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Reinvestigation of the occurrence of cutan in plants: implications for the leaf fossil record

Published online by Cambridge University Press:  08 April 2016

Neal S. Gupta
Affiliation:
Organic Geochemistry Unit, Biogeochemistry Research Centre, School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, United Kingdom Department of Earth Sciences, University of Bristol, Queen's Road, Bristol BS8 1RJ, United Kingdom
Margaret E. Collinson
Affiliation:
Department of Geology, Royal Holloway University of London, Egham, Surrey TW20 0EX, United Kingdom. E-mail: m.collinson@gl.rhul.ac.uk
Derek E. G. Briggs
Affiliation:
Department of Geology and Geophysics, Yale University, Post Office Box 208109, New Haven, Connecticut 06520. E-mail: derek.briggs@yale.edu
Richard P. Evershed
Affiliation:
Organic Geochemistry Unit, Biogeochemistry Research Centre, School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, United Kingdom. E-mail: R.P.Evershed@bristol.ac.uk
Richard D. Pancost
Affiliation:
Organic Geochemistry Unit, Biogeochemistry Research Centre, School of Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, United Kingdom. E-mail: R.D.Pancost@bristol.ac.uk

Abstract

Cutan, a resistant non-hydrolyzable aliphatic biopolymer, was first reported in the cuticle of Agave americana and has generally been considered ubiquitous in leaf cuticles along with the structural biopolyester cutin. Because leaves and cuticles in the fossil record almost always have an aliphatic composition, it was argued that selective preservation of cutan played an important role in leaf preservation. However, the analysis of leaves using chemical degradation techniques involving hydrolysis to test for the presence of cutan reveals that it is absent in 16 of 19 taxa (angiosperm and gymnosperm), including many previously reported to contain cutan on the basis of pyrolysis data. Cutan is clearly much less widespread in leaves than previously thought, and its presence or absence does not exert any major bias on the preservation of leaves in the fossil record. In the absence of cutan, other constituents—cutin, plant waxes, and internal plant lipids—are incorporated into the geomacromolecule and contribute to the formation of a resistant aliphatic polymer by in situ polymerization during diagenesis.

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Articles
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Copyright © The Paleontological Society 

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References

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