Arizona: Araucarioxylon arizonicum (state fossil)
Arizona: Araucarioxylon arizonicum (state fossil)
The state fossil of Arizona is both world-famous and immensely popular with collectors. It is the type of petrified wood called Araucarioxylon arizonicum. It was given this name because the structure of the wood resembles that of the modern araucarias (Norfolk Island Pine and Monkey Puzzle Tree), although how closely related to them it may be is an open question.
This wood is the petrified remains of large trees that grew in Arizona during the Triassic Period, about 220 million years ago. The most famous of these deposits, the Chinle Formation, produces the beautiful agatized logs which are preserved at Petrified Forest National Park. The area was a lowland, sometimes dry basin which received abundant runoff and sediment from mountains to the south during the monsoons and volcanic eruptions. These conditions led to the burial of millions of trees, which over time, turned to stone.
Stone logs were first reported during early surveys of the area after the Civil War. Logs were sent to the Smithsonian and word of the "petrified forests" spread. Soon collecting endangered the area, and in 1906 the area was protected as a National Monument to preserve the fossil trees for future generations.
Because of this immense popularity with scientists, collectors, and tourists alike, Araucarioxylon arizonicum was designated the Arizona state fossil in 1988.
For further information:
Petrified Forest National Park
Field Adventures in Paleontology - Petrified Forest