A. mirabilis are known from large amounts of very well preserved silicified wood and cones from the Cerro Cuadrado Petrified Forest, including tree trunks that reached 100 m (330 ft) in height in life.

Fossils of Araucaria mirabilis are found in great abundance in the Cerro Cuadrado Petrified Forest of Patagonia, Argentina.

[2] However, the Italian-Argentinean botanist Carlo Luigi Spegazzini had also acquired specimens from the petrified forest from various sources.

[2] An American paleontological expedition led by Elmer S. Riggs (1923–1924) of the Field Museum of Natural History also discovered the petrified forests.

Wieland and Gothan interpreted the absence of separate petrified seeds as evidence that the cones did not shed their scales at the final growth year.

The latter is a form genus, usually used for incomplete plant fossil specimens that resemble Araucaria but lack enough preserved details for more accurate classifications.

[8] The genus name Araucaria is derived from the Spanish exonym Araucanos ("from Arauco"), referring to the Mapuche people of Chile and Argentina.

[12] In addition, no reliably identifiable fossils of members of the section Bunya have been recovered from Australia, the native range of A.

[15] Setoguchi et al. (1998) have recommended that the extinct members of the section Bunya (which includes Araucaria sphaerocarpa of the United Kingdom) be treated as a separate group.

[2] The fossils of the putative bracket fungus Phellinites digiustoi are also found in the Cerro Cuadrado Petrified Forest.

[17] It is believed that the long necks of sauropod dinosaurs may have evolved specifically for browsing the foliage of the typically very tall A. mirabilis and other Araucaria trees.

This and the global distribution of vast forests of Araucaria makes it likely that they were the primary food sources for adult sauropods during the Jurassic.

Juveniles, however, which lacked the bulk of the adults and required larger amounts of proteins for growth, probably subsisted on other plants.

[21] Araucaria forests were distributed globally and formed a major part of the woody flora of the Mesozoic era.

[19] The Cerro Cuadrado Petrified Forest is part of the La Matilde Formation, dated to the Bathonian to Oxfordian ages (164.7 to 155.7 million years ago) of the Middle to Upper Jurassic.

[3][4] The area was once part of the subtropical and temperate regions of the southern supercontinent Gondwana in the Mesozoic era, a more or less continuous landmass consisting of what is now modern South America, Africa, Antarctica, India, Australia, New Zealand, and New Guinea.