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

Authors: Stockey, Ruth A.; Stanich, Nicholas A.; Rothwell, Gar W.;

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

Abstract

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.

Country
Canada
Related Organizations
Keywords

Euphyllophyte phylogeny, Fossils, Clade age, Equisetum, Lower Cretaceous, Equisetales

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selected citations
These citations are derived from selected sources.
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
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