New Fossil Suggests Dinosaur Ate Like a Duck

Aug. 29 -- It walked on slim hind limbs, swung a long tail, stretched 15 feet in length and, to scientists' surprise, nourished its hulking body by straining tiny aquatic creatures through a filter in its beak.

An extremely well-preserved 70-million-year-old fossil from Mongolia has revealed for the first time that a group of ostrich-like dinosaurs may have eaten much the same way as ducks and flamingos.

Rather than hunting and devouring other hefty creatures like its cousin Tyrannosaurus Rex, the 1,000-pound theropods known as ornithomimids likely had a more delicate diet.

"We are used to conceiving of theropods as dinosaurs with big teeth adapted to hunting large prey," says Peter Makovicky, an assistant curator of dinosaurs at the Field Museum of Chicago who discovered the fossil known as Gallimimus last August. "But these beaked theropods adapted very differently and may have lived on tiny invertebrates similar to brine shrimp."

Food Strainers

The specimen, a member of the theropod suborder which included Tyrannosaurus Rex and featured dinosaurs with small forelimbs, was found in the southern Gobi desert in Mongolia and is one of the best-preserved on record. Most remarkable was the detection of a comb-like filter, located near the tip of its duck-like bill, that was likely made of keratin. Keratin is the same material found in birds' beaks, human fingernails and horse hooves and is more fragile than bone so it rarely survives centuries, let alone millions of years.

But this animal died in a way that would prove fortuitous to future paleontologists. Makovicky guesses the animal expired and was buried quickly in mud or sand. The excavation team found the creature's bones had all been neatly fossilized in their natural positions. This specimen was likely a juvenile since it measured about half the height of a normal, 15-foot-long adult.

Until now, scientists have guessed that ornithomimids (meaning "Bird Mimics" in Latin), fed on small animals and plant material. But the filter found in Gallimimus' beak resembles devices known as lamellae in ducks' or flamingos' bills. And these contemporary birds use the filter as a sieve to extract invertebrates and plant material from water.