Dinosaurs Were Doting Parents, Fossil Find Suggests
for National Geographic News
|September 8, 2004|
A newly announced dinosaur discovery in China suggests that the prehistoric creatures put in some quality parenting time.
Last year researchers unearthed the fossil remains of a Psittacosaurus, a plant-eating, parrotlike dinosaur that grew to be a meter (three feet) tall. The adult was surrounded by 34 juveniles, a close association that indicates that the dinosaur continued to care for its young even after they hatched from eggs.
The discovery suggests that the care that crocodiles, birds, and other modern descendents of archosaurs give to their young may be an ancestral characteristic. (Archosaurs are a subclass of reptiles that includes dinosaurs, pterosaurs, and crocodilians.)
"People often thought that parental care evolved in birds. But now we're accumulating evidence for parental care in dinosaurs," said David Varricchio, an assistant professor of earth sciences at Montana State University in Bozeman.
The growing data "argues that parental care is a much more primitive thing that birds really just inherited from dinosaurs," Varricchio said. His findings appear in tomorrow's issue of the science journal Nature.
The Psittacosaurus lived in northeastern Asia more than a hundred million years ago. Also known as a "parrot lizard" for its parrotlike beak, the herbivore was a strong, agile dinosaur that walked on its two hind legs. It ate mostly tough stems and fruit.
The Psittacosaurus fossils, which are 125 million years old, were found by farmers in the northeast Chinese province of Liaoning, and are now housed in the province's Dalian Natural History Museum.
The specimens are in excellent condition. The researchers found no separated bones or partial skeletons, which suggests that the dinosaurs were rapidly entombed while still alive.
"They are not in a typical death pose, where animals die on the side," Varricchio said. "These specimens are upright with their heads exposed."
Varricchio speculates that the animals may have been buried by volcanic debris, trapped in a collapsed burrow, or flooded in their nest.
"We know there wasn't time for scavengers to come and pick at the carcasses," he said.
Scientists study the death assemblages of species to learn more about how the animals behaved while alive.
The close proximity of the Psittacosaurus fossilsthe adult and juvenile skeletons were all located within half a square meter (5.4 square feet)points to a biological relationship and post-hatching parental care.
The hatchling size of the Psittacosaurus is not known. But the juvenile bones found were wellformed and fully hardened, or ossified. The youngsters' apparently healthy state suggests the adult had cared for its children.
"Recognizing parental care in the fossil record has been difficult in the past, because behavior isn't typically discernable from a single time-slice," said Jeff Wilson, a paleontologist at the University of Michigan in Ann Arbor.
"This specimen is a rare snapshot of a momentthe last momentin these dinosaurs' lives and shows them clustering around an adult. I think that is a compelling case that there was a strong bond between these animals," he said.
Past studies have suggested that other dinosaur species displayed parental care by, for example, feeding their children. But researchers were not sure if such behavior extended to all dinosaurs.
"This suggests maybe all dinosaurs did it," Varricchio said.
Crocodiles and birds assist their young by hatching them, feeding them, providing warmth and shelter, and protecting them from predators.
If these modern animals inherited such parental skills from their predecessors, the dinosaurs, it may help explain why dinosaur descendants have been so successful, Varricchio says.
The discovery "adds to the ever increasing picture of dinosaurs as being more sophisticated and more complex animals than what we imagined 50 years ago, when we had these sluggish, cold reptiles," Varricchio said.
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