Magazine article Science News

Fossils Contain Earliest Signs of Shells: Microscopic Eukaryotes Made Armor 809 Million Years Ago

Magazine article Science News

Fossils Contain Earliest Signs of Shells: Microscopic Eukaryotes Made Armor 809 Million Years Ago

Article excerpt

Life on Earth got into the shell game more than 200 million years earlier than previously thought.

Fossilized eukaryotes--complex life-forms that include animals and plants--discovered in Canada are decked out in armorlike layers of mineral plates, paleobiologist Phoebe Cohen said September 27. At 809 million years old, the find is the oldest evidence of organisms controlling the formation of minerals, a process called biomineralization.

This earlier origin of biomineralization coincides with major changes that mark the end of a period known as the "boring billion" (SN: 11/14/15, p. 18), said Stanford University paleontologist Erik Sperling, who was not involved in the discovery. "There were big things going on with ocean chemistry," he said. "It's interesting to see the biological response."

These ancient microscopic eukaryotes built their exoskeletons using a very different process from most modern shell-making microbes. That uniqueness offers insights into how mineral-making abilities first evolved, said Cohen, of Williams College in Williamstown, Mass.

Donning an exoskeleton of minerals protects microbes from predators. Previous clear evidence of eukaryote biomineralization dates back to about 560 million years ago.

Odd fossils discovered in the late 1970s and covered in mineral plates shaped like circles, squares and "Honeycomb cereal" (as Cohen described them) hinted that the skill evolved much earlier. Dating techniques had put the age of the fossils somewhere between 811 million and 717 million years ago, but scientists couldn't rule out that the scalelike minerals had formed after these organisms died. …

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