Washington A mouse-like animal that lived some 195 million years ago had a body so tiny that it could have curled up on a half dollar. But researchers say the wee mammal may have been the ancestor of us all.
A fossil of the animal's skull was found in China and scientists have identified it as a previously unknown species that had a proportionately bigger brain and more complex skull structure than other mammals of the era.
Zhe-Xi Luo of the Carnegie Museum of Natural History in Pittsburgh, the first author of a study appearing today in the journal Science, said the animal was the smallest mammal of the dinosaur age weighing just 2 grams, like a paper clip. But the animal's brain was outsized compared to other mammals.
"It was a little smart cookie with an extended brain," said Luo, sort of like a wise miniature mouse that managed to survive in a world dominated by huge and powerful dinosaurs. The animal has been named Hadrocodium wui, using Greek words meaning larger and full head.
The ancient animal was only slightly bigger than the smallest mammal now in existence the bumblebee bat of Thailand that weighs about 1.7 grams. There are about 28 grams in an ounce.
"It could represent an extinct lineage, our distant cousin," he said. "Or it could be our great, great grand uncle, ancestral to us, but not in the direct lineage.
"Or it could be our great, great grandfather, 195 million years removed," said Luo. "We cannot distinguish between the three possibilities. We're not sure where it fits in."