Scientists have discovered a new species of small mammal that lived at the same time as dinosaurs, offering fresh clues about how early mammals survived one of the most devastating events in Earth’s history.
The fossil belongs to a newly identified species called Cimolodon desosai, a rodent-like animal that lived about 75 million years ago during the Late Cretaceous period.
At that time, dinosaurs still dominated the planet, but small mammals like this one were quietly living alongside them.
Researchers say the animal was about the size of a modern golden hamster. It likely moved both on the ground and in trees, feeding on fruits and insects.
Its small size and flexible diet may have helped its relatives survive the mass extinction event that happened around 66 million years ago, when an asteroid impact wiped out about 75% of life on Earth, including all non-avian dinosaurs.
The discovery was made by a research team led by the University of Washington. The fossil was found at a site in Baja California, Mexico, after years of careful searching. The team first spotted a tiny tooth sticking out of a rock crack.
As they looked closer, they realized there was much more buried inside, including parts of the skull, jaws, and even bones from the limbs.
Finding such a complete fossil is rare, especially at this site, where fossils are usually difficult to uncover. Because of this, the discovery provides valuable information about the animal’s body shape, movement, and lifestyle.
Cimolodon desosai belongs to a group of early mammals called multituberculates. These animals first appeared during the Jurassic period and survived for over 100 million years before eventually going extinct. They were among the most successful early mammals and are known for their distinctive teeth, which had multiple ridges and were well-suited for chewing a variety of foods.
To study the fossil in detail, researchers used advanced imaging techniques, including micro-CT scanning. This allowed them to see inside the fossil without damaging it and to compare its teeth with those of related species. Teeth are especially important in identifying ancient mammals because they preserve well and carry unique patterns.
The new species was named in honor of Michael de Sosa VI, the field assistant who first spotted the fossil. He passed away while the team was still studying the find, and the researchers chose to recognize his contribution in this way.
This discovery helps scientists better understand how small mammals lived during the age of dinosaurs and why some of them were able to survive when so many other species disappeared.
