Courtesy of the Dalian Natural History Museum
The bones of a dinosaur parent or caretaker—whose large skull is at left—lie curled around the skeletons of many dino babies.
There is something forlorn about the scene, even 125 million years later: An adult dinosaur lies in a nestlike depression with 34 young, suggesting that death struck suddenly. But to paleontologists, the find at Liaoning, in northeastern China, is an exquisite family snapshot that gives the clearest picture yet of how dinosaurs tended to their offspring.
The Liaoning dinosaurs were psittacosaurs, small, squat plant eaters with parrotlike beaks. All 34 babies were about the same size, roughly that of a Chihuahua. The cause of their death is unclear, partly because amateur fossil hunters dug up the ground around the specimens before paleontologists arrived. David J. Varricchio of Montana State University, who led the study of the remains, speculates that a collapsing burrow or a sudden flood might have suffocated the psittacosaurs.
Varricchio feels more confident in reading the social significance of the bones. “It’s always a leap of faith to infer behavior from fossils,” he says, but he is hard-pressed not to see a dinosaur parent who perished while guarding her (or his) babies. This evidence bolsters the argument that conscientious parenting behavior appeared early on and so must have evolved in an ancestor common to all dinosaurs, birds, and crocodiles.
Paleontologist Jack Horner, who found the first hints that dinosaurs tended their young, is thrilled. “In the old days, when people found a dinosaur in a nest full of eggs, they assumed it was an egg stealer. Now we’re thinking of them more like birds, animals that can be caring parents.”