Cambrian on EARTH Magazine

Precambrian rumblings of the Cambrian Explosion

Mon, 19 Jun 2017 20:30:25 -0400

Cloudina, one of the earliest-known skeletal animals, was once thought to have lived only in the Ediacaran Period, but it now seems that it lived during the Cambrian as well, implying an earlier history for Cambrian animals. Credit: Shuhai Xiao, Virginia Tech.

The Cambrian Explosion, when the ancestors of most of today’s animal groups began appearing in the fossil record about 542 million years ago, was — as the name suggests — a geologically abrupt event. Paleontologists have long thought of the event as marking a boundary between distinct Precambrian and Cambrian faunas. In new research published in Geology, however, scientists report that small, shelly fossils once thought to occur only in Cambrian rocks have been found in rocks dating to the late Ediacaran, just before the Cambrian, implying an earlier start to the explosion than previously thought.

Did a geographic shift trigger the Cambrian Explosion?

Fri, 06 Mar 2015 11:17:27 -0500

The location of the continents at the beginning of the Cambrian Period has long been difficult to resolve. Whereas one model based on paleomagnetism, for example, suggested that the oceanic separation between Laurentia and Gondwana was already fairly wide by that time (left), a new study based on geologic data proposes that the opening between the landmasses (red arrows) only initiated shortly before the Cambrian Explosion 530 million years ago (right). Credit: Kathleen Cantner, AGI.

Roughly 530 million years ago, Earth’s living cast of characters ballooned as a surge of evolutionary development led to the sudden appearance of almost all modern animal groups. Fossils from this period document the change in species, but the geologic, atmospheric and/or biotic factors that may have caused the radiation remain mysterious. Now, a new study suggests that massive changes in the positions of the continents may have played a significant role in sparking the Cambrian Explosion.

Oldest-known skeletal animals found

Tue, 04 Nov 2014 12:02:02 -0500

Researchers have discovered a 548-million-year-old reef in southern Namibia. Credit: Rachel Wood.

The Ediacaran Period, which lasted from 635 million to 541 million years ago, is famous for the evolution of soft-bodied organisms that pre-dated the Cambrian Explosion, the relatively brief period during which most of the major animal phyla appeared. Now, Ediacaran-aged animals with skeletons have been found.

Did tidal zone trilobites lead the way onto land?

Mon, 23 Jun 2014 10:52:13 -0400

Artist's rendering of trilobites on an Early Cambrian tidal flat. Trilobites first appeared about 520 million years ago and thrived for 270 million years until the end-Permian extinction, making them one of the most successful lineages to ever live. Kathleen Cantner, AGI.

During the Cambrian, when trilobites thrived in Earth’s early oceans, the continents were devoid of animal life. “The Cambrian explosion was an open marine event,” says Gabriela Mángano, a geologist at the University of Saskatchewan in Saskatoon, and lead author of the new study, published in Geology. “The typical story is that colonization of the terrestrial settings didn’t happen until the middle of the Paleozoic with organisms moving from the sea, into brackish water, then freshwater and then onto land.”

Getting there and getting around the Burgess Shale

Mon, 03 Dec 2012 16:44:11 -0500

A Burgess Shale Geoscience Foundation guide helps three young paleontologists identify fossils found in the Walcott Quarry. Mary Caperton Morton

Traveling to the Burgess Shale requires a plane ticket, a guide, and the legs and lungs to hike high into the Canadian Rockies.

The Burgess Shale bestseller

Mon, 03 Dec 2012 16:35:37 -0500

The Burgess Shale owes much of its fame to a book called “Wonderful Life” by the late Harvard paleontologist Stephen Jay Gould. Published in 1989, the book was a bestseller. The title is a reference to the scene in the movie “It’s a Wonderful Life,” in which George Bailey’s guardian angel replays the tape of life as if George had never been born, to dramatic effect.

Travels in Geology: Famous fossils and spectacular scenery at British Columbia's Burgess Shale

Mon, 03 Dec 2012 15:07:45 -0500

The Burgess Shale's Walcott and Raymond quarries lie on the ridge between Mount Wapta (left) and Mount Field (right), across from Burgess Mountain in Canada's Yoho National Park. Mary Caperton Morton

_Marella_, nicknamed the "lace crab," is the most common fossil in the Walcott Quarry. It has never been found anywhere else in the world. Mary Caperton Morton

The author's father searches through slabs in the Walcott Quarry. Mary Caperton Morton

The mouth, jaws and body of Anomalocaris were originally discovered separately and thought to belong to different creatures. The whole specimen, shown here as a replica, helped knit together the formidable Cambrian predator. Mary Caperton Morton

The animals of the Burgess Shale lived in calm waters on the muddy seafloor at the base of the Cathedral Escarpment a hundred meters below the sea surface, as shown in this artist's depiction. Kathleen Cantner, AGI

Of all the famous fossil localities in the world — Mongolia’s Flaming Cliffs, Tanzania’s Olduvai Gorge, Wyoming’s Green River, Germany’s Solnhöfn Quarry — perhaps none is as widely celebrated as British Columbia’s Burgess Shale. High in the Canadian Rockies, the Burgess Shale contains some of the oldest and most exquisitely detailed fossils of early life on Earth. Visiting the Burgess Shale requires some preparation — you must hire a guide and hike 22 kilometers at high elevation — but for a fossil enthusiast, the payoff is worth every step.

Re-examining the Burgess Shale

Thu, 05 Jan 2012 06:41:58 -0500

Allison Daley in Walcott's original quarry in 2008. Robert Gaines

Jean-Bernard Caron at the Burgess Shale site in 2008. Robert Gaines

The Burgess Shale discovery site in the Canadian Rockies today. Robert Gaines

Jason Loxton and Michael Streng at the Burgess Shale on Mount Stephen in 2008. Robert Gaines

About 505 million years ago, the continent that would become North America straddled the equator. With no terrestrial plants or animals, the land was a barren landscape. The warm, shallow sea bordering the continent, however, hosted a carbonated reef teeming with a diverse array of organisms, most of which were relatively small bottom-dwellers. Periodically, the animals would get washed over the reef and deposited at its base, where their bodies accumulated in the muddy sediments. Today, these creatures are beautifully preserved in the Burgess Shale.