Majonicaceae
| Majonicaceae | ||||||||||||
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| Temporal occurrence | ||||||||||||
| Perm | ||||||||||||
| 299 to 251 million years | ||||||||||||
| Locations | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Majonicaceae | ||||||||||||
| Clem. West. |
The Majonicaceae are an extinct family of conifers from the order of the Voltziales .
features
The shoots of the Majonicaceae have whole-margined, bifacial leaves in a spiral arrangement . Heterophyllia can occur. The leaves are up to 3 cm long.
The seed cones are compound. On the cone axis there are whole- edged bracts in a spiral arrangement , in whose armpits the seed-bearing short shoots sit. The short rungs are free or partially fused with the bract. They are bilaterally symmetrical and consist of 1 to 15 sterile scales and two to three fertile scales. Each has a single ovule at the base on the abaxial surface (abaxial relative to the axis of the short shoot). Two fertile scales stand laterally and are bent back, the third scale, if present, sits medially on the adaxial side of the short shoot. The ovules on the lateral scales are clearly located laterally or are shifted towards the adaxial side. This means that the ovules are not in one plane, a characteristic of this family. The fertile and sterile scales are more or less fused together. The lower part of the short shoot is stem-like. Ovules or seeds are bilaterally symmetrical. The seed axis is straight. The nucellus is egg-shaped and only fused with the integument at the base. A pollen chamber is available. The shell of the megaspore is cutinized .
The pollen-forming cone has a simple structure. The microsporophylls sit in a spiral arrangement on the pin axis . The pollen is bisaccoid.
The epidermis of the leaves, bracts, scales and microsporophylls is amphistomatic, the stomata are located on the top and bottom. The stomata often sit in conspicuous rows. The stomata consist of a circle of five to ten papillary secondary cells.
Systematics
The Majonicaceae family was established in 1987 by Clement-Westerhof, including some of the previously described genera. It includes the following genera:
- Majonica , type genus , restricted to the Upper Permian of the Alps, here an important component of the flora.
- Dolomitia , restricted to the Upper Permian of the Alps
- Pseudovoltzia , widespread in the Upper Permian of Europe
- Lebowskia , first described in 2007, Early Permian North America
supporting documents
- Thomas N. Taylor, Edith L. Taylor, Michael Krings: Paleobotany. The Biology and Evolution of Fossil Plants . Second Edition, Academic Press 2009, pp. 816ff., ISBN 978-0-12-373972-8
- Johanna A. Clement-Westerhof: Morphology and Phylogeny of Paleozoic Conifers . In: Charles B. Beck (Ed.): Origin and Evolution of Gymnosperms . Columbia University Press, New York 1988, ISBN 0-231-06358-X , pp. 298-337, especially pp. 311-316.
Individual evidence
- ^ Cindy V. Looy: Extending the Range of Derived Late Paleozoic Conifers: Lebowskia gen. Nov. (Majonicaceae) . International Journal of Plant Sciences, Volume 168, 2007, pp. 957-972. doi : 10.1086 / 518256