Dinosaurs may have dominated the planet during the Jurassic Period, but they shared the landscape with little rodentlike creatures. Two new species of these pocket-size early mammals have been discovered in China — one was a horny-clawed tree-dweller, and the other was a tunnel-digger with shovel-like paws.
Researchers say these new specimens show that early mammals, though small, were surprisingly diverse.
Agile tree climber and its burrow-dwelling cousin
One of the newly discovered creatures, now known as Agilodocodon scansorius, is the earliest tree-dwelling mammal ever found. It had several features that made it fit for climbing: long claws, spadelike front teeth to chew into bark, and flexible elbows and ankles. At most, it might have weighed about 40 grams (1.4 ounces). [See Images of the Newfound Mammal Ancestors]
It lived in a temperate climate zone on the supercontinent Laurasia, surrounded by lush plants and lots of insects on the hilly shores of a lake, where it probably met an unlucky end. One day, it perhaps fell from a treetop and into the lake, where it drowned and, over time, became entombed in the sediment settling on the bottom.
Fast-forward 165 million years, and that lake bed has long dried up. It now lies within the borders of Inner Mongolia, where a fossil-hunting farmer found the creature's remarkably well-preserved skeleton in 2011
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http://www.scientificamerican.com/article/2-jurassic-mini-mammals-discovered-in-china/
