Coral reefs are rough places to live, so their residents often use camouflage to stay safe. And when it comes to living incognito among coral, the pygmy seahorse wrote the book.
Less than an inch long and studded with coral-like "tubercles," this seahorse has all its evolutionary chips on just two species of gorgonian corals in the Pacific Ocean (with a matching color pattern for each). It blends in so well, though, that it was only discovered by humans after showing up with wild-caught corals in an aquarium. It mates in pairs that may be monogamous, according to the IUCN, but its conservation status is unknown due to insufficient data.