2021-10-22

Research: Dinosaurs 193 million years ago had complex social gregarious behavior

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4f0f20c39b52d11 - Research: Dinosaurs 193 million years ago had complex social gregarious behavior

since 2013, the team members have excavated more than 100 dinosaur eggs (about the size of eggs) in a rich fossil bed in southern Patagonia And partial skeletons of 80 young and adult dinosaurs

Research: Dinosaurs 193 million years ago had complex social gregarious behavior

by using X-ray tomography, researchers were able to examine the contents of the egg without opening the egg and found preserved embryos in it. Using these embryos, they confirmed that the fossils were members of mussaurus patagonicus, a plant eating dinosaur that lived in the early Jurassic and was classified as a long nosed dinosaur. It was the predecessor of the huge long necked long nosed dinosaur that later roamed the earth

surprisingly, the researchers observed that these fossils were grouped by age. Dinosaur eggs and young dragons were found in one area, while the skeleton of young dragons was concentrated in a nearby place. Meanwhile, the remains of adult dinosaurs were found alone or in pairs throughout the site

researchers believe that this “age segregation” is a powerful sign of a complex social structure similar to cattle. Dinosaurs may have worked as a group and laid eggs in a common nest. Young dragons gather in the “school”, while adult dragons wander and forage in the group

team member jahandar ramezani, a research scientist in the Department of earth, atmosphere and Planetary Sciences at MIT, said: “this may mean that the young dragons did not follow their parents in a small family structure. Instead, they had a larger community structure, and adults shared and participated in raising the whole community.”

ramezani measured the ancient sediments in fossils, The dinosaur group can be traced back to the early Jurassic about 193 million years ago. The team’s results represent the earliest evidence of dinosaur social gregariousness

Research: Dinosaurs 193 million years ago had complex social gregarious behavior(1)

living in groups may bring evolutionary advantages to mussaurus and other social long legged animals. These early dinosaurs originated in the Late Triassic, not long before an extinction event wiped out many other animals. Whatever the reason, the giant animals persisted and finally dominated the terrestrial ecosystem in the early Jurassic

ramezani said: “we have now observed and recorded the earliest social behavior of dinosaurs. This now raises the question whether living in a group may have played an important role in the early evolutionary success of dinosaurs. This gives us some clues about how dinosaurs evolved.”

since 2013, The team’s paleontologists have been working on the Laguna korolada formation in southern Patagonia, which is famous for producing fossils of early animals. When scientists first found fossils in this stratum in the 1970s, they named it mussaurus, which means “mouse lizard”, because they thought these skeletons were the bones of miniature dinosaurs

it was not until later that scientists, including members of the Argentine team, found larger bones, suggesting that the adults of mussaurus were much larger than their rodent name. However, the name persisted, and the team continued to excavate abundant mussaurus fossils from a small area of the stratum with an area of kilometers

Research: Dinosaurs 193 million years ago had complex social gregarious behavior(2)

so far, the fossils they have identified are found in three closely spaced sedimentary layers, indicating that the area may be a common breeding ground, and dinosaurs will return regularly, perhaps to take advantage of favorable seasonal conditions

in the fossils they found, the research team found a group of 11 jointed juvenile skeletons, which intertwined and overlapped with each other, just like being suddenly thrown together. In fact, judging from the remarkable preservation properties of the whole series, the research team believes that this special mussaurus group is “synchronous death” and may be buried by sediments soon

according to the evidence of ancient plants exposed nearby, the Laguna korolada formation has long been considered to be relatively old on the time scale of dinosaurs. The group wants to know. Will these dinosaurs start living in groups very early

ramezani said: “it has been known that in the late Jurassic and Cretaceous, large herbivorous dinosaurs showed social behavior – they lived in groups and had nests. But the question has always been, when was the earliest time of this social behavior?”

in order to find the answer, Diego pol, a paleontologist at the Egidio feruglio Museum of Paleontology in Argentina, who led the study, looked for samples of volcanic ash in fossils and sent them to the ramezani laboratory at the Massachusetts Institute of technology. Volcanic ash may contain zircon – mineral particles containing uranium and lead, and ramezani can accurately measure its isotopic ratio. Based on the half-life of uranium or the time when half the element decays into lead, he can calculate the age of zircon and the volcanic ash that found it. Finally, ramezani successfully identified zircons from two volcanic ash samples. He determined that the age of all these zircons was about 193 million years

because volcanic ash was found in the same sedimentary layer as fossils, ramezani’s analysis strongly shows that dinosaurs were buried while volcanic ash was deposited. One possibility is that drought and wind blown dust starved the dinosaurs and quickly buried them, while volcanic ash from distant volcanic eruptions happened to float over, which is very lucky for scientific research. Zircon was deposited in the sediments

overall, the results of the research team show that mussaurus and possibly other dinosaurs have evolved to live in complex social groups as early as 193 million years ago, before and after the dawn of the Jurassic period

Raymond Rogers, a professor of Geology from McAlester college who did not participate in the study, said: “Evidence suggests that in the early Jurassic, mussaurus optimized foraging potential through age-based social division of labor – newborns, adolescents and adults apparently foraged and died in age-based groups. This social behavior is very common in today’s large terrestrial herbivores. It is surprising to see clear evidence of the same phenomenon in this early dinosaur species.”

scientists suspect that two other early dinosaurs, massondylus from South Africa and Lufeng from China, also lived in groups at the same time, although the dating of these dinosaurs is not accurate. If multiple independent dinosaur families lived in groups, researchers believe that this social behavior may have evolved earlier and may be traceable Back to their common ancestor, the Late Triassic.

“now we know that there was social behavior 193 million years ago,” ramezani said. “This is the earliest evidence of dinosaur social behavior. But the understanding of paleontology is that if you find social behavior in this type of dinosaur at this time, it must have originated earlier.”