Dinosaur Bones, Beaks, and Claws

Today is a great time to be a dinosaur paleontologist. Now that it is commonly accepted that birds really are living dinosaurs, scientists have expanded their studies beyond fossilized bones. Whether comparing the claws of living birds and with those of extinct dinosaurs or experimenting to learn how bird beaks might have evolved, researchers are finding out more about dinosaurs—living and extinct—than they ever thought possible.

Artist's rendering of Khaan mckennai.
Zhao Chuang; courtesy of Peking Natural Science Organization  

Making comparisons to living birds can help researchers draw new conclusions about extinct dinosaurs. In Dinosaurs Among Us, you’ll be able to see the fossilized specimens of Khaan mckennai known as Sid and Nancy. These animals are oviraptorids, a group of fairly small, bird-like dinosaurs with toothless beaks, wishbones, and skulls filled with air pockets.

These Khaan mckennai dinosaurs are similar to birds in many ways. 
©AMNH/M. Ellison

While these animals are nearly identical, scientists suspect the specimen on the left is a male, based on the presence of large structures beneath its tail that have a triangular, spearheaded shape. Those structures are smaller in the animal on the right, and lack the triangular, or “chevron,” shape, suggesting that the larger structures could have supported the muscles used in a tail-feather display, much like those still put on by birds like the sage grouse and peacock.

Some male dinosaurs may have displayed their feathers during courtships the way peacocks do.
Courtesy of Wikimedia Commons

Birds have hollow bones, and most scientists assumed this trait evolved along with flight: lighter bones should make it easier to fly. But studies have shown that Allosaurus, a fairly primitive theropod, also had hollow bones. Allosaurus was a big animal with tiny arms, so it wasn’t flying anywhere—like so many other bird traits, hollow bones appear early in the dinosaur family tree. 

Fossils show that some dinosaurs, including Allosaurus, were hollow-boned.
©AMNH/C. Chesek

Hollow bones are of among several traits that made early birds well prepared for flight before they could take to the skies. Another is the development of the furcula, or wishbone, so common in birds. Once thought unique to birds, wishbones started turning up in some bipedal, meat-eating dinosaurs, such as Velociraptor, almost as soon as scientists started looking.

Wishbones appear in dinosaurs like Deinonychus.
©AMNH/D. Finnin 

Once you start seeing the resemblances between non-bird dinosaurs and living birds, you won’t be able to stop! While dinosaurs and birds have similar brains and feathers, the similarities are especially striking when it comes to legs, feet, and claws. The four-inch talons of the harpy eagle, for instance, are as large as those of a Velociraptor, and let this modern predator carry off prey weighing up to 20 pounds.

Harpy eagles have some of the largest talons found in any living animal. 
Courtesy of Wikimedia Commons

Lead image: The bird-like traits of Velociraptor mongoliensis included hinged ankles, swivel-jointed wrists, and a furcula, or wishbone. © American Museum of Natural History/R.Mickens