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"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.
Full horseshoe crab guide →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 closest living fish relatives of all land vertebrates.
Full lungfish guide →Modern form ~20–30 million years old
A browsing relative of horses and rhinos with a short grasping trunk, little changed since the Miocene. Five species survive in South America and Southeast Asia, the remnant of a group that was once far more widespread.
Full tapir guide →Its lineage split from all other frogs ~120 million years ago
A bloated, burrowing Indian frog whose family separated from its closest relatives — now living in the Seychelles — when the two landmasses were still joined in Gondwana. It has ridden the Indian plate across an ocean and spends 50 weeks a year underground.
Full purple frog guide →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.
Full velvet worm (onychophora) guide →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.
Full goblin shark guide →The only living member of its order; relatives ~165 million years old
Neither a squid nor an octopus but the sole survivor of the order Vampyromorphida, keeping features of both. It drifts in the ocean’s low-oxygen midwater eating "marine snow," a refuge so hostile that little else can follow it there.
Full vampire squid guide →Recognisable fossils over 100 million years old
Sturgeons and paddlefishes are an ancient branch of ray-finned fish that keep a cartilage skeleton, a shark-like tail, rows of bony scutes instead of scales, and a toothless sucking mouth with sensory barbels. The beluga is the giant of the group.
Full sturgeon guide →A jawless lineage older than any fish with jaws
One of the only living jawless vertebrates, from the earliest branch of the vertebrate tree — before jaws, bone, and paired fins. It has a skull but no true backbone, four hearts, no stomach, and turns seawater to slime when attacked.
Full hagfish guide →Diamond-armoured, air-breathing, ~100 million years old
Gars have barely changed since the age of the dinosaurs. The alligator gar keeps enamel-coated diamond scales, a shark-like spiral-valve gut, and a swim bladder it uses as a lung to survive stagnant water.
Full alligator gar guide →Toothless plankton-strainer with an electric snout
A close cousin of the sturgeon, little changed in 120 million years, with a near-cartilage skeleton and a metre-long electroreceptive paddle. Its only relative, the Chinese paddlefish, was declared extinct in 2022.
Full american paddlefish guide →A jawless vertebrate from before jaws existed
Lampreys and hagfish are the only survivors of the earliest vertebrates — no jaws, no bone, no paired fins. In place of a jaw the sea lamprey has a round sucker disc ringed with horny teeth, a body plan barely changed in 350 million years.
Full sea lamprey guide →Little changed in roughly 100 million years
A long, armour-scaled ambush predator with a needle-toothed snout and a lung-like swim bladder that lets it gulp air at the surface — a primitive feature retained from a lineage that has barely shifted shape since the age of dinosaurs.
Full longnose gar guide →A lineage over 100 million years old
An armoured, bony-plated fish with a mostly cartilaginous skeleton, retaining primitive features from a sturgeon lineage that predates most modern fish groups. A 19th-century caviar boom nearly wiped it out before it ever got the chance to keep changing shape.
Full atlantic sturgeon guide →Six gill slits instead of five — a trait from early sharks
Most modern sharks reduced to five gill slits; the sixgill kept six, along with a single dorsal fin and a conservative jaw. Its family has close fossil relatives more than 150 million years old, and its heavy, deep-water body has changed little since.
Full bluntnose sixgill shark guide →The last living member of an entire order of fish
Every other species in the order Amiiformes, common in the age of the dinosaurs, has gone extinct, leaving the bowfin alone. It still carries archaic traits like a lung-like gas bladder it uses to gulp air in stagnant swamps that would suffocate other fish.
Full bowfin guide →The sole survivor of a frog family 100+ million years old
The only living species of the family Rhinophrynidae, whose fossil relatives once ranged across North America. It kept a distinctly un-froglike tongue that fires straight forward rather than flipping out, an adaptation for raiding ant and termite galleries underground.
Full mexican burrowing toad guide →Barely changed in more than 100 million years
Fossils of the genus Neoceratodus from over 100 million years ago are almost identical to the heavy, olive-scaled lungfish still living in a few rivers of southeast Queensland. It breathes air with a single lung when its pool turns stagnant, but unlike its African cousins it cannot survive the water drying up.
Full australian lungfish guide →The only living species of a genus otherwise known from fossils
Declared extinct in 1996 and rediscovered in an Israeli marsh in 2011, it was then found by bone and DNA study to belong not to the living painted frogs but to Latonia, a genus previously known only from fossils across Europe going back millions of years.
Full hula painted frog guide →Body plan barely changed since the Jurassic
One of a few surviving New Zealand frogs in the ancient genus Leiopelma, it keeps traits every other living frog has lost — small tail-wagging muscles though it has no tail, an extra vertebra, no eardrum, no croak, and no tadpole stage, with the male carrying the froglets on his back.
Full archey's frog guide →The last of a frog family known from Cretaceous fossils
A dinner-plate-sized aquatic frog of central Chile, one of the largest in the world, and the only living species of the family Calyptocephalellidae, a lineage that split from all other frogs more than 100 million years ago and appears in Late Cretaceous rocks of Patagonia.
Full helmeted water toad guide →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.