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Permanent link (DOI): https://doi.org/10.7939/R32P24

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Phylogenetic diversification of Equisetum (Equisetales) as inferred from Lower Cretaceous species of British Columbia Open Access

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Author or creator
Stanich, Nicholas A.
Rothwell, Gar W.
Stockey, Ruth A.
Additional contributors
Subject/Keyword
Equisetum
Lower Cretaceous
clade age
fossils
Equisetales
euphyllophyte phylogeny
Type of item
Journal Article (Published)
Language
English
Place
Time
Description
Three types of anatomically preserved vegetative shoots with features that characterize crown group Equisetum have been discovered in Lower Cretaceous deposits ( ≈ 136 Ma) of British Columbia, Canada, suggesting the genus is much older than currently believed. Specimens include two types of aerial shoots described as E. haukeanum sp. nov. and E. vancouverense sp. nov. and one type of subterranean rhizome. Shoots are 1 – 2 mm in diameter, jointed, and in cross section have fluted stems with a hollow pith. Distinctive patterns of cortical sclerenchyma and different ridge morphologies characterize each shoot morphotype. Nodes display irregular branching, highly fused leaf sheaths, and a nodal diaphragm. The aerial stem morphospecies have vallecular canals on alternating radii with carinal canals of an equisetostele surrounded by only a few tracheids. No secondary tissues are produced. Bands of surficial stomata flank the furrows of one morphospecies. Rhizomes and aerial shoots are of a similar size, suggesting that the plants were equivalent in stature to the smallest living Equisetum species. These fossils augment our understanding of evolutionary transformations that led from Paleozoic Archaeocalamitaceae and Calamitaceae to crown group Equisetaceae, suggesting that the initial diversification of Equisetum began far earlier than suggested by molecular-clock-based estimates.
Date created
2009
DOI
doi:10.7939/R32P24
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This version of this article is open access and can be downloaded and shared. The original author(s) and source must be cited.
Citation for previous publication
Nicholas A. Stanich, Gar W. Rothwell, and Ruth A. Stockey (2009) Phylogenetic diversification of Equisetum (Equisetales) as inferred from Lower Cretaceous species of British Columbia, Canada Am. J. Bot. 96:1289-1299; doi:10.3732/ajb.0800381
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