The Lycopodiales of the British Isles (Isoetes, Lycopodium, Selaginella)


L. Watson and M. J. Dallwitz

Extinct Lycopsida

Including Lycopodiales, Selaginellales, Isoetales.

Comments. Interest in extinct Lycopsida “ .... has centred largely on the Carboniferous members of the group because of the abundance of fossils, the diversity of forms they exhibit, and their arborescent habit. Some of them vie in size with all but the largest of modern forest trees, and the fossil record indicates that they grew in more or less pure stands. As a result, they enter our economy today as important contributors of the raw material that became coal" (Andrews (1961). Rermarkably, however, fossil remains of plants morphologically and anatomically very similar to extant Lycopodium occurred much earlier in the Paleozoic, as exemplified by Baragwanathia longifolia from the Silurian of Australia, and by Lycopodites from the Carboniferous and Mesozoic. Heterosporous, herbaceous plants closely comparable with present day Selaginella, variously referred to Selaginellites and even to Selaginella itself, also occur in Paleozoic and Mesozoic deposits; and it is clear from the fossil record that the genus Isoetes was represented in essentially its present form by the mid-Cretaceous. While the spectacular arborescent lycopods which dominated Carboniferous forests disappeared around the end of that epoch, their herbaceous relatives have shown extraordinary resilience.

Ilustrations. • Lepidodendraceae, Pleuromeiaceae.

To view the illustrations with detailed captions, go to the interactive key. This also offers full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, and distributions of character states within any set of taxa.

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2007 onwards. The Lycopodiales of the British Isles (Isoetes, Lycopodium, Selaginella). Version: 1st September 2009.’.