We know very little about the world and the species that have inhabited it throughout its existence because scientific research in this regard just dates a few hundreds of years back at most. So it has become normal for scientists to discover new species that live or lived on the planet at some point.

Scientists discovered two new species of burrowing semi-mammals that lived 120 million years ago in the northeast region of what is now China. They are two species related to each other but that evolved differently from a common ancestor and now become the first excavators discovered in that part of the world.

Although they have a common ancestor, the kinship between these two species is quite distant, which means that evolution can provide very specific but similar tools to two distant animals if needed.

The species found were identified as clear predecessors of mammals. One is a foot-long semi-mammalian reptile that they named Fossiomanus sinensis. The other specimen is a distant relative of modern placental mammals and marsupials of 7 inches long and was named Jueconodon cheni.

Long cabbage and short but very strong limbs are the most important characteristics of the burrowing animals and these were found in the two new species, determining that both did their excavations with the claws of their front limbs.

“This is the first convincing evidence for fossorial life in those two groups. It also is the first case of scratch diggers we know about in the Jehol Biota, which was home to a great diversity of life, from dinosaurs to insects to plants,” said lead author Jin Meng, a curator in the American Museum of Natural History’s Division of Paleontology.

What most impressed the scientists was the similarities between some modern mammals and the variations that occur in the embryonic process that cause some animals to have very long torsos and necks, such as elephants, manatees, and hyraxes. In these new species, they found that the same variation also occurred and as a consequence they had vertebral columns of 28 and 38 vertebrae each.

The discovery is impressive and goes straight to completing at least a tiny part of the evolutionary puzzle that scientists are just getting to know.