Iridopteridales

Features

The representatives are characterized by a highly indented, ribbed protostele, which has permanent protoxylem strands. The vascular bundles branch off in whorls. The branching is done iteratively, the branching pattern that is repeated several times in the side branches of higher order. At the nodes of two types of side axes are formed, each of which is supplied with a single Leitbündelspur that springs from a rib of the stele. The xylem is mesarch, the largest tracheids are thereby located near the center of Xylemrippen. The main feature by which the Iridopteridales different from the otherwise similar Pseudosporochnales, is the emergence of Leitbündelspur on the stele rib.

System

The systematic position of the Iridopteridales is unclear. They are near the base of ferns. From Taylor, Taylor and Krings (2009) they are placed in the Cladoxylopsida with the Pseudosporochnales.

Arachnoxylon is a genus of anatomically preserved stelae fragments. Se have a ribbed protostele, consisting only of primary tissue. In cross-section is at the end of each Xylemarmes a protoxylem strand or a cave, which corresponds to a peripheral loop. Of the leaf traces, there are three types, which differ in size and position. The side axes are arranged in whorls. The primary xylem is mesarch, the secondary wall of tracheids is ladder-like or circular to elliptical bordered pits. There are two types, Arachnoxylon kopfii ( Givetian of New York) and Arachnoxylon minor.

Compsocradus dates from the mid to late Devonian and similar Arachnoxylon. The findings are interpreted as pseudomonopodial with erect branches of the first order. The last appendages are bent back. The fertile terminate in paired sporangia. Fertile like sterile appendages are in whorls, are up to 64 in the fertile in a whorl. Spores are unknown. The stele consists of six primary xylem ribs, fon each carrying a strand of protoxylem at the top. The tracheids have single-row, round to oval bordered pits.

Iridopteris has a fünfrippige protostele with mesarchem xylem. Iridopteris eriensis has axes with more than 5.5 cm in diameter and shows two types of leaf traces. The smaller ones are round in cross section and are formed by radial division at the edge of the primary ribs. The larger tracks are elliptical, and carrying at each end a protoxylem strand. Iridopteris Arachnoxylon similar, but differs by the bilateral symmetry and the smaller size of this.

Metacladophyton from the Givetian of China has farmers celled lateral axes of the first order of two to seven axes per whorl. The stems have a diameter of 1.5 cm, the lobed primary xylem forms a U-shaped stele

Ibyka amphikoma dates from the Middle Devonian and was initially expected to Sphenophyta, later it was put to the Iridopteridales. The plant has a monopodiales branching system with whorled standing side axes. The appendages are formed at several orders of lateral axes. The plant is covered with delicate hairs. The vascular system consists of a three-lobed stele. Some of the arms branch out gabeligund form roundish leaf traces. Near the top of the Xylemlappen sit protoxylem - tracheids and parenchyma and form a perennial protoxylem. The sporangia of the last branches are ovate and about 1 mm long. A, also from the Middle Devonian, originally asked in its own genus Hyenia species was 2005 also transferred as Ibyka vogtii in this genus.

Serripteris from the middle Tournaisian of Southern France is expected temporarily to the Iridopteridales. It has several orders of lateral axes. The stele is vierrippig and mesarch.

Astopteris from the late Devon has a star-shaped protostele with flashy protoxylem strands.

Anapaulia moodyi from the Middle to Late Devonian Venezuela is expected to provisionally to the Iridopteridales. It is reconstructed as a monopodial plant with side branches in Pseudowirteln. The last side branches have recurved tips. The sporangia are elliptical. The whole plant is covered with delicate spines.

Rotoxylon dawsonii from the late Devonian has a variable xylem. The xylem maturation occurs mesarch, at the top of each Xylemarmes are one to three permanent protoxylem strands. The tracheids have elliptic to oblong bordered pits. The classification of the Iridopteridales is not secured, the type could also be among the Pseudosporochnales.

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. 398-400.

• Extinct plant
• Ferns
• Moniliformopses