Zosterophyllopsida

The Zosterophyllophyta are a group of extinct plants, which were common in the Devonian. They occupy an intermediate position between the basal vascular plants, the Rhyniophyta, and the Bärlapppflanzen.

  • 4.1 Notes and references

Features

Most representatives are dichotomously ( dichotomous ) branches. Some species also show pseudomonopodiale branching. The vascular tissue in the axis forms a protostele. It is always exarch, that is, located on the outside and the protoxylem stele matures from the outside inwards. The shape of the Xylemstrangs often elliptical in cross -section.

The main distinguishing feature to the other primitive vascular plants is the position of the sporangia: they are laterally along the stem axis or attached by a short branch side of the stem axis. In many species the sporangia sit huddled together at the terminal regions of the axes. The shape of the sporangia ranging from spherical to kidney-shaped. The opening is usually carried out along the distal side by the sporangium springs open into two halves. Zosterophyllum deciduum seems to have dropped the sporangia at maturity. The Zosterophyllophyta were probably homospor, even if the size of the spores can vary greatly. In Barinophyton and Pseudobarinophyton a sporangium contains large and small spores.

System

The Zosterophyllophyta were prepared by Harlan P. Banks, when he realized that the Psilophyten are an extremely heterogeneous group. The distribution of Psilophyten he formed the Zosterophyllophyta, 1992 were as follows as:

  • Zosterophllophytina Zosterophyllaceae "Terminal standing sporangia " Zosterophyllum
  • Rebuchia ( = Bucheria )
  • Gumuia
  • Sawdonia
  • Gosslingia
  • Crenaticaulis
  • Bathurstia
  • Serrulacaulis
  • Oricilla
  • Konioria
  • Margophyton
  • Tarella
  • Anisophyton
  • Thrinkophyton
  • Discalis
  • Deheubarthia
  • Barinophytales Barinophytaceae Barinophyton
  • Pectinophyton
  • Protobarinophyton
  • Barinostrobus
  • Hsua
  • Nothia
  • Hicklingia
  • Huia

Kenrick and Crane presented due kladistischer analyzes following cladogram of basal branches leading to the lycophytes clade on:

Anisophyton

Konioria

Crenaticaulis

Serrulacaulis

Deheubarthia

Sawdonia

Thrinkophyton

Barinophyton citrulliforme

Barinophyton obscurum

Protobarinophyton

Hsua

Gosslingia

Oricilla

Tarella

Zosterophyllum divaricatum

Zosterophyllum fertile

Zosterophyllum llanoveranum

Rebuchia

Discalis

Zosterophyllum deciduum

Huperzia

Asteroxylon

Baragwanathia

Drepanophycus

Nothia

Adoketophyton

Zosterophyllum myrtonianum

Gumuia

Huia

Hicklingia

According to these results the Zosterophyllophyta paraphyletisch are in relation to the Bärlapppflanzen ( Lycopodiopsida ). Kenrick and Crane have therefore restricted the definition of Zosterophyllophyta and this indicated also by the change of name to Zosterophyllopsida.

Zosterophyllopsida

The Zosterophyllopsida are those of Kenrick and Crane newly defined group of extinct plants bärlappartiger, which was represented mainly in Devon. The growth takes place with rolled ( circinaten ) shoot tips, similar as occurs in ferns. The sporangia are arranged in two rows on the side of the stem axis. The xylem in the vascular bundles axis is elliptical in cross-section, but this might apply also to the more basal representative of the lycophytes.

The Zosterophyllopsida include the diverse group of Dawsoniales as well as some types of Zosterophyllum and possibly also Rebuchia and Discalis.

The majority of the species are the Sawdoniales. Basal representatives of Zosterophyllopsida that are not included among the Dawsoniales are Rebuchia, Discalis and Zosterophyllum divaricatum, Zosterophyllum fertile and Zosterophyllum llanoveranum.

Temporal distribution

The first clear the Zosterophyllophyta identifiable fossils ( Zosterophyllum, Drepanophycus ) come from the Lochkovian, which began about 416 million years. The dating of some findings in the upper Silurian ( Ludlow ) graptolites based on is not generally accepted. The highest diversity they reached in the early Devonian.

The latest findings are those of Protobarinophyton from the Tournaisian, the lowest level of the carbon, which ended 345 million years ago.

Documents

  • Paul Kenrick, Peter R. Crane: The Origin and Early Diversification of Land Plants. A Cladistic Study. Smithsonian Institution Press, Washington, D.C. 1997, ISBN 1-56098-729-4
  • Thomas N. Taylor, Edith L. Taylor: The Biology and Evolution of Fossil Plants. Prentice Hall, Englewood Cliffs 1993, pp. 203-216, ISBN 0-13-651589-4
Mya (unit) Archaeplastida Viridiplantae Charophyta Stele (biology)
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