Agathoxylon


Agathoxylon is a form genus of fossil wood, including massive tree trunks. Although identified from the late Palaeozoic to the end of the Mesozoic, Agathoxylon is common from the Carboniferous to Triassic. Agathoxylon represents the wood of multiple conifer groups, including both Araucariaceae and Cheirolepidiaceae, with late Paleozoic and Triassic forms possibly representing other conifers or other seed plant groups like "pteridosperms".

Description

Agathoxylon were large trees that bore long strap-like leaves and trunks with small, narrow rays. Often the original cellular structure is preserved as a result of silica in solution in the ground water becoming deposited within the wood cells. This mode of fossilization is termed permineralization.

Systematics

As a genus, Dadoxylon was poorly defined, and apart from Araucariaceae, has been associated with fossil wood as diverse as Cordaitales, Glossopteridales and Podocarpaceae. Furthermore, it may be the same form genus as Araucarioxylon, hence the usage Dadoxylon. The genus Agathoxylon, classified under the family Araucariaceae, has nomenclatural priority over the genera Araucarioxylon and Dadoxylon.
Several Dadoxylon species, such as D. brandlingii and D. saxonicum have been identified as Araucarites. D. arberi and D. sp.1 were synonymised with the glossopterid species Australoxylon teixterae and A. natalense, respectively; while D. sp. 2 was transferred to Protophyllocladoxylon.

Species

Agathoxylon is common in many parts of the world, found in sites of both Gondwana and Laurasia and reported from southern Africa, Asia, the Middle East, Europe, South America, and North America.
In southern Africa, Agathoxylon is widespread in the Karoo Supergroup. In Zimbabwe, it is especially encountered in the Pebbly Arkose Formation, and also reported frequently from the Angwa Sandstone Formation.