More than 100 eggs have been dug up in a dinosaur cemetery in Argentina, the world’s first evidence of herd behavior.
Scans show they belong to the same species – a primitive long-necked herbivorous animal called Mussaurus patagonicus.
Embryo shells from 193 million years ago are still inside.
The fossilized bones of 80 juveniles and adults were also excavated at the site in southern Patagonia.
In addition, the remains were grouped by age in an area of about half a square mile on the dry shore of a lake.
The eggs and hatchlings were in one area, with juveniles and adults scattered whole-singly or in pairs nearby.
Isolation is characterized by a complex, social structure. The dinosaurs worked as a community, laying their eggs in a common nesting ground.
The young would congregate in ‘schools’, while the adults roamed around and made forage for the flock.
Co-author Dr Jahandar Ramzani, a geologist at MIT (Massachusetts Institute of Technology), said: “This could mean that the young were not rearing their parents in a small family structure.
“There’s a great community structure, where adults share and participate in growing the entire community.”
Eggs are approximately the size of a chicken. Using state-of-the-art X-ray imaging, the team was able to examine the material without tearing it apart.
Remarkably, embryos were preserved within which they were identified as Mussaurus patagonicus.
The plant eater is up to 20 feet tall and weighs over a ton. It lived in the early Jurassic and is a member of the sauropodomorphs.
They were the forerunners of Brontosaurus, Diplodocus and other massive sauropods – the largest animals that ever roamed the Earth.
Fossils point to a communal nesting ground and adults who raised and cared for the young as a herd.
Dr Ramzani said: “To borrow a line from the movie ‘Jurassic Park’ – dinosaurs walk in herds.
“And they lived in herds 40 million years earlier than the fossil record shows.”
The international team, including experts from Argentina and South Africa, has been excavating the ancient sediments since 2013.
Living in herds may have given Mussaurus and other sauropodomorphs an evolutionary advantage, they say.
Early dinosaurs originated at the end of the Triassic, shortly before the extinction event that wiped out many other animals.
For whatever reason, sauropodomorphs took over and eventually dominated the terrestrial ecosystem in the early Jurassic.
Dr Ramazani said: “We have now observed and documented this early social behavior in dinosaurs.
“This now raises the question of whether herd living may have played a major role in the early evolutionary success of dinosaurs. This gives us some clues about how dinosaurs evolved.”
The first sauropodomorph fossils were discovered about 50 years ago in the Laguna Colorada Formation.
Scientists named them Mussaurus, which translates as ‘mouse lizard’, because they believed they belonged to a miniature dinosaur.
Large skeletons were found much later – indicating the larger size of Mussaurus adults. But the name stuck.
The bones are spread closely in three sedimentary layers. This area would have been a common breeding ground.
To take advantage of favorable weather conditions, dinosaurs would return regularly.
A collection of 11 articulated juvenile skeletons intertwined and overlapping each other, as if they were suddenly thrown together
This particular herd of Mussaurus is thought to have died out “synchronously” – and was quickly buried.
Dr Ramazani said: “People already knew that in the late Jurassic and Cretaceous, large herbivorous dinosaurs exhibited social behavior – they lived in herds and had nesting sites.
“But the question has always been, when was the first time this kind of cowboy behavior first occurred?”
The fossils were properly dated through chemical analysis of volcanic ash from a distant eruption.
The dinosaurs may have been buried by a flash flood or wind-blown dust at the same time it was deposited.
Scientific Reports’ study suggests that Mussaurus and possibly other dinosaurs evolved to live in complex groups around the dawn of the Jurassic.
Two other types of early dinosaurs—Masspondylus from South Africa and Lufengosaurus from China—are also believed to have lived in herds.
Social behavior may have evolved even earlier, probably as in their common ancestor, in the late Triassic.
Added Dr Ramzani: “We now know that animal husbandry was going on 193 million years ago.
“This is the earliest confirmed evidence of sociable behavior in dinosaurs.
“But paleontological understanding says, if you find social behavior in this type of dinosaur at this time, it must have originated earlier.”
Credit: www.independent.co.uk /