Fossils may show how mammals were able to live long and prosper

The remains of a diminutive mouselike creature that lived 166 million years ago could help answer one of biology's biggest questions, fossil experts say: how did mammals become so successful?

- Nicola Davis

Krusatodon kirtlingtonensis belongs to the immediate predecessors of mammals and lived alongside the dinosaurs during the middle Jurassic age.

While it was originally known only from individual teeth, researchers have now reported two partial skeletons which, they say, not only show that the creature lived far longer than similar-sized mammals today, but that it also developed at a slower pace.

Dr Elsa Panciroli, first author of the study from National Museums Scotland, said the research could help shed light on why mammals have become so successful.

"[Mammals] have the biggest range of body sizes; they're living in the most habitats; they have the widest range of ecologies, and so everybody's asking, why?" she said.

"Of course, to understand that, we have to understand where their unique biology comes from. So this is a piece of that puzzle." Found on the Isle of Skye, one set of remains, discovered in 2016, is a juvenile, while the other, discovered in the 1970s but not studied, is an adult.