Stauropteridales
| Stauropteridales | ||||||||||||
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| Temporal occurrence | ||||||||||||
| Devonian to Pennsylvania | ||||||||||||
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Europe, North America |
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Stauropteridales | ||||||||||||
The Stauropteridales are an extinct group of plants that live near the base of the ferns .
features
The representatives are small, bush-shaped plants. The branching occurs in four or two rows (quadriseriat or biseriat). There are no flat leaf blades. The xylem cord is four-lobed in cross section and slightly bilaterally symmetrical. The branch anatomy is repeated in the higher order branches. The sporangia are terminal, both homospore and heterospore forms are known.
distribution
The finds range from the Devonian to the Pennsylvania of Europe and North America.
Systematics
The Stauropteridales are a basal group of ferns. But they differ significantly from the groups of recent ferns. In the past they were often combined with other groups to form the Coenopteridales . A number of representatives of this order were identified as representatives of the real ferns, while the stauropterids like the zygopteridales are regarded as basal. They are therefore led as a separate order that consists of only one family, the Stauropteridaceae.
They consist of three genera that clearly belong to the order: Stauropteris , Gillespiea and Rowleya .
Stauropteris
In Stauropteris oldhamia the side branches are in pairs. The lateral axes are branched up to six times and three-dimensionally, with the vascular bundles becoming smaller and smaller. The xylem develops mesarchically. Secondary tissue is unknown. There are ladder tracheids in the xylem. The phloem is in the furrows between the lobes of the xylem. At the base of each lateral axis of Stauropteris oldhamia there are heavily divided aphlebae (abnormal leaflets). These have thick-walled cells and are stiff, similar to thorns or thorns in recent plants. The sporangia have thick walls and are at the end of the last side branches. You may have opened through an apical pore. The spores are spherical and 32 to 40 micrometers in diameter. They were homosexual.
Stauropteris burntislandica is native to the Mississippian . The axes are similar to Stauropteris oldhamia , but the Aphlebae are quite variable. The aphlebae are irregularly branched, individual segments are up to 4 mm long. This species is heterosporous. The megasporangia were described under the name Bensonites fusiformis . They are spindle-shaped and around 1.3 mm long. The lower half is parenchymal , the upper half is hollow with a wall made of a layer of cells. There are usually two megaspores. Their size is up to 580 micrometers. The microsporangia are egg-shaped and around 0.6 mm long, their wall is a layer of cells thick. The microspores are around 30 micrometers in size and triple. It is not known whether micro- and megasporangia were on one plant or on different plants.
Stauropteris biseriata is native to the lower to central Pennsylvania of North America. The lateral axes stand in two rows (distich) and stand in the axils of Aphlebae, which are supplied by vascular bundles . Reproductive structures are not known here.
Other genera
Multifurcatus tenellus is similar to the Stauropteridales. It comes from the carbon of China. Its main axis has a diameter of up to 3 mm and forms three lateral axes per node . At the nodes of the side branches there are dichotomously branched side axes with a terminal sporangium. You could be straight.
Gillespiea is regarded as a Devonian representative of the Stauropteridales. Gillespiea randolphensis has smooth, quadriseriat branched axes. Larger axes have a protostele and are triangular to square in cross-section, small axes are round. The megasporangia are spindle-shaped with a blunt end. They stand singly or in pairs on small axes that stand where the Aphlebiae are in other Stauropteridales. Megasporangia are 1 mm long and contain one to two trilete spores around 160 micrometers in size. The microsporangia are not known.
Rowleya trifurcata comes from the Westfalium A of Lancashire and has a protostele and triseriate lateral axes. The protostele is tetrarchic and resembles that of Stauropteris . Small side axes are round, stand in pairs and are interpreted as leaves.
supporting documents
- Thomas N. Taylor, Edith L. Taylor, Michael Krings: Paleobotany. The Biology and Evolution of Fossil Plants . Second Edition, Academic Press 2009, ISBN 978-0-12-373972-8 , pp. 405-407.