Relic aragonite from Ordovician-Silurian brachiopods; implications for the evolution of calcification

Understanding the influence of aragonite/calcite sea conditions on the evolution of biocalcification relies strongly on the correct interpretation of the original composition of calcareous taxa. Aragonite dissolves or inverts into calcite over geological time, and its preservation is currently unkno...

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Bibliographic Details
Published in:Geology (Boulder) 2011-10, Vol.39 (10), p.967-970
Main Authors: Balthasar, U, Cusack, M, Faryma, L, Chung, P, Holmer, L. E, Jin, J, Percival, I. G, Popov, L. E
Format: Article
Language:English
Subjects:
adaptation
aragonite
biochemistry
biologic evolution
biomineralization
Brachiopoda
calcification
calcite
carbonates
experimental studies
fossilization
Invertebrata
invertebrate
Magnesium
marine environment
Ordovician
paleoecology
Paleontology
Paleozoic
Precipitation
preservation
Recrystallization
relict materials
shallow-water environment
Silurian
Temperature
Trimerellidae
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Summary:Understanding the influence of aragonite/calcite sea conditions on the evolution of biocalcification relies strongly on the correct interpretation of the original composition of calcareous taxa. Aragonite dissolves or inverts into calcite over geological time, and its preservation is currently unknown to predate the Pennsylvanian. Here we present direct evidence for the common occurrence of relic aragonite in Ordovician and Silurian trimerellid brachiopods, thereby extending the known range of aragonite preservation by more than 130 million years. Together with associated hypercalcifying taxa of putatively original aragonite or high-magnesium calcite composition and considerations of the temperature dependence of aragonite and calcite precipitation, our results suggest that the evolution of aragonite biomineralization might have presented an adaptive advantage in shallow marine tropical waters of calcite seas. A targeted search for Paleozoic aragonite should both resolve the original composition of consistently recrystallized taxa and enable the reassessment of the aragonite/calcite sea paradigm in a paleoenvironmental context.
ISSN:0091-7613
0016-8505
1751-7656
1943-2682
DOI:10.1130/G32269.1