Nature
This spiny mammal lays eggs, has no nipples, and sweats milk through its skin
Echidnas are one of only two kinds of mammal that lay eggs instead of giving birth — the other being the platypus. A female incubates a single leathery egg in a temporary pouch; the hatchling, called a puggle, then laps up milk that oozes directly through patches of its mother's skin, since echidnas have no nipples at all. Despite looking like a spiky anteater, they're more closely related to you than to any reptile.