undifferentiated rock units

Paleontology and geology

Extensive lowlands dominated the Arizona landscape during the Triassic Period. Forests with giant trees provided a variety of habitats for both plants and animals. Large, armored reptiles, such as Desmatosuchus, browsed the vegetation, and early dinosaurs left their bones and tracks in the Triassic sediments. Remnants of the giant conifers from this time can now be seen as fossil logs weathering out of the sedimentary rocks in Petrified Forest National Park.