Dinosaurs among us: an exhibition explores the link between birds--living dinosaurs--and their extinct ancestors.

• Position: Science & Technology - "Dinosaurs Among Us" exhibition

THE NEXT TIME you dodge a pigeon on the sidewalk, watch a sparrow eat from a feeder in a backyard, or order chicken for dinner, know that you just had an encounter with a modern dinosaur. Dinosaurs never really vanished from Earth. Most did go extinct, but their evolutionary legacy lives on all around us--in birds.

"Dinosaurs Among Us" highlights the unbroken line between the charismatic dinosaurs that dominated the planet for about 170,000,000 years and modern birds, a link that is marked by shared features that include feathers, wishbones, enlarged brains, and extremely efficient respiratory systems. The fossil record of this story and the biological research it inspires grow richer by the day--so rich, in fact, that the boundary between the animals we call birds and those we traditionally called dinosaurs practically is obsolete.

"With this ... exhibition, we invite visitors to question what they think they know about dinosaurs--how they looked and behaved and even whether all of them actually became extinct," says Ellen V. Futter, president of the American Museum of Natural History. "While paleontology has been a proud part of this institution's legacy for more than 100 years, we live today in an exciting new era of advancement in dinosaur research. There has never been a more interesting time to enjoy dinosaurs or a more fascinating time to learn about their behavior, appearance, and connection to current life, specifically modern birds."

Living birds belong to a group, or clade, called the Dinosauria. It includes the extinct dinosaurs and all of their living descendants, which is why most scientists now agree that birds are a kind of dinosaur just like we are a kind of mammal. Fossils, genes, behavior, and the anatomy of living animals tell us that birds share a common ancestor with dinosaurs that were not birds--and that alligators and crocodiles are birds' closest living relatives.

"The idea that birds are dinosaurs isn't a new one--it was first proposed by Thomas Huxley about 150 years ago, but now it's taken on a whole new dimension as different technologies and, as a result, different ideas, are being applied to the field," explains Michael Novacek, senior vice president and provost for science at AMNH.

"Dinosaurs Among Us" features ancient, rarely seen fossils and lifelike models, including a 23-foot-long tyrannosaur (Yutyrarmus huali) with a shaggy coat of filaments called proto-feathers and a small dromeosaur (Anchiomis huxleyi) with a 22-inch wingspan and vivid, patterned plumage on all four limbs. Visitors will encounter a tiny dinosaur whose sleeping posture precisely echoes that of a living bird; a fossilized dinosaur nest containing remains of the adult that guarded the hatchlings; and a relative of Triceratops that had simple plumes on its body.

The exhibition, which comes on the heels of the unveiling of a 122-foot-long titanosaur cast on permanent display in the museum's Orientation Center, is part of a series of events, public programs, exhibitions, and digital offerings highlighting dramatic developments in paleontology. "This exhibition is based on lots of new evidence amassed over the last two decades," says exhibition curator Mark Norell, Macaulay Curator in the Division of Paleontology and the Division's chair. "I think this is really going to shake up the way people think of dinosaurs."

Making nests, laying eggs, and tending to babies are not just bird traits. Crocodiles do these things, and to some extinct dinosaurs did, too. Today, scientists use observations of living relatives to learn about the lifestyles of animals that have been extinct for more than 65,600,000 years. That includes Citipati osnwlskae, whose fossilized nest is on display as a cast.

The humble eggshell is the structure that allowed animals to colonize the land. A complete life-support system, the eggshell holds water and food for the developing embryo, while letting oxygen in and carbon dioxide out. Similarities between the eggshell structure of some groups of dinosaurs and living birds are another link in the chain of evidence connecting them.

One extraordinary fossil on view preserves a recently hatched Troodontid dinosaur--a member of a group of small, feathered, non-bird dinosaurs with large brains--atop the eggs of what would have been its nestmates. In that fossil, the eggs are not paired, suggesting the parent had only one egg tube--as modem birds do--as opposed to the two present in their ancient ancestors. The exhibition offers a climbable, full-scale model of a nest with 20 eggs discovered in China, likely laid by one of the largest oviraptorosaurs ever found, Gigantoraptor.

Museum-goers can look through a microscope to discover more about eggshell layers (which can tell scientists what type of dinosaur laid the egg) and growth rings (which allow researchers to track maturation in dinosaurs and their relatives). Learning about prehistoric eggs like these and how they differ in size, shape, composition, and more can teach researchers about the transition from nonbird dinosaurs to modem birds.

Feathers come in different colors, sizes, and shapes and serve a wide range of functions: peacocks display them to attract mates; penguins rely on them to reduce drag underwater; and herons create shade with them. Today, birds are the only feathered animals alive, but 150,000,000 years ago, it was a different story. Early birds had feathers, but so did dinosaurs of all shapes and sizes. One reason is that feathers are one of the most useful skin coverings ever to evolve.

Thousands of feathered...