Earliest tree-dweller, burrower join mammal tree of life
Deep ancestors maybe not as boring ecologically as thought
By Susan Milius
Meet two newly discovered ancestral mammals: the oldest known subterranean specialist from the depths of mammalian history and the group’s oldest known tree-dweller.
Fossils of both, found in northeastern China, belong to an extinct group of mostly small creatures called docodonts, researchers report in a pair of papers in the Feb. 13 Science. Docodonts, sometimes not considered strictly mammals, branched off early from the ancient lineage that eventually gave rise to modern mammals.
The fossil of what looks like a shrew-sized specialized burrower, now named Docofossor brachydactylus, is estimated to be about 160 million years old. It “had a supercapacity to dig but was not very good at much else,” says Zhe-Xi Luo of the University of Chicago, an author on both papers.