Zygopteridales
| Zygopteridales | ||||||||||||
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Alloiopteris erosa , upper carbon |
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| Temporal occurrence | ||||||||||||
| Mississippium ( Tournaisium ) to Permian | ||||||||||||
| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Zygopteridales | ||||||||||||
The Zygopteridales are an extinct group of plants that can be found near the base of the ferns .
features
The representatives have elaborate, three-dimensional fronds that have plumage in four rows (quadriseriat). The fronds have a characteristic stalk configuration in cross-section, which resembles a C, E, H, I, X or Y and was used to subdivide the order.
The sporangia are elongated and stand in large groups on the underside of leaflets or at the tip of frond branches. The sporangia have clearly recognizable opening mechanisms ( annulus ). The annulus is V-shaped or consists of two longitudinal ligaments. Fertile fronds or at least the fertile frond parts are likely to be built morphologically differently in most representatives.
The rachis is radially symmetrical in cross-section and is also known as a phyllophor to differentiate it from the C-shaped vascular bundles of real ferns. The phyllophore has bipolar primary xylem strands, some with terminal loops. The traces to the feathers leave the xylem cord as crescent-shaped vascular bundles, from which further bundles branch off. The zygopteridales are sometimes divided into two groups based on their frond morphology and anatomy: etapteroids, with four rows of primary leaflets and open lateral loops; and the clepsydroids, with two rows of primary pinnacles as in living ferns, and a phyllophore shaped like a clock-glass in cross-section.
Systematics
The Zygopteridales contain only one family, the Zygopteridaceae. Some authors also put this in the order Coenopteridales . The family contains 13 genera with around 45–50 species.
The representatives are:
- Alloiopteris
- Asterochlaenopsis
- Austroclepsis
- Biscalitheca
- Brittsia
- Clepsydropsis
- Corynepteris
- Diplolabis
- Protoclepsydropsis
- Symplocopteris
- Yulebacaulis
- Zygopteris
evolution
The Zygopteridales evolved from the clepsydroid phyllophor type to the forms of Zygopteris . In Viseum flat leaflets first occur, but they always remain rather small.
Many features indicate adaptations to dry growing conditions and high light exposure at the sites. Among them is the strong hairiness, the presence of locked shoot tips, which indicate a periodic dormancy.
The precursors of the Zygopteridales are likely to have been tree-shaped, just like the earliest forms, the Clesydroids, are also tree-shaped. These are unbranched ( Asterochlaenopsis ) or have the wrong trunk ( Symplocopteris and Austroclepsis ).
A cladistic investigation saw the Zygopteridales together with the Pseudosporochnales and Rhacophytales in one clade, while the Stauropteridales and the eusporangiaten and leptosporangiaten ferns formed two further clades.
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. 408-418.
Individual evidence
- ↑ a b Wolfgang Frey, Eberhard Fischer, Michael Stech: Bryophytes and seedless Vascular Plants . In: Wolfgang Frey (Ed.): Syllabus of Plant Families - A. Engler's Syllabus of Plant Families . 13th edition. tape 3 . Borntraeger, Berlin / Stuttgart 2009, ISBN 978-3-443-01063-8 , pp. 325 .