Long before humans left their caves some seven million years ago, animal species of unimaginable shapes and sizes had already walked the earth and swam in its waters.

Today in museums, people can see the fossilised remains of plants and animals that used to populate the Earth.

But nature has a funny way of doing things, and recently, scientists have discovered that supposedly extinct species are still thriving in the most isolated parts of the planet.

Here are six ancient species that have barely changed throughout the course of history.

Horseshoe crab

These strange arthropods are possibly the most obvious ancient creatures, with their appearance seemingly more alien than an earthbound animal.

They share an uncanny resemblance to their ancestors, of which fossils have been found dating back to 445 million years ago!

Today, four species of the horseshoe crab have been found, one living in the eastern United States and the remaining three in Southeast Asia, including in Malaysia.

While their name may suggest that they are crustaceans like crabs and lobsters, they are actually related closer to spiders.

Aside from being an unusual curiosity, horseshoe crabs also have blue blood with unique properties that pharmaceutical companies use to test vaccines and drugs.

Nautilus

If you ever find a relatively large shell with a distinct spiral appearance on the beach, it’s most likely that you’ve found a nautilus.

These sea creatures have been swimming around in the Earth’s oceans for over 500 million years, with their earliest ancestors being called nautiloids.

Based on fossil records, there used to be thousands of species of nautiluses, but today, just six remain. They belong to the cephalopod family and thus, are related to octopuses, squid and cuttlefish.

While not critically endangered at the moment, their numbers are decreasing due to human activity, with the shells being turned into souvenirs and their meat sold as seafood.

Sea sponge

They may not live in a pineapple under the sea, but they can live for a very, very long time; sponges have been living on seabeds for about 600 million years and counting.

With around 7,500 different species, sponges have survived several extinction events and catastrophes, and can be found in ocean waters across the globe.

Simple animals without any semblance of organs, they consist only of their sac-like bodies and obtain food and oxygen by maintaining a constant water flow through their bodies.

Sponges are also believed by scientists to be the first group to separate from the evolutionary tree that started with the last universal common ancestor (LUCA).

Gingko

The ginkgo leaf is known by Asians to be a beautiful herb with a distinct smell and an expensive price tag. For scientists though, the ginkgo tree is actually a living fossil, with its ancestors believed to have lived during the time of dinosaurs.

The ginkgo is one of the world’s strangest plants, due to the fact that it consists of only one species. 200-million-year-old fossils of ginkgo leaves show that little has changed in terms of its appearance.

They have proven time to be extremely hardy plants, and in fact, during the atomic bombing of Hiroshima, six gingko trees that were caught directly in the blast survived and still grow today.

Red panda

Not all ancient creatures have to look scaly or completely alien; they can also be absurdly cute and cuddly in appearance, just like the red panda.

Originating from the mountains of China, the red panda is only distantly related to the giant panda, but it is not a close relative of the raccoon either.

They belong to their own mammalian family called Ailuridae, being the only surviving members of that family.

There are two subspecies of red pandas, namely the Himalayan and the Chinese, both of which share the same ancestral roots which appeared some eight million years ago.

Platypus

This fantastical, warm-blooded mammal, with its duck-like beak and webbed feet, is known as one of only two living egg-laying mammals left on the planet. The Platypus also happens to be among the most venomous animals alive.

There is only a single species of platypus which belongs to the Ornithorhynchidae family.

They are also extremely unusual due to their possession of ten sex chromosomes, when most mammals, including humans, have two, namely X and Y.

While the oldest platypus fossil dates back to 100,000 years ago, there is evidence that they have been around for about 100 million years already, sharing the Earth with the dinosaurs.

It’s certainly an impressive feat for a creature better known today to teenagers and children as a secret agent in a certain Disney cartoon.