Baragwanathia

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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.

[edit] 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.

[edit] 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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