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Escalation in Late Cretaceous-early Paleocene oysters (Gryphaeidae) from the Atlantic Coastal Plain
Journal article   Peer reviewed

Escalation in Late Cretaceous-early Paleocene oysters (Gryphaeidae) from the Atlantic Coastal Plain

Gregory P. Dietl, Richard R. Alexander and Walter F. Bien
Paleobiology, v 26(2), pp 215-237
2000

Abstract

adaptation Atlantic Coastal Plain Bivalvia Cenozoic Cretaceous Delaware Exogyrinae Gryphaeidae indicators Invertebrata Invertebrate paleontology lower Paleocene Maryland Mesozoic Mollusca New Jersey ornamentation Paleocene Paleogene predation Pycnodonteinae shells statistical analysis Tertiary theoretical studies United States Upper Cretaceous
More than 1600 valves of Late Cretaceous and early Paleocene Northern Atlantic Coastal Plain gryphaeid oysters (Exogyrinae and Pycnodonteinae) were examined for breakage-induced shell repair and morphologic variability to evaluate the hypothesis of escalation. The Exogyrinae show disproportionately higher average repair frequency (0.41) relative to the ecologically and functionally similar unornamented pycnodonts (0.19). An increase in repair frequency (independent evidence of the action of a selective agent, e.g., predation) through the stratigraphic interval supports escalation. Variation in repair frequencies may reflect differences in oyster morphology and in the strength and diversity of shell crushers across an onshore-offshore gradient. Escalation of antipredatory adaptation characterized the evolutionary response of gryphaeid oysters to their durophagous predators. Adaptation generally occurred by the enhancement of existing traits in both oyster lineages. Characters that confer a selective advantage against predators are not all expressed or improved concurrently in both oyster lineages. Morphologic adaptations to minimize shell breakage include the development of expansive, broad commissural shelves, thickened valves, and surface ornamentation (Exogyrinae). Surface ornament in the Exogyrinae gradually increased with time. For some characters, such as thickness, conflicting functional demands (e.g., valve stabilization) may have limited adaptation to predators.

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Collaboration types
Domestic collaboration
Web of Science research areas
Biodiversity Conservation
Ecology
Evolutionary Biology
Paleontology
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