The petrified wood of the famous Petrified Forest east of Holbrook, Arizona are fossil Araucariaceae. During the Upper (Late) Triassic the region was moist and mild. The trees washed from where they grew in seasonal flooding and accumulated on sandy delta mudflats, where they were buried by silt and periodically by layers of volcanic ash which mineralized the wood. The fossil trees belong generally to three species of Araucariaceae, the most common of them being Araucarioxylon arizonicum. Some of the segements of trunk represent giant trees that are estimated to have been over 50 meters tall when they were alive.
There are relatively few genera alive today, widely distributed but confined to the southern hemisphere, relicts of a group that formerly existed almost worldwide
Genera include the following: