In what may rank as one of the most important fossil
discoveries in decades, researchers have found exquisitely
preserved remains of tiny creatures, opening a long-hidden window
on early animal life.
Ranging from 570 million to 580 million years old, the
microscopic animal fossils reveal their secrets in surprising
detail - down to the level of individual cells. This is raising
hopes that paleontologists will be able to document, at the most
basic biological levels, key stages in the evolution of animals as
they shifted from soft-bodied, microscopic forms to those visible
to the naked eye.
In particular, researchers are keenly interested in finding
fossil evidence for the evolutionary fuse that led to the Cambrian
explosion - a burst in the diversity of life unmatched in Earth's
The explosion, which began roughly 550 million years ago and
lasted a few tens of millions of years, gave rise to virtually
every body plan seen in the animal kingdom today.
"This is going to trigger a flurry of activity," says Sean
Carroll, a developmental biologist at the Howard Hughes Medical
Institute and the University of Wisconsin at Madison, referring to
the latest discoveries. "There is tremendous interest in the
Cambrian explosion, when there was a huge increase in the size and
diversity of animals. Before the Cambrian, we do not see that level
of innovation," he says. "People thought that some of it was there
in small, poorly preserved animals, or maybe it wasn't there at
Two groups reported the fossil finds independently this week.
One research team, based in Taiwan and the People's Republic
of China, looked at phosphate deposits in southern China and found
highly detailed remains of early sponges. They are reporting their
findings in tomorrow's issue of the journal Science.
Meanwhile, Shuhai Xiao and Andrew Knoll of Harvard
University, in Cambridge, Mass., and Yun Zhang of Beijing
University analyzed microfossils taken from a phosphate mine also
in southern China. They describe their work in today's issue of the
Combing the phosphate deposits, part of a 57-square-kilometer
(22-square-mile) formation known as the Doushantuo phosphorites,
they uncovered several specimens of multicelled algae, whose
structure and reproductive features also appear in modern marine
algae. They also discovered tiny globules that, after Shuhai Xiao's
detective work, appear to be embryos from the same kind of
organism. The embryos show different stages of division. …