Nothia
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Nothia Temporal range: Pragian |
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| Scientific classification | |
| Kingdom: | Plantae |
| Division: | Tracheophytes |
| Subdivision: | Lycophytina |
| Class: | †Zosterophyllopsida (?) |
| Genus: |
†Nothia A.G.Lyon ex El-Saadawy & Lacy |
| Species: | †N. aphylla |
| Binomial name | |
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Nothia aphylla Lyon ex El-Saadawy & Lacy |
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Nothia was a genus of Early Devonian vascular plants whose fossils were found in the Rhynie chert in Scotland. It had branching horizontal underground stems (rhizomes) and leafless aerial stems (axes) bearing lateral and terminal spore-forming organs (sporangia). Its aerial stems were covered with small 'bumps' (emergences), each bearing a stoma. It is one of the best described early land plants. Its classification remains uncertain, although it has been treated as a zosterophyll. There is one species, N. aphylla.
Fossilized remains, including bare stems (axes) and detached spore-forming organs (sporangia), were first described by Kidston and Lang in 1920 from the Rhynie chert of Aberdeenshire, Scotland – rocks which are of Pragian age (411 to 408 million years ago). The fragments were considered to be parts of Asteroxylon mackiei. In 1964 Lyon described sporangia belonging to Asteroxylon mackiei and suggested that Kidston and Lang's specimens were a new species which he called Nothia aphylla. The first full description based on further specimens was published in 1979. A very detailed description was published in 2001, making this species one of the best-known early polysporangiophytes.
The sporophyte of Nothia aphylla consisted of thin underground and aerial stems (axes). The underground stems or rhizomes were up to 2 mm in diameter and branched laterally. The underside of the rhizomes had a longitudinal ridge from which unicellular rhizoids emerged. There were no true roots. At intervals the rhizomes turned upwards to emerge as upright stems. Around the region of the upwards bend, horizontal branches appeared at right angles to continue the growth of the rhizomes. The upright stems were generally less than 2.5 mm in diameter; a reconstruction suggests a height of around 20 cm. Aerial stems branched dichotomously in a three-dimensional pattern, with the last two sets of branches bearing sporangia. The sporangia were attached by short stalks at the end and along the sides of the stem, in a more-or-less spiral fashion. The stalks curved upwards so that the sporangia were roughly upright. Spores were released through a longitudinal slit which appeared at the apex of the sporangia. The spores were trilete and around 65 µm in diameter. Both the horizontal rhizomes and the vertical stems had vascular tissue which formed a central core (protostele), and is described as having centrarch development. The precise structure of the vascular core varied between the rhizomes and the aerial stems.
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