- Araucarioxylon arizonicum
name = "Araucarioxylon arizonicum"
image_width = 240px
image_caption = Petrified "Araucarioxylon arizonicum"
classis = Pinopsida
genus = "
species = "A. arizonicum"
binomial = "Araucarioxylon arizonicum"
binomial_authority = Knowlton
"Araucarioxylon arizonicum" is an extinct
coniferthat is the state fossilof Arizona.
Triassicperiod, the Araucarioxylon tree grew in what today's Black Forest, a part of the 378.51 km² (93,492 acre) Petrified Forest National Parkin eastern Arizona. Prehistoric Arizona was a flat tropical expanse in the northwest corner of the supercontinent Pangaea.
The trees towered as high as 60 m (200 ft) and measured more than 60 cm (2 ft) in diameter. Fossils frequently show boreholes of
insects, as well as fossilized hives of prehistoric bees.
The genus "Araucarioxylon" is regarded by some paleobotanists as synonymous with the modern genus "
Araucaria", though this view is not universal.
petrified woodof this tree is frequently referred to as "Rainbow wood" because of the large variety of colors some specimens exhibit. The red and yellow are produced by large particulate forms of iron oxide, the yellow being limoniteand the red being hematite. The purple hue comes from extremely fine spherules of hematite distributed throughout the quartzmatrix, and not from manganese, as has sometimes been suggested.
* F. H. Knowlton, New species of fossil wood ("Araucarioxylon arizonicum") from Arizona and New Mexico, "Proceedings of the United States National Museum", 1889.
* [http://www.smithsonianmag.com/science-nature/object_june97.html Smithsonian Magazine article on "A. arizonicum"]
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