Buriadiaceae
| Buriadiaceae | ||||||||||||
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| Temporal occurrence | ||||||||||||
| Carbon to Permian | ||||||||||||
| Locations | ||||||||||||
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India, Korea, Brazil |
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Buriadiaceae | ||||||||||||
The Buriadiaceae are an extinct family of conifers from the order of the Voltziales . The only reliable representative is Buriadia heterophylla .
features
The woody branches of Buriadia heterophylla are irregularly branched. They carry the leaves in a spiral arrangement. The leaves are up to 3 cm long and polymorphic: single, single or multiply forked, as well as bifacial or trifacial.
Originally it was assumed that the fertile sections are located at the end of the shoot axes: They have single, stalked, backward-directed ovules that stand on the side . These replace a leaf in the phyllotactic spiral. However, later investigations showed that none of the ovules in these fossils had attached to the stem axis. It therefore remains open whether the ovules are combined in any form to form a cone.
The ovule is platyspermic, up to 4.5 mm long and narrows to a narrow micropylene region . This is keeled, with one keel extended to the stem, the other ending in a small horn. The micropyle sits between the stem and the horn. The integument has a tough outer and a delicate inner cuticle . The nucellus is free to the base. The skin of the megaspore is not cutinized.
The epidermis of the leaves is epistomatic. The stomata are arranged in longitudinal ligaments on the adaxial side. The epidermal cells have papillae that are elongated into hairs on the edge of the leaf. The seeds have few stomata, the epidermal cells are papilous. The secondary cells of the stomata are arranged in one or incompletely two circles, each circle with 5 to 7 papillary cells.
The pollen grains are asaccat (have no air sac), monocolpat (have a germ pore) and are similar to the genus Ginkgocycadophytus .
Systematics
The Buriadiaceae are generally placed among the Voltcials. Their systematic assignment is difficult and uncertain due to the lack of female cone fossils. Buriadia was not included in the usual cladistic analyzes of the Voltziales .
Buriadia heterophylla is the only species that can clearly be placed in the family. It is limited to Gondwana . The main finds come from the Karbon-Perm-Temporal Karharbari Formation in India. There are other finds in Brazil and Korea.
In addition to Buriadia , there are two other genera that may be placed in their vicinity:
- Paraburiadia was described from the Upper Permian of Primorye ( Kaliningrad Oblast ). It resembles Buriadia macroscopically , but has simple leaves and erect ovules with bifid apices. The anatomy of the epidermis and ovules is not known.
- Coricladus from the Lower Permian of Brazil was first described in 2005. At the ends of the vegetative branches sit four seed scales, each with a bifid tip and two ovules.
supporting documents
- Thomas N. Taylor, Edith L. Taylor, Michael Krings: Paleobotany. The Biology and Evolution of Fossil Plants . Second Edition, Academic Press 2009, p. 826, 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. 324ff.
Individual evidence
- ^ Gar W. Rothwell, Gene Mapes, Genaro R. Hernandez-Castillo: Hanskerpia gen. Nov. and phylogenetic relationships among the most ancient conifers (Voltziales) . Taxon, Vol. 54, 2005, pp. 733-750.