September 29, 2023

Fossil Treasure Trove Shows Complex Social Herd Behavior in Dinosaurs 193 Million Years Ago

Creative reconstruction of a Mussaurus patagonicus nest. Credit: Jorge Gonzalez
Fossils suggest a communal nesting ground and adults who took and foraged care of the young as a herd, researchers say.
To obtain a line from the motion picture “Jurassic Park:” Dinosaurs do relocate herds. And a new study reveals that the prehistoric creatures lived in herds much earlier than previously believed.
In a paper appearing today (October 21, 2021) in Scientific Reports, researchers from MIT, Argentina, and South Africa detail their discovery of an exceptionally maintained group of early dinosaurs that shows indications of complicated herd habits as early as 193 million years back– 40 million years earlier than other records of dinosaur herding.

These early dinosaurs originated in the late Triassic, quickly before a termination event wiped out numerous other animals.” Weve now observed and documented this earliest social behavior in dinosaurs,” Ramezani says. “This raises the question now of whether living in a herd may have had a major function in dinosaurs early evolutionary success. It is fantastic to see clear proof of the same phenomenon in this early dinosaur species.”
Paleontological understanding says, if you discover social habits in this type of dinosaur at this time, it should have come from earlier.”

Since 2013, members of the team have actually excavated more than 100 dinosaur eggs (about the size of chicken eggs) and the partial skeletons of 80 juvenile and adult dinosaurs from a rich fossil bed in southern Patagonia.
New research on a huge fossil website in Patagonia shows that some of the earliest dinosaurs, the Mussaurus patagonicus, resided in herds and suggests that this habits might have been among the keys to the success of dinosaurs. Credit: Jorge Gonzalez
Utilizing X-ray tomography imaging, they had the ability to analyze the eggs contents without breaking them apart, and found maintained embryos within, which they used to verify that the fossils were all members of Mussaurus patagonicus– a plant-eating dinosaur that resided in the early Jurassic period and is classified as a sauropodomorph, a predecessor of the massive, long-necked sauropods that later wandered the Earth.
Surprisingly, the researchers observed that the fossils were organized by age: Dinosaur hatchlings and eggs were found in one location, while skeletons of juveniles were organized in a neighboring location. On the other hand, remains of adult dinosaurs were found alone or in pairs throughout the field website.
From CONICET Documental: “Earliest proof of herd-living and age segregation among dinosaurs.”
This “age segregation,” the researchers believe, is a strong sign of a complex, herd-like social structure. The dinosaurs likely worked as a neighborhood, laying their eggs in a common nesting ground. Juveniles gathered together in “schools,” while grownups strolled and foraged for the herd.
” This may suggest that the young were not following their moms and dads in a small household structure,” says staff member Jahandar Ramezani, a research study scientist in MITs Department of Earth, Atmospheric and Planetary Sciences. “Theres a bigger neighborhood structure, where grownups shared and participated in raising the whole neighborhood.”
Ramezani dated ancient sediments amongst the fossils and identified that the dinosaur herd go back to around 193 million years back, throughout the early Jurassic duration. The teams results represent the earliest evidence of social herding amongst dinosaurs.
Paleontologists in Argentina uncovered a neighborhood of dinosaurs in Patagonia, consisting of a nest of chicken-sized eggs, such as the one revealed here. Credit: Roger Smith
Residing in herds might have given Mussaurus and other social sauropodomorphs an evolutionary advantage. These early dinosaurs originated in the late Triassic, quickly prior to an extinction occasion erased numerous other animals. For whatever reason, sauropodomorphs hung on and eventually controlled the terrestrial community in the early Jurassic.
” Weve now observed and documented this earliest social behavior in dinosaurs,” Ramezani states. “This raises the question now of whether living in a herd might have had a major function in dinosaurs early evolutionary success. This gives us some hints to how dinosaurs evolved.”
Early herding
Because 2013, paleontologists on the group have actually operated in the Laguna Colorada Formation, a site in southern Patagonia that is understood for bearing fossils of early sauropodomorphs. When scientists first discovered fossils within this formation in the 1970s, they called them Mussaurus for “mouse lizard,” as they assumed the skeletons were of miniature dinosaurs.
Just much later on did scientists, consisting of members of the Argentinian group, find bigger skeletons, indicating Mussaurus adults were much bigger than their rodent namesakes. The name stuck, however, and the group has actually continued to uncover a rich collection of Mussaurus fossils from a small, square kilometer of the formation.
Using X-ray imaging, the researchers scanned eggs to find preserved embryo skeletons, which they used to verify the fossils as members of the plant-eating dinosaur, Mussaurus patagonicus. Credit: Vincent Fernandez
The fossils they have determined so far were found in three sedimentary layers spaced close together, showing that the region may have been a typical breeding place where the dinosaurs returned routinely, perhaps to take benefit of favorable seasonal conditions.
Among the fossils they discovered, the team discovered a group of 11 articulated juvenile skeletons, linked and overlapping each other, as if they had actually been suddenly thrown together. Judging from the remarkably preserved nature of the whole collection, the team believes this particular herd of Mussaurus passed away “synchronously,” perhaps rapidly buried by sediments.
Based upon proof of ancient flora in the close-by outcrops, the Laguna Colorada Formation has actually long been assumed to be reasonably old on the dinosaur timescale. The group wondered: Could these dinosaurs have been herding from early?
” People already understood that in the late Jurassic and Cretaceous, the big herbivore dinosaurs displayed social behavior– they lived in herds and had nesting areas,” Ramezani states. “But the question has constantly been, when was the earliest time for such herding behavior?”
A gregarious line
To find out, Diego Pol, a paleontologist at the Egidio Feruglio Paleontological Museum in Argentina who led the research study, looked for samples of volcanic ash amongst the fossils to send to Ramezanis laboratory at MIT. Ramezani effectively recognized zircons in two ash samples, all of which he dated to around 193 million years old.
Given that the ashes was discovered in the exact same sediment layers as the fossils, Ramezanis analyses strongly suggest that the dinosaurs were buried at the exact same time the ash was deposited. A likely circumstance may have included dry spell and wind-blown dust that starved and quickly buried the herd, while ash from a distant eruption occurred to wander over and, luckily for science, deposit zircons in the sediments.
The group of scientists utilized high-energy X-rays at the European Synchrotron (ESRF) to penetrate the dinosaur eggs without damaging them and get a full view inside them. Credit: Vincent Fernandez/Diego Pol/ESRF
Taken together, the groups outcomes reveal that Mussaurus and potentially other dinosaurs developed to live in complex social herds as early as 193 million years ago, around the dawn of the Jurassic duration.
” Evidence suggests that Mussaurus enhanced foraging capacities throughout the early Jurassic by means of age-based social partitioning– neonates, juveniles, and adults obviously foraged, and died, in age-based groups,” says Raymond Rogers, a teacher of geology at Macalester College, who was not associated with the research study. “This kind of gregarious behavior prevails today in big terrestrial herbivores. It is fantastic to see clear evidence of the very same phenomenon in this early dinosaur species.”
Researchers suspect that 2 other types of early dinosaurs– Massospondylus from South Africa and Lufengosaurus from China– also lived in herds around the same time, although the dating for these dinosaurs has actually been less precise. If multiple different lines of dinosaurs lived in herds, the researchers think the social behavior might have evolved previously, maybe as far back as their common forefather, in the late Triassic.
” Now we know herding was going on 193 million years earlier,” Ramezani states. “This is the earliest confirmed evidence of gregarious behavior in dinosaurs. But paleontological understanding states, if you discover social habits in this kind of dinosaur at this time, it must have stemmed earlier.”
Referral: “Earliest evidence of herd-living and age segregation amongst dinosaurs” by Diego Pol, Adriana C. Mancuso, Roger M. H. Smith, Claudia A. Marsicano, Jahandar Ramezani, Ignacio A. Cerda, Alejandro Otero and Vincent Fernandez, 21 October 2021, Scientific Reports.DOI: 10.1038/ s41598-021-99176-1.
This research study was supported, in part, by National Science Foundation in the U.S. and the National Scientific and Technical Research Council of Argentina.