Wooster’s Fossil of the Week: Marrella splendens (Burgess Shale, Middle Cambrian, British Columbia)

January 15th, 2012

The first story about this iconic fossil is the trouble I went through to get the photograph above. Our specimen of Marrella splendens is preserved in the common Burgess Shale fashion as a thin dark film on a black piece of shale. A normal photograph would show just a black rock with a grayish smudge. To increase the contrast, I coated the fossil with mineral oil and used very bright lights to capture the image. I then tweaked the contrast further with Photoshop. Curiously, a black envelope appeared around the specimen that resembles the famous dark stain found with some Burgess Shale fossils. It may be remnants of body fluids.

Before I go further, I must clarify the origins of this fossil from the Burgess Shale (Middle Cambrian) near Burgess Pass, British Columbia, Canada. I did NOT collect it. The Burgess Shale is a UNESCO World Heritage Site, so collecting there is restricted to a very small group of paleontologists who have gone through probably the most strict permitting system anywhere. I had a wonderful visit to the Burgess Shale with my friend Matthew James in 2009, and we followed all the rules. (The above is a photo of the Burgess Shale outcrop and its extraordinary setting.) Our Wooster specimen was in our teaching collection when I arrived. I suspect it was collected in the 1920s or 1930s. Marrella splendens is one of the most common Burgess Shale fossils, so no doubt there are many out there in older collections.

(Reconstruction from Stephen Jay Gould's famous Burgess Shale book titled "Wonderful Life".)

Marrella splendens is supposedly the first fossil Charles Doolittle Walcott discovered in the Burgess Shale in 1909. He called it a “lace crab”, and then later as a strange trilobite. Later work by Harry Whittington demonstrated that it was neither a crab nor a trilobite. It is likely a stem-group arthropod (near the base of arthropod phylogeny).

Marrella splendens was probably a bottom-dwelling deposit-feeder living on organic material in the seafloor sediment. There are thousands and thousands of specimens known in the Burgess Shale. They are preserved in many different angles, providing the first evidence that some sort of sedimentary mass movement was involved in the formation of this famous unit.

Walcott invented the name Marrella in honor of John Edward Marr (1857-1933). Marr was a paleontologist at Cambridge University in England. By the end of his career he was a Fellow of the Geological Society and the Royal Society, hence FGS and FRS follow his name.

Reference:

García-Bellido, D.C. and Collins, D.H. 2006. A new study of Marrella splendens (Arthropoda, Marrellomorpha) from the Middle Cambrian Burgess Shale, British Columbia, Canada. Canadian Journal of Earth Sciences 43: 721-742.

Wooster’s “Fossil” of the Week: The most famous pseudofossil ever (Proterozoic of Canada)

May 8th, 2011

This week’s specimen is a piece of obscure paleontological history, although it represents a “fossil” that was for a short time one of the most prominent in the world. In 1864, the uber-geologist Charles Lyell claimed it was “one of the greatest geological discoveries of my time”. Charles Darwin cited it in his fourth edition of On the Origin of Species as the most critical find yet to show the rise of life from single-celled ancestors. Yet it is only a metamorphic rock with no evolutionary relevance whatsoever. Wooster obtained a sample of this material sometime in the nineteenth century, early enough in the story that it was cataloged into the fossil collection and labeled with its original name: Eozoön canadense.

In 1864, two major figures in North American geology met to discuss a set of layered rocks found just west of Montreal and now known to be about 1.1 billion years old (Proterozoic Eon). William E. Logan (1798-1875),  the Director of the Geological Survey of Canada, showed John William Dawson (1820–1899), Principal of McGill University, specimens he believed represented evidence of Precambrian life. Dawson not only agreed that these were fossils, he published a description in 1865 announcing them as “one of the brightest gems in the scientific crown of the Geological Survey of Canada”. He named the fossil Eozoön canadense — the dawn animal of Canada.

Eozoön canadense; (A) as illustrated by Dawson; (B) the holotype in the U.S. National Museum of Natural History. (Scale bars = 1 cm; figures from Schopf, 2000.)

Dawson concluded that Eozoön canadense was the test of a single-celled protistan known as a foraminiferan — even though it is staggeringly larger than any foraminiferan ever known. Eozoön was an immediate hit, attracting the attention of Darwin, Lyell and others intensely interested in finding the deepest roots of the fossil record.

Oddly enough, Dawson had an opposite opinion of the importance of Eozoön. He was an anti-evolutionist anxious to discredit Darwin’s ideas that were quickly sweeping the scientific world. He wrote:

“There is no link whatever in geological fact to connect Eozoön with the Mollusks, Radiates, or Crustaceans of the succeeding [rock record] … these stand before us as distinct creations. [A] gap … yawns in our imperfect geological record. Of actual facts [with which to fill this gap], therefore, we have none; and those evolutionists who have regarded the dawn-animal as an evidence in their favour, have been obliged to have recourse to supposition and assumption.”

In other words, Dawson thought his new fossil would be the death of evolutionary theory because it opened up an unbridgeable “gap” between “primitive” and “advanced” animals. Ironically, at the same time Darwin was grateful to at last have a single-celled fossil at the base of the family tree.

Eozoön canadense had a short and contentious life as a fossil. It was immediately challenged as inorganic by many scientists. In 1879, a German zoologist named Karl Möbius published a study showing that whatever it is, Eozoön canadense has no relationship with the foraminiferans and probably no other organism. Dawson held firm to his beliefs. The final blow came in 1894 when two geologists found Eozoön in boulders of marble shot out of Mount Vesuvius. Apparently the “fossil” is a metamorphic rock made of layers of white calcite and green serpentine. Dawson was unmoved and was actually working on yet another Eozoön paper when he died in 1899.

So our Fossil of the Week turns out not to be a fossil at all, and the name Eozoön canadense is now a nomen nudum — a “naked name” signifying a taxonomic mistake. At one time, I imagine, the geologists at Wooster were pleased to have a fragment of the oldest evidence of life. Now I treasure our specimen as a connection to the early passions of our science.

References:

Hofmann, H.J., 1971. Precambrian fossils, pseudofossils, and problematica in Canada. Geological Survey of Canada Bulletin 189.

O’Brien, C.F., 1970. Eozoon canadense “The dawn animal of Canada”. Isis 61: 206-223.

Schopf, J.W., 2000. Solution to Darwin’s dilemma: Discovery of the missing Precambrian record of life. PNAS 97: 6947-6953.

Wooster paleontologist at the Royal Tyrrell Museum of Palaeontology

August 10th, 2009

DRUMHELLER, ALBERTA, CANADA–The last activity for our IPREP group this summer was a guided visit to the Royal Tyrrell Museum of Palaeontology. David Lloyd, a paleontological technician at the museum, gave us a fantastic “behind the scenes” tour of the preparation laboratories and collections. The emphasis of the museum and the town is dinosaurs, of course, and I’ve never seen a better collection up close, but there were plenty of invertebrate fossils as well. The museum has one of the best exhibits on the Burgess Shale in the world, including a giant diorama visitors essentially walk into.

The Royal Tyrrell Museum of Palaeontology sits within a basin with badlands exposures of dinosaur-loaded Late Cretaceous terrestrial sediments.

The Royal Tyrrell Museum of Palaeontology sits in a basin with badlands exposures of dinosaur-loaded Late Cretaceous terrestrial sediments.

The dinosaur reconstructions inside and outside the museum are very well done.  This is a Cretaceous pachyrhinosaur with fearsome ornamentation.

The dinosaur reconstructions inside and outside the museum are very well done. This is a Cretaceous pachyrhinosaur with fearsome ornamentation.

The main collections storeroom is filled with paleontological treasures.

The main collections storeroom is filled with paleontological treasures.

REbecca Perlman, Matt James, and Kurt Burmeister (in the back) examine an opened plaster jacket with dinosaur fossils inside awaiting preparation. Layers of plaster and burlap were applied to the fossils in the field to protect them during transport to the museum.  This technique goes back over a century.

Rebecca Perlman, Matt James, and Kurt Burmeister (in the back) examine an opened plaster jacket with dinosaur fossils inside awaiting preparation. Layers of plaster and burlap were applied to the fossils in the field to protect them during transport to the museum. This technique goes back over a century.

This is the main paleontological preparation lab at the museum.  It is filled with equipment designed for the most part to remove rock from bone.

This is the main paleontological preparation lab at the museum. It is filled with equipment designed for the most part to remove rock from bone.

On the left is a giant ammonite we found mounted in a dim hallway.  They are usually about the size of a fist!  On the right is part of the Burgess Shale diorama showing the ubiquitous Marella.

On the left is a giant ammonite we found mounted in a dim hallway. They are usually about the size of a hand! On the right is part of the Burgess Shale diorama showing the ubiquitous Marella.

Saying goodbye to the Canadian Rockies — for now

August 10th, 2009

FIELD, BRITISH COLUMBIA–The IPREP team left the Canadian Rockies yesterday morning with many educational and research ideas, new friends, and thousands of photographs to be shared with students and colleagues. It was an extraordinary experience. We thank Matthew James of Sonoma State University in California for organizing this complex trip, and Randle Robertson of the Burgess Shale Geoscience Foundation for his generous support of our work and arranging the trail guides. I highly recommend a visit to Field, British Columbia, for anyone interested in paleontology, geology, and natural history. If you go, I guarantee you’ll enjoy your stay at the immaculate and well-designed Fireweed Hostel. Kim and Craig Chapman were friendly, efficient and generous hosts.

There is one more post to come from this trip — a visit to the Royal Tyrrell Museum of Palaeontology in Drumheller, Alberta.

The IPREP team just below Helen Lake on the hike to the Cambrian stromatolites.

The IPREP team just below Helen Lake on the hike to the Cambrian stromatolites.

Wooster geologist at Lake Louise, Banff National Park, Canada

August 10th, 2009

LAKE LOUISE, ALBERTA–On our free day the IPREP study group (this apparently means “International Paleontological Research Exchange Program”) drove to the spectacular Lake Louise in Banff National Park for a hike up the valley to the “Plain of Six Glaciers”. It was one of those many places where I know just how fortunate I am to be a geologist. The weather could not have been better, and there was even a tea house near the end of the trail for sandwiches, peachade, and perfect chocolate cake!

Lake Louise as seen from its outlet looking up the valley. Our hiking trail proceeded from here along the right side of the lake and up the valley almost to the ice of the hanging glaciers.

Lake Louise as seen from its outlet looking up the valley. Our hiking trail proceeded from here along the right side of the lake and up the valley almost to the ice of the hanging glaciers.

We could not help but be delightfully distracted by these brilliant trace fossils in the rocks along the lake shore. The bilobed structure which looks like a deer footprint is an excavation made by a trilobite -- the trace fossil itself is called Rusophycus. The sinuous tubes are trails made by burrowing worms. These features protrude form the rock surface because they are actually on the bottom of the bed. Sediment filled the original holes and is now preserved as ... wait for it ... convex hyporeliefs.  You knew we had a name for it! (Middle Cambrian, Gog Formation).

We could not help but be delightfully distracted by these brilliant trace fossils in the rocks along the lake shore. The bilobed structure which looks like a deer footprint is an excavation made by a trilobite -- the trace fossil itself is called Rusophycus. The sinuous tubes are trails made by burrowing worms. These features protrude form the rock surface because they are actually on the bottom of the bed. Sediment filled the original holes and is now preserved as ... wait for it ... convex hyporeliefs. You knew we had a name for it! (Middle Cambrian, Gog Formation).

The water of Lake Louise has a pastel emerald color because it is loaded with very fine sediment called "glacial flour". It is produced by glacial ice finely grinding the rocks in the highlands above. This sediment fills the streams to near capacity and makes an extensive delta at the inlet to the lake.

The water of Lake Louise has a pastel emerald color because it is loaded with very fine sediment called "glacial flour". It is produced by glacial ice finely grinding the rocks in the highlands above. This sediment fills the streams to near capacity and makes an extensive delta at the inlet to the lake.

Looking down the valley to Lake Louise from one of the many glacial moraines. This unsorted sediment was pushed here by glacial ice when it filled this valley.

Looking down the valley to Lake Louise from one of the many glacial moraines. This unsorted sediment was pushed here by glacial ice when it filled this valley.

The glacial ice above the Lake Louise valley. This is a classic hanging glacier. We had the privilege of seeing (and mostly hearing) a large piece of ice break off and crash into the valley below on this warm and sunny day.

The glacial ice above the Lake Louise valley. This is a classic hanging glacier. We had the privilege of seeing (and mostly hearing) a large piece of ice break off and crash into the valley below on this warm and sunny day.

Middle Cambrian stromatolites high in the Canadian Rockies

August 9th, 2009

FIELD, BRITISH COLUMBIA, CANADA–Our study group was fortunate to meet Whitey Hagadorn (Amherst College and Denver Museum of Natural History) and Sally Walker (University of Georgia) for a hike to an exposure of stromatolites in the Pika Formation (Middle Cambrian) near Lake Helen and Lake Katherine in Banff National Park. A stromatolite is a finely-laminated sedimentary rock produced by mats of cyanobacteria in a shallow sea collecting and trapping thin layers of sediment. They are relatively common features in Precambrian sediments (the oldest of fossils, in fact) and become significantly more rare in younger rocks (although they are still around today). These Cambrian stromatolites are interesting because of what they can tell us about Cambrian marine conditions, including tidal dynamics, bioturbation, and grazing herbivore pressures.

stromatoliteoutcrop080809

Stromatolites exposed as domal structures in this eroding outcrop of the Pika Formation (Middle Cambrian) above Helen Lake in Banff National Park.

A natural cross-section of the Pika Formation stromatolites showing their laminated nature and sediment which has accumulated around their heads.

A natural cross-section of the Pika Formation stromatolites showing their laminated nature and sediment which has accumulated around their heads.

A hardground (light unit) exposed in cross-section in the sediment between stromatolite heads.  This is a layer of carbonate sediment which was cemented on the seafloor and then eroded by currents.  The dark sediment was deposited later on top of the scoured surface.  The hardground layer had been previously burrowed when still soft.

A hardground (light unit) exposed in cross-section in the sediment between stromatolite heads. This is a layer of carbonate sediment which was cemented on the seafloor and then eroded by currents. The dark sediment was deposited later on top of the scoured surface. The hardground layer had been previously burrowed when still soft.

Beautiful folds in the rocks above the Pika Formation stromatolites.  They are nearly recumbent in some parts.  I'll leave their interpretation to my structural geologist colleagues Sam Root and Shelley Judge!

Beautiful folds in the rocks above the Pika Formation stromatolites. They are nearly recumbent in some parts. I'll leave their interpretation to my structural geology colleagues Sam Root and Shelley Judge!

A marmot on the banks of Helen Lake.  Not at all camera shy, this little guy.

A marmot on the banks of Helen Lake. Not at all camera shy, this little guy.

Mt. Stephen Trilobite Beds (Middle Cambrian)

August 8th, 2009

FIELD, BRITISH COLUMBIA, CANADA–After a very steep and long climb, our little field party visited another restricted quarry of famous Middle Cambrian fossils: the Mt. Stephens Trilobite Beds. Charles Walcott also collected from this site when he was working on the Burgess Shale. The fossiliferous unit is about a million years old (more or less) than the Burgess Shale itself, and it has a rather different fauna dominated by large trilobites. One of the most exciting new ideas is that these fossils may represent an ancient cold seep community associated with methane degassing from the sediments.

Our Canadian guide (and paleontologist) Paul McNeil and our trip leader Matthew James in the Mt. Stephen Trilobite Beds Quarry.

Our Canadian guide (and paleontologist) Paul McNeil and our trip leader Matthew James in the Mt. Stephen Trilobite Beds Quarry.

A view from the Mt. Stephen Trilobite Beds down the mountain to Field and the Trans-Canada Highway. Note the steepness.  Nearly did me in!

A view from the Mt. Stephen Trilobite Beds down the mountain to Field and the Trans-Canada Highway. Note the steepness. Nearly did me in!

Trilobites in the Mt. Stephen Trilobite Beds. (I know -- I should have had a Canadian quarter for scale!)

Trilobites in the Mt. Stephen Trilobite Beds. (I know -- I should have had a Canadian quarter for scale!)

A beautiful complete trilobite. Very common here.

A beautiful complete trilobite. Very common here.

An appendage of one of the most famous Middle Cambrian fossils: Anomalocaris. The Mt. Stephen Trilobite Beds also have soft-bodied preservation.

An appendage of one of the most famous Middle Cambrian fossils: Anomalocaris. The Mt. Stephen Trilobite Beds also have soft-bodied preservation.

The wondrous Burgess Shale

August 7th, 2009

FIELD, BRITISH COLUMBIA, CANADA–I stepped on Paleontological Holy Ground when I visited the Burgess Shale earlier this week. It is often cited as the most important fossil locality ever. I felt the historical as well as the scientific vibrations in the Walcott Quarry, the site where the extraordinary Charles Walcott began his explorations of the unit in 1909.

The Walcott Quarry of the Burgess Shale.

The Walcott Quarry of the Burgess Shale.

There are numerous websites illustrating the famous Burgess Shale Fauna. I’ll just share some of the favorite fossils I found. (We could pick up and examine any fossil, but collecting, of course, is strictly forbidden.)

The humble sponge Vauxia. I like the less charismatic taxa in the Burgess Shale. The fancy arthropods get plenty of love!

The humble sponge Vauxia. I like the less charismatic taxa in the Burgess Shale. The fancy arthropods get plenty of love!

The primitive mollusc Scenella on the left and a trilobite on the right. The Burgess Shale fauna has plenty of skeletonized fauna along with the soft-bodied forms.

The primitive mollusc Scenella on the left and a trilobite on the right. The Burgess Shale fauna has plenty of skeletonized fauna along with the soft-bodied forms.

This is an odd breccia at the base of the Burgess Shale. The white parts are limestone fragments and the black is calcite. This may be an indication of carbonate hardgrounds -- features I study.

This is an odd breccia at the base of the Burgess Shale. The white parts are limestone fragments and the black is calcite. This may be an indication of carbonate hardgrounds -- features I study.

It is a tradition among paleontologists to pose with Charles Walcott at his famous quarry! I lack the knickers, though.

It is a tradition among paleontologists to formally pose with Charles Walcott at his famous quarry. I lack the knickers, though, and that certain set of jaw.

The Walcott Quarry of the Burgess Shale on a beautiful day

August 6th, 2009

FIELD, BRITISH COLUMBIA, CANADA–We have a small group of seven people for this expedition organized by Matthew James of Sonoma State University in California. Everyone is from California except me (although I was invited through my California roots). Our guide to the Walcott Quarry didn’t show up yesterday morning, so we joined a much larger group from Chevron — an interesting and productive mix of industry professionals and academics. Here is a movie of our exploration in the quarry:

Our Burgess Shale group.  Clockwise starting with the guy in the orange shirt: Matthew James, Howard Adams, Rebecca Perlroth, Mark Wilson, Bob Rubin, Bob Davies, Kurt Burmeister.

Our Burgess Shale group. Clockwise starting with the guy in the orange shirt: Matthew James, Howard Adams, Rebecca Perlroth, Mark Wilson, Bob Rubin, Bob Davies, Kurt Burmeister.

Wooster geologist at the Burgess Shale

August 6th, 2009

FIELD, BRITISH COLUMBIA, CANADA–I’ve been waiting to write those words! More later when I get better wireless access. The summary: my colleagues and I successfully made the long hike to the Walcott Quarry of the famous Middle Cambrian Burgess Shale today (5.5 hours to get there); it rained all morning, and then the sun appeared in time to dry out the outcrop before we arrived; we saw many wonderful fossils on this iconic outcrop.

walcottquarry01

Walcott Quarry of the Burgess Shale in the lower right, with Emerald Glacier and Mount Wapta in the background. Stunning in all respects!