What makes the discovery especially surprising and puzzling is that the heart resembles a mammal's or bird's but it belonged to an ornithischian, or bird-hipped, dinosaur, one of the two main lineages of these great reptiles. Despite the name, these dinosaurs were far removed from those that were presumed by many paleontologists to have been ancestors of birds; these ancestors were presumed to be theropods, members of the other main lineage known as the saurischian, or lizard-hipped, dinosaurs.
It is therefore possible, Dr. Russell said, that dinosaurs of both lineages -- not just the bird ancestors -- had advanced hearts and high metabolisms. This physiology may have evolved independently or it could stretch all the way back to a common ancestor, some 235 million years ago.
''This means our entire conception of dinosaurs may have to be revised,'' said Dr. Norell of the American Museum of Natural History.
What makes the discovery especially surprising and puzzling is that the heart resembles a mammal's or bird's but it belonged to an ornithischian, or bird-hipped, dinosaur, one of the two main lineages of these great reptiles. Despite the name, these dinosaurs were far removed from those that were presumed by many paleontologists to have been ancestors of birds; these ancestors were presumed to be theropods, members of the other main lineage known as the saurischian, or lizard-hipped, dinosaurs.It is therefore possible, Dr. Russell said, that dinosaurs of both lineages -- not just the bird ancestors -- had advanced hearts and high metabolisms. This physiology may have evolved independently or it could stretch all the way back to a common ancestor, some 235 million years ago.''This means our entire conception of dinosaurs may have to be revised,'' said Dr. Norell of the American Museum of Natural History.
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