Feathered dinosaur

A feathered dinosaur was a dinosaur whose body was at least partially covered with feathers at some point in its life. For almost two centuries, paleontologists believed that dinosaurs were closely related to lizards and shared physical characteristics with modern reptiles. However, thanks to fossils discovered in China during the mid-1990s, paleontologists found that some types of dinosaurs actually sported feathers and evolved into modern-day birds. In some dinosaurs, the feathers were more of a protofeather, a type of fuzz that likely helped keep the creatures warm. However, other dinosaurs may have developed a fuller coat of feathers that they could have used during mating rituals or as a way to appear more fearsome. Feathers were more common in a type of dinosaur called a theropod, a two-legged dinosaur that included many of the most ferocious prehistoric carnivores, such as the iconic Tyrannosaurus rex.

Background

Dinosaurs first evolved between 240 million and 230 million years ago during a geological period known as the Triassic. The earliest dinosaurs were dog- and horse-sized creatures that had a mostly upright posture with their legs underneath their bodies rather than out to the side. This gave them an evolutionary advantage because they were able to run faster and more efficiently. This upright posture also left their front legs free to grasp tree branches and kill prey with their claws.

By the time of the Jurassic period, about 200 million to 145 million years ago, dinosaurs had become the dominant creatures on the planet. The largest dinosaurs lived during the Cretaceous period, which lasted from about 145 million years ago to 66 million years ago.

As of the early 2020s, paleontologists have identified more than 1,500 types of dinosaurs that lived from the Triassic to the Cretaceous periods. All known dinosaurs can be divided into three basic types: ornithischians, sauropods, and theropods. Ornithischians were beaked dinosaurs that fed on plants. Many walked on all fours, but a few walked on two hind legs. Some, like the Ankylosaurus, were covered in strong armor, while others, such as the Stegosaurus, had large bony plates along their back and spiked tails.

Sauropods were very large dinosaurs characterized by their small heads, long necks, bulky bodies, and long tails. Sauropods were also plant eaters and were among the largest land animals ever to exist. The Brachiosaurus and Brontosaurus are among the best-known types of sauropods. The theropods, a name meaning “beast-footed,” were two-legged dinosaurs with long bodies and hollow bones. They were primarily meat eaters, although some later evolved a diet that consisted of both plants and animals. An example of this type of theropod was the Ornithomimosauria, a fast-moving dinosaur that resembled an ostrich. The purely carnivorous theropods had a mouth full of sharp, curved teeth, and clawed feet and hands. The most famous of these theropods is the Tyrannosaurus rex, a deadly predator that could grow close to 40 feet (12 meters) in length.

Overview

Feathered dinosaurs were not a new concept to paleontologists prior to the late twentieth century. An Archaeopteryx, a feathered cross between a bird and a dinosaur, was discovered in Germany in the 1860s. The Archaeopteryx was considered to be one of the oldest ancestors of modern birds and sported feathered wings along with a long bony tail. They were seen as different than the other dinosaurs, which were thought of as giant lizards. In fact, the word dinosaur comes from the Greek words for “terrible lizard.”

In 1996, Chinese paleontologists working in the province of Liaoning in northeastern China discovered the fossil of a 5-foot (1.5-meter) long theropod they called Sinosauropteryx. The head, back, and tail of the Sinosauropteryx were covered with a soft, fuzzy type of feather similar to down. The feathers would not have been able to allow the creature to fly. Scientists speculated that they could have been used as an insulating material for warmth. The region in which the Sinosauropteryx fossil was discovered is covered in fine-grained sediment that includes volcanic ash. While most fossil sites preserve only bones, the environment in Liaoning preserves soft tissue, making it ideal for discovering feathered dinosaurs. The fossils from the region date to between 135 million and 120 million years ago.

Since 1996, paleontologists have unearthed the fossils of more than fifty feathered dinosaurs at sites around the world. Most of them have been found at Liaoning, but feathered dinosaur fossils have also been found elsewhere in China and at sites in Burma, Canada, Germany, Madagascar, Mongolia, and Russia. Some have traces of fluffy down similar to the Sinosauropteryx, while others have fully formed feathers. Some fossils display a distinctive tailbone that could have acted as a connecting point for feathers. Still others have forearm bumps known as quill knobs where feathers could have been connected to ligaments as is the case with modern birds.

Based on the discoveries at Liaoning and later research, scientists believe that most theropod dinosaurs had some form of feathers. Feathers have also been discovered in some ornithischian species, leading to speculation that other types of dinosaurs may have been feathered. The oldest feathered theropods likely used their feathers for warmth, but later therapods evolved more distinctive feather patterns that could have been used for display purposes, such as in a mating display or to intimidate other dinosaurs. However, even the more evolved feathered dinosaurs did not use their feathers for flight. Their underlying muscles and body structure were not strong enough to permit true flight. Feathered dinosaurs most likely used their feathers to glide between trees.

Scientists believe that feathered theropods slowly evolved to become modern birds. They first evolved to walk on two legs; developed smaller bodies, hollow bones, and rudimentary feathers; then developed more advanced quill-like feathers that eventually enabled flight. Based on the new research, paleontologists now classify the Archaeopteryx as a sort of intermediary species between feathered theropods and modern birds.

Examples

Arguably, the most famous dinosaur ever discovered was the Tyrannosaurus rex, or the T. rex. The T. rex was a large carnivorous dinosaur that was about 40 feet (12 meters) long and stood about 12 to 15 feet (4 to 5 meters) tall. It lived between 85 and 65 million years ago in North America.

Based on fossils discovered in Liaoning, a smaller relative of the T. rex, Dilong paradoxus, was found to have a thin coat of feathers. This suggests that the T. rex may have also been a feathered theropod. Paleontologists theorize that the Tyrannosaurus rex may have been born with feathers as an insulating feature. However, the feathers may have disappeared as the creature matured.

Another type of feathered dinosaur was the Velociraptor. Movie fans may know of the name from the Jurassic Park film series, but the dinosaur featured in the films is not a Velociraptor. Real Velociraptors lived about 70 million years ago and were about the size of a large turkey. Velociraptors were covered in feathers and sported claws on their wing-like arms. They were carnivores and likely used their claws and arms to pin down their prey. Scientists speculate that their feathers could have been used for warmth and for mating displays. Despite having arms that resembled wings, Velociraptors could not fly.

The Zhenyuanlong suni was a 6-foot (2-meter) long dinosaur that was related to the Velociraptor. Zhenyuanlong fossils were first discovered in Liaoning in 2015. Its body was covered in fine hair-like feathers with larger quilled feathers on its tail and wings. The creature lived about 125 million years ago and had the largest-known feathered wings found on a dinosaur. It resembled a large eagle that ran and hunted on the ground. Its appearance was such that Scottish paleontologist Steve Brusatte described the Zhenyuanlong suni as a “fluffy feathered poodle from hell.”

The smallest-known dinosaur is a feathered theropod known as a Microraptor. First discovered in 2000 at Liaoning, the Microraptor, a name meaning “small thief,” was about the size of a pigeon. It had feathered wings on its forearms and hind legs, making it a four-winged dinosaur. Microraptors could not fly, but likely used their wings to glide between trees.

Another small feathered theropod was the Epidexipteryx, which was about a foot long when its distinctive tail was included. The Epidexipteryx was covered with fuzz-like downy feathers, but had four longer feathers emerging from its tail. Paleontologists believe these feathers were used solely for display or ornamentation, making the Epidexipteryx the oldest-known feathered dinosaur that used its feathers for these purposes. The Epidexipteryx is also noteworthy for its elongated third finger, which it may have used to dig out insects nesting in trees or in the ground.

In 2014, paleontologists at a site in Russian Siberia discovered fossils of a feathered ornithischian dinosaur. The creature, dubbed Kulindadromeus, was about 5 feet (1.5 meters) long and lived between 165 and 145 million years ago. The Kulindadromeus was a plant eater and was covered in a short coat of bristle-like feathers about a half-inch long. The discovery raised the idea that all dinosaurs could have had feathers, although most paleontologists do not subscribe to that theory.

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