurs we only have bone. We don’t have feathers or featherless skin,” Sullivan says.

The find renews longstanding questions about the role feathers played early in dinosaur evolution. Full-feathered dinosaurs that have been discovered so far have been much smaller, and much more likely to lose body heat because of their size. So scientists thought these petite creatures used a fluffy layer to stay warm.

The study authors think that the newfound dinos might have also needed some insulation. But Norell is not convinced. Many large animals that live in warm climates, such as modern giraffes and wildebeests, have external covering but don’t need it for insulation, he says.

Both the authors and Norell say that the feathers might also have helped the dinosaurs show off and attract mates.

Other traits the new dinos had include a high, bumpy nose plate, known as a midline crest. And although it’s unclear what type of posture the animals maintained, Sullivan estimates that the full-grown dino stood about 2.5 meters tall.

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