Cambrian fossil relative of today’s molluscs discovered

Cambrian animals

Reuters reports:

Spiky oddball prowled ocean half billion years ago

Saturday March 03, 2007

WASHINGTON – A spectacularly quirky creature with long, curved spines protruding from its armored body prowled the ocean floor half a billion years ago near the dawn of complex life forms on Earth, scientists said.

In research appearing in Friday’s edition of the journal Science, scientists identified an ancient invertebrate they named Orthrozanclus reburrus from 11 complete fossils retrieved from Canada’s fossil-rich Burgess Shale rock formation.

“It’s a tiny beast,” Jean-Bernard Caron of the Royal Ontario Museum in Toronto, who described the newly identified species along with Simon Conway Morris of the University of Cambridge in Britain, said in an interview.

Orthrozanclus, about half an inch (one centimetre) long, lived about 505 million years ago during the Cambrian Period.

The Cambrian was an important moment in the history of life on Earth and a time of radical evolutionary experimentation when many major animal groups first appeared in the fossil record.

This proliferation of life is dubbed the “Cambrian Explosion” because of the relatively brief time span in which this diversity of forms arose.

Orthrozanclus had no eyes and no limbs and apparently moved along the ocean floor with a muscular foot, like a snail does, while dining on bacterial growths, the researchers said.

Orthrozanclus seems to have been built to prevent predators from turning it into a quick snack.

It was covered in a shell and had almost three dozen long, pointy, curved spines sticking out from the edge of its body, and many smaller ones, too.

“You probably don’t want to have them in your slippers. They’re kind of spiky,” Caron said.

Early animal evolution

The newly identified invertebrate helps clarify early animal evolution, the scientists said.

The scientists think Orthrozanclus may belong to a newly identified group of organisms characterized by a similar type of body armour, and that this group was related to present-day snails, earthworms and mollusks, which include snails, clams, squid and octopuses.

The researchers described the animal based on complete and beautifully preserved fossils — nine at the Royal Ontario Museum and two at the Smithsonian Institution in Washington.

The Burgess Shale, an important rock layer from the Cambrian in the Canadian Rockies of southeastern British Columbia, has yielded a treasure trove of fossils from this critical period in the history of life.

These include such weirdos as Hallucigenia, a spiky animal so unusual that the scientists who named it seemed to think it was a hallucination, and the predator Anomalocaris with large, grasping limbs, the largest animal found in the Burgess Shale.

Some creatures found as fossils in the Burgess Shale are ancestors of animals alive today, while others have long since gone extinct and are not like any existing living thing.


Cambrian and Precambrian evolution explosions: here.

A unique set of fossils indicates that 525 million years ago marine animals congregated in Earth’s ancient oceans, most likely for migration, according to an international team of scientists: here.


12 thoughts on “Cambrian fossil relative of today’s molluscs discovered

  1. Fossils From Canadian Rockies, Dating To Cambrian Explosion, Preserved In Ancient Mud Slide

    ScienceDaily (Feb. 19, 2008) — Geologists at the University of Leicester have solved a puzzle found in rocks half a billion years old.

    Some of the most important fossil beds in the world are the Burgess Shales in the Canadian Rockies. Once an ancient sea bed, they were formed shortly after life suddenly became more complex and diverse — the so-called Cambrian explosion — and are of immense scientific interest.

    Normally, only hard parts of ancient animals became fossilised; the bones, teeth or shells. Soft parts were rarely preserved: many plants and invertebrate animals evolved, lived for millions of years and became extinct, but left no trace in the fossil record.

    The Burgess Shales preserved soft tissue in exquisite detail, and the question of how this came to happen has troubled scientists since the discovery of the fossils in 1909.

    Now, painstaking work by Sarah Gabbott and Jan Zalasiewicz of the University of Leicester, with Desmond Collins of the Royal Ontario Museum, has provided an answer.

    They analysed the shales millimetre by millimetre, and found that unlike most rocks of this type, they weren’t slowly deposited, mud flake by mud flake. Instead, a thick slurry powered down a steep slope and instantly buried the animals to a depth where normal decay couldn’t occur.

    Dr Gabbott said, “Not a nice way to go, perhaps, but a swift one- and one that guaranteed immortality (of a sort) for these strange creatures.”

    This research has been published in the Journal of the Geological Society (2008, vol.165, pp. 307-318)

    Adapted from materials provided by University of Leicester


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