Pseudosporochnales

Eospermatopteris erianus, roots

The Pseudosporochnales are an extinct group of plants that is systematically near the base of ferns. With Eospermatopteris you belong to the oldest known tree-like plants.

Features

Many representatives of the Pseudosporochnales now be regarded as tree -shaped. Some representatives are available at the terminal branches three-dimensional appendages, others flattened, foliage leaf-like structures. The sporangia are terminal and are usually in pairs. Some representatives they are grouped together and are in Pseudowirteln. All species are considered homospor (only equal spores).

System

The Pseudosporochnales will be provided to Cladoxylopsida because of their totems structure.

The genus Cladoxylon was erected in 1856 by Unger for anatomically preserved stem axis. Today the genus by most authors is used as a form genus for fossil stem axis with a characteristic anatomy, the primary xylem is at least partially broken down into segments. Cladoxylon radiatum dates from the Mississippian of Germany. The Stems have a diameter of up to 6.5 cm and own approximately 17 steles segments. The side branches are spirally. There are only primary xylem with Leitertracheiden. In the ground tissue of the stem thick-walled cells occur. With the emergence of side branches axes four to six Xylemarme in the petiole from to branch further and form a flattened ring of up to eight Xylemsträngen. Taeniatum When only 3.5 cm in diameter measured Cladoxylon located in the root stele two zones. Around the master peripherals are numerous, but less than 20 radially extended Xylemstränge; in the center of the trunk there are three to four cylindrical Xylemstränge. Each of these produces bipolar leaf traces (with two protoxylem poles ).

Several findings have been described with cladoxylopsider anatomy from the Mississippian of Scotland. Cladoxylon waltonii is known of Stems and petioles of two size classes. The group includes a radially symmetrical trunks with a diameter of less than 1.2 cm and spirally arranged petioles with clepsydroid -like ( dumbbell-shaped ) Xylemsträngen. The second group includes small strains of 2 to 7 mm in diameter with alternating constant petioles. The major tribes include 9 to 15 xylem arms, the smaller 4 to 9, which are in a U-shape.

Polyxylon australe from the Upper Devonian of Australia has small stem axis with diameter of 2.7 cm. In cross section, you can see 19 elongated arms mesarche primary xylem ( mesarch: the protoxylem is located in the center of the Metaxylems, the maturation of the xylem takes place from the center to the inside and outside ). Each of the arms branched dichotomously at the end and forms at least six traces running in the whorled standing side axes.

From Hierogramma small shoot axes are known, in which a bilateral vascular system with two elongated Xylembändern, one of which is T-shaped. Slightly higher the vascular system is then U-shaped. In Hierogramma mysticum the leaf traces go alternate from as small, circular strands.

Pseudosporochnus nodosus was a small tree reconstructed with bulbous base. He was probably 2 to 4 m high. The side axes seem to have been dropped after a certain time. The side branches branched several times dichotomous. The terminal branches are three-dimensional. Sterile and fertile units are not very different, the latter possessing couples sitting, ellipsoidal sporangia. The sporangia are long and 3 mm. The spores are unknown., Around - elongated structures, these represent nests of bark fibers are dar. to all parts of the plant

Pseudosporochnus hueberi dates from the Middle - to Upper Devonian of eastern New York. The axes are up to 58 cm long and have a diameter of several centimeters. In the major axis, it is 40 to 50 xylem segments in the side shafts 20 to 25

Wattieza givetiana dates from the Middle Devonian of Belgium. There are also finds from Venezuela. The branches are still more highly branched than Pseudosporochnus the last axes are three-dimensional.

Lorophyton from the Givetian has bifurcated roots, the side branches are branched partly dichotomous. The last page axes branch also dichotomous. The fertile units consist of bent-back last segments of each of these are two sporangia.

Eospermatopteris was first described in 1924 by Winifred Goldring basis of finds from the Middle Devonian of Gilboa (New York). At that time only Stammausgüsse were known. It has been estimated that the plant has been around 9 to 12 m high, with massive, fern fronds and seeds at the ends of the branches. Eospermatopteris was thus considered for some time as the oldest seed fern. 2007 further discoveries were published. These findings showed that Eospermatopteris a crown of short, erect branches possessed the type Wattieza, which are finger-like branches and their last appendage branched three-dimensional. True leaves are missing. The findings suggest that the plant was about 8 m high. The branches were regularly shed and replaced by new branches at the top of the plant.

Pietzschia similar anatomically Pseudosporochnus. The stems have a diameter of about 2.5 cm and have a cylinder of radially arranged xylem plates. In Pietzschia polyupsilon from the New Albany Shale of Kentucky, the number of Xylemsegmente 54 At some points are located between the Xylemsegmenten Sklerenchymplatten. The track in the lateral axes formed by four bundles. A little further from the junction, these strands an inverted U-shaped strand. The main axis of Pietzschia polyupsilon had determinate ( limited) growth, the lateral axes were arranged in whorls. Pietzschia levis from the lower Famennian ( Upper Devonian ) of Morocco has base fabric with aerenchyma and lived in wetlands. Pietzschia Schulleri, also from the Famennian of Morocco, has only primary tissues. The trunk diameter is often more than 15 cm, the tribe has both central as well as peripheral Xylemstränge.

For Xenocladia from the middle to late Devonian a liana growth form was proposed. Copies of Xenocladia medullosina have a diameter of about 10 cm and possess secondary xylem.

Stenoxylon has plenty of secondary and reduced primary xylem. Stenoxylon ludwigii has vessel segments anastomose to form a complex network of vascular systems. At the trunk are numerous small petioles in schraubiger arrangement. Stenoxylon irvingense from the New Albany Shale has on one side of Xylemarms a stronger form secondary xylem than on the other. The vascular bundles are more circular. In the parenchymatous ground tissue, there are irregular strips of thick-walled fibers.

Rhymokalon trichium from the Upper Devonian of New York is known to 3 cm thick stem axis. The second and third order lateral axes are in schraubiger arrangement. Cross sections show a vielrippigen primary xylem strand of less than 1.8 cm in diameter. The xylem consists of Tracheidenplatten between which is parenchyma. The metaxylem has conductor and Tüpfeltracheiden. The bark consists of elongated parenchyma cells.

Duisbergia mirabilis dates from the Middle Devonian. The plant is used as an upright, unbranched stem reconstructed by about 2 m height with a club-shaped base. Is a dense crown of leaves, which are arranged in a tight screw on the top of the stem. The leaves are apparently doing in vertical rows. The last segments consist of fan-shaped, about 5 cm long leaves. Are lines that indicate a Blattnervatur on the surface. Well-preserved specimens have up to 60 tape-shaped xylem strips, which is interpreted as secondary xylem, which is arranged in a ring. Duisbergia macrociccatricosus resembles the root Pseudosporochnus. This Duisbergia could represent the lower part of the trunk of Pseudosporochnus.

Polypetalophyton dates from the late Devonian of China and was first described in 2003. At each node, there are four side branches, the internodes between them are long. The vascular system consists of several strip-shaped, located at the periphery of the primary xylem strands. In the center of the axle is a central, circular vascular bundles. Sporangia are terminal on fertile branches. The sterile terminal segments are flattened and match the type Sphenopteridium.

Calamophyton is a few tens of centimeters tall plant with dichotomous branching.

Other genera that correspond anatomically to Pseudosporochnales are SynCardia, Voelkelia and Arctopodium.

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. 388-398.