Fossils that were discovered recently, seem to imply that feathers were more widespread than previously assumed. Many of Tyrannosaurus Rex' relatives had feathers, paleontologists now believe T-Rex may have also had them, at an early development stage. Hatchlings may have shed down as they aged.

Full Scale Image or click, here.
This species, Archaeoraptor liaoningensis was discovered in Liaoning Province, China having arms of a primitive bird and a tail of a dinosaur. This fossil represents a missing link between dinosaurs and birds. Studies that have been done on the arms suggest it was better equipped at flight than Archeopteryx.
Archaeoraptor liaoningensis shares similarities to a family of predatory dinosaurs known as dromaeosaurs. A mixture of advanced and primitive traits is what scientists anticipated to find in experimental flight. Says Stephen Czerkas, who lead the study on the newly discovered species, "This fossil is perhaps the best evidence since Archeopteryx that birds did, in fact, evolve from certain types of carnivorous dinosaurs."
Modified image from an original by O. Louis Mazzatenta

Four dinosaur fossils with birdlike bones and trace of feathers have been discovered, not that any of these dinosaur species flew, but the evidence points to feathers being widespread among the carnivorous dinosaurs, including Tyrannosaurus rex.

Beipiaosaurus inexpectus
Largest dinosaur, seven feet long, found with 2" plumage.

Three fossils were recently discovered (November 1999), in Liaoning Province, China. Further discoveries of flightless feathered dinosaurs have also been unearthed in this region, 1996-1997. All four of the new fossils, are theropods, classified as meat-eating. Dromaeosaur, belonging to a family of predators that includes the raptors made famous in Jurassic Park. An oviraptorosaur from Mongolia with bird-like tail and seven foot therizinosaur, and one other fossil, which has arms like a bird, but a tail like a dinosaur.

Un-named Oviraptorosaur
Mongolian fossil specimen, an unidentified Oviraptorosaur which has a birdlike tailbone.

Yale University paleontologist, John Ostrom, proposed that modern birds descended from theropods. Clear impressions of feathers on the Liaoning fossils increase the growing number of known feathered theropod species.

Surrounding the bones on Archaeoraptor liaoningensis, are what clearly appears to be feathers. Some are similar to hairlike protofeathers of the flightless Sinosauropteryx, discovered in 1996. Others look long, broad and suggest feathers suited for flight. Stephen tells us, "It's a missing link. We can't prove that it flew, but even aside from its feathers, its' anatomy [contains] long arms, birdlike shoulders, hands and wrists, [which] doesn't make sense unless it did."

Sinornithosaurus millenii
Classic example of dromaeosaur tail makes it a dinosaur, but other features in strongly resemble bird anatomy.

Fast, bipedal meat-eaters called theropods have four new species:

• Sinornithosaurus millenii
• Beipiaosaurus inexpectus
• Archaeoraptor liaoningensis
• one un-named oviraptorosaur.

Archaeoraptor liaoningensis
Preliminary studies reveal this fossil specimen shares similarities with both birds and dinosaurs.

All theropods, including T. rex, may have had feathers, one of the adaptations that led to flight in Archaeopteryx and perhaps Archaeoraptor.
November 1999, National Geographic

Sinornithosaurus millenii, a dromaeosaur, was the size of an eagle, fierce in appearance, with teeth resembling a barracuda and long, curved claws. Paleontologist Xu Xing explained how the shoulder girdle; scapula, coracoid and furcula, are more similar to bones of a bird, than a dinosaur. These bones are critical for flight, joining at the glenoid fossa, an area determining the degree at which birds can raise their wings above the shoulders to flap. "If you saw just this shoulder girdle, you would think it was Archeopteryx, the earliest bird."

Beipiaosaurus inexpectus is only one of a few therizinosaur fossils known. An important feature is the hollow cores. Hollow, hairlike structures are characteristic of protofeathers -an evolutionary intermediate between feathers and the skin of a reptile. It is the largest known dinosaur with feathers, at a length of seven feet. One theory holds that dinosaurs may have evolved feathers for insulation, which raises another question: were dinosaurs warm blooded?

The final five vertebrae of a Mongolian oviraptorosaur's tail are fused into a pygostyle, but for birds this serves the purpose of holding tail feathers serving as crucial flight-control aid. Velociraptor's tail is composed of many vertebrae. But in an oviraptorosaur's tail, it ends with an incipient version of the pygostyle, and has fewer vertebrae. As birds have evolved, their tails have shortened. The pygostyle's tail feathers assist birds in flight maneuvers and possibly like the oviraptorosaur, used in mating ritual displays or intimidation of rivals.
Adapted from an image by P. Sloan

A small birdlike fossil, discovered in Mongolia, named Shuvuuia deserti, has been studied by Biologist Mary Schweitzer of Montana State University, who is helping to answer the question of warm-blooded dinosaurs. Tests performed on the fossil have shown the fibers are similar to feathers, both chemically and structurally. "The only animals living today with body coverings of hair or feathers have the high metabolic rates of warm-blooded creatures. It seems reasonable to assume that this was true in the past as well. Dinosaurs that possessed body coverings were probably either warm-blooded or had metabolic rates significantly higher than those of modern cold-blooded animals."

The article concludes with, a large-bodied animal likeTyrannosaurus Rex in the sub-tropical Cretaceous did not likely have need of feathers, unless they were for purpose of display. The larger the body of an animal, the more heat it could produce, but juvenile T-Rex hatchlings may have had down on their bodies.

Sinornithosaurus millenii

Scientists can say that BIRDS ARE THEROPODS with the same confidence, when they say humans are mammals.
Impressions of feathers surround the fossilized bones of the 120 million year old Sinonithosaurs millenii. According to paleontologist Xu Xing, this birdlike dinosaur likely fed on lizards and small mammals. The creature was likely covered in small (down) feathers. It could leap, but not fly. It's furcula, or wishbone was boomerang-shaped and resembled that of Archaeopteryx. The tail vertebrae contain bundles of slim rods that stiffened the tail which assisted the bird in maneuvering. This characteristic helped scientists identify the fossil as a dromaeosaur. This fossil contributes to the theory that feathers evolved for insulation or display, rather than flight, and that quite possibly, some species of dinosaurs were warm-blooded.

Images adapted from, and text paraphrased from an article by National Geographic Magazine, November 1999
Feathers for T. Rex, by Christopher P. Sloane, with Photographs by O. Louis Mazzatenta

REFERENCES
The Complete National Geographic, 111 Years; 1888-2000

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Article last updated September 3, 2006
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