User:Una Smith/Araucarioxylon

Araucarioxylon is a genus of fossil wood, including massive tree trunks. First occurring in the Triassic, the genus is widely believed to be related to modern Araucariaceae. The genus has been used as a form taxon.

Because the genus is known only from its wood, Araucarioxylon is an organ taxon. Some authors have suggested that Araucarioxylon wood, Brachyphyllum leaves, and Protodammara cones may belong to the same species.

Distribution
In North America, Araucarioxylon has been reported from the Triassic to the lower Cretaceous. In the eastern United States, several species occur in Connecticut, New York, Pennsylvania, Virginia, and North Carolina. In the central and western United States, A. hoppertonae occurs in South Dakota and A. arizonicum occurs in Arizona and New Mexico. In Arizona, Petrified Forest National Park is famous for the enormous trunks of A. arizonicum that in some areas litter the ground.

The genus has also been reported from the Permian of Silesia and the Jurassic (A. wurtemburgiacum).

Systematics
Some species at one time assigned to Araucarioxylon have been removed to Cordaites, Dadoxylon, Calamopitys, and Pitys.

Species that Knowlton removed from Araucarioxylon to Cordaites include A. ouangondianus from the Devonian of Canada, A. brandlingii from western Europe, A. medullosum from the Permian of Germany, and A. acadianum from England.

Knowlton, and Felix before him, points out that leaves and cones of the Araucarian type first appear in the Mesozoic. Knowlton uses the absence of such leaves and cones from the Paleozoic as a reason to exclude Paleozoic non-Cordaites fossil woods from Araucarioxylon. Thus, Paleozoic species of Araucarioxylon that Knowlton did not remove to Cordaites he removed instead to Dadoxylon. Dadoxylon is a form taxon. Species that Knowlton thus removed from Araucarioxylon to Dadoxylon include A. beinertianum, A. buchianum, A. angustum, and A. aegyptiacum. Conversely, Knowlton removed all Mesozoic species of non-Cordaites fossil woods from Dadoxylon to Araucarioxylon.

Scotland's largest fossil, a trunk nearly 4 feet in diameter, was originally named Araucarioxylon withami; it was removed from Araucarioxylon to Pitys.

Jeffrey reviewed the affinities of Mesozoic Araucarioxylon to woods of modern plants, finding only two genera with similar wood anatomy: Araucaria and Agathis. At the time, 1912, these were the only known extant genera of Araucariaceae; Wollemia was discovered in 1994. The most notable similarities between Araucarioxylon and modern Araucariaceae are that the tracheids have pits (see Xylem) in multiple rows, and the rows are alternating rather than opposite. However, the pits are closely packed and angular in the modern plants but less closely packed and round in Araucarioxylon.

A. telentangensis occurs in Malaysia. Because the holotype specimen was found out of its stratigraphic context, in a boulder that could have come from the Jasin volcanics or the Tebak Formation, its age can only be estimated to be from the Upper Permian to the Lower Cretaceous.

Species
Species currently classified under the genus Araucarioxylon are the following:


 * Araucarioxylon arizonicum Knowlton 1889
 * Araucarioxylon cupreum Kraus
 * Araucarioxylon edvardianum (Dawson) Knowlton, 1890
 * Araucarioxylon hoppertonae Knowlton 1899
 * Araucarioxylon keuperianum Kraus
 * Araucarioxylon noveboracense Hollick and Jeffrey 1909
 * Araucarioxylon prosseri Penhallow 1900
 * Araucarioxylon stigmolithos Kraus
 * Araucarioxylon telentangensis Idris 1989
 * Araucarioxylon valdajolense Kraus
 * Araucarioxylon vanartsdaleni Wherry 1912
 * Araucarioxylon virginianum Knowlton 1889
 * Araucarioxylon withami Lindley and Hutton
 * Araucarioxylon woodworthi Knowlton 1899
 * Araucarioxylon wurtemburgiacum Göppert