Possible dinosaur nest may have had ‘babysitter,’ Penn study finds

University of Pennsylvania researchers have uncovered evidence of a possible 120 million-year-old dinosaur nest that may have been overseen by a dinosaur "babysitter."

The finding, published in the September issue of Cretaceous Research, comes from a reexamination of a rock slab found in the Lujiatun beds of the Yixian Formation, located in northeastern China's Liaoning province.

Embedded in the slab are the fossils of 24 dinosaur hatchlings, along with the skull of one larger creature, believed to have been between 4 and 5 years old, according to the study, led by Penn environmental sciences doctoral student Brandon P. Hedrick and paleontology professor Peter Dodson.

All 25 remains are from the species Psittacosaurus lujiatunensis, a type of plant-eating dinosaur that existed in the Early Cretaceous period.

The older dinosaur "may well have been a big brother or sister" helping to care for its younger siblings, researchers pointed out in a news release issued by the University of Pennsylvania.

The older dinosaur's skull was found embedded in the same layer of rock as the fossils of the 24 smaller animals and was intertwined with two of them, suggesting the creatures were closely associated at the time of their death, the researchers said.

Dodson and Hedrick will next examine the smaller animals' bones in an attempt to establish whether they are all at the same developmental stage, which would support the idea the creatures were part of one clutch.

Still, the researchers emphasized they can't yet say for sure whether the fossils comprised a nest.

"It certainly seems like it might be a nest, but we weren't able to satisfy the intense criteria to say definitively that it is," Hedrick said in the release. "It's just as important to point out what we don't know for sure as it is to say what we're certain of."