To navigate the currents of ecological fate, most creatures adapt — but a few have stuck to their evolutionary guns.

Known as living fossils, they lasted for millions of years with barely a change, even as their relatives went extinct or took different paths across the tree of life.

Many are now threatened or endangered. But with some luck and a little help, living fossils will be able to survive the age of humans, too.

The Purple frog, discovered just five years ago in western India, likely escaped detection because it lives underground, emerging for just two weeks during the monsoon season. Distinguished by a pointed snout, it's related to a family of frogs now found only on the Seychelles islands, which split from India 100 million years ago.

Image: WikiMedia Commons

Scientists disagree over whether the frilled shark has survived for 380 milllion years, or a mere 95 million years. Only two living specimens have been found — both off the coast in Japan, in the late 19th century and again in 2007 — but they are sometimes caught accidentally by deep-sea fishing nets.

Video: Xagtho Channel

Until a preserved specimen was found in the Smithsonian in 1975, the 10-footed, lobster-like Jurassic shrimp was thought to have gone extinct 50 million years ago. Living Jurassic shrimp have since been found.

Image: Census of Marine Life

What it lacks in convenient nomenclature, the Siberian Sikhotealinia zhiltzovae

makes up for in uniqueness: it's the only three-eyed beetle. Some scientists consider it a forerunner of nearly all winged insects.

Image: St. Petersburg Zoological Institute

Found mostly in Southern Hemisphere rain forests, velvet worms have legs and — unlike other worms — bear live young. Closely related to tardigrades, their legs are hollow and supported by fluid pressure. After a few early adaptations for land, they've hardly changed in 360 million years.

Video: InfiniteWorld

The most widespread of all living fossils, crocodiles have barely changed in the 230 million years since dinosaurs roamed the Earth.

Image: Flickr/**Keven Law

One of the relatively few mammalian living fossils, duck-billed platypuses have been weird for 110 million years: in addition to their bills, they lay eggs and have venom-filled leg spurs. No wonder they were considered a hoax by early naturalists.

Video: Springbreakwas2short

Its spiraling chambered shell was a symbol of perfection in ancient Greece, and the nautilus has changed little in 500 million years.

Image: Flickr/**Ethan Hein

Found commonly on Atlantic beaches, horseshoe crabs are more closely related to spiders, ticks and scorpions than crabs. Their ancestors evolved in the Paleozoic's shallow seas, and they've evolved only slightly in the last 445 million years. If you see one on its back, flip it over: They can regrow lost limbs, but can't right themselves when tossed in the surf.

Image: Flickr/Chris Howard

Better known as the "Ant from Mars," Martialis heureka is a direct-line descendant of the last common ancestor of all ants — a subterranean forager who wouldn't go above-ground until flowering plants evolved 120 million years ago.

Image: Christian Rabeling

Coelacanth vanished from the fossil record 410 million years ago — and then one was caught in 1938 off the coast of South Africa. A second species was discovered in Indonesian waters in 1999.

Video: Pinktentacle3

Neither a mantis nor a shrimp, the mantis shrimp has changed little in 400 million years. It has the world's most complex eyes, and its prey-killing claw motion is the second-fastest animal motion. To quote mantis shrimp eye researcher Tom Cronin, "Whenever they get into any type of situation, they smash things. You can't pick these up. They're really great animals to have around."

Image: Tom Cronin

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