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Araucariaceae – also known as araucarians – is an extremely ancient family of coniferous trees. The family achieved its maximum diversity during the Jurassic and Cretaceous periods, when it was distributed almost worldwide. Most of the Araucariaceae in the Northern Hemisphere vanished in the Cretaceous–Paleogene extinction event, and they are now largely confined to the Southern Hemisphere, except for a few species of Agathis in Malesia.
The trunks are columnar and have relatively large with cortices. The branching is usually horizontal and tiered, arising regularly in whorls of three to seven branches or alternating in widely separated pairs.
The leaves can be small, needle-like, and curved, or they can be large, broadly ovate, and flattened. They are spirally arranged, persistent, and usually have parallel venation.
Like other conifers, they produce Conifer cone. Each tree can have both male and female cones (monoecious) or they can have only male or female cones (dioecious).
Male cones are among the largest among all conifer cones, on average. They are cylindrical and drooping, somewhat resembling . They are borne singly on the tips of branches or the of leaves. They contain numerous arranged in whorls or spirals. Each has four to 20 elongated pollen sacs attached to the lower surface at one end. The pollen grains are round and do not possess wings or air sacs.
Female cones are also very large. They are spherical to ovoid in shape and borne erect on thick, short shoots at branch tips. The numerous bracts and scales are either fused to each other or separate for half of their lengths. The scales almost always bear only one seed on its upper surface, in contrast to two in true pines (family Pinaceae). They are very large, among the largest seeds among conifers. They are dispersed by wind, usually using wing-like structures. On maturity, the female cones detach and fall to the ground. Due to their size, they can cause serious injuries if they hit a person. The cones of the bunya bunya, Araucaria bidwillii, for example, weigh up to , about the size and weight of a large pineapple. They can drop from heights of .
| Araucaria Jussieu |
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| Agathis Salisbury |
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| Wollemia W.G. Jones, K.D. Hill & J.M. Allen | endemic to Australia. It was known only from fossil remains before the discovery of the living species in 1994. | |
Relationships between living members of Araucariaceae.
Molecular evidence supports Araucariaceae and Podocarpaceae having diverged from each other during the late Permian.
By far the greatest diversity is in New Caledonia (18 species), with others in Australia, Argentina, New Zealand, Chile, southern Brazil, and Malesia. In Malesia, Agathis extends a short distance into the Northern Hemisphere, reaching 18°N in the Philippines.
Skillful artisans in the Erzurum Province, Turkey, have used fossilized wood of Araucariaceae for centuries to manufacture jewelry and decorative items. It is known as "Oltu stone", the name deriving from the town of Oltu, where it is most commonly excavated. Despite the fact that this semiprecious gemstone is classified as “stone”, wood anatomy reveals it was fossilized pieces of trunks of Araucariacea. Oltustone, also called ‘Black Amber’ is unique to Turkey. It is dull and black, but when polished, acquires an attractive black sheen.
The oldest definitive records of Araucariaceae are from the Early Jurassic, though there are potential earlier Late Triassic records. Early representatives of Araucaria are widespread across both hemispheres by the Middle Jurassic, such as Araucaria mirabilis and Araucaria sphaerocarpa from the Middle Jurassic of Argentina and England respectively. The oldest records of the Wollemia- Agathis lineage from the Cretaceous, including Emwadea from the Albian aged Winton Formation of Australia and Wairarapaia from the Albian-Cenomanian of New Zealand. The oldest fossils currently confidently assignable to Agathis are those of Agathis immortalis from the Salamanca Formation of Patagonia, which dates to the Paleocene, approximately 64.67–63.49 million years ago. Agathis-like leaves are also known from the slightly older Lefipán Formation of the same region, which date to the very end of the Cretaceous.
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