The extra appendage helps propel the mole through its subterranean world.

BBC: Mystery of mole's second thumb solved

NPR's John Nielsen reports dancing ants, disgusting worms and the world's laziest mole-rats have the attention of serious scientists.

NPR: Mole-Rats, Ants Making Science Headlines

In today's world, the giant panda and the mole are anomalies among vertebrates: both have a second thumb, giving them a total of 12 digits.

BBC: Mystery of mole's second thumb solved