Araucariaceae

Araucarians Temporal range: Jurassic to present PreЄ Є O S D C P T J K Pg N
Araucaria araucana in South America
Scientific classification
Kingdom:	Plantae
Division:	Pinophyta
Class:	Pinopsida
Order:	Pinales
Family:	Araucariaceae Henkel & W. Hochstetter
Type genus
Araucaria Juss.
Genera
Agathis Araucaria Wollemia †Araucarioxylon †Araucarites †Brachyphyllum †Protodammara

Araucariaceae, commonly referred to as araucarians, is a very ancient family of coniferous trees. It achieved its maximum diversity in the Jurassic and Cretaceous periods, when it was distributed almost worldwide. At the end of the Cretaceous, when dinosaurs became extinct, so too did the Araucariaceae in the northern hemisphere.

Description

Tāne Mahuta ("The Lord of the Forest"), a massive Agathis australis tree from New Zealand

Members of Auracariaceae are typically very tall evergreen trees,^[1] reaching heights of 60 m (200 ft) or more.^[2] They can also grow very large. A New Zealand kauri tree (Agathis australis) named Tāne Mahuta ("The Lord of the Forest") has been measured at 45.2 m (148 ft) tall with a diameter at breast height of 491 cm (16.11 ft). Its total wood volume is calculated to be 516.7 m³ (18,250 cu ft),^[3] making it the third largest conifer after Sequoia and Sequoiadendron (both from the family Cupressaceae).^[1]

The trunks are columnar and have relatively large piths with a resinous cortex.^[4] The branching is usually horizontal and tiered, arising regularly in whorls of three to seven branches or alternating in widely separated pairs.^[5]

The leaves can be small, needle-like, and curved or they can be large, broadly ovate, and flattened.^[6] They are spirally arranged, persistent, and usually have parallel venation.^[1]

Each tree can have both male and female gametes (monoecious) or they can be male or female, but not both (dioecious).^[7] Like other conifers, they produce cones.

Male cones are among the largest among all conifer cones, on average. They are cylindrical and drooping somewhat (resembling catkins). They are borne singly on the tips of branches or the axils of leaves. They contain numerous sporophylls arranged in whorls or spirals. Each has four to twenty elongated pollen sacs attached to the lower surface at one end. The pollen grains are round and do not possess wings or air sacs.^[1][5][6]

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.^[1][5][6] The scales almost always bear only one seed on its upper surface, in contrast to two in true pines (family Pinaceae).^[8] 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.^[1][5][6] 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 10 to 15 lb (4.5 to 6.8 kg), about the size and weight of a large pineapple. They can drop from heights of 23 m (75 ft).^[8]

Classification and genera

Araucaria heterophylla

Agathis robusta

Wollemia nobilis

Araucariaceae is classified under the order Pinales, class Pinopsida of the division Pinophyta. The division includes all living conifers. Recently however, some authorities treat Araucariaceae as a separate order, Araucariales.^[1]

Araucariaceae contains three extant genera and about 41 species.^[4]

• Araucaria Jussieu

Contains 19 living species. Found in New Caledonia (where 13 species are endemic), Norfolk Island, Australia, New Guinea, Argentina, Chile, and southern Brazil.

• Agathis Salisbury

Contains 21 living species. Found in Australia, Vanuatu, New Caledonia, Papua New Guinea, Indonesia, Malaysia, and the Philippines

• Wollemia W.G. Jones, K.D. Hill & J.M. Allen

Contains only one living species endemic to Australia. It was known only from fossil remains before the discovery of the living species in 1994.

Phylogeny

Below is the phylogeny of the Pinophyta based on cladistic analysis of molecular data. It shows the position of Araucariaceae within the division.^[9]

Distribution and habitat

Today 41 species are known, in three genera: Agathis, Araucaria and Wollemia. All are derived from the Antarctic flora^{[citation needed]} and distributed largely in the southern hemisphere.

By far the greatest diversity is in New Caledonia (18 species), with others in Australia, Argentina, New Zealand, Chile, Southern Part of Brazil and Malesia. In Malesia Agathis extends a short distance into the northern hemisphere, reaching 18°N in the Philippines.

Uses

Several are very popular ornamental trees in gardens in subtropical regions, and some are also very important timber trees, producing wood of high quality. Several have edible seeds similar to pine nuts, and others produce valuable resin and amber. In the forests where they occur, they are usually dominant trees, often the largest species in the forest; the largest is Araucaria hunsteinii, reported to 89 m tall in New Guinea, with several other species reaching 50–65 m tall. A. heterophylla, the Norfolk Island Pine, is a well-known landscaping and house plant from this taxon.

Fossil record

Fossils widely believed to belong to Araucariaceae include the form genera Araucarites (various), Araucarioxylon (wood), Brachyphyllum (leaves), and Protodammara (cones).

In Arizona, the petrified woods of the famous petrified forest in Petrified Forest National Park belong to several species of Araucarioxylon, the most common of them being Araucarioxylon arizonicum. 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. Some of the segments of trunk represent giant trees that are estimated to have been over 50 meters tall when they were alive.

The Cerro Cuadrado Petrified Forest of Argentina, also buried by volcanic ash during the Middle Jurassic, are also composed primarily of exquisitely preserved cones and wood of Araucaria mirabilis.

See also

Wikimedia Commons has media related to: Araucariaceae

Wikispecies has information related to: Araucariaceae

	Plants portal
	Paleontology portal

• List of extinct plants
• Norfolk Island Pine
• Paleobotany
• Petrified wood
• Te Matua Ngahere
• Thuja plicata

References

Further reading

• Cookson, I. C. and Duigan, S. L. (1951) "Tertiary Araucariaceae from South-eastern Australia, with notes on living species" Australian Journal of Scientific Research Series B (Biological Sciences) 4: pp. 415–449
• Kendall, Mabel W. (1949) "A Jurassic member of the Araucariaceae" Annals of Botany, New Series 13(50): pp. 151–161
• Kershaw, Peter and Wagstaff, Barbara (2001) "The Southern Conifer Family Araucariaceae: History, Status, and Value for Paleoenvironmental Reconstruction" Annual Review of Ecology and Systematics 32: pp. 397–414, doi: 10.1146/annurev.ecolsys.32.081501.114059
• Krasilov, Valentin A. (1978) "Araucariaceae as indicators of climate and paleolatitudes" Review of Palaeobotany and Palynology 26: pp. 113–124
• Pye, Matthew G.; Henwood, Murray J. and Gadek, Paul A. (2009) "Differential levels of genetic diversity and divergence among populations of an ancient Australian rainforest conifer, Araucaria cunninghamii" Plant Systematics and Evolution 277(3/4): pp. 173–185, doi: 10.1007/s00606-008-0120-1
• Setoguchi, Hiroaki et al. (1998) "Phylogenetic relationships within Araucariaceae based on rbcL gene sequences" American Journal of Botany 85(11): pp. 1507–1516
• Stockey, Ruth A. (1982) "The Araucariaceae: an evolutionary perspective" Review of Palaeobotany and Palynology 37: pp. 133–154
• Stockey, Ruth A. (1994) "Mesozoic Araucariaceae: morphology and systematic relationships" Journal of Plant Research 107(4): pp. 493–502, doi: 10.1007/BF02344070