Word: cambrian
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Soon, inspired reconstructions of the Cambrian bestiary began to create a stir at paleontological gatherings. Startled laughter greeted the unveiling of oddball Opabinia, with its five eyes and fire-hose-like proboscis. Credibility was strained by Hallucigenia, when Conway Morris depicted it as dancing along on needle-sharp legs, and also by Wiwaxia, a whimsical armored slug with two rows of upright scales. And then there was Anomalocaris, a fearsome predator that caught its victims with spiny appendages and crushed them between jaws that closed like the shutter of a camera. "Weird wonders," Harvard University paleontologist Stephen Jay Gould called...
...even as Wonderful Life was being published, the discovery of new Cambrian-era fossil beds in Sirius Passet, Greenland, and Yunnan, China, was stripping some of the weirdness from the wonders. Hallucigenia's impossibly pointed legs, for example, were unmasked as the upside-down spines of a prehistoric velvet worm. In similar fashion, Wiwaxia, some scientists think, is probably allied with living bristle worms. And the anomalocaridids - whose variety is rapidly expanding with further research - appear to be cousins, if not sisters, of the amazingly diverse arthropods...
...real marvel, says Conway Morris, is how familiar so many of these animals seem. For it was during the Cambrian (and perhaps only during the Cambrian) that nature invented the animal body plans that define the broad biological groupings known as phyla, which encompass everything from classes and orders to families, genera and species. For example, the chordate phylum includes mammals, birds and fish. The class Mammalia, in turn, covers the primate order, the hominid family, the genus Homo and our own species, Homo sapiens...
...period of 75 million years, and even that seemed impossibly short. Then two years ago, a group of researchers led by Grotzinger, Samuel Bowring from M.I.T. and Harvard's Knoll took this long-standing problem and escalated it into a crisis. First they recalibrated the geological clock, chopping the Cambrian period to about half its former length. Then they announced that the interval of major evolutionary innovation did not span the entire 30 million years, but rather was concentrated in the first third. "Fast," Harvard's Gould observes, "is now a lot faster than we thought, and that's extraordinarily...
...done was travel to a remote region of northeastern Siberia where millenniums of relentless erosion had uncovered a dramatic ledger of rock more than half a mile thick. In ancient seabeds near the mouth of the Lena River, they spotted numerous small, shelly fossils characteristic of the early Cambrian. Even better, they found cobbles of volcanic ash containing minuscule crystals of a mineral known as zircon, possibly the most sensitive timepiece nature has yet invented...