Work at the Burgess Shale Formation

Siobhan Roberts of Smithsonian.com is reporting on work that is going on at the Burgess Shale formation in Canada. They write:

The Burgess Shale is Mecca for paleontologists. Charles Doolittle Walcott, the fourth Secretary of the Smithsonian Institution, discovered this rich fossil bed a century ago, in the summer of 1909, and named it for nearby Mount Burgess. At the end of his first field season here, Walcott wrote in a letter to a colleague that he had "found some very interesting things." Talk about understatement. The Burgess fossils tell nothing less than the story of the Cambrian explosion—evolution's Big Bang—when relatively simple organisms rapidly diversified into the sorts of animals that live today. The exquisitely preserved Burgess specimens (most likely entombed by underwater mudslides) include the remnants of soft-bodied organisms, which are rare in the fossil record. The animals inhabited the ocean floor 505 million years ago, near the end of the Cambrian Period.

"Most of the phyla we know today we can see already in the Cambrian and the animals of the Burgess Shale," said Caron. But the fossils still look very strange. "They certainly show evidence of evolution," Caron said. "The animals that you see there don't look like the ones we have today."

This is critical to an understanding of the Cambrian Explosion, that the animals alive during this time largely don't resemble animals alive today. How strange were they?

In 1989, paleontologist Stephen Jay Gould popularized Burgess' "weird wonders" in his bestselling book Wonderful Life. But he argued that Walcott [the discoverer of the formation] had erroneously shoehorned the fossils into existing taxonomic groups. He suggested that the curious "problematica" fossils that had long defied scientific identification—such as Hallucigenia, an inch-long creature with two rows of spines on its back—deserved their own taxonomic groupings.

Things to keep in mind the next time a creationist says that all of the modern phyla arrived fully formed at the beginning of the Cambrian.

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