Anomalocaris canadensis, whose name means “unlike the other shrimp, from Canada,” at first seems to have little in common with shrimp we are familiar with today. First described in 1892, this 505 million year old animal from British Columbia’s Burgess Shale has a complex history of description because parts of its body were described in isolation before it was realized they all belonged to the same animal. Trying to reassemble Anomalocaris fossils was like trying to put together a jigsaw puzzle where no one has seen the picture on the box for 505 million years.
Anomalocaris canadensis, whose name means “unlike the other shrimp, from Canada,” at first seems to have little in common with shrimp we are familiar with today. First described in 1892, this 505 million year old animal from British Columbia’s Burgess Shale has a complex history of description because parts of its body were described in isolation before it was realized they all belonged to the same animal. Trying to reassemble Anomalocaris fossils was like trying to put together a jigsaw puzzle where no one has seen the picture on the box for 505 million years.

© 2011, Royal Ontario Museum. All Rights Reserved.

A complete fossil of Anomalocaris canadensis

Anomalocaris canadensis (ROM 51211).The most complete specimen ever found was collected in 1991 by the Royal Ontario Museum. You can see from right to left, the pair of eyes, claws, lateral lobes along the body and the posterior fan. Specimen length = 222 mm. (Raymond Quarry).

Photo: Jean-Bernard Caron

© 2011, Royal Ontario Museum. All Rights Reserved.


The frontal appendage of Anomalocaris was initially described as the body of a shrimp. The mouth parts (or oral ring) were described as a jellyfish (Peytoia nathorsti). And a decomposed full body anomalocaridid specimen was originally described as a sea cucumber (it is now known as Laggania cambria). Upon re-examination of this particular specimen, it was then incorrectly decided that it was actually a superimposition of a jellyfish on top of a sponge.
The frontal appendage of Anomalocaris was initially described as the body of a shrimp. The mouth parts (or oral ring) were described as a jellyfish (Peytoia nathorsti). And a decomposed full body anomalocaridid specimen was originally described as a sea cucumber (it is now known as Laggania cambria). Upon re-examination of this particular specimen, it was then incorrectly decided that it was actually a superimposition of a jellyfish on top of a sponge.

© 2011, Royal Ontario Museum. All Rights Reserved.

A fossil appendage of Anomalocaris canadensis

Anomalocaris canadensis (GSC 3418) – Holotype. Individual claw. Specimen length = 76 mm. Mount Stephen Trilobite Beds (McConnell collection).

Photo: Jean-Bernard Caron

© 2011, Geological Survey of Canada. All Rights Reserved.


Mouth parts of Anomalocaris canadensis

Anomalocaris canadensis (USNM 57538) – Part and counterpart. Mouth parts originally described by Walcott as the holotype of Peytonia nathorsti, but this species is now invalid. Specimen diameter = 64 mm. Walcott Quarry.

Photo: Jean-Bernard Caron

© 2011, Smithsonian Institution - National Museum of Natural History. All Rights Reserved.


Incomplete specimen of Laggania cambria

Laggania cambria (USNM 57555) – Holotype – Part and counterpart (top and bottom). Ventral view of an incomplete individual showing the mouth parts and eyes. Specimen length = 100 mm. Walcott Quarry.

Photo: Jean-Bernard Caron

© 2011, Smithsonian Institution – National Museum of Natural History. All Rights Reserved.


In the early 1980s, palaeontologist Harry Whittington was preparing a Burgess Shale fossil when he solved the mystery of Anomalocaris’s identity. Much to his surprise, Whittington uncovered two Anomalocaris “shrimps” attached to the head region of a large body, which also had the jellyfish Peytoia as its mouth apparatus. Collecting at the Burgess Shale by the Royal Ontario Museum in the early 1990s led to the discovery of several complete specimens, which allowed for the reconstruction of Anomalocaris canadensis with greater accuracy. Anomalocaris is now classified as a kind of primitive arthropod, a group that contains modern insects, arachnids, and crustaceans.

Why are only fragments of Anomalocaris canadensis fossils so often found? It is possible that as Anomalocaris decayed, body parts fell off and may have been fossilized in different locations. Mouth parts and claws were made of chitin (the same material composing the exoskeletons of insects) which Read More
In the early 1980s, palaeontologist Harry Whittington was preparing a Burgess Shale fossil when he solved the mystery of Anomalocaris’s identity. Much to his surprise, Whittington uncovered two Anomalocaris “shrimps” attached to the head region of a large body, which also had the jellyfish Peytoia as its mouth apparatus. Collecting at the Burgess Shale by the Royal Ontario Museum in the early 1990s led to the discovery of several complete specimens, which allowed for the reconstruction of Anomalocaris canadensis with greater accuracy. Anomalocaris is now classified as a kind of primitive arthropod, a group that contains modern insects, arachnids, and crustaceans.

Why are only fragments of Anomalocaris canadensis fossils so often found? It is possible that as Anomalocaris decayed, body parts fell off and may have been fossilized in different locations. Mouth parts and claws were made of chitin (the same material composing the exoskeletons of insects) which made them more susceptible for preservation. It is equally (or perhaps even more) likely that individual body components were separated during regular moulting, and only the more resilient exoskeletal elements of the feeding apparatus (claws and oral ring) were preferentially preserved. Less resilient parts were probably rapidly degraded. The claws and complete oral ring would also behave differently in currents, and end up being deposited in different places. Claws, consisting of a single more-or-less continuous sheath, would survive much more commonly than complete oral rings, which would separate fairly quickly into smaller elements.

© 2011, Royal Ontario Museum. All Rights Reserved.

Anomalocaris specimen which show a pair of claws and part of the mouth

Anomalocaris canadensis(GSC 75555) – Part and counterpart. The specimen prepared by Harry Whittington that unlocked the mystery. It shows a pair of claws and part of the mouth (left). Specimen length = 127 mm. Raymond Quarry. (GSC 1966-1967 collection).

Photo: Jean-Bernard Caron

© 2011, Geological Survey of Canada. All Rights Reserved.


We now know that Anomalocaris was a carnivore reaching a maximum length of 100 cm. Anomalocaris’s streamlined body would have been ideal for swimming. Undulatory movements of the side flaps propelled the animal through the water column. While swimming, Anomalocaris’s frontal appendages would hang below the body, but it would thrust its head and appendages forward 180° to attack prey as needed.

Dietary habits are usually inferred from preserved gut contents (directly showing what the animals ate) and from specialized body structures, such as those used in feeding. Anomalocaris had large eyes, grasping limbs with sharp pointed spines, mouthparts with numerous blade-like teeth, and lateral lobes used for swimming (see above animation). Together with its large size, these features strongly suggest Anomalocaris was a predator. But what kind of prey did this animal feed upon? There is no evidence of gut contents in the few known complete bodies of Anomalocaris, indicating that perhaps it only fed on soft-bodied prey. “Soft” prey is Read More
We now know that Anomalocaris was a carnivore reaching a maximum length of 100 cm. Anomalocaris’s streamlined body would have been ideal for swimming. Undulatory movements of the side flaps propelled the animal through the water column. While swimming, Anomalocaris’s frontal appendages would hang below the body, but it would thrust its head and appendages forward 180° to attack prey as needed.

Dietary habits are usually inferred from preserved gut contents (directly showing what the animals ate) and from specialized body structures, such as those used in feeding. Anomalocaris had large eyes, grasping limbs with sharp pointed spines, mouthparts with numerous blade-like teeth, and lateral lobes used for swimming (see above animation). Together with its large size, these features strongly suggest Anomalocaris was a predator. But what kind of prey did this animal feed upon? There is no evidence of gut contents in the few known complete bodies of Anomalocaris, indicating that perhaps it only fed on soft-bodied prey. “Soft” prey is less likely to be preserved in the gut than the remains of “shelly” animals with hard mineralized exoskeletons. Shelly remains have been found within the gut of other predatory animals known from the Burgess Shale, such as the priapulid worm Ottoia prolifica, and the arthropod Sidneyia inexpectans.

© 2011, Royal Ontario Museum. All Rights Reserved.

A digital animation of an Anomalocaris canadensis swimming through an assemblage of sponges.

A digital animation of an Anomalocaris canadensis swimming through an assemblage of sponges. This giant predator belongs to a primitive group of arthropod and probably swam with formidable speed using the numerous lobes along its body. The non-mineralized bodies of many Burgess Shale animals were no protection against the powerful, spine-edged claws.

 

© 2011, Phlesch Bubble. All Rights Reserved.


The Burgess Shale records what life was like during the “Cambrian Explosion”. The Cambrian Explosion refers to the sudden appearance in the fossil record of complex animals starting about 540 million years ago. It may represent the most important evolutionary event in the history of life on Earth. The “explosion” is particularly remarkable because all major animal phyla (representing different body plans) appeared during this time, changing the biosphere forever.

Despite being separated by 505 million years, the structure of the food web from the Burgess Shale ecosystem is surprisingly similar to what we see in modern marine communities, although the individual species involved are clearly quite different. This suggests that basic feeding relationships were quickly established during the Cambrian Explosion and have remained relatively unchanged to the present.

Various feeding strategies are known in the Burgess Shale, including herbivory, detritus feeding (consuming decaying organic matter), suspension feeding (straining food particles suspended Read More
The Burgess Shale records what life was like during the “Cambrian Explosion”. The Cambrian Explosion refers to the sudden appearance in the fossil record of complex animals starting about 540 million years ago. It may represent the most important evolutionary event in the history of life on Earth. The “explosion” is particularly remarkable because all major animal phyla (representing different body plans) appeared during this time, changing the biosphere forever.

Despite being separated by 505 million years, the structure of the food web from the Burgess Shale ecosystem is surprisingly similar to what we see in modern marine communities, although the individual species involved are clearly quite different. This suggests that basic feeding relationships were quickly established during the Cambrian Explosion and have remained relatively unchanged to the present.

Various feeding strategies are known in the Burgess Shale, including herbivory, detritus feeding (consuming decaying organic matter), suspension feeding (straining food particles suspended in water), and predation and scavenging. The accurate reconstruction of Anomalocaris canadensis led to the recognition that other large predators akin to Anomalocaris existed during that time (Laggania cambria first described as a sea cucumber and Hurdia victoria). The evolution of predation is regarded as one of the most significant feeding strategies to appear during the Cambrian Explosion. Today, predators play an important role in structuring animal communities by controlling prey populations. Although Anomalocaris was relatively rare in the Burgess Shale, its position in the food chain as a top predator made it an important part of the ecosystem.

© 2011, Royal Ontario Museum. All Rights Reserved.

A graphic illustrating the food web in the Burgess Shale community

Reconstruction of the Burgess Shale food web. Spheres represent taxa. The taxa at the bottom of this network are primary producers and the taxa at the top are predators. (modified from Dunne et al.).

Graphic: Jacquie Jeanes

© 2011, Royal Ontario Museum. All Rights Reserved.


A specimen of the trilobite Olenoides exhibiting a healed bite mark

Olenoides serratus (ROM 54365). Nearly complete individual; presumed carcass with healed injury on left thorax. Specimen length = 65 mm. Specimen dry – direct light (left) and coated with ammonium chloride sublimate to show details (right). Trilobite Beds on Mount Stephen.

Photos: Jean-Bernard Caron

© 2011, Royal Ontario Museum. All Rights Reserved.


Predation was likely an important driving force for the diversification seen in the Cambrian Explosion, as animals evolved new strategies to eat and avoid being eaten. The development of swimming as a means of escape or the emergence of hardened exoskeletons and defensive features is also thought to have been a response to increased pressure from predators like Anomalocaris canadensis. Trilobites like Olenoides had hard mineralized exoskeletons. Some Olenoides fossils show unmistakable evidence of healed injuries, suggesting they may have been preyed upon, likely in their “soft-shell” growth phase, by larger arthropods such as Anomalocaris. The development of rows of spines on the back of Hallucigenia and the body armour of small, overlapping scales and blades on Wiwaxia are both examples Read More
Predation was likely an important driving force for the diversification seen in the Cambrian Explosion, as animals evolved new strategies to eat and avoid being eaten. The development of swimming as a means of escape or the emergence of hardened exoskeletons and defensive features is also thought to have been a response to increased pressure from predators like Anomalocaris canadensis. Trilobites like Olenoides had hard mineralized exoskeletons. Some Olenoides fossils show unmistakable evidence of healed injuries, suggesting they may have been preyed upon, likely in their “soft-shell” growth phase, by larger arthropods such as Anomalocaris. The development of rows of spines on the back of Hallucigenia and the body armour of small, overlapping scales and blades on Wiwaxia are both examples of potential defensive mechanisms against predators.

© 2011, Royal Ontario Museum. All Rights Reserved.

Two methods of defence as illustrated by the spiny Hallucigenia and the armoured Wiwaxia

The lobopod animal Hallucigenia (left, size = 2 cm) and the armoured slug-like animal Wiwaxia (right, size = 3 cm). Hallucigenia possesses rows of spines on the back of its body while Wiwaxia developed a body armour of small, overlapping scales and blades. Both traits may have evolved as a defensive mechanism against predators.

Photos: Jean-Bernard Caron

© 2011, Royal Ontario Museum. All Rights Reserved.


When attempting to reconstruct the 505 million year old Burgess Shale ecosystem, researchers must consider how the Burgess Shale fossils formed. Reconstructing the original anatomy of fossilized organisms is often based on fragmentary or incomplete material and often requires assumptions. Failing to understand the connection between the original organism and how it became a fossil may lead to a misinterpretation of some anatomical characters, or the improper classification of a fossil. Over the past one hundred years, our view of Anomalocaris has gone from it being a strange shrimp, to the largest known Cambrian predator. Changes in our interpretation of Anomalocaris canadensis fossils have radically altered both our view of this animal and its role in its environment.

Select an animal, extinct or extant (still living today), and imagine its remains were scattered during the process of fossilization.

1. Describe how isolated body parts might be interpreted by palaeontologists (i.e. in Anomalocaris canadensis the isolated mouth was considered to be a jellyfish).
2. If some body parts were mi Read More

When attempting to reconstruct the 505 million year old Burgess Shale ecosystem, researchers must consider how the Burgess Shale fossils formed. Reconstructing the original anatomy of fossilized organisms is often based on fragmentary or incomplete material and often requires assumptions. Failing to understand the connection between the original organism and how it became a fossil may lead to a misinterpretation of some anatomical characters, or the improper classification of a fossil. Over the past one hundred years, our view of Anomalocaris has gone from it being a strange shrimp, to the largest known Cambrian predator. Changes in our interpretation of Anomalocaris canadensis fossils have radically altered both our view of this animal and its role in its environment.

Select an animal, extinct or extant (still living today), and imagine its remains were scattered during the process of fossilization.

1. Describe how isolated body parts might be interpreted by palaeontologists (i.e. in Anomalocaris canadensis the isolated mouth was considered to be a jellyfish).
2. If some body parts were missing, how might the ecology of this animal be reconstructed differently (i.e. if we did not have Anomalocaris’s grasping claws we might not know that it was a predator)?

Let’s consider the ramifications of mistakes made when interpreting the fossil record. Consider the animal you selected above.

3. What ecosystem does your animal belong to?
4. What is the niche (ecological role) of your animal?
5. If you were to remove your animal from its ecosystem, how would the ecosystem function differently (i.e. if we remove Anomalocaris canadensis from the fossil record we lose the largest predator in the ecosystem)?


© 2011, Royal Ontario Museum. All Rights Reserved.

Learning Objectives

Learn about our current interpretations of the largest known predator from the Burgess Shale - Anomalocaris canadensis.

Explore the challenges faced in interpreting the fossil record of the Burgess Shale.

Discover the importance of predators like Anomalocaris canadensis in driving the diversification seen in the Burgess Shale community.


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