Discover the Giant Armored Mollusks With Spikes From 500 Million Years Ago

Written by Austin S.
Updated: October 10, 2022
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The evolution of life began with the explosion of life during the Cambrian period. This second period of the Paleozoic era features many strange-looking multicellular organisms. It was the era for some of evolution’s significant achievements that exist in today’s organisms.

While there were floating jelly-like fishes like the Hakouihthys, the creature described in this article was like a porcupine of the seas. It is called a Wiwaxia. Wiwaxia was a genus of invertebrate marine animals. It was a small animal with spikes on its back. It has been featured on ‘First Life’ by David Attenborough.

This animal lived close to the ocean floor as it helped with survival. It was not a swimmer, so it likely slugged on the ocean floor. We will discuss what Wiwaxia is and when it existed. We will also discuss how it lived and went extinct millions of years ago.

Description & Size

Wiwaxia was a small marine organism that lived like a slug in the seas. It belongs to the Mollusca animal group and the Wiwaxiidae family. It was an invertebrate with a soft body and smooth underbelly. While the underbelly was not protected, it had protection on its back. It had leaf-like scales on its underbelly.

Wiwaxia lived between the early and mid-Cambrian periods of the Paleozoic era. They were part of the multicellular organisms that evolved during the Cambrian explosion. They existed between 541 to 485 million years ago. This animal has traits that still exist in many mollusks today.

Some key facts about Wiwaxia are:

  • Length – about 2 inches long
  • Height – about 1 cm without the spikes
  • Diameter – around 30 mm
  • Attributes – very small, spike on its back, no head and tail,slug-like  smooth ventral side

Wiwaxia is one of evolution’s creatures that developed an obvious defense mechanism. They were animals prone to being easy prey. It is due to their lack of abilities and skills to fight and attack. It also means that they were at the bottom of the food chain. Their defensive back featured long, sharp spikes and armor plating.

The spikes on its back could grow as long as its body. It used this spike to defend itself from predator attacks. Wiwaxia had small armor plates that covered its back. These armor plates acted as shields against predator attacks. It means that while the plates shielded it, it could attack and fend off predators with its sharp spikes.

The armor plates are called sclerites. They are arranged in 8 rows, and they are flat on its body. They are also overlapped to form five regions of its armor. This armor is periodically changed as the animal grows. Wiwaxia had a mouth with small sharp teeth. As it was incapable of hunting, it likely used them to better access algae from the ocean floor. 

Wiwaxia didn’t have a head which means it had no eyes. It was likely a blind animal that relied on smell and its senses to navigate the ocean floors. There are four known species of Wiwaxia which are; Wiwaxia corrugata, Wiwaxia foliosa, Wiwaxia papilio, and Wiwaxia taijiangnsis.

Fossilized remains of Wiwaxia from the Burgess Shale.

Mature Wiwaxia specimen, with incipient spines, and partial scleritome exposing underlying tissue.

©Wiwaxia corrugata from the Burgess Shale. ROM 61151 (Fig. 3G) – Mature specimen, with incipient spines, and partial scleritome exposing underlying tissue – License

Diet – What Did the Wiwaxia Eat?

Wiwaxia was a bottom feeder of this period. Its mouth was on its soft underbelly. It had two to three small rows of teeth. They were backward-facing conical-shaped teeth. Scientists suggest that Wiwaxia used its teeth to scrub and feed on organisms from the ocean floor. 

Wiwaxia was an animal without a head and any hunting skills or abilities. It was a bottom feeder that likely used its mouth and teeth to scrub algae from the sea and ocean floor. It belonged to the bottom of the food chain. Its slow movement and lack of maneuverability mean that it likely couldn’t trap smaller organisms.

They were likely regulars of the microbial mats on the ocean floor at the time. Later in the Cambrian period, these microbial bats had to give way to new developments on the ocean floor. Scientists suggest that Wiwaxia disappearing around the mid-Cambrian period is due to the eradication of the microbial mats.

Habitat – When and Where the Wiwaxia Lived

Wiwaxia was a marine animal that lived in the seas and oceans of its time. It existed during a period when Earth mainly was water. The evolution of life during this period was focused on marine life. This restriction of evolution to the waters and the Cambrian explosion ushered in the Wiwaxia into the oceans.

Wiwaxia was spread across the world. This animal lived on an 85% water earth, which meant space to explore and diversify. They were mainly present in the Burges shale of British Columbia. Other key locations are the Kaili formation of China, Emu Bay Shale of Australia, and Buchava formation of the Czech Republic. 

Threats and Predators to the Wiwaxia

Wiwaxia was an animal with no ability to be a predator. It was a slow animal with no maneuvering skills. It had no abilities for swimming and no tail. Wiwaxia shows it was prey to every predator in the sea. It was a period when the seas had some ferocious predators.

This period features evolution’s first apex predator, Anomalocaris. Anomalocaris was likely a predator to the Wiwaxia. Anomalocaris was a highly maneuverable animal. It also had mouth parts that could aid it in overcoming a Wiwaxia’s defense.

The course of evolution was also a threat to this animal. As the Cambrian period progressed, one of Wiwaxia’s likely primary food sources was eradicated. The food source called microbial mats gave way to an oxygenated ocean floor that organisms could inhabit. Scientists believe this caused the Wiwaxia to die off before the Cambrian period ended.

Discoveries and Fossils – Where the Wiwaxia Was Found

Wiwaxia was first discovered in 1899. The first discovery was of a single spike from its defensive back. In 1911, Charles Walcott Doolittle discovered more fossils in the Burgess Shale. More fossils were discovered in 1966 and 1967 on another expedition by Harry B. Wittington. 

Wiwaxia had a worldwide presence during its time. Its fossils have been found in the Czech Republic, China, Canada, and Australia. Its fossils have been found in different parts of the world. 

Extinction – When Did the Wiwaxia Die Out?

Scientists suggest that Wiwaxia did not exist beyond the mid-Cambrian period. It is because there are no traces of it, and none of its fossils dates after that period. Some scientists have linked its extinction to a lack of its most convenient food source.

Wiwaxia could have also died out during the Cambrian extinction events. The end of this period marked the extinction of many species. If the Wiwaxia survived on another food source till the end of the period, it likely went extinct due to an extinction event.

Similar Animals to the Wiwaxia

Wiwaxia was a unique creature of its time, as was the trend. It belongs to a class of mollusks that still exist in today’s ecosystem. Some similar animals to Wiwaxia are:


Slugs are animals that belong to the mollusks group. They are similar to the Wiwaxia with their flat and soft underbelly. However, a slug has a soft body all over with no protection. They are also slow creatures and live on land. They’re slimy creatures that leave make trails of slime as they move. There exist around 5,000 species of slugs around the world.


Snails are mollusks that have a shell on their backs. Unlike Wiwaxia, they can retract into their shells for protection. Their shells do not have spikes and are a single unit. Like many mollusks are, snails are slow animals. They are invertebrates that can live in the sea and on land. There are about 40,000 species of snails around the world.


Periwinkles are a form of sea snails. They possess smooth shells of around 1-inch length. This shell can be brown or gray. While they are marine animals, they could live on land for days in extreme situations. They are also mollusks and leave trails of their movement. There are about 80 species of periwinkles around the world.


An octopus is an eight-tentacle animal that lives in the ocean. This animal is a soft-bodied creature with claspers on its tentacles for grasping things. Octopuses have three hearts. They can also camouflage their skin color to match the environment. There are about 300 species of Octopuses in the oceans.


Squids are tentacled creatures like octopuses. They also can camouflage their skin. They are one of the fastest invertebrate swimmers in the oceans. While an octopus has a round head, a squid has a triangular-shaped head. There are around 300 species of squid around the world.


Wiwaxia is a strange gift of evolution to earth. It features a very unique and rare body structure. It was like a slug of the oceans and lived through the Cambrian oceans. Wiwaxia was prey to the predators of its time, with only its spiny and armored back to protect it.

Up Next:

Discover more secrets evolution has to offer. Understanding what ancient animals have existed helps to appreciate today’s ecosystem better. We offer more articles on ancient animals and events on this site.

The photo featured at the top of this post is © Wiwaxia corrugata from the Burgess Shale. ROM 61151 (Fig. 3G) – Mature specimen, with incipient spines, and partial scleritome exposing underlying tissue – License / Original

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About the Author

Growing up in rural New England on a small scale farm gave me a lifelong passion for animals. I love learning about new wild animal species, habitats, animal evolutions, dogs, cats, and more. I've always been surrounded by pets and believe the best dog and best cat products are important to keeping our animals happy and healthy. It's my mission to help you learn more about wild animals, and how to care for your pets better with carefully reviewed products.

FAQs (Frequently Asked Questions) 

Was the Wiwaxia a fish?

Wiwaxia was a marine creature, but it wasn’t a fish. It belongs to the Mollusca group, which is related to slugs and snails of today. They were not swimmers like ancient fish relatives were.

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