The araucaria family (Araucariaceae) contains three remarkable genera of cone-bearing trees: Araucaria, Agathis and Wollemia. They are tall trees native to forested regions of South America and Australia. In majestic size and beauty, they certainly rival the coniferous forests of North America and Eurasia. In fact, they are considered the southern counterpart of our northern pine forests. The type genus Araucaria is derived from "Arauco," a region in central Chile where the Araucani Indians live. This is also the land of the "monkey puzzle" tree (A. araucana), so named because the prickly, tangled branches would be difficult for a monkey to climb. Fossil evidence indicates that ancestral araucaria forests resembling the present-day monkey puzzle date back to the age of dinosaurs. In fact, it has been suggested that the tree's armor of daggerlike leaves was designed to discourage enormous South American herbivorous dinosaurs, such as Argentinosaurus weighing an estimated 80 to 100 tons! Another ancient South American species called pino paraná or paraná pine (A. angustifolia) grows in southern Brazil and Argentina.

Australian members of the Araucariaceae include the prickly-leaved bunya-bunya (A. bidwillii) with huge pineapple-shaped cones, the hoop pine (A. cunninghamii) an important Australian timber tree, the Cook pine (A. columnaris) native to New Caledonia, and the Norfolk Island pine (A. heterophylla) native to Norfolk Island. [Both islands are located off the east coast of Australia.] The latter species is commonly grown in containers in southern California and is sold as "star pine" because of its horizontal tiers of radiating limbs. Throughout San Diego County "star pines" can easily be recognized by their tall, slender spires of tiered limbs. This species was discovered by Captain James Cook during his second voyage to Australia and New Zealand (1772-1775). The closely related Cook pine of New Caledonia that is naturalized throughout the Hawaiian Islands is named after this famous English explorer. Like the Norfolk Island pine, the bunya-bunya has an unmistakable silhouette with its barren, horizontal limbs tufted at the ends with spiny leaves. The huge seed cones of tall trees pose a serious threat to unsuspecting persons sitting beneath its cone-laden limbs.

Also in the araucaria family is the genus Agathis with more than a dozen species of large, resinous trees scattered throughout Australia, New Zealand and the Malay Archipelago. Several species of Agathis are the source of timber and valuable copal varnish, including kauri pine (A. australis), amboina pine (A. dammara) and dammar pine or Queensland kauri (A. robusta). Copals are a group of resins that form particularly hard varnishes. In addition to Agathis, there are New World sources of copal from resinous leguminous trees, including the West Indian locust (Hymenaea courbaril) and several species of Copaifera. Dammars are another group of hard, durable varnishes that turn shiny and transparent when dry. Although some species of Agathis are named dammar, most dammar resins come from tropical Asian trees of the genus Shorea in the Diptocarpaceae. Copals and dammars are used extensively in oil paintings. When painting with oils, colored pigment is squeezed onto a palette and then taken up in a thinning solution of linseed oil mixed with either copal or dammar. The resins "hold" the paint when dry and provide the luminous depth characteristic.

In 1994, David Noble discovered an unknown cone-bearing tree in rugged Wollemi National Park northwest of Sydney, Australia. About 40 trees in deep narrow canyon turned out to be an undescribed species. They were named Wollemi pine (Wollemia nobilis), a remarkable new member of the Araucariaceae. This rare conifer was thought to be extinct because its last fossil record was dated at about two million years ago. Choroplast DNA studies show no discernable genetic variation among the 40 trees. Like the rare Torrey pine (Pinus torreyana) of San Diego County, this is truly a relict population that was more widespread millions of years ago. Because of its small population size, a lot of its genetic diversity has been lost through thousands of years of isolation. The Wollemi pine is a great botanical discovery and is truly a "living fossil." Trees are being propagated from seeds, and who knows, maybe some day this tree will be cultivated in San Diego County like other living fossils such as the maidenhair tree (Ginkgo biloba) and dawn redwood (Metasequoia glyptostroboides).

Although they are often referred to as pines, members of the araucaria family have seed cones and foliage that is very different from the pine family (Pinaceae). Conifers in the pine family have cone scales with a pair of ovules (seeds) on the upper surface. Each cone scale is subtended by a distinct bract which is conspicuously exerted in some California species, such as the Douglas fir (Pseudotsuga menziesii) and Santa Lucia fir (Abies bracteata). Members of the araucaria family have only one ovule per scale and have bracts that are fused to the scale or none. Unlike the long, slender needles of pines (Pinus), araucarian leaves are typically short, overlapping and often prickly. Some species have broad leaves that superficially resemble leaves of flowering plants. In their native habitats, the araucarias become tall timber trees up to 200 ft. (61 m).

Fossil evidence indicates that the araucaria family reached its maximum diversity during the Jurassic and Cretaceous periods between 200 and 65 million years ago, with worldwide distributions. At the end of the Cretaceous, when dinosaurs became extinct, so did the Araucariaceae in the northern hemisphere. Until the middle of the Tertiary Period (135 million years ago), trees of the Araucariaceae grew in forests of the southern supercontinent called Gondwanaland, when South America and Africa were connected with each other and with Anarctica, India and Australia. By 65 million years ago, the continents had divided into positions resembling their present-day configuration. During this time interval, araucariads began a slow decline in range and diversity as flowering plants, better adapted to climatic changes, began to evolve and gradually displace conifers.

In 1915 Alfred Wegener, a German climatologist and geophysicist, published an expanded version of his 1912 book The Origin of Continents and Oceans. This novel hypothesis, which has now been confirmed by other scientists, states that continents are not fixed; instead, their relative positions and the positions of the oceans have changed over time. Wegener's hypothesis led to the science of plate tectonics, where scientists study the gradual movement of large plates of the earth's crust along major fault zones. About 200 million years ago, the continents were joined into one supercontinent that Wegener called Pangea (Figure A). By 135 million years ago, Pangea had divided into two large subcontinents called Gondwanaland and Laurasia (Figure B). In the great southern subcontinent Gondwanaland, South America and Africa were connected with each other and with Antarctica, India, and Australia. This is roughly the time when the first flowering plants began to appear on earth. By 65 million years ago, about the time when dinosaurs became extinct, the continents had divided into positions resembling the present-day configuration (Figure C). As of April 2000, the continents resembled the configuration shown in Figure D.

Petrified Forest National Park in northeastern Arizona contains hundreds of acres of perfectly preserved logs from an ancient conifer forest that dates back to the late Triassic Period (approximately 225 million years ago). The trees of this forest coexisted with dinosaurs. Most of the petrified logs were previously assigned to the extinct species Araucarioxylon arizonicum, a presumed distant relative of Araucaria; however, new evidence indicates that these fascinating deposits of petrified logs represent a broad diversity of conifer species. Streams carried dead logs into this once swampy lowland region where they were buried in sediments rich in volcanic ash. Over countless centuries, the woody tissue has been replaced by minerals and gradually turned into stone. These ancient trees flourished during a time when all of the continents were united into the vast supercontinent Pangea. The area of Petrified National Park was located near the equator, at approximately the latitude of present-day Central America. Many of the reddish, agatized logs do not show cellular detail; however, there are some permineralized specimens in which minerals permeated the porous cell walls and filled the cell cavities (lumens). Thin sections of these samples viewed under a microscope show remarkable cellular detail.

Although the binomial Araucarioxylon arizonicum has been used in the literature for more than a century, Rodney A. Savidge of the University of New Brunswick (Bulletin of Geosciences Vol. 82 No. 4: 301-328, 2007) states that it is superfluous and therefore an illegitimate name (nomen superfluum). He examined thin sections of the original three specimens (syntypes) housed at the Smithsonian Institute upon which the species was first described by F.H. Knowlton in 1889. He concluded that they represented different species within two new genera of extinct trees. According to the International Code of Botanical Nomenclature, a valid species can have only one type specimen or holotype. Consequently, only one of the three specimens was retained as the new type or lectotype Pullisilvaxylon arizonicum. Savidge examined several other logs previously identified as A. arizonicum and concluded that they also represented additional new genera and species. His extensive anatomical studies indicate that the majority of logs at Petrified Forest National Park do not belong to a single species. It appears that the superfluous name "A. arizonicum" actually refers to a complex of extinct conifers. Based solely on the tracheid structure of permineralized wood (including resin canals, rays and tracheid pitting), and without DNA evidence, it is difficult to be certain which trees in the complex are ancestral relatives of the araucaria family. According to Dr. Savidge (personal communication, 2008), an immense amount of research into petrified woods is needed before the ancestries leading to modern trees will be clearly understood. At this time it would be purely conjectural to assign a scientific name to most logs in Petrified Forest National Park without detailed microscopic examination of the wood.

Trees of "Araucarioxylon arizonicum" grew to a height 200 feet (61 m) with a trunk diameter from 4 to 9 feet. According to Sidney R. Ash and Geoffrey T. Creber (Paleontology Vol. 43 No. 1: 15-28, 2003), the living tree did not closely resemble any of the present-day Araucaria trees of the southern hemisphere as postulated in past reconstructions. The branches did not occur in whorls as they do in most conifers, instead they grew irregularly along the trunk. Sydney Ash and Rodney Savidge also studied the bark anatomy of Araucarioxylon arizonicum ("The Bark of Late Triassic Araucarioxylon arizonicum from Petrified Forest National Park, Arizona," IAWA Journal 25 No. 3: 349-368, 2004), and concluded that it was quite unlike the banded bark of extant Araucaria heterophylla. These ancient conifers grew in a tropical rain forest with marshes and river lakes, in an environment very different from today's Arizona landscape.

Trees of the "Araucarioxylon arizonicum" grew to a height 200 feet (61 m) with a trunk diameter from 4 to 9 feet. According to Sidney R. Ash and Geoffrey T. Creber (Paleontology Vol. 43 No. 1: 15-28, 2003), the living tree did not closely resemble any of the present-day Araucaria trees of the southern hemisphere as postulated in past reconstructions. These ancient conifers grew in a tropical region with marshes and river lakes, an environment very different from today's Arizona landscape.