Thucydiaceae
| Thucydiaceae | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Temporal occurrence | ||||||||||||
| Late Pennsylvania | ||||||||||||
| 318.1 to 299 million years | ||||||||||||
| Locations | ||||||||||||
| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Thucydiaceae | ||||||||||||
| Hernandez-Castillo , GW Rothwell & Mapes |
The Thucydiaceae are an extinct family of conifers from the order of the Voltziales . The only known species is Thucydia mahoningensis .
features
Thucydia mahoningensis was a small tree with an upright trunk and plagiotropic branches. On these are two rows of branches in a regular, feathery arrangement.
The trunk is an endarche ( protoxylem lies inside) Eustele . The wood is dense. A periderm is formed on the branches of all degrees of branching . The marrow is parenchymatic and contains epithelial-covered resin ducts.
The leaves vary in size depending on the branch, but are simple and in a spiral arrangement.
Ovules -carrying fertile zones are made between vegetative zones along the strains. They consist of compact bracts , each of which has an axillary short shoot . This in turn consists of 10 to 15 sterile scales and three to four fertile scales. The latter, the sporophylls , have a backward curved tip and carry a single ovule.
The male pollen cone is remarkable in that it is a compound cone here. A cone consists of small, screw-like, leaf-like bracts with short rungs in their axils. These again consist of sterile and fertile scales, the latter carry pollen sacs . This organization is unique among the Coniferopsida and is reminiscent of that of the Cordaitales and the recent Gnetales . The pollen cones are at the end of the branches. The pollen is of the Potonieisporites type.
Leaves have different distributions of the stomata : in bracts and sterile scales the stomata are evenly distributed on the underside, on vegetative leaves they are in two abaxial rows.
Systematics
The Thucydiaceae family was first described in 2001 based on the new genus Thucydia and the new species Thucydia mahoningensis . The generic name honors the Greek historian Thucydides . The family was placed in the Voltziales order by the first authors .
Aljos Farjon sees the Thucydiaceae as a very basal sideline of the Voltziales. Only the Ferugliocladaceae are still more basal. The Thucydiaceae would therefore be the sister group of all conifers and Voltziales with the exception of the Ferugliocladaceae.
supporting documents
- Thomas N. Taylor, Edith L. Taylor, Michael Krings: Paleobotany. The Biology and Evolution of Fossil Plants . Second Edition, Academic Press 2009, pp. 814f., ISBN 978-0-12-373972-8
- Genaro R. Hernandez-Castillo, Gar W. Rothwell, Gene Mapes: Thucydiaceae fam. nov., with a review and reevaluation of paleozoic Walchian conifers . International Journal of Plant Science, Vol. 162, 2001, pp. 1155-1185.
Individual evidence
- ^ Aljos Farjon: A Natural History of Conifers . Timber Press, Portland 2008, ISBN 978-0-88192-869-3 , p. 69.