They reveal that mammal ancestors evolved to glide between trees in a similar way to some mammals today. This adds to evidence that mammals were more diverse during the age of dinosaurs than previously realised. The work is published by an international team of scientists in this week's Nature. The two new fossil species exhibit highly specialised characteristics, including adaptations that allowed them to climb trees, roost on branches and glide. This means that the ability of mammals to glide evolved much earlier than previously thought. Prof Zhe-Xi Luo, from the University of Chicago, US, said: "These Jurassic mammals are truly the first to glide.