Two fossils show that early mammals had a more varied anatomy and behaviour than was thought.

Credit: Zhe-Xi Luo, Univ. Chicago

A team led by Zhe-Xi Luo at the University of Chicago, Illinois, and Qing-Jin Meng at the Beijing Museum of Natural History analysed a 160-million-year-old fossil from China. The creature, Docofossor brachydactylus, had short, wide digits for burrowing underground, similar to those seen in moles. Some of the team members studied another fossilized mammal of about 165 million years old, Agilodocon scansorius (pictured; US cent shown for scale). It seems to have been adapted to tree-climbing, and its teeth bear hallmarks of a diet of tree gum and sap.

The two species, which belong to an extinct group called docodonts, show that the earliest mammals lived in diverse habitats, the team says.

Science 347, 760–764; 764–768 (2015)