HideShark list
"Living fossil" is a loose term for a species whose body plan closely resembles ancient relatives known from the fossil record, usually because it lives in a stable environment — the deep sea, a cave, an isolated island. None of these animals has actually stopped evolving; their genes and physiology keep changing even when their shape does not.
Lineage ~400 million years old; thought extinct until 1938
A deep-sea lobe-finned fish known only from fossils — the youngest 66 million years old — until a live one was hauled up off South Africa. Its fleshy, limb-like fins link it to the ancestors of all land vertebrates.
Full coelacanth guide →The last of an order older than the dinosaurs
A New Zealand reptile that looks like a lizard but is the sole survivor of the Rhynchocephalia, which split from lizards and snakes over 240 million years ago. It has a working third eye and runs on a cold, slow metabolism.
Full tuatara guide →Nautiloids date back ~500 million years
The last shelled cephalopods, barely changed from fossil forms while their cousins the ammonites went extinct and the octopuses and squid became fast, soft, big-brained animals. It has up to 90 tentacles and pinhole eyes with no lens.
Full chambered nautilus guide →Nearly identical fossils are ~445 million years old
Not a crab but a relative of spiders and scorpions, with a hinged shell, ten eyes, and blue, copper-based blood that is harvested to test medicines and vaccines for bacterial contamination. It has outlasted several mass extinctions.
Body plan ~80 million years old
An eel-bodied deep-sea shark with six gill slits, a forward-set mouth, 300 trident teeth, and a notochord only partly replaced by vertebrae — all features most sharks lost long ago.
Full frilled shark guide →Near-identical fossils ~30 million years old
The giant salamanders of Japan, China, and (a smaller relative) North America form an ancient lineage that split from other salamanders very early and has kept the same wrinkled, aquatic, skin-breathing body ever since.
Full giant salamander guide →An isolated branch with no close living relatives
An Amazonian bird that ferments leaves in a cow-like foregut and whose chicks have clawed wings for climbing. Its lineage has been evolving on its own for tens of millions of years, though the wing claws are a modern adaptation, not a dinosaur leftover.
Full hoatzin guide →Recognisable fossils ~400 million years old
Freshwater fish with true lungs that can breathe air and, in the African and South American species, survive drought sealed in a mud cocoon for months. The Australian lungfish in particular has changed little for around 100 million years.
Almost unchanged for ~500 million years
A soft, caterpillar-like animal with stubby legs and a pair of slime cannons for catching prey, occupying a branch of the tree of life between the arthropods and the worms. Cambrian fossils of near-identical creatures are among the oldest of any land animal.
Its family goes back ~125 million years
A pink, flabby deep-sea shark with a long flat snout and jaws that shoot forward to grab prey. It is the only surviving member of a shark family known mostly from fossils, and it lives too deep to be more than rarely glimpsed.
It is an informal term, coined by Darwin, for a living species that closely resembles organisms known only from fossils, and that has few or no close living relatives. Classic examples include the coelacanth, the tuatara, the nautilus, the horseshoe crab, and the ginkgo tree. The resemblance is usually to a body plan, not to a specific ancient species.
No — that is the main criticism of the term. Their outward form has stayed similar, usually because they live in stable environments where the old design still works, but their DNA, immune systems, behaviour, and physiology have continued to change like any other lineage. The coelacanth, for instance, is genetically quite different from its fossil relatives even though it looks similar.
Stable, low-competition environments favour keeping a working design rather than innovating. The deep sea changes slowly and has few new competitors or predators; isolated islands and caves shield their inhabitants from the arms races playing out on the mainland. Many living fossils are also large or slow-breeding, traits that persist best where conditions do not change fast.