A species
Platypus
Ornithorhynchus anatinus
An egg-laying mammal that senses electricity and glows green-blue.
You and the platypus last shared an ancestor about 180 million years ago (on 16 December, if life's history were one year).
Imagine a furry mammal that lays eggs, hunts with a bill that senses touch and electricity and glows green-blue under ultraviolet light. That is the platypus. Its closest living relatives are echidnas. Together they are called monotremes, the egg-laying branch of mammals, and they are cousins to all live-bearing mammals.
When it dives to hunt, it shuts its eyes, ears and nose. Its soft, leathery bill holds about 40,000 tiny electricity sensors, plus touch sensors. They pick up weak electric signals from the muscles of small animals it hunts, such as insect grubs, worms and shrimp. Apart from echidnas and one dolphin species, it is one of the only mammals that can sense electricity in this way.
About as long as a house cat without its tail, it has thick brown waterproof fur, big webbed front feet for paddling and a broad flat tail for storing fat. In daylight the fur looks mostly brown, but under ultraviolet light it glows green-blue. It lives in clean rivers and lakes in eastern Australia and Tasmania, where it digs burrows in leafy banks.
Venomous males
Only males make venom, held in spurs above the heels of the hind legs. This makes it one of very few venomous mammals, and the sting causes very strong pain.
No teeth as adults
Grown platypuses have no teeth and crush food with hard grinding pads. Babies grow five or six small teeth, then lose them before they leave the burrow.
Mistaken for a hoax
When the first skin and sketch reached England, naturalists thought someone had sewn a duck beak onto a mammal body. One scientist checked the skin for stitches before accepting it was real.