Sawdoniales
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| Temporal occurrence | ||||||||||||
| Lower Devonian ( Lochkovian ) to Lower Carboniferous ( Tournaisian ) | ||||||||||||
| 416 to 345 million years | ||||||||||||
| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Sawdoniales | ||||||||||||
The Sawdoniales are a group of extinct plants that are mainly known from the Devonian and belong to the Zosterophyllopsida , relatives of the bear moss plants .
features
Kenrick and Crane give the pseudomonopodial branching (which developed independently of the Euphyllophyten ), which occurs in one plane, as common derived characteristics ( synapomorphies ) . In addition, there is a subordinate branch, where a small stem axis forms at or just below a dichotomous branch that forms a right angle to the level of the main branches. The tips of these side rungs are rolled up (circinat). The vascular bundle that leads into this side branch is cylindrical, in contrast to the otherwise elliptical vascular bundles.
The sporangia sit on richly branched axes of various orders.
Systematics
The Sawdoniales make up the majority of the Zosterophyllopsida, one of the two large groups within the Lycophytes .
Several subgroups can be distinguished within the Sawdoniales. Kenrick and Crane made the following cladogram of the Sawdoniales on the basis of cladistic analyzes:
| Sawdoniales |
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Sawdoniaceae
The Sawdoniaceae are quite a large group and are characterized by showy, multicellular thorns. Some genera, such as Anisophyton and Konioria, have the sporangia on the ventral side of the main axis. Another group with Crenaticaulis and Serrulacaulis carries the thorns in clear rows. The family includes the following genera:
Bathurstia is probably also part of this family.
Barinophytaceae
The Barinophytaceae are characterized by a unique form of heterosporia : they form micro and mega spores in the same sporangium. The sporangia stand in a dense, unbranched cone. They are in two rows in umklammernder ( clasping ) position arranged: a sporangium includes the axle on which it stands. A thickened opening line on the sporangium does not occur in the Barinophytaceae in contrast to the other zosterophylls, the sporangium does not open with two valves either. The opening mechanism is unclear. The family includes two genera:
Gosslingiaceae
This family is characterized by an ear-shaped sporangia position: the sporangia protrude perpendicularly from the axis, with the longitudinal axis of the kidney-shaped sporangium pointing in the longitudinal direction of the axis. The family includes the following genera:
Hsuaceae
The Hsuaceae consist of the only species Hsua robusta .
Temporal spread
The first fossils assigned to the Sawdoniales come from the Lochkovian , which began around 416 million years ago. They achieved the greatest diversity in the Lower Devonian . The latest finds are those of Protobarinophyton from the Tournaisian , the lowest stage of the Carboniferous, which ended 345 million years ago.
supporting documents
- Paul Kenrick, Peter R. Crane: The Origin and Early Diversification of Land Plants. A Cladistic Study . Smithsonian Institution Press, Washington DC 1997. ISBN 1-56098-729-4
Individual evidence
- ↑ Kenrick, Crane: The Origin and Early Diversification of Land Plants. A Cladistic Study , 1997, part of Fig.5.26.
