Exceptionally preserved crustaceans from western Canada reveal a cryptic Cambrian radiation

Harvey, Thomas H. P. and Vélez, Maria I. and Butterfield, Nicholas J. (2012) Exceptionally preserved crustaceans from western Canada reveal a cryptic Cambrian radiation. Proceedings of the National Academy of Sciences, 109 (5). pp. 1589-1594. DOI 10.1073/pnas.1115244109

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Abstract

The early history of crustaceans is obscured by strong biases in fossil preservation, but a previously overlooked taphonomic mode yields important complementary insights. Here we describe diverse crustacean appendages of Middle and Late Cambrian age from shallow-marine mudstones of the Deadwood Formation in western Canada. The fossils occur as flattened and fragmentary carbonaceous cuticles but provide a suite of phylogenetic and ecological data by virtue of their detailed preservation. In addition to an unprecedented range of complex, largely articulated filtering limbs, we identify at least four distinct types of mandible. Together, these fossils provide the earliest evidence for crown-group branchiopods and total-group copepods and ostracods, extending the respective ranges of these clades back from the Devonian, Pennsylvanian, and Ordovician. Detailed similarities with living forms demonstrate the early origins and subsequent conservation of various complex food-handling adaptations, including a directional mandibular asymmetry that has persisted through half a billion years of evolution. At the same time, the Deadwood fossils indicate profound secular changes in crustacean ecology in terms of body size and environmental distribution. The earliest radiation of crustaceans is largely cryptic in the fossil record, but “small carbonaceous fossils” reveal organisms of surprisingly modern aspect operating in an unfamiliar biosphere.

Item Type: Article
Uncontrolled Keywords: 2011AREP; IA64;
Subjects: 04 - Palaeobiology
Divisions: 04 - Palaeobiology
Journal or Publication Title: Proceedings of the National Academy of Sciences
Volume: 109
Page Range: pp. 1589-1594
Identification Number: 10.1073/pnas.1115244109
Depositing User: Sarah Humbert
Date Deposited: 21 Jan 2012 15:30
Last Modified: 23 Jul 2013 10:03
URI: http://eprints.esc.cam.ac.uk/id/eprint/2345

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