An Appetite for Dinosaurs

It was a dog-eat-dinosaur world.

The evidence was found in the 130-million-year-old fossil of a carnivorous mammal with the squat stance and punishing jaws of a feral pit bull, exhumed by farmers in northeastern China in the winter of 2002 and made public this week in the journal Nature.

Nestled under its rib cage researchers discovered the preserved remains of the creature’s last meal: the limbs, fingers and teeth of a small parrot-beaked dinosaur called a psittacosaur, once common in Asia, according to scientists at the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing and the American Museum of Natural History in New York.

“This is the first evidence that a mammal ate dinosaurs,” said Meng Jin, curator of paleontology at the museum. “We are very excited.”

Until now, most mammals from the age of dinosaurs were thought to be tiny rat-like creatures subsisting on insects and doing their utmost to avoid being trampled by the reptilian predators that dominated Earth for more than 100 million years.

But the new fossils from China promise to transform the scientific understanding of the origins of the mammalian kingdom, experts said.

“This changes the picture quite a bit,” Meng said. “It shows that mammals were not just hiding in the darkness. Nobody thought that a mammal could eat a dinosaur.”

So far, researchers have discovered five new species of mammals dating from 130 million years ago at the site in Liaoning.

The researchers made public two of those discoveries this week. They were confident the fossils had not been forged because they were discovered essentially intact inside single blocks of sediment.

The first creature, which died as it was digesting its dinosaur appetizer, is named Repenomamus robustus. Its fangs offer further evidence that the primitive mammals were aggressive carnivores, said Hu Yaoming, lead author of the paper describing the fossils.

Based on the state of its stomach contents, the 12-pound creature apparently wolfed its food in chunks.

The second creature, named Repenomamus gigantus, probably weighed closer to 30 pounds as an adult and certainly could have preyed on small dinosaurs.