Baragwanathia

Baragwanathia

Taxobox
name = "Baragwanathia"
fossil_range = Early Ludlow (Gorstian, late Silurian)cite journal
author = Rickards, R.B.
year = 2000
title = The age of the earliest club mosses: the Silurian Baragwanathia flora in Victoria, Australia
journal = Geological Magazine
volume = 137
issue = 2
pages = 207–209
url = http://geolmag.geoscienceworld.org/cgi/content/abstract/137/2/207
accessdate = 2007-10-25
doi = 10.1017/S0016756800003800
format = abstract] - Early Devonian
regnum = Plantae
divisio = Lycopodiophyta
classis = Lycopodiopsida
ordo = Drepanophycales
familia = Drepanophycaceae
genus = "Baragwanathia" †
genus_authority = Lang & Cookson, 1935
subdivision_ranks = Species
subdivision =
*"Baragwanathia longifolia" aut|Lang & Cookson (Type species)
*"Baragwanathia abitibiensis" aut|Hueber
*"Baragwanathia" sp. aut|Hao & Gensel

"Baragwanathia" is a genus of extinct plants of the division Lycopodiophyta of Late Silurian to Early Devonian age, fossils of which have been found in Australia, Canada and China.

Description

"Baragwanathia" is a primitive lycopod, differing from such taxa as "Asteroxylon" in the presence of vascular tissue in its leaves - "Asteroxylon" has vascule-free enations. It is set apart from the closely related genus "Drepanophycus", of the same period, in the position of the sporangia, the type of stele, and the arrangement and shape of the leaves. (See Drepanophycaceae for more details.)These extinct terrestrial vascular plants of the ?Late Silurian has stems several mm to several cm in diameter and several cm to several metres long, erect or arched, dichotomizing occasionally, furnished with true roots at the base. Vascular bundle actinostele, tracheids of primitive annular or helical type (so-called G-type). Leaves are unbranched strap-shaped microphylls 1-2 cm long with a single prominent vascular thread, arranged spirally on the stem. Sporangia axillary (exact position not known), broader than long, dehiscing by a slit on top. Spores were trilete; the gametophyte is currently unknown.

References

Lang WH and Cookson IC (1935) On a flora, including vascular land plants, associated with Monograptus, in rocks of Silurian age, from Victoria, Australia. "Philosophical Transactions of the Royal Society of London" B224, 421-449.

Hueber, FM (1983) A new species of "Baragwanathia" from the Sextant Formation (Emsian) Northern Ontario, Canada. "Journal of the Linnean Society (Botany)" 86, 57-79.

Hao SG and Gensel PG (2001) The Posongchang Floral Assemblages of Southeastern Yunnan, China - Diversity and Disparity in Early Devonian Plant Assemblages. In "Plants Invade the Land. Evolutionary and Environmental Perspectives", pp. 103-119. Eds PG Gensel and D Edwards. (Columbia University Press, New York).


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