Opabinia regalis was first described in 1912 by its discoverer Charles Walcott. Because of its clearly unique morphology, 505 million year old Opabinia became one of the most iconic fossils from the Burgess Shale. With such an unusual body, speculation about its affinities and lifestyle soon followed.

It wasn’t until a major redescription in 1975 that Opabinia was revealed to be truly one of the most enigmatic of all fossils. It was so unusual, in fact, that when palaeontologist Harry Whittington, an expert on the Burgess Shale, showed an early version of his reconstruction in a meeting of palaeontologists in 1972, the whole room burst out laughing!
Opabinia regalis was first described in 1912 by its discoverer Charles Walcott. Because of its clearly unique morphology, 505 million year old Opabinia became one of the most iconic fossils from the Burgess Shale. With such an unusual body, speculation about its affinities and lifestyle soon followed.

It wasn’t until a major redescription in 1975 that Opabinia was revealed to be truly one of the most enigmatic of all fossils. It was so unusual, in fact, that when palaeontologist Harry Whittington, an expert on the Burgess Shale, showed an early version of his reconstruction in a meeting of palaeontologists in 1972, the whole room burst out laughing!

© 2011, Royal Ontario Museum. All Rights Reserved.

Photograph of a complete specimen of Opabinia regalis

Opabinia regalis (USNM 57683) – Lectotype. Complete specimen preserved laterally showing the proboscis, mouth and gut, four of the five eyes and lateral lobes. Specimen length (with proboscis) = 72 mm. Walcott Quarry.

Photo: Jean-Bernard Caron

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


Artist's rendering of Opabinia regalis

Reconstruction of Opabinia regalis.

 

© 2011, Marianne Collins. All Rights Reserved.


Opabinia regalis lived near the close of the “Cambrian Explosion”. The Cambrian Explosion refers to the sudden appearance in the fossil record of complex animals. It may represent the most important evolutionary event in the history of life on Earth.

The beginning of the “Explosion” is generally placed about 542 million years ago, during the Cambrian Period at the start of the Palaeozoic Era. The Burgess Shale, at 505 million years old, records the tail end of this event. By the end of the Cambrian, every major animal phylum (i.e. different body plans) was firmly established, and life after the Cambrian was radically different from what had gone before. So it is safe to call this event an "Explosion" - it was crucial to the evolution of life on Earth as we know it.

Why did the Cambrian Explosion happen when it did, and why was it such a unique event? While there is no current consensus among scientists, most researchers agree the Explosion cannot be ascribed to a single, simple mechanism. The potential triggers can be class Read More
Opabinia regalis lived near the close of the “Cambrian Explosion”. The Cambrian Explosion refers to the sudden appearance in the fossil record of complex animals. It may represent the most important evolutionary event in the history of life on Earth.

The beginning of the “Explosion” is generally placed about 542 million years ago, during the Cambrian Period at the start of the Palaeozoic Era. The Burgess Shale, at 505 million years old, records the tail end of this event. By the end of the Cambrian, every major animal phylum (i.e. different body plans) was firmly established, and life after the Cambrian was radically different from what had gone before. So it is safe to call this event an "Explosion" - it was crucial to the evolution of life on Earth as we know it.

Why did the Cambrian Explosion happen when it did, and why was it such a unique event? While there is no current consensus among scientists, most researchers agree the Explosion cannot be ascribed to a single, simple mechanism. The potential triggers can be classified in three main categories: environmental, genetic, and ecological. Deciphering the impact of each of these factors remains one of the most important challenges faced by palaeontologists today. For more information on the triggers of the Cambrian Explosion, click here.

© 2011, Royal Ontario Museum. All Rights Reserved.

Like Opabinia, many fossils found in the Burgess Shale are difficult to classify. Part of the problem is that some species are poorly known - i.e., there is not enough well-preserved fossil material to describe the anatomy of the animals with certainty. Opabinia fossils are rare, with only 42 specimens currently (as of 2011) known from all collections, but overall its anatomy is relatively well preserved. Thus difficulties in interpreting the affinities of Opabinia are more related to its bizarre anatomy: Opabinia displays only some of the traits associated with familiar groups and possesses a combination of traits that remains at odds with what we know for any living or extinct organisms.

Because of the jointed claws on its proboscis, Opabinia is classified, along with another iconic animal from the Burgess Shale, Anomalocaris canadensis, as a primitive arthropod in a group called the anomalocaridids (see learning object Anomalocaris canadensis). Today, arthropods are the most Read More
Like Opabinia, many fossils found in the Burgess Shale are difficult to classify. Part of the problem is that some species are poorly known - i.e., there is not enough well-preserved fossil material to describe the anatomy of the animals with certainty. Opabinia fossils are rare, with only 42 specimens currently (as of 2011) known from all collections, but overall its anatomy is relatively well preserved. Thus difficulties in interpreting the affinities of Opabinia are more related to its bizarre anatomy: Opabinia displays only some of the traits associated with familiar groups and possesses a combination of traits that remains at odds with what we know for any living or extinct organisms.

Because of the jointed claws on its proboscis, Opabinia is classified, along with another iconic animal from the Burgess Shale, Anomalocaris canadensis, as a primitive arthropod in a group called the anomalocaridids (see learning object Anomalocaris canadensis). Today, arthropods are the most diverse of all animal groups, a distinction they have probably held over the last 500 million years. Characterized by a segmented body, a rigid, articulated external covering (exoskeleton), and jointed limbs, arthropods are represented today by spiders, shrimps, insects, and millipedes. While Opabinia regalis does not closely resemble modern arthropods, it is believed to represent one of the most primitive species in the evolution of this group.

© 2011, Royal Ontario Museum. All Rights Reserved.

Opabinia is quite unlike any animal on our planet today. It had five compound eyes (each mounted on a short stalk), a frontal “nozzle” or proboscis, a body with repeated lobes and gills, and a prominent tail fan. Body length ranged between 4.3 and 7.0 cm - excluding the proboscis, which was four times longer than its head.

Opabinia was a swimmer. Rippling waves along its lobes propelled it forward, while it used its tail fan to steer or maintain stability. The proboscis was highly flexible, ending with two opposing claws each with five or six spines. Opabinia was likely a carnivore and used the claws on its proboscis to grasp soft food items and carry them towards its mouth, which was located under the base of the proboscis.
Opabinia is quite unlike any animal on our planet today. It had five compound eyes (each mounted on a short stalk), a frontal “nozzle” or proboscis, a body with repeated lobes and gills, and a prominent tail fan. Body length ranged between 4.3 and 7.0 cm - excluding the proboscis, which was four times longer than its head.

Opabinia was a swimmer. Rippling waves along its lobes propelled it forward, while it used its tail fan to steer or maintain stability. The proboscis was highly flexible, ending with two opposing claws each with five or six spines. Opabinia was likely a carnivore and used the claws on its proboscis to grasp soft food items and carry them towards its mouth, which was located under the base of the proboscis.

© 2011, Royal Ontario Museum. All Rights Reserved.

A digital animation of an Opabinia regalis swimming around an assemblage of sponges.

A digital animation of an Opabinia regalis swimming around an assemblage of sponges. This primitive arthropod with five eyes and a "trump" was probably an efficient predator.

 

© 2011, Phlesch Bubble. All Rights Reserved.


Canada Post stamp commemorating Opabinia regalis

Opabinia regalis – Commemorative stamp showing the famous animal on the top right corner as part of a series on prehistoric life.

Photo: Jean-Bernard Caron

 


Cambrian seas teemed with animals of various sizes, shapes, and ecologies. Strategies for obtaining nutrients expanded to include suspension feeding (filtering particles of food out of the water), deposit feeding (gathering particles of food that settled on the sea floor), predation (actively capturing and devouring other animals), scavenging (finding and eating dead organisms), and grazing (munching algae and microbial mats). Some lived on or in the sea floor (benthic), while others (including Opabinia regalis) actively swam in the water column, but were still dependent on the benthos for foraging (nektobenthic). The rapid appearance of such a wide variety of animals during the Cambrian Explosion led to the development of radical new ecological interactions. As the number and variety of organisms increased, they occupied a variety of newly created marine environments and habitats.

New ecological niches (particular spaces in an ecosystem) would have been created by the organisms interacting with their environment. Moving into previously-unexploited environments would have allowed even a poorly-adapted animal to survive, perhaps with one of the more "exoti Read More
Cambrian seas teemed with animals of various sizes, shapes, and ecologies. Strategies for obtaining nutrients expanded to include suspension feeding (filtering particles of food out of the water), deposit feeding (gathering particles of food that settled on the sea floor), predation (actively capturing and devouring other animals), scavenging (finding and eating dead organisms), and grazing (munching algae and microbial mats). Some lived on or in the sea floor (benthic), while others (including Opabinia regalis) actively swam in the water column, but were still dependent on the benthos for foraging (nektobenthic). The rapid appearance of such a wide variety of animals during the Cambrian Explosion led to the development of radical new ecological interactions. As the number and variety of organisms increased, they occupied a variety of newly created marine environments and habitats.

New ecological niches (particular spaces in an ecosystem) would have been created by the organisms interacting with their environment. Moving into previously-unexploited environments would have allowed even a poorly-adapted animal to survive, perhaps with one of the more "exotic" body plans. For example, the emergence of predators like Opabinia might have stimulated the evolution of hardened exteriors for protection, or swimming as a means of escape. Before predation became widespread, early "experiments" in different body plans could have briefly thrived because species interactions were probably more limited.

© 2011, Royal Ontario Museum. All Rights Reserved.

Pie chart illustrating relative abundance of different lifestyles in the Burgess Shale

This pie chart illustrates the relative abundance of different lifestyles in the Burgess Shale: Nektonic (swimmers), Nektobenthic (swimmers/crawlers), Endobenthic (burrowers) and Epibenthic (crawlers).

Graphic: Jacquie Jeanes

© 2011, Royal Ontario Museum. All Rights Reserved.


By the end of the Cambrian, every major animal phylum known today was firmly established. Primitive members of animal phyla found in the Burgess Shale include the following:

Annelida: These elongate, many-segmented animals are represented today by earthworms and leeches. The annelid body is covered by a thin flexible cuticle that is not moulted after the adult stage is reached.

Arthropoda: Today, arthropods are the most diverse of all animal groups. Characterized by a segmented body, rigid exoskeleton, and jointed limbs, this group is represented today by insects, spiders, centipedes, and crustaceans. Arthropods grow by shedding their exoskeleton (a process called moulting), which can harden or even mineralize in some cases (such as in crabs).

Brachiopoda: Brachiopods are bottom-dwelling marine suspension-feeding animals enclosed in a two-part shell. Most forms attach to a surface (either the sea floor or on other organisms) via a flexible cylindrical organ called a pedicle. Although some species still survive, the phylum was hit hard by the Permian mass extinction about 250 million years ago.

Chordata: Chordates are a group of anima Read More
By the end of the Cambrian, every major animal phylum known today was firmly established. Primitive members of animal phyla found in the Burgess Shale include the following:

Annelida: These elongate, many-segmented animals are represented today by earthworms and leeches. The annelid body is covered by a thin flexible cuticle that is not moulted after the adult stage is reached.

Arthropoda: Today, arthropods are the most diverse of all animal groups. Characterized by a segmented body, rigid exoskeleton, and jointed limbs, this group is represented today by insects, spiders, centipedes, and crustaceans. Arthropods grow by shedding their exoskeleton (a process called moulting), which can harden or even mineralize in some cases (such as in crabs).

Brachiopoda: Brachiopods are bottom-dwelling marine suspension-feeding animals enclosed in a two-part shell. Most forms attach to a surface (either the sea floor or on other organisms) via a flexible cylindrical organ called a pedicle. Although some species still survive, the phylum was hit hard by the Permian mass extinction about 250 million years ago.

Chordata: Chordates are a group of animals united by the possession of a notochord. Members of this phylum include mammals, fish, and reptiles with their defining backbone and spinal chord.

Ctenophora: Ctenophores are radially organized animals with a simple body plan superficially resembling that of a jellyfish. Living representatives are termed "comb jellies" because they have 8 comb-like rows of cilia (small elongated extensions of cells which can reach up to 2 mm) to propel them through the water.

Echinodermata: The echinoderms form a distinctive group of mostly benthic animals characterized by a mineralized skeleton. Almost all adult echinoderms exhibit fivefold symmetry. Modern groups include sea stars, sea urchins, and sea lilies (crinoids).

Mollusca: A large group of animals, today characterized by a cavity-forming mantle. Modern molluscs include snails, squids, and clams.

Onychophora (Lobopoda): Worm-like animals with unspecialized pairs of non-jointed limbs. The modern onychophorans (velvet worms) are all terrestrial.

Porifera: The sponges are among the most primitive animals; their simple body is not organized into true tissues. Sponges are mostly bottom-dwelling suspension feeders, and many forms possess a supporting mesh-work of fine needle-like spicules composed of various minerals.

For more information on these animal phyla and their Burgess Shale representatives click here.

© 2011, Royal Ontario Museum. All Rights Reserved.

Pie chart illustrating the relative abundance of species in the Burgess Shale

This pie chart illustrates the relative abundance of groups of related species, such as the arthropods, in the Burgess Shale of the Walcott Quarry.

Graphic: Jacquie Jeanes

© 2011, Royal Ontario Museum. All Rights Reserved.


When paleontologists examine animal fossils they must determine which animal phyla they belong to. Since fossils are not found with labels attached, different techniques are used to help with identification. One such method is a dichotomous key, which simplifies the identification of an unknown organism. The key consists of a series of two mutually exclusive statements that describe characteristics of various organisms. At each step the user determines which statement is correct and is led to the next step in the dichotomous key. The last step ends with the name of the organism.

If you were trying to identify a Tiger, a Gray Wolf, a King Cobra, and a Bald Eagle, the key might read as follows:

1. a) Animal is covered in feathers..................................................................Bald Eagle
    b) Animal is not covered in feathers................................................................go to 2

2. a) Animal has long narrow body covered in scales.......................................King Cobra
    b) Animal is covered in fur......................................................... Read More

When paleontologists examine animal fossils they must determine which animal phyla they belong to. Since fossils are not found with labels attached, different techniques are used to help with identification. One such method is a dichotomous key, which simplifies the identification of an unknown organism. The key consists of a series of two mutually exclusive statements that describe characteristics of various organisms. At each step the user determines which statement is correct and is led to the next step in the dichotomous key. The last step ends with the name of the organism.

If you were trying to identify a Tiger, a Gray Wolf, a King Cobra, and a Bald Eagle, the key might read as follows:

1. a) Animal is covered in feathers..................................................................Bald Eagle
    b) Animal is not covered in feathers................................................................go to 2

2. a) Animal has long narrow body covered in scales.......................................King Cobra
    b) Animal is covered in fur..............................................................................go to 3

3. a) Animal has black and orange stripes...............................................................Tiger
    b) Animal has fur which is not striped black and orange.................................Gray Wolf

Your task is to create a dichotomous key for six of the following organisms (the list contains animals from ten different phyla). Clicking on their names will lead you to information and pictures to help with the creation of your key: Anomalocaris, Canadia, Choia, Ctenorhabdotus, Echmatocrinus, Hallucigenia, Micromitra, Nectocaris, Olenoides, Opabinia, Pikaia.


© 2011, Royal Ontario Museum. All Rights Reserved.

Learning Objectives

Learn about our current interpretations of the bizarre Burgess Shale predator Opabinia regalis.

Discover the significance of the fossils of the Burgess Shale as related to the diversity of life found within their Cambrian sea-bed community, and their relevance to living animals today.

Investigate and classify the animal populations of the Burgess Shale.


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