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Science 11 February 2005:
Vol. 307. no. 5711, p. 811
DOI: 10.1126/science.307.5711.811n
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This Week in Science

The evolution of hard body parts during the Cambrian Period vastly improved the preservation of organisms in the fossil record. However, calcite skeletal elements are thought to be better preserved than their more reactive aragonite counterparts--and such bias would affect the interpretation of the history of the biosphere from rocks. Kidwell (p. 914) addressed the question of this potential "calcite bias" by analyzing the preservation of the various calcite and aragonite forms of bivalve mollusk shells through evolutionary time. Unexpectedly, aragonite shell types show trends in abundance contrary to the anticipated biases when looked at as a group, in singleton taxa, or in the duration of genera with such shells. Thus, the fossil record is potentially a faithful representation of the evolutionary patterns for skeletonized organisms.




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Science. ISSN 0036-8075 (print), 1095-9203 (online)