Baragwanathia
| Baragwanathia Temporal range: Early Ludlow (Gorstian, late Silurian)[1] - Early Devonian |
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| Scientific classification | |
| Kingdom: | Plantae |
| Division: | Lycopodiophyta |
| Class: | Lycopodiopsida |
| Order: | Drepanophycales |
| Family: | Drepanophycaceae |
| Genus: | Baragwanathia † Lang & Cookson, 1935 |
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Baragwanathia is a genus of extinct plants of the division Lycopodiophyta of Late Silurian to Early Devonian age (423 to 398 million years ago), fossils of which have been found in Australia, Canada and China.
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[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 and the arrangement and shape of the leaves. (See Drepanophycaceae for more details.) These extinct terrestrial vascular plants had stems varying in diameter and length (up to a few cm for the diameter and a few metres for the length). They were erect or arched, dichotomized occasionally, and were furnished with true roots at the base. Vascular bundle actinostele, tracheids of primitive annular or helical type (so-called G-type). Leaves were 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. The name derives from William Baragwanath, director of the Victorian Geological Survey at the time of discovery.[2]
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[edit] References
Lang, William H.; Cookson, Isabel C. (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 B 224 (517): 421-449. doi:10.1098/rstb.1935.0004. http://rstb.royalsocietypublishing.org/content/224/517/421.full.pdf. Retrieved 2012-01-31.
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).
Rickards, R.B. (2000). "The age of the earliest club mosses: the Silurian Baragwanathia flora in Victoria, Australia" (abstract). Geological Magazine 137 (2): 207–209. doi:10.1017/S0016756800003800. http://geolmag.geoscienceworld.org/cgi/content/abstract/137/2/207. Retrieved 2007-10-25.
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