Rhynia

From Palaeos

Rhynia gwynne-vaughanii is a primitive vascular plant with branching leafless stems that reached a height of about 18 cm and culminated in fusiform sporangia. The upright stems branched from creeping branching horizontal rhizomes that bore delicate hair-like roots. The lateral branches could overtop the sporangia-bearing stems, and the upright portions of the plant would have had a thicket-like appearance. Small bumps along the stems may contain archegonia, which indicate a possible bryophyte-like life history, although this is still unclear. But there is also a distinct protostele composed of distinct phloem and only a handful of xylem cells.

Rhynia is named after the Rhynie Chert (Pragian epoch, Devonian period of Euramerica), a fossil paleocommunity of which it is the most common member, both numerically and in terms of ground cover.

The species is commonly present as monotypic stands, and seems to have been an early colonizer of well-drained sinter (hot spring sedimentary deposits) and sandy substrates. It is also found associated with all other Rhynie plants except (apart from very rarely) Horneophyton, suggesting that Rhynia was a vigorous, perhaps weed-like, form tolerant of a wide range of habitats and able to withstand interspecies competition within the Early Devonian ecosystem.

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MAK021023