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Science & Nature • Paleontology

Anomalocaris

Anomalocaris is an extinct genus of radiodont, an early-diverging group of marine arthropods from the Cambrian Period.

By Ethan Anderson| Reviewed by Olivia Bennett, Standards & Fact-Checking Lead| Updated July 26, 2026|2 min read| Fact-checked

Anomalocaris is an extinct genus of radiodont, an early-diverging group of marine arthropods from the Cambrian Period. It is known for its large size, grasping front appendages, circular mouth, and unusually advanced compound eyes. Fossils are especially associated with the Burgess Shale in British Columbia, Canada, and other Cambrian deposits worldwide.

Description

Anomalocaris had a streamlined body, paired front appendages with spines, and large compound eyes that suggest strong vision. It is often reconstructed as a fast-swimming predator adapted for catching prey in the water column.

Fossil history

The genus is especially associated with the Burgess Shale and the Stephen Formation in British Columbia, Canada. Related fossils have also been reported from China, Greenland, Australia, and the western United States.

Classification

Anomalocaris belongs to Radiodonta, a group of stem-arthropods. It is not a shrimp, lobster, or crab, although its common name reflects its shrimp-like appearance.

Ecology

Anomalocaris was an active marine predator and one of the largest animals in its ecosystems. Its anatomy suggests it fed on soft-bodied or lightly armored prey rather than hard-shelled animals.

Key facts

  • Anomalocaris is an extinct radiodont and an early relative of modern arthropods.
  • It is best known from Cambrian fossils, especially the Burgess Shale of British Columbia.
  • It had grasping frontal appendages, large compound eyes, swimming flaps, and a circular mouth.
  • It is widely interpreted as a major predator in Cambrian marine ecosystems.
  • Fossils attributed to Anomalocaris occur in several Cambrian deposits outside Canada.
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Canadian context

Anomalocaris is strongly associated with Canada because key fossils come from the Burgess Shale and related Cambrian deposits in British Columbia, making it one of the best-known animals from Canada’s fossil record.

Frequently asked questions

What is Anomalocaris?
Anomalocaris is an extinct genus of Cambrian marine arthropod relative, classified as a radiodont.
Was Anomalocaris a shrimp?
No. It only looked shrimp-like; it was a radiodont, not a true shrimp or crustacean.
When did Anomalocaris live?
It lived during the Cambrian Period, over 500 million years ago.
Where have Anomalocaris fossils been found?
Fossils are known from the Burgess Shale in Canada and from Cambrian sites in China, Greenland, Australia, and Utah.
How big was Anomalocaris?
Some reconstructions estimate it at about 1.8 m long, making it one of the largest animals in its environment.
What did Anomalocaris eat?
It is generally interpreted as a predator, probably feeding on soft-bodied or lightly armored marine animals.

References

  1. Shape of Life — https://www.shapeoflife.org/news/featured-creature/2018/02/26/anomalocaris
    Supports: General description, Cambrian age, widespread fossil occurrences, predator status, large size, and Canadian fossil record.
  2. Royal Ontario Museum — https://burgess-shale.rom.on.ca/fossils/anomalocaris-canadensis/
    Supports: Burgess Shale occurrence, type species Anomalocaris canadensis, age, anatomy, and Canadian locality information.
  3. University of California Museum of Paleontology — https://undsci.berkeley.edu/this-is-not-the-shrimp-youre-looking-for/
    Supports: Radiodont interpretation and explanation that the animal was not a true shrimp but an early arthropod relative.
  4. Wikipedia — https://en.wikipedia.org/wiki/Anomalocaris
    Supports: Taxonomic placement as an extinct radiodont genus and general overview of the type species and fossil distribution.