Monday, February 14, 2005


Fossil Record Passes Test

The fossil record may not be perfect, but it passed a critical test with flying colors, according to a study by University of Chicago paleontologist Susan M. Kidwell that will be published in the Feb. 11 issue of the journal Science.
While fossils of the glamorous dinosaurs get most of the attention, they are too few and far between to answer the most important questions about the evolution of life on Earth. So for decades, paleontologists have turned to humble shelled creatures like sea urchins or mollusks, whose enormous numbers and geographic range make their fossils a much better marker of the history of life. But paleontologists also have worried that some of those fossils decayed much faster than others, so that the remains collected today might misrepresent the true proportions of past life, thereby throwing off their conclusions.
To test this suspicion, Kidwell carefully analyzed the fossil record of marine bivalves, a diverse group of shellfish that includes scallops, oysters, cockles and mussels. Her study ruled out longstanding predictions that patterns in the fossil record would be dictated by differences in shell toughness among evolutionary lineages.
All of her analyses on how shell composition might distort the bivalve record over the past 500 million years showed either no effect, or the opposite effect, compared to what was expected if shell preservation was the most important factor. “The broad outlines of the bivalve record can be counted on as a reliable picture of evolutionary history,” said Kidwell, whose work was supported by a grant from the National Science Foundation. Link


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