Bizarre egg-laying mammals once ruled Australia, but then lost their teeth
Enlarge / The echidna, an egg-laying mammal, does not develop teeth. Outliers among mammals, monotremes lay eggs instead of producing live young. Only two species of monotremes still exist, the platypus and the echidna, but about 100 million years ago there were more monotreme species. Some of them may be even stranger than their descendants. … Read more
