Fossils indicate a communal nesting ground and adults who foraged and took care of the young as a herd, scientists say.
Using X-ray tomography imaging, they were able to examine the eggs’ contents without breaking them apart, and discovered preserved embryos within, which they used to confirm that the fossils were all members of Mussaurus patagonicus — a plant-eating dinosaur that lived in the early Jurassic period and is classified as a sauropodomorph, a predecessor of the massive, long-necked sauropods that later roamed the Earth.
Surprisingly, the researchers observed that the fossils were grouped by age: Dinosaur eggs and hatchlings were found in one area, while skeletons of juveniles were grouped in a nearby location. Meanwhile, remains of adult dinosaurs were found alone or in pairs throughout the field site.
From CONICET Documental: “Earliest evidence of herd-living and age segregation amongst dinosaurs.”
This “age segregation,” the researchers believe, is a strong sign of a complex, herd-like social structure. The dinosaurs likely worked as a community, laying their eggs in a common nesting ground. Juveniles congregated in “schools,” while adults roamed and foraged for the herd.
“This may mean that the young were not following their parents in a small family structure,” says team member Jahandar Ramezani, a research scientist in MIT’s Department of Earth, Atmospheric and Planetary Sciences. “There’s a larger community structure, where adults shared and took part in raising the whole community.”
Ramezani dated ancient sediments among the fossils and determined that the dinosaur herd dates back to around 193 million years ago, during the early Jurassic period. The team’s results represent the earliest evidence of social herding among dinosaurs.
Living in herds may have given Mussaurus and other social sauropodomorphs an evolutionary advantage. These early dinosaurs originated in the late Fossil Treasure Trove Shows Complex Social Herd Behavior in Dinosaurs 193 Million