Scientists have found an ancient "hamster" that lived alongside dinosaurs

The finding helps us understand which mammals were able to survive the catastrophe that wiped out the dinosaurs.

Details

The new species has been named Cimolodon desosai. Its remains were found in Baja California, in what is now Mexico.

This animal belonged to multituberculates - an ancient group of mammals, which appeared in the Jurassic period and existed for more than 100 million years.

The researchers estimate that Cimolodon desosai was small, about the size of a golden hamster. It probably moved around on the ground and in trees, and fed on fruit and insects.

Particularly valuable was the fact that scientists found not only teeth, as is often the case with such ancient mammals, but also parts of the skull, jaws and skeleton. This allowed a more accurate understanding of what the animal looked like and how it might have moved.

At first, the researchers only noticed a small tooth in the rock. But then it turned out that there were many more bones preserved inside.

Why it matters

The find helps to better understand how mammals survived a mass extinction 66 million years ago.

Scientists believe that descendants of closely related species of Cimolodon were able to survive the asteroid impact, when dinosaurs and many other animals disappeared.

They were probably helped by several features: small size, omnivorousness and the ability to live in different environments. Such animals were able to find food and shelter more quickly in changing environments.

It was mammals like these that became part of the evolutionary story that later led to the huge variety of modern animals.

Background

Before the extinction of the dinosaurs, mammals had already existed for millions of years, but were more often small and occupied more modest ecological niches.

That changed after the catastrophe 66 million years ago, as many large animals disappeared and mammals began to spread rapidly and occupy new places in ecosystems.

The new species shows that some of the future "winners" of this evolutionary realignment were already living alongside the dinosaurs long before their extinction.

Source

The study is published in the Journal of Vertebrate Paleontology (2026). The new species Cimolodon desosai was described by a team led by scientists at the University of Washington.