Rhyniopsida
| Rhyniopsida Temporal range: Early Devonian |
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| Reconstruction of Rhynia gwynne-vaughanii | |
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| Kingdom: | Plantae |
| Division: | Tracheophytes |
| Class: |
†Rhyniopsida Kryshtofovich 1925 |
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Rhyniopsida is a class of extinct early vascular plants, with one family, Rhyniaceae, found in the Early Devonian (around 419 to 393 million years ago). They are polysporangiophytes, since their sporophytes consisted of branched stems bearing sporangia (spore-forming organs). They lacked leaves or true roots but did have simple vascular tissue. The group was first placed in a subdivision of the division Tracheophyta under the name Rhyniophytina (see Polysporangiophyte: Taxonomy for alternative names). Informally, they are often called rhyniophytes. More recently the name paratracheophytes has been suggested, to distinguish such plants from 'true' tracheophytes or eutracheophytes.
As originally defined, the group was found not to be monophyletic since some of its members are now known to lack vascular tissue; these have been moved to the class Horneophytopsida, which is defined as lacking true vascular tissue. Currently, Rhyniopsida includes the genera Huvenia, Rhynia, and , all from the Devonian.
One of the most important radiations for land plants occurred in the early Devonian (Pragian), when the first certain rhyniophytes appear in the fossil record, making this rich fossil discovery of major importance to paleobotany. It has been suggested that the poorly preserved Eohostimella, found in deposits of Early Silurian age (Llandovery, around 440 to 430 million years ago), may be a rhyniophyte.
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