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13 Oldest Known Animal Fossils (Living Species)

With the help of paleontology, we have learned much about the evolution of life on Earth. One of the most exciting discoveries in this field has been the identification of some of the oldest animal fossils on record that still exists in our time. With more than 40 million fossils found, we could see how animals changed and grew in the early stages of evolution. In this article, we‘ll look at some of the oldest living fossils ever found, ranging from simple sponges to complex vertebrates.

13 Oldest animal fossils

1. Sponge

  • Scientific Name: Porifera
  • Fossil age: 550 million years

The Sponges are one of the oldest fossils that are still in existence today. They’ve been around for approximately 550 million years and can be discovered in the oceans of every continent on Earth.

Sponges are marine animals whose skeleton has allowed them to thrive in various environments. These animals also lack the organs and systems that are typical of multicellular animals, and their sole source of nutrition and oxygen comes from the flow of water that they absorb. 

2. Velvet worms

Velvet worm
Velvet worm | image by caspar s via Flickr | CC BY 2.0
  • Scientific Name: Udeonychophora
  • Fossil age: 505 million years

A velvet worm is a small worm that ranges up to 10 cm in length, with antennae and clawed legs that make them look like caterpillars. They belong to one of the categories of animals referred to as “living fossils,” meaning that they haven’t undergone much evolution over the course of millions of years. Typically, velvet worms live in humid coastal areas but can also be found in tropical and temperate rainforests.

3. Jellyfish

Jellyfish | Image by tarakko from Pixabay
  • Scientific Name: Scyphozoa
  • Fossil age: more than 500 million years

The Jellyfish, which have been around for more than 500 million years, are one of the oldest fossils still around today and are considered one of the most ancient of all living things. They have a body that resembles jelly and are equipped with tentacles that they use to capture their prey. These animals with soft bodies are able to survive in a wide variety of environments due to their exceptional level of adaptability and intelligence. 

4. Horseshoe crabs

Horseshoe crab
Horseshoe crab
  • Scientific Name: Limulidae
  • Fossil age: 445 million years

The horseshoe crab is one of the oldest living animals, having evolved before humans but still being found in the modern world. They have been around for 445 million years, and their origin can be traced back to the Paleozoic Era, which occurred between 540 and 248 million years ago. Located in shallow water, these animals are easily identified by their horseshoe-shaped shells.

5. Elephant shark 

Elephant shark on sand bed
Elephant shark on sand bed | image by Totti via Wikimedia Commons | CC BY-SA 4.0
  • Scientific Name: Callorhinchus milii
  • Fossil age: 400 million years

The Elephant shark is a type of fish that has been around for over 400 million years and also holds the record for the slowest evolution. They’re not true sharks, but they’re part of the group of cartilaginous fish, which also includes sharks, rays, and skates.

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Elephant sharks can be found all over Australia, Tasmania, and New Zealand, in places like shallow bays and large estuaries. They’re silver in color, but their distinctive “trunk-like” snout is what gives them their common name.

6. Tadpole shrimp 

tadpole shrimp
Tadpole shrimp | image by CanyonlandsNPS via Flickr
  • Scientific Name: Notostraca
  • Fossil age: 300 million years

Some animals have remained virtually unchanged for almost 300 million years, and tadpole shrimps are among those. This species of shrimp can endure extended periods of drought and can be found living in temporary ponds.

Their eggs are also highly adaptive; they begin to hatch only after the ponds have been filled with water. Tadpole shrimps look like tiny horseshoe crabs with long flexible tails.

7. Tuatara 

Tuatra on ground
Tuatra on ground | image by Sid Mosdell via Flickr | CC BY 2.0
  • Scientific Name: Sphenodon
  • Fossil age: 190 million years

The tuatara is a fascinating creature that’s well-known for being the largest species of reptile that can be found in New Zealand. This lizard-like reptile is the sole surviving member of a species of lizard-like reptiles that existed many millions of years ago. 

Although the tuatara may look similar to other large lizards, these animals are distinct and not like any other living reptile on the planet. One thing that makes them special is that they have teeth that can’t be replaced because they’re sharp projections of their jaw bones.

8. Arowana 

Asian arowana
Asian arowana | image by Aneo via Flickr | CC BY 2.0
  • Scientific Name: Scleropages formosus
  • Fossil age: 140 million years

The Arowana is a fish found in freshwater habitats in South America, Asia, and Africa. These fish have elongated bodies that are covered with large and heavy scales that serve as protection from potential predators. 

They’re one of the oldest fossils that have been discovered that still exist up to this day. Arowanas are considered to be among the oldest living fossils because the earliest fossil of their species was discovered to have existed approximately 140 million years ago.

9. Nautilina

Nautilina | image by Cliff via Wikimedia Commons | CC BY 2.0
  • Scientific Name: Nautilina
  • Fossil age: 120 million years

Since Nautilina are classified as mollusks, this indicates that they’re related to mollusks such as clams, oysters, and squid. Fossils of Nautilina have been discovered that date back to approximately 120 million years ago. Their soft bodies are protected by a shell that’s spiral in shape and opens at one end. 

These stunning animals are endemic to the Indo-Pacific region and can be found living on the steep sides of coral reefs in that region. They’re opportunistic predators and scavengers that feed on crab molts and other dead animals.

10. Platypus

Platypus in shallow water
Platypus in shallow water | image by Klaus via Wikimedia Commons | CC BY 2.0
  • Scientific Name: Ornithorhynchus anatinus
  • Fossil age: 61 million years

The Platypus is a unique semi-aquatic mammal that’s a monotreme, which means that it lays eggs. It’s found in rivers and streams, and its body has a number of unique characteristics, such as having webbed feet and a bill that’s comparable to that of a duck. Because they have been around for over 60 million years, platypi are among the oldest fossil animals that are still around today. 

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11. Pelicans

Pelican in the river
Pelican in the river | image by Azwari Nugraha via Flickr | CC BY 2.0
  • Scientific Name: Pelecanus
  • Fossil age: 36 million years

The Pelicans are a family of water birds that you can discover in every region of the planet. They‘re one of the oldest birds still around today, and there is evidence of their existence in the form of fossils that date back at least 36 million years ago. 

Pelicans are social birds that gather in large flocks and are able to hunt by diving into the water after their prey. These birds have a pouch under their throats that they use to store fish after they catch them.

12. Opossums

Virginia Opossum
Virginia Opossums | Image by daynaw3990 from Pixabay
  • Scientific Name: Didelphis virginiana
  • Fossil age: 23 million years

Opossums are a type of marsupial that’s found only in the United States. It stands on short, dark legs, a pointed snout, and a long, prehensile tail. Opossums are descended from marsupials that have been around for millions of years.

They have evolved unique adaptations such as prehensile tails and the ability to play dead that have helped them survive in various environments. Opossums themselves have been around for at least 70 million years, making them one of the oldest mammal groups in the world.

13. Aardvark 

Aardvark | image by CucombreLibre via Flickr | CC BY 2.0
  • Scientific Name: Orycteropus afer
  • Fossil age: 5 million years

The aardvark is a species of mammal that can only be found on the continent of Africa. It’s classified as a uranotherian, which refers to a group of primitive animals with hooves.

These extraordinary creatures make their homes in burrows and make use of their long, powerful claws to dig underground in search of termites and other insects in the ground. Even though these animals look like pigs, they’re more closely related to elephants.