Last updated: May 27, 2024
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Anomalocaris Scientific Classification

Scientific Name

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Anomalocaris Physical Characteristics

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About half a billion years ago, life on earth was restricted to the sea. The planet was home to several bizarre and odd-looking creatures that occupied the oceans. One of the peculiar life forms that occupied the Earth’s ocean at the time was the Anomalocaris. This mysterious shrimp-like creature was a major predator that ruled the ancient seas during an era known as the Cambrian period. Present-day fossil discoveries indicate that it had widespread distributions with fossils found in various places, including Canada, Australia, Greenland, Utah, and China

Description & Size

The Anomalocaris’s name means “unlike other shrimp” or “abnormal shrimp.” The name Anomalocaris is a reference to the first fossil of the animal that was discovered which scientists thought was similar to the abdomen of a crustacean, hence the name.

Anomalocaris was a large apex predator with a unique appearance. It swam the oceans using the rows of undulating overlapping lobes (flexible flaps) on the sides of its body. These lobes formed a single fin that allowed it to propel itself fast through the water. It also had a large fan-shaped tail which the animal probably used for propulsion. 

The widest part of the animal’s body was between the third to fifth lobe, then it gradually narrowed towards the tails. The body of the Anomalocaris had 14 podomeres or segments.

The Anomalocaris has a large head with a pair of large compound eyes on both sides. It also has an unusually large disk-like mouth consisting of 32 overlapping plates. These plates gave the Anomalocaris’ head the appearance of a pineapple ring. 

The Anomalocaris was a large predator. Early estimates suggest its length was about 1m. However, experts now say it could have been up to 2-3m long. Like modern-day shrimps, it had two large tooth-like prongs. These prongs extended from the walls of its gullet to outside its body and were at least seven inches long when extended. 


Anomalocaris was a large, shrimp-like creature that lived during the Cambrian period.

Diet – What Did Anomalocaris Eat?

For a long time, paleontologists considered the Anomalocaris an active predator. Experts believed it could stalk its prey with its large compound eyes, swim quickly to catch up with it, and grab the prey with its strong, spiked front limbs. Its large size suggests it was one of the first apex predators ever. The Anomalocaris’ mouth had 32 overlapping plates, which scientists believed the animal used to crush prey. Fossil evidence suggests that its diet might have consisted of trilobites, a group of extinct marine arthropods that lived in the Cambrian Period.

However, recent research seems to suggest differently. There are indications that the Anomalocaris could not close its mouth all the way, and its mouth plates were too small. This would make a trilobite diet impractical because the Anomalocaris would be unable to crush trilobite shells.

Some scientists now believe that instead of solid food, the Anomalocaris might have fed on softer animals that were available in the Cambrian waters 500 million years ago. If this is true, the diet would be more similar to modern-day shrimps, lobsters, and crabs. 

Habitat – When and Where It Lived

Paleontologists found fossils of the type species of this genus, Anomalocaris Canadensis in the Burgess shale formation of Canada. The formation contained relatively great numbers of Anomalocaris fossils, which suggests that they were present in abundance in this area. However, they have discovered Anomalocaris fossils in several other places too. This means the species adapted well to a vast range of environments, including the shallow tropical sea in Australia and what is now modern-day China. 

Threats And Predators

The 3-feet long “unusual shrimp” is unlikely to have had any major competitor at the time it lived. Scientists believed it was the largest animal in its habitat. So far, the fossil is the largest to have been discovered in any formation from that period. Thus, the Anomalocaris is thought to have been an apex predator that ruled this primordial world. 

Discoveries and Fossils – Where It Was Found

The discovery of the Anomalocaris fossil is just as mysterious as the animal itself. The first recorded discovery of this animal was in 1886 by Richard G. McConnell. However, the scientist had no idea that what he found was merely a feeding appendage of a much larger animal. Instead, they interpreted the find as the abdomen of Phyllocarid crustaceans (a sub-class of crustaceans that includes the Leptostraca and the now extinct Hymenocaris). The name Anomalocaris was assigned to this fossil in 1892. 

Later in 1911, another group of scientists found mouth parts of the Anomalocaris and thought it belonged to a jellyfish, so they gave the specimen the name Peytoia. Around the same time, more fossils were discovered, and paleontologists wrongly identified these as belonging to a type of sea sponge. This time, they named it Laggannia.

Finally, in the 1980s, scientists discovered that these three different fossils were body parts of the same strange-looking animal. The scientists named it Anomalocaris because that was the species’ first given name.

The majority of Anomalocaris fossils that have been identified were found in the Burgess Shale formation in Canada. However, fossils have been found in other countries as well. Recently, scientists found compound eyes believed to be that of the Anomalocaris during a paleontological dig on Kangaroo Island in Australia. This find especially suggested that the Anomalocaris was indeed an arthropod. 

Extinction – When Did It Die Out?

The Anomalocaris disappeared during the Great Permian Extinction, a mass extinction event that took place towards the end of the Cambrian period. This species disappeared along with up to 90% of all life on the planet. 

Similar Animals to The Anomalocaris 

  • Hallucigenia: this is an extinct genus of animal that was found fossilized in the same Burgess Shale Formation where the Anomalocaris was first found. Initially, scientists thought the species had no living relative in the present age. However, more recent research shows that it is related to modern arthropods, just like the Anomalocaris. 
  • Opabinia: this is another extinct animal that lived around the same time as the Anomalocaris. It is also related to the arthropods and had a strange appearance as well.  
  • Aysheaia: this is a genus of caterpillar-like organisms with a soft body. They also lived in the middle Cambrian and have been found in abundance in the Burgess Shale formation. 

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Anomalocaris FAQs (Frequently Asked Questions) 

When was the Anomalocaris alive?

The Anomalocaris lived during the Cambrian period about 500 million years ago. It was an apex predator that lived in the seas.



How big was the Anomalocaris?

The Anomalocaris was about 1 to 2 meters long. Due to its large size, the animal is considered one of the earliest examples of an apex predator.

 What did the Anomalocaris feed on?

For a long time, scientists believed that this Anomalocaris was an apex predator, and its main diet might have consisted of trilobites. However, recent research points to the possibility that if fed on softer-shelled animals on the sea floor.

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