Sawdoniales

Sawdonia ornata

The Sawdoniales are a group of extinct plants that are known mainly from the Devonian and the Zosterophyllopsida, relatives of Bärlapppflanzen belong.

  • 4.1 Notes and references

Features

As common features derived ( synapomorphies ) give Kenrick and Crane pseudomonopodiale the branch at ( which has developed independently of the Euphyllophyten ), which takes place in a plane. In addition, there is a subordinate branch, in which a small shoot axis is at or just below a dichotomous branching that forms a right angle to the main branch level. The tips of these side shoots are rolled ( circinat ). The vascular bundles, which results in these side branch, cylindrical, in contrast to the otherwise elliptical vascular bundles.

The sporangia are sitting on rich branched axes of different order.

System

The Sawdoniales represent the majority of the Zosterophyllopsida, one of two major groups within the lycophytes.

Within the Sawdoniales several subgroups can be distinguished. Kenrick and Crane presented due kladistischer analyzes following cladogram of Sawdoniales on:

Anisophyton

Konioria

Crenaticaulis

Serrulacaulis

Deheubarthia

Sawdonia

Thrinkophyton

Barinophyton citrulliforme

Barinophyton obscurum

Protobarinophyton

Hsua

Gosslingia

Oricilla

Tarella

Sawdoniaceae

The Sawdoniaceae are a fairly large group and characterized by distinctive, multicellular spines. Some genera, such as Anisophyton and Konioria bear the sporangia on the ventral side of the main axis. Another group with Crenaticaulis and Serrulacaulis wearing the thorns in distinct rows. The family includes the following genera:

  • Anisophyton
  • Konioria
  • Crenaticaulis
  • Serrulacaulis
  • Deheubarthia
  • Sawdonia

Probably Bathurstia is to provide in this family.

Barinophytaceae

The Barinophytaceae are characterized by a unique form of heterospory: they form micro-and megaspores in the same sporangium. The sporangia are in a dense, unbranched pins. They are arranged in two rows in an embracing ( clasping ) position: a sporangium contains the pin on which it stands. A bulbous opening line on the sporangium does not occur in the Barinophytaceae unlike the other Zosterphylls, the sporangium also does not open with two flaps. The opening mechanism is unclear. The family includes two genera:

  • Barinophyton
  • Protobarinophyton

Gosslingiaceae

This family is characterized by an ear-shaped Sporangienstellung The sporangia are perpendicular from the axis, wherein the longitudinal axis of the kidney-shaped sporangium shows in longitudinal direction of the axis. The family includes the following genera:

  • Gosslingia
  • Tarella
  • Oricilla

Hsuaceae

The Hsuaceae consist of a single type Hsua robusta.

Temporal distribution

The first Sawdoniales the associated fossils date from the Lochkovian, which began about 416 million years. The highest diversity they reached in the Lower 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. In 1997. ISBN 1-56098-729-4
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