Earliest evidence of dinosaur herd behavior found

The single fossil site containing the remains of dozens of people of different age groups is the earliest evidence that long-necked and four-legged dinosaurs lived in herds.

“This is an amazing new fossil site,” Steven Brusatt, a paleontologist at the University of Edinburgh who was not involved in the new study, wrote to me by email. “This is compelling evidence that these herbivorous dinosaurs were social, formed groups, and probably cared for their eggs and young in some way.”

A team led by Diego Paul of the Egidio Feruglio Museum of Paleontology discovered fossils in the Laguna Colorada Formation in Patagonia, Argentina. They belong Mussaurus patagonicus– a long-necked sauropod from the early Jurassic, standing on four legs. Over the past 15 years, the team has conducted research and excavation at the fossil site, resulting in the discovery of over 100 eggs and nearly 80 skeletons. Musavr…

The fossils, scattered over their apparent breeding grounds, spanned the entire life cycle of dinosaurs, from embryos still hidden inside eggs to fully grown adults. Incredibly, the fossils were grouped by age group – an indication that these giant herbivores lived in herds. These early Jurassic fossils are 192 million years old and predate previous evidence of such complex social behavior by dinosaurs by about 40 million years. Details of this find were published today in Scientific Reports.

“The samples we found showed that herding behavior has been characteristic of long-necked dinosaurs since their early history,” Paul explained in an email. “They were social animals and we think this may be an important factor in their success.”

General Musavr the spawning ground was located on the outskirts of a dried-up lake. The climate was warm, but evidence of drought points to a possible cause of death and a reason why some dinosaurs were buried in the dust.

Most of the eggs were grouped into groups of eight to 30 eggs and placed along a row of trenches, indicating a common breeding environment. X-ray images were used to identify embryos as belonging to Musavr…

Analysis of the fossilized skeletons revealed a surprising presence of age groups, including a group of 11 young (all under one year old), a group of nine adolescents and two adults. The discovery of age groupings is potential evidence that Musavr people lived in herds, that they did so throughout their lives and that they preferred to hang out with members of their own age. I asked Paul to explain the age groups.

“Musavr was tiny when he was born – the entire skeleton fits in the palm of your hand – but the adults were 1.5 tons, which is about the weight of a hippopotamus, ”he replied. “The daily movement, speed, and daily search for food probably varied greatly among newborns, children, and adults.” He said that animals of the same size usually spend time together and coordinate their actions. This is especially true for small, inexperienced young adults, who are more vulnerable to predator attacks, Paul says.

This complex social behavior may have resulted from the increase in body size that began in sauropods between 227 and 208 million years ago. According to the study, these dinosaurs had to feed long distances to meet their enormous energy needs, requiring a new set of adaptive social skills.

Ryan Felice, an anatomist at University College London who was not involved in the study, called it “a truly exciting discovery.” As he explained, paleontologists already knew that non-avian dinosaurs were good parents, as evidenced by clusters of nests cretaceous dinosaur Mayasaurais a name that literally means “good mother lizard.”

“From these discoveries, we could conclude that dinosaurs had a reproductive strategy similar to today’s crocodiles: the mother protects the babies when they are very young, but as soon as they can take care of themselves, the family falls apart, and everyone goes their own way,” she said. Felice. “What makes this discovery so exciting is that [hatchlings], young and adult Mussaurus – all in one place. This means that multi-family groups came together not only for breeding and nesting, but also potentially forming lifelong herds, more like modern elephants or wildebeests. “

What makes the new discovery particularly important is that Musavr is a fairly ancient species of dinosaur, “so the authors hypothesized that perhaps social groups and parenting were things that arose early in dinosaur history,” Felice said.

Brusatte suggested a similar approach.

“Since they are early Jurassic dinosaurs, from the early stages of dinosaur history, this is the oldest record, from that first stage of dinosaur history, this is the oldest record of social life for dinosaurs,” he explained. “It seems that dinosaurs were very social animals from the start, which may have played a role in their tremendous evolutionary success.”

Looking ahead, Paul and his colleagues will continue to survey the site in hopes of gaining a better understanding of the nests and how they were built, along with looking for evidence of predators and plants they eat. Musavr…

More: Unusual Fossil: Oviraptor dinosaur nesting next to unhatched offspring…