Buteoxylonales
| Buteoxylonales | ||||||||||||
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| Temporal occurrence | ||||||||||||
| Mississippium | ||||||||||||
| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Buteoxylonales | ||||||||||||
The Buteoxylonales are an order of the extinct plant group of seed ferns . Signs of the order are trilobed vascular bundles in the petiole in cross section .
features
Buteoxylon gordonianum is known from a stem fragment that is 12 cm long and 2.5 cm in diameter. Leaf stalks 1.4 cm in diameter sit on the trunk in a spiral arrangement (2/5 phyllotaxis ). Both stem and petioles have an outer bark of the Sparganum type: hypodermic fiber strands are arranged vertically and do not anastomose . On the radial walls of the tracheids sit elliptical court pits .
Triradioxylon is another genus. The trunk has a small, three-lobed protostele . Protoxylem is located both in the center of the protostele and at the ends of the lobes. This arrangement is similar to that of early fern-like plants. The petioles of around one centimeter in diameter are in 1/3 phyllotaxis. The wood of Triradioxylon primaevum is loose, the tracheids have pits, the vascular rays are high and narrow. The bark is of the sparganum type. Leaf stalks with three-lobed conductive tissue, which were described as Lygionorachis whittaderensis from the same localities as Trirdioxylon , are also placed in the order Buteoxylonales.
The leaf genus Triphyllopteris from the Lower Mississippian is discussed as a possible genus of the Buteoxylonales or the Calamopityales . The leaflets are very variable, the shape ranges from unlobed to fan-shaped, toothed or pointed. Fertile specimens have dense associations of elongated sporangia with triple spores (three- pointed stigma ).
Systematic position
The Buteoxylonales are considered to be the least understood group of seed ferns . It is known only in a few finds, pollen organs or seeds are unknown.
supporting documents
- Thomas N. Taylor, Edith L. Taylor: The Biology and Evolution of Fossil Plants . Prentice Hall, Englewood Cliffs 1993, pp. 492-494. ISBN 0-13-651589-4