Rhyniophyta

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Rhyniophytes
Fossil range: Early Devonian^[1]

Kingdom:	Plantae
Division:	Rhyniophyta †
Class:	Rhyniopsida †

Rhyniophyta is a division of early vascular plants including the class Rhyniopsida. Its circumscription of included species has changed as additional information is revealed in the form of new fossils or new analysis. In particular, some specimens previously included in the group are now known to lack vascular tissue, and so cannot be included in the group if it is to be monophyletic. Currently, the group is reduced to include the genera Huvenia, Rhynia, and Stockmansella,^[1] all from the Devonian. One of the most important radiations for land plants occurred in the early Devonian (Pragian), when the first rhyniophytes appear in the fossil record,^[1] making this rich fossil discovery of major importance to paleobotany.

Cladogram of the land plants showing the position of the "rhyniophytes" (in blue). Diagram based on Kenrick & Crane 1997. More recent molecular research reverses the position of the hornworts and mosses.^[2]

The general term "rhyniophytes" or "rhyniophytoids" is sometimes used for the assemblage of plants found in the Rhynie chert Lagerstätte - rich fossil beds in Aberdeenshire, Scotland, and roughly coeval sites with similar flora. Thus, these terms refer to a floristic assemblage of more or less related early landplants, not a taxon. Though the rhyniophytes are well-represented, plants with simpler anatomy, like Aglaophyton, are also common.

The Rhynie flora are unusual for their excellent preservation of very early fossils of primitive vascular plants, in addition to plants with uncertain vascular traces, and non-vascular plants. The fossils contain sufficient cellular detail to to tell which plants are the sporophyte generation due to the presence of sporangia. In addition, because the plants were buried in-situ, rather than transported before burial, important distinguishing features, such as reproductive structures, are found attached to their parent plants. The site appears to include sporophytes and gametophytes of the same species and other organisms, such as arthropods, that lived in the Rhynie ecosystem. All of this gives an insight into the sort of ecosystems early plants evolved in.

[edit] References

^ ^a ^b ^c Kenrick, Paul; Peter R. Crane (1997). The Origin and Early Diversification of Land Plants : A Cladistic Study. Washington, D.C.: Smithsonian Institution Press, pp. 139-140, 249. ISBN 1-56098-730-8.
^ Qiu et al. 2006