17 Animals That Are Living Fossils

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From another era

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A living fossil is an organism that has retained the same form over millions of years, has few or no living relatives, and represents a sole surviving lineage from an epoch long past.

Many living fossils alive today have bizarre, eccentric traits that make them seem more like aliens than anything from this world. They have often survived several mass extinctions, and many scientists consider them to be a rare glimpse at how life on Earth was long ago.

Here are some examples of these amazing creatures. Some are recognizable, but others look like nothing you've seen before.

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Komodo dragon

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Most people would agree that no other lizard in the world looks more prehistoric than a komodo dragon. They can be traced back to the genus, Varanus which dates back about 40 million years. First seen in Asia, the komodo dragons later migrated to Australia, where they grew into their current massive size. They are the largest and heaviest lizards in the world.

While they are famously named after the Indonesian island of Komodo, they arrived there long after they first appeared in Australia — some 900,000 years ago.

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Sandhill crane

A sandhill crane taking flight over the Jasper-Pulaski Fish and Wildlife Area in Indiana. (Photo: Haricharan [CC BY-ND 2.0]/Flickr)

While many birds can trace their ancestry back to dinosaurs, fossils show that the sandhill crane itself dates back 2.5 million years. Ancient sandhill cranes varied in size compared to today. Now, there are several subspecies of sandhill cranes that live in North America — some of which are listed as endangered.

Sandhill cranes are popular with bird enthusiasts because of their annual migration. Hundreds of thousands migrate from Mexico and the southern U.S. all the way up to the Arctic.

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Aardvark

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Best known for being first on any alphabetical listing of wildlife, an aardvark is a nocturnal, burrowing animal and the only living species in the order Tubulidentata.

Genetically, the animal can be considered a living fossil because of the ancient arrangement of its chromosomes. Aardvarks are excellent diggers and, bizarrely enough, elephants are one of their closest living relatives (although the relationship is very distant).

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Red panda

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Hailing from the temperate forests of the Himalayas, these adorable creatures are the only surviving members of the family Ailuridae.

Despite the name, red pandas are barely related to the giant panda. They represent a lineage that more closely marks a cross section of bears and skunks, weasels and raccoons. They are truly in a world all their own.

Their association with the giant panda may have to do with the animals' similar diets, which includes a lot of bamboo, than it does any sort of evolutionary relationship.

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Tuatara

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They may look like lizards, but tuataras are actually part of a different order called Sphenodontia. Only two species of tuatara exist today, and they have much the same form as ancient ancestors that thrived 200 million years ago. These reptiles are truly prehistoric.

There are tuataras alive today that are well over 100 years old, and some experts believe they could live to be more than 200 years old under the right conditions.

Unfortunately, these amazing creatures are endangered, and can be found only on small islands off the coast of New Zealand.

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Nautilus

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The nautilus represents the only living member of the subclass Nautiloidea. The nautiluses are cephalopods that retain an outer shell unlike other distantly related animals such as squid and octopus.

Their beautiful shells have inspired many artists over the centuries, and they are also among the finest natural examples of a logarithmic spiral or the golden ratio.

Because of their shells, the fossils of nautiluses are easier to come by than remains of other cephalopods, and fossil hunters have discovered ancient shells dating back at least 500 million years.

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Purple frog

Photo: David V. Raju/Wikimedia Commons

Discovered as recently as 2003, this living fossil has been described by researchers as a "bloated doughnut with stubby legs and a pointy snout." Looking at this portly purple creature, it's hard to disagree with that assessment. Even more bizarre, its cry sounds like that of a chicken.

Though found in India, its closest living relatives can only be found on the Seychelles islands, meaning these frogs have been around for at least 100 million years, when India, Madagascar and Seychelles were connected as a single land mass.

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Platypus

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There's no limit to the number of bizarre adjectives you could use to describe a platypus. They have a snout like a duck but a hairy body like a mammal; they lay eggs and are one of the only venomous mammals in the world.

Even more bizarre, they have 10 sex chromosomes as opposed to the two (X and Y) that most other mammals have. It's no surprise that they are the sole living representative of the family Ornithorhynchidae.

Platypuses and echidas are the only egg-laying mammals on Earth, making them extremely valuable for studying mammalian evolution. Platypus-like fossils that date as far back as at least 167 million years ago.

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Mantis shrimp

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Though their name suggests otherwise, mantis shrimp are not shrimp nor mantids. They often come in a variety of beautiful colors and are known for their powerful claws, which have been known to break through aquarium glass with a single strike.

Known for their feisty dispositions, mantis shrimp are bad news for any prawn that swims past, but they do have a softer side. Some mantis shrimp form monogamous pair bonds and stay together for as long as 20 years. They also have some of the most advanced eyes in the animal kingdom.

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Hagfish

Photo: NOAA/Wikimedia Commons

These animals may look like slimy eels, but many experts don't consider them to be fish. In fact, some taxonomists are hesitant to consider them vertebrates, since they are the only living animals that have a skull but not a vertebral column.

One descriptor that is not a misnomer is slimy. In fact, hagfish secrete a gooey slime when handled or threatened, which in the wild helps them to escape from predators.

From an evolutionary point of view, they can be recognized from fossils that date back to 330 million years ago, and they represent a crucial living link between vertebrates and invertebrates.

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Hoatzin

Photo: Kate Tann [CC BY-SA 2.0]/Flickr

These odd-looking, pheasant-sized birds are arguably the most debated living birds because their evolutionary tree is missing so many branches.

It is the only member of its family (Opisthocomidae), though some taxonomists also place them in their own order. They retain some characteristics that are not found in any other birds. For instance, as chicks they still retain claws on the ends of their wings, which aid them in climbing and clinging to trees.

Regardless of how they fit into the evolutionary picture, they are stunning ancient animals.

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Koala

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These Australian marsupials are an icon for wildlife across the globe — a familiarity that overshadows their uniqueness.

Though often referred to as bears, they are not related to bears at all. In fact, they are members of the family Phascolarctidae.

As marsupials, they carry their young in a pouch. Fossils of koalas are rare, but these marsupials have been around for at least 20 million years. Back then, they evolved to live in rain forests rather than the eucalypti forests where they currently reside.

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Pig-nosed turtle

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As the only living member of the family Carettochelyidae, the pig-nosed turtle is one of a kind — and not just because of its distinctive snout. Unlike most freshwater turtles, these guys have flippers which more closely resemble those of marine turtles, making them almost entirely aquatic.

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Horseshoe crab

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Despite their namesake, horseshoe crabs are not crabs at all. In fact, they aren't even crustaceans, being more closely related to arachnids like spiders than to anything else. But for years, there was doubt about their relationship to arachnids. Then, a team of evolutionary biologists from the University of Wisconsin-Madison analyzed a collection of genetic data in 2019 and confirmed that horseshoe crabs are in fact related to arachnids.

"By showing that horseshoe crabs are part of the arachnid radiation, instead of a lineage closely related to but independent of arachnids, all previous hypotheses on the evolution of arachnids need to be revised," Jesús Ballesteros, a postdoctoral researcher, wrote in the study. "It's a major shift in our understanding of arthropod evolution."

Horseshoe crabs have been around for about 450 million years. They are truly alien-looking — they even have blue blood. Horseshoe crabs also have a unique immune system, and studying them has led to breakthroughs in cancer research and spinal meningitis treatments, among other things.

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Goblin shark

Photo: Wikimedia Commons

These frightening creatures look more like something that should be climbing out of the womb of an alien than anything from this world.

In fact, they are ancient deep sea sharks with unusual snouts that are longer than any other type of shark. They can grow as long as 11 feet. The only good news is that they are never seen in the surface waters where humans swim.

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Elephant shrew

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Their common name suggests otherwise, but these odd-nosed animals are not related to shrews. Though their taxonomic classification is still debated, elephant shrews share a relationship to other distant and distinct animals such as aardvarks, elephants and even manatees.

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Crocodiles

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No other animal deserves the title of living dinosaur like a crocodile does. These beasts have exhibited the same body form since dinosaurs walked the Earth, surviving the mass extinctions that wiped out nearly all of their mammoth brethren.

In fact, they are the closest living relatives of birds, representing a long-diverged connection between birds and reptiles.