Trimerophytopsida

The Trimerophytophyta are a group of extinct vascular plants, especially from the early Devonian, which are in their characteristics between the Rhyniophyta and the extant ferns and seed plants.

Features

The Trimerophyten are generally more complex than the Rhyniophyta or Zosterophyllophyta. The axes branch monopodial or pseudomonopodial. The side branches ramify dichotomously or trident. From the three-pronged junction where the name comes from. The axes are smooth, dotted, or prickly. The xylem strands are clearly pronounced, the protoxylem lies inside ( endarch ). The tracheids are head - tracheids or they possess bordered pits.

The sporangia are terminal on the axles, mostly they are focused on rich branched side branches. Some species have few sporangia, others have a lot of small.

System

The Trimerophytophyta were erected in 1968 by Harlan P. Banks as one of the three groups, when he dissolved the diverse and polyphyletic group of Psilophyten. The Trimerophytophyta are one of the three basal groups of vascular plants. Banks made ​​the following genera to the subdivision Trimerophytophytina:

• Trimerophytales Trimerophytaceae Psilophyton
• Trimerophyton
• Pertica
• Dawsonites
• Hostinella
• Yunia (assignment just as likely )

• Oocampsa
• Gothanophyton
• Tursuidea

Taylor and Taylor 1993 took the last three genera not in their discussion of the Trimerophytophyta now levied for the department.

Cladistic analyzes showed, however, that the Trimerophyten sensu Banks or sensu Taylor and Tayler, 1993 no natural affinity group. Pertica is the seed plants quite close, even though many of its features are difficult to interpret; the rest is paraphyletisch with respect to the non- vascular plants bärlappartigen.

Kenrick and Crane, therefore, no longer recognize the Trimerophyten as taxon. The hitherto not asked to Trimerophyten Eophyllophyton bellum is close to the other Trimerophyten, but they turn the previous Trimerophyte Yunia dichotoma to Bärlapppflanzen.

The Trimerophyten are generally regarded as descendants of the Rhyniophyta. You yourself are at the base of Euphyllophyta, the group to which the ferns and seed plants belong.

Temporal distribution

Most finds of Trimerophyten date from the early Devonian ( Pragian ). This era began 417 million years ago. Pertica, which actually does not belong to this stage of development, goes back to the middle Devonian ( Givetian ), which lasted until 385 million years. Perhaps some finds are also classified into the Lower Carboniferous ( Mississippian ).

Documents

• Paul Kenrick, Peter R. Crane: The Origin and Early Diversification of Land Plants. A Cladistic Study. Smithsonian Institution Press, Washington, D.C. 1997, especially pp. 140, 319F. ISBN 1-56098-729-4
• Thomas N. Taylor, Edith L. Taylor: The Biology and Evolution of Fossil Plants. Prentice Hall, Englewood Cliffs, 1993, pp. 191-203. ISBN 0-13-651589-4