Pleuromeia

Pleuromeia Sternbergi

Worldwide

The Pleuromeiales are an extinct group of Bärlapppflanzen ( Lycopodiopsida ) and came in before the Mesozoic ( Triassic to Cretaceous ).

Features

The representatives were with a maximum height of 2 m much smaller than the coal- forming Lepidodendrales and herbaceous. They have features of Lepidodendrales as the Isoetales and were formerly thought to be a link of these two groups.

The Pleuromeiales are unbranched and bear one or more terminal pins. Your rooting structures are lobed, kormusartig and have Stigmariae -like appendages.

The journals of some forms are bisporangiat ( heterospory ), while others only spores of a size form ( called homospory ). The sporangia are slightly recessed into the sporophyll. Most forms form trilete megaspores and microspores monolete. However Pleuromeia rossica has trilete microspores.

Representative

Pleuromeia

The genus Pleuromeia is limited to the Triassic and is of localities known around the world, including Germany, France, Spain, Russia, China, Japan, Argentina and Australia. Their representatives are likely to have inhabited a variety of locations. Finds north Sydney are interpreted as coastal halophytes. Specimens from China are interpreted as representative of dry habitats, possibly near Desert Oasis, another from Australia alternately wetter than plant locations. Findings from the new red sandstone of Eifel show that the type occurring here Pleuromeia Sternbergii along with the fern Anomopteris mougeotii formed dense stands.

Pleuromeia occurred in the early Triassic on quite suddenly. This is interpreted as re-colonization of many terrestrial ecosystems after the end-Permian mass extinction.

Pleuromeia has an unbranched, erect stem up to two meters in height. The base ( rhizomorphic ) is vierlappig, go to schraubiger of the arrangement, the roots from. Sitting at the top of Pleuromeia longicaulis a crown of elongated leaves with ligule. Each sheet is supplied by two vascular bundles. Below the crown is followed by a zone of persistent leaf bases, which merges into a zone of widely spaced leaf scars down. The trunk should have has a secondary growth, whether the tissue of bark or xylem formed thereby was, is not known.

Pleuromeia carries a relatively large pin at the top. Some species may also have worn for several journals. This is less of the occurrence of large numbers, Cylostrobus called closed cones that occur at the same sites as Pleuromeia and may have been produced by these plants. Some types of Cylostrobus are bisporangiat, the Megasporangien sit at the base of the pin. The megaspores are up to 700 microns in size, trilet and covered with numerous long spines. The microspores are monolet and up to 30 microns in size. Due to its shape, it is assumed that the Megasporophylle were spread with the aid of water.

• Pleuromeia Sternbergii from Germany is the type species of the genus and possessed two types of leaves.
• Pleuromeia jiaochengensis from the early Triassic of Shanxi is about 50 cm tall. The trunk is unbranched, awl-shaped and the leaves were about 3 mm long. At the end of the trunk sits a large pin from verkehrteiförmigen sporophylls that bear discus-shaped sporangia. The megaspores are great to 500.
• Pleuromeia Epicharis from North China is quite fully known.

For more genres

Pleuromeia rossica was transferred to a separate genus Lycomeia. Micro-and megaspores possess ultrastructural characteristics that they associate with the Isoetales.

Pleuromeia longicaulis is placed by some authors in a separate genus Cylomeia, you are assigned to the pins of the Skilliostrobus type. This is an early Triassic, hanging, bisporangiater pin from Australia and Tasmania. The sporophylls are wedge-shaped and sit in schraubiger arrangement. In an adaxial mine sit verkehrteiförmigen sporangia. The pin is 8 cm in diameter and about half as long. The microspores are monolet, about 40 microns in size and resemble Aratrisporites, the megaspores are trilet and up to 1.1 mm in size and resemble Horstisporites.

The petrified logs from North America described under the name Chinlea probably belong in the near Pleuromeia. The tribe has a siphonostele with external phloem. The parenchyma is thin-walled. The leaf traces are very numerous, there are up to 165 in a cross section, the vascular bundles are collateral.

Ferganodendron is known having a diameter of 20 to 30 cm of strains, which is covered with numerous elliptical to rhombic, spirally arranged blade bases. The leaves are small and sit on the distal portions of the stem. Internal construction or reproductive organs are unknown.

Lycostrobus is a genus that has been established for isolated found, bisporangiate pins. She is known by several Triassic sites. It will be made partly because of the monoleten microspores near the Pleuromeiales. The sporophylls are arranged spirally and bear the sporangia adaxial.

Annalepis was long known only from isolated sporophylls found, now long cones are also known to 10 cm. The sporangia are sitting on the adaxial sporophylls and are laterally at least partially enclosed by the leaf blades of the sporophylls.

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. 316-320.

• Extinct plant
• Bärlapppflanzen
• Lycopodiopsida