Squirrel-size mammals scampered through the trees above dinosaurs' heads, newfound Chinese fossils show, revising our image of the first furry beasts. Three newly described species suggest that mammals evolved earlier, and faster, than previously thought.

Called haramiyids, the recently discovered mammals lived in Jurassic China around 160 million years ago. Slender and graceful, the animals appear to have been specialized for life in the trees, with hands and feet that could grasp branches and a long prehensile tail like today's monkeys.

"The picture that Mesozoic mammals were shrew-like insectivores that lived in the shadow of the dinosaurs needs to be repainted," says American Museum of Natural History paleontologist Jin Meng, a coauthor of the new study. Discoveries during the past few