Marrella splendens was one of the first Burgess Shale fossils found by palaeontologist Charles Walcott, and sketches appear in his notebook as early as August 31st, 1909 (see picture below). Walcott informally named them “lace crabs” at the time.

The next summer, on August 9, 1910, Walcott and his son Stuart found the “lace crab beds” marking the discovery of the fossil-bearing horizon of the Walcott Quarry in British Columbia’s Burgess Shale.

Of the hundreds of thousands of fossil specimens subsequently obtained from the Burgess Shale, Marrella splendens is one of the most common species, with more than 25,000 specimens collected.

The genus was named Marrella after Dr. John Marr, a palaeontologist at Cambridge University and friend of Walcott. The species name comes from the Latin word splendens for beautiful or brilliant.
Marrella splendens was one of the first Burgess Shale fossils found by palaeontologist Charles Walcott, and sketches appear in his notebook as early as August 31st, 1909 (see picture below). Walcott informally named them “lace crabs” at the time.

The next summer, on August 9, 1910, Walcott and his son Stuart found the “lace crab beds” marking the discovery of the fossil-bearing horizon of the Walcott Quarry in British Columbia’s Burgess Shale.

Of the hundreds of thousands of fossil specimens subsequently obtained from the Burgess Shale, Marrella splendens is one of the most common species, with more than 25,000 specimens collected.

The genus was named Marrella after Dr. John Marr, a palaeontologist at Cambridge University and friend of Walcott. The species name comes from the Latin word splendens for beautiful or brilliant.

© 2011, Royal Ontario Museum. All Rights Reserved.

Charles Walcott's field notebook showing sketches of Marrella, Waptia, Naraoia and Vauxia

In his 1909 field notebook Charles Walcott mentioned the discovery of soft-bodied fossils from the "Stephen Formation" (today's Burgess Shale). Here he sketched fossils depicting three arthropods and one sponge. The sketch on the top left, would later be known as Marrella splendens.

Photo: Brian Boyle

© 2011, Smithsonian Institution Archives. All Rights Reserved.


A photograph of the fossil Marrella splendens

Marrella splendens, (size = 16 mm) a common fossil from the "Phyllopod bed".

Photo: Jean-Bernard Caron

© 2011, Royal Ontario Museum. All Rights Reserved.


Marrella is a small arthropod (maximum size 3 cm) with a wedge-shaped head shield bearing two pairs of prominent spines that extend back along most of the length of the body. The head has a pair of long, thin, segmented antennae projecting towards the front, and a pair of paddle-like appendages with numerous bushy bristles along their edges positioned more laterally.

Behind the head, the body consists of 26 segments, each bearing a pair of two-branched appendages. The lower branches were used for walking, and the upper branches bore many long filaments which functioned mainly as respiratory organs called gills. The lower branches of the last twelve pairs of appendages curve inwards, forming a tapering net-like structure below the body that was used to trap food particles in water currents and pass them towards the mouth which was positioned near the front of the animal on the ventral side (see 3D animation). Marrella walked along the sea floor while deposit feeding; swimming was achieved in part by “rowing” with the paddle-like head appendages and also by swinging the upper branches of the appendages sequentially to create undulatory mo Read More

Marrella is a small arthropod (maximum size 3 cm) with a wedge-shaped head shield bearing two pairs of prominent spines that extend back along most of the length of the body. The head has a pair of long, thin, segmented antennae projecting towards the front, and a pair of paddle-like appendages with numerous bushy bristles along their edges positioned more laterally.

Behind the head, the body consists of 26 segments, each bearing a pair of two-branched appendages. The lower branches were used for walking, and the upper branches bore many long filaments which functioned mainly as respiratory organs called gills. The lower branches of the last twelve pairs of appendages curve inwards, forming a tapering net-like structure below the body that was used to trap food particles in water currents and pass them towards the mouth which was positioned near the front of the animal on the ventral side (see 3D animation). Marrella walked along the sea floor while deposit feeding; swimming was achieved in part by “rowing” with the paddle-like head appendages and also by swinging the upper branches of the appendages sequentially to create undulatory movements. Its antennae would be used to sense the environment and locate food items.


© 2011, Royal Ontario Museum. All Rights Reserved.

Digital animation of Marrella splendens swimming near an assemblage of sponges.

Digital animation of Marrella splendens swimming near an assemblage of sponges. This small arthropod erupts in front of camera, and swims away using a pair of paddle-like antennae and numerous specialized swimming appendages along its body.

 

© 2011, Phlesch Bubble. All Rights Reserved.


The original Burgess Shale site refers to a fossil-rich horizon in the Rocky Mountains of British Columbia. The most important excavations were done within a two-metre-thick rock section made up of a series of thin layers containing the exquisitely preserved soft-bodied fossils. This section was named the "Phyllopod bed" by Walcott, in reference to the leaf-like structure of the appendages of certain abundant arthropods, including Marrella.

The Burgess Shale fossils are preserved in a type of sedimentary rock known as shale. Shale is a variety of mudstone (originally formed from deposits of fine mud) that can be easily split apart. The different fossil layers of the Burgess Shale represent different mud deposits, originally laid down in sheet-like horizontal beds ranging from a few millimetres up to several centimetres in thickness. The individual beds can still be seen in the Burgess Shale today, but the layers are now much thinner due to dewatering and compression caused by the accumulated weight of hundreds of metres of sediments deposited on top of them. Compression is most easily grasped by looking at the fossils themselves, which show how th Read More

The original Burgess Shale site refers to a fossil-rich horizon in the Rocky Mountains of British Columbia. The most important excavations were done within a two-metre-thick rock section made up of a series of thin layers containing the exquisitely preserved soft-bodied fossils. This section was named the "Phyllopod bed" by Walcott, in reference to the leaf-like structure of the appendages of certain abundant arthropods, including Marrella.

The Burgess Shale fossils are preserved in a type of sedimentary rock known as shale. Shale is a variety of mudstone (originally formed from deposits of fine mud) that can be easily split apart. The different fossil layers of the Burgess Shale represent different mud deposits, originally laid down in sheet-like horizontal beds ranging from a few millimetres up to several centimetres in thickness. The individual beds can still be seen in the Burgess Shale today, but the layers are now much thinner due to dewatering and compression caused by the accumulated weight of hundreds of metres of sediments deposited on top of them. Compression is most easily grasped by looking at the fossils themselves, which show how the animals have lost their original three dimensionality and are squashed almost flat.

The compressed seafloor muds of the Burgess Shale were transformed into shale when they encountered increased temperature and pressure during their geological history. It was during the main stage of the formation of the Rocky Mountains (about 65 million years ago, at the end of the age of dinosaurs!) that most of the transformations occurred.

During these changes, the original mudstone minerals and parts of the fossils which were originally preserved as carbon were secondarily replaced by different minerals with flatter structures which aligned with each other to form parallel layers. The resulting shale tends to split apart into thin sheets. The presence of a fossil in the shale creates a zone of weakness between layers, so when the rock is broken open it is more likely to split along a plane containing a fossil, leaving some of the fossil on each mirror-imaged surface (as part and counterpart).


© 2011, Royal Ontario Museum. All Rights Reserved.

An image of the wall of the Walcott Quarry showing the extent of the Phyllopod Bed

The limits of the Phyllopod Bed in the Walcott Quarry are indicated by a double arrow.

Photo: Desmond Collins

© 2011, Royal Ontario Museum. All Rights Reserved.


The creatures found in the Burgess Shale lived 505 million years ago during the Cambrian Period near the start of the Palaeozoic Era. These organisms lived in a relatively deep water basin at the base of a large submarine cliff known as the Cathedral Escarpment. The Escarpment was about 200 metres high before mud and other sediments began to fill in the basin. Periodically, the calm sea floor would be overwhelmed by torrents of mud – rapidly burying living and dead organisms in a disorganized mass. This process continued for perhaps hundreds of thousands of years, with successive layers of sediment eventually filling the original basin. This rapid burial accounts, in part, for the exceptional preservation of the Burgess Shale fossils.
The creatures found in the Burgess Shale lived 505 million years ago during the Cambrian Period near the start of the Palaeozoic Era. These organisms lived in a relatively deep water basin at the base of a large submarine cliff known as the Cathedral Escarpment. The Escarpment was about 200 metres high before mud and other sediments began to fill in the basin. Periodically, the calm sea floor would be overwhelmed by torrents of mud – rapidly burying living and dead organisms in a disorganized mass. This process continued for perhaps hundreds of thousands of years, with successive layers of sediment eventually filling the original basin. This rapid burial accounts, in part, for the exceptional preservation of the Burgess Shale fossils.

© 2011, Royal Ontario Museum. All Rights Reserved.

A 3 dimensional reconstruction of the palaeoenvironment of the Burgess Shale

A 3 dimensional reconstruction of the palaeoenvironment of the Burgess Shale showing the the underwater topography along with the relative positions of the modern-day mountains and fossil localities.

Graphic: Jacquie Jeanes

© 2011, Royal Ontario Museum. All Rights Reserved.


A 3-dimensional representation of the first stage of fossilization: the death of the organism

The process of fossilization: Step 1 – death

Graphic: Jacquie Jeanes

© 2011, Royal Ontario Museum. All Rights Reserved.


Step 2: Sediment quickly covers bodies, protecting them from scavengers and decomposition

The process of fossilization: Step 2 – burial

Graphic: Jacquie Jeanes

© 2011, Royal Ontario Museum. All Rights Reserved.


Step 3: more sediments accumulate and organisms and sediments are compressed. Fossilization begins.

The process of fossilization: Step 3 – fossilization

Graphic: Jacquie Jeanes

© 2011, Royal Ontario Museum. All Rights Reserved.


Step 4: Over time the layers of sediment resurface and the fossils are exposed.

The process of fossilization: Step 4 – Exhumation and discovery of the fossils

Graphic: Jacquie Jeanes

© 2011, Royal Ontario Museum. All Rights Reserved.


The Burgess Shale is famous for the exquisite preservation of its soft-bodied fossils. It is exceptional to find nearly complete animals fossilized, especially ones like priapulid worms or ctenophores (comb jellies) that had only soft tissues and no mineralized structures. Typically it is only the hard parts of organisms (e.g. shell or bone) that become fossils. When soft tissues fossilize, palaeontologists can gain a tremendous amount of ecological and biological information about a particular time in the Earth’s history. The Burgess Shale is such a site, providing the best window on animal communities during the middle part of the Cambrian. For more information about why soft body parts were preserved in the Burgess Shale click here.

In modern marine settings, animals with mineralized body parts (e.g. shells or carapaces) account for only a minor component of the total diversity. This is also the case in most Burgess Shale deposits where the shelly assemblage usually represents a small percentage of specimens collected. Thus, without the fossilized remai Read More
The Burgess Shale is famous for the exquisite preservation of its soft-bodied fossils. It is exceptional to find nearly complete animals fossilized, especially ones like priapulid worms or ctenophores (comb jellies) that had only soft tissues and no mineralized structures. Typically it is only the hard parts of organisms (e.g. shell or bone) that become fossils. When soft tissues fossilize, palaeontologists can gain a tremendous amount of ecological and biological information about a particular time in the Earth’s history. The Burgess Shale is such a site, providing the best window on animal communities during the middle part of the Cambrian. For more information about why soft body parts were preserved in the Burgess Shale click here.

In modern marine settings, animals with mineralized body parts (e.g. shells or carapaces) account for only a minor component of the total diversity. This is also the case in most Burgess Shale deposits where the shelly assemblage usually represents a small percentage of specimens collected. Thus, without the fossilized remains of soft-bodied organisms, especially from the Burgess Shale, our knowledge of Cambrian ecosystems would be extremely limited.

© 2011, Royal Ontario Museum. All Rights Reserved.

Reconstruction of the Burgess Shale community (as seen in the Walcott Quarry)

Reconstruction of the Burgess Shale community (as seen in the Walcott Quarry).

 

© 2011, Marianne Collins. All Rights Reserved.


A reconstruction of the community if only animals with mineralized parts were present.

The reconstruction shows how the community would look if only animals with mineralized parts were present.

 

© 2011, Marianne Collins. All Rights Reserved.


Exceptionally well-preserved soft-bodied fossils dating from the Cambrian were first found from the Burgess Shale in British Columbia over 100 years ago. Today, dozens of Burgess Shale-type deposits with comparable assemblages of fossils have been found around the world. These deposits are characterized by a similar mode of preservation called "Burgess Shale-type preservation".

The most notable sites for Burgess Shale-type preservation are the Burgess Shale localities in British Columbia (Walcott Quarry – the original site, Raymond Quarry, and Collins Quarry in Yoho National Park), along with the Maotianshan Shales of China. Other significant occurrences include the Kaili deposit in China, sites in the western United States of America (Spence Shale and Marjum and Wheeler Formations in Utah, Pioche Formation in Nevada), Greenland (Sirius Passet), and Australia (Emu Bay Shale).

Similarities among various Burgess Shale-type deposits around the world suggest that the deep marine ecosystem was geographically uniform. Similar types of animal fossils have been recovered through this whole interval, spanning at least 15 million years. The characteri Read More
Exceptionally well-preserved soft-bodied fossils dating from the Cambrian were first found from the Burgess Shale in British Columbia over 100 years ago. Today, dozens of Burgess Shale-type deposits with comparable assemblages of fossils have been found around the world. These deposits are characterized by a similar mode of preservation called "Burgess Shale-type preservation".

The most notable sites for Burgess Shale-type preservation are the Burgess Shale localities in British Columbia (Walcott Quarry – the original site, Raymond Quarry, and Collins Quarry in Yoho National Park), along with the Maotianshan Shales of China. Other significant occurrences include the Kaili deposit in China, sites in the western United States of America (Spence Shale and Marjum and Wheeler Formations in Utah, Pioche Formation in Nevada), Greenland (Sirius Passet), and Australia (Emu Bay Shale).

Similarities among various Burgess Shale-type deposits around the world suggest that the deep marine ecosystem was geographically uniform. Similar types of animal fossils have been recovered through this whole interval, spanning at least 15 million years. The characteristic assemblage of organisms is often referred to as the Burgess Shale-type biota.

© 2011, Royal Ontario Museum. All Rights Reserved.

A map of the locations of the main Burgess Shale-type deposits in the world

Locations of Main Burgess Shale-Type Deposits.

Graphic: Jacquie Jeanes

Yoho National Park of Canada, British Columbia, CANADA
© 2011, Royal Ontario Museum. All Rights Reserved.


Fossils of Marrella are not limited to the Walcott Quarry. Other Burgess Shale locations with Marrella fossils include the Raymond Quarry, Mount Field, Mount Stephen, and Mount Odaray. Recently, Marrella species have also been found in the Kaili Biota of southwest China.
Fossils of Marrella are not limited to the Walcott Quarry. Other Burgess Shale locations with Marrella fossils include the Raymond Quarry, Mount Field, Mount Stephen, and Mount Odaray. Recently, Marrella species have also been found in the Kaili Biota of southwest China.

© 2011, Royal Ontario Museum. All Rights Reserved.

Image of trail leading to Kaili locality, Guizhou Province, China

View taken along the trail leading to the Middle Cambrian Kaili locality, Guizhou Province, China.

Photo: Jean-Bernard Caron

© 2011, Royal Ontario Museum. All Rights Reserved.


Photograph of a Marrella specimen from Kaili, China

Specimen of the arthropod Marrella (size = 6.4 cm) from the Kaili Biota in Ghuizhou Province (China). This is the only occurrence of Marrella outside the Burgess Shale localities in Yoho National Park.

Photo: Jih-Pai Lin

© 2011, Nanjing Institute of Geology and Palaeontology. All Rights Reserved.


For palaeontologists, the Burgess Shale provides the best window on animal communities during the middle part of the Cambrian. Other fossil sites around the world provide rare glimpses to other important times in the Earth’s past.

Pick one of the following significant fossil sites:

• Ashfall Fossil Beds
• Auca Mahuevo
• Dinosaur Provincial Park
• Florissant Fossil Beds
• Green River Formation
• La Brea Tar Pits
• Messel Oil Shale
• Mistaken Point
• Solnhofen Limestone

Conduct research to answer the following questions:

1. What time period does this fossil site represent?
2. What types of organisms are found at this location? Are any specimens famous?
3. How did the organisms fossilize? What makes the preservation at this site significant?
4. What clues does this fossil site provide about the history of the Earth?
5. What steps been taken to protect this site and to manage how the fossils are collected, maintained, and studied?

For palaeontologists, the Burgess Shale provides the best window on animal communities during the middle part of the Cambrian. Other fossil sites around the world provide rare glimpses to other important times in the Earth’s past.

Pick one of the following significant fossil sites:

• Ashfall Fossil Beds
• Auca Mahuevo
• Dinosaur Provincial Park
• Florissant Fossil Beds
• Green River Formation
• La Brea Tar Pits
• Messel Oil Shale
• Mistaken Point
• Solnhofen Limestone

Conduct research to answer the following questions:

1. What time period does this fossil site represent?
2. What types of organisms are found at this location? Are any specimens famous?
3. How did the organisms fossilize? What makes the preservation at this site significant?
4. What clues does this fossil site provide about the history of the Earth?
5. What steps been taken to protect this site and to manage how the fossils are collected, maintained, and studied?


© 2011, Royal Ontario Museum. All Rights Reserved.

Learning Objectives

Learn about our current interpretations of the common Burgess Shale arthropod Marrella splendens.

Explore how the Burgess Shale formed.

Describe how fossils are formed and why the fossilization seen in the Burgess Shale is extremely unusual and why sites like the Burgess Shale provide a wealth of biological and ecological information about ancient life.


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