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The cuddles may go further than we thought, as scientists have unearthed the remains of a 75.5-million-year-old lair containing fossils of cuddled rodents.
US paleontologists made the discovery – the oldest evidence of social behavior among mammals – at a well-known dinosaur nesting site called Egg Mountain in Montana.
The small mammals – nicknamed “Filikomys primaevus”, which translates to “young and friendly mouse” – represent a new genus of the so-called multituberculates.
Previously, social behavior was thought to have first appeared in mammals following the asteroid-induced mass extinction that killed the dinosaurs.
Furthermore, it has also been speculated that it was largely confined to Placentalia, the group in which mothers carry the fetus to an advanced stage before birth.
However, the discovery – of nesting and excavating multigenerational groups – expands our notion of how such sociability developed.
The snuggles may go further than we thought, as scientists unearthed the remains of a 75.5-million-year-old lair containing fossils of cuddled rodents. In the photo, an artist’s impression of a social group of Filikomys primaevus nesting in their shared den
“These fossils change the game,” said article author Gregory Wilson Mantilla of the University of Washington and the Burke Museum of Natural History and Culture.
“As paleontologists work to reconstruct the mammalian biology of this time period, we’re usually stuck staring at individual teeth and possibly a jaw rolled along a river,” he added.
“But here we have multiple, almost complete skulls and skeletons, preserved in the exact place where the animals lived.”
‘We can now credibly see how mammals actually interacted with the dinosaurs and other animals that lived during this period.
In their study, Professor Wilson Mantilla and colleagues analyzed the fossil remains of 22 individuals of F. primaevus, most of which were found clustered in groups of two to five.
In fact, 13 of the specimens were found in a single 323 square foot (30 square meter) rock area and the clusters contained mixtures of adults and young adults, suggesting that the finds do not represent just parents and their young.
Based on the nature of the surrounding rock, the conservation of the fossils and their powerful shoulders and elbows, the team concluded that the mammals lived in burrows.
The remains represent the most complete mammalian fossils ever from the Mesozoic – the time period between 252 and 66 million years ago – in North America.
The small mammals – nicknamed “Filikomys primaevus”, which translates to “young and friendly mouse” – represent a new genus of the so-called multituberculates. In the photo, the fossil remains of two adult and one juvenile Filikomys primaevus
“Multituberculates are one of the oldest mammal groups and have been extinct for 35 million years, yet in the late Cretaceous they interacted in groups similar to those seen in modern day ground squirrels,” said Luke Weaver of the University. of Washington
“It was insane to finish this article just as stay-at-home orders were taking effect,” commented article author and biologist Luke Weaver, also from the University of Washington.
“We’re all doing our best here to socially distance and isolate, and I’m writing about how mammals interacted socially long ago, when dinosaurs still roamed Earth,” he added.
“I think it’s really powerful to see how deeply ingrained social interactions are in mammals.”
“Because humans are such social animals, we tend to think that sociability is somehow unique to us, or at least to our close evolutionary relatives, but we can now see that social behavior goes back much further back in family tree of mammals. “
“Multituberculates are one of the oldest mammal groups and have been extinct for 35 million years, yet in the late Cretaceous they interacted in groups similar to those seen in modern-day ground squirrels.”
The full study results were published in the journal Nature Ecology & Evolution.
US paleontologists made the discovery – the oldest evidence of social behavior among mammals – at a famous dinosaur nesting site called Egg Mountain, Montana
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