Araucariaceae is afamily of conifers with three livinggenera,Araucaria,Agathis, andWollemia. While the family's native distribution is now largely confined to the Southern Hemisphere, except for a few species ofAgathis inMalesia, it was formerly widespread in the Northern Hemisphere during theJurassic andCretaceous periods.[1]
Members of Araucariaceae are typically extremely tall evergreen trees,[2] reaching heights of 60 m (200 ft) or more.[3] They can also grow very large stem diameters; a New Zealandkauri tree (Agathis australis) namedTāne Mahuta ("The Lord of the Forest") has been measured at 45.2 m (148 ft) tall with adiameter at breast height of 491 cm (16.11 ft). Its total wood volume is calculated to be 516.7 m3 (18,250 cu ft),[4] making it the third-largest conifer afterSequoia andSequoiadendron (both from the Cupressaceae subfamilySequoioideae).[2]
The trunks are columnar and have relatively largepiths withresinouscortices.[5] The branching is usually horizontal and tiered, arising regularly in whorls of three to seven branches or alternating in widely separated pairs.[6]
The leaves can be small, needle-like, and curved, or they can be large, broadly ovate, and flattened.[7] They are spirally arranged, persistent, and usually haveparallel venation.[2]
Like other conifers, they produce cones. Each tree can have both male and female cones (monoecious) or, more commonly, they can have only male or female cones (dioecious).[8]
Male cones are among the largest among all conifer cones, on average. They are cylindrical and drooping, somewhat resemblingcatkins. They are borne singly on the tips of branches or in theaxils of leaves. They contain numeroussporophylls 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.[2][6][7]
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.[2][6][7] The scales almost always bear only one seed on its upper surface, in contrast to two in true pines (familyPinaceae).[9] 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.[2][6][7] 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 10 kg (22 lb),[10] about the size and weight of a large pineapple. They can drop from heights of 23 m (75 ft).[9]
Araucariaceae is classified under theorderPinales,classPinopsida of thedivisionPinophyta. The division includes all living conifers. Recently however, some authorities treat Araucariaceae as a separate order,Araucariales.[2]
Araucariaceae contains three extant genera and about 41 species.[5]
Today, 41 species are known, in three genera:Agathis,Araucaria andWollemia, 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 Brazil, and Malesia. In Malesia,Agathis extends a short distance into the Northern Hemisphere, reaching 18°N in the Philippines.
Several species 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 valuableresin andamber. In the forests where they occur, they are usually dominant trees, often the largest species in the forest; the largest isAraucaria 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.
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 "Oltustone", the name deriving from the town ofOltu, 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.[14]
The oldest definitive records of Araucariaceae are from theEarly Jurassic, though there are potential earlier Late Triassic records. Early representatives ofAraucaria are widespread across both hemispheres by theMiddle Jurassic, such asAraucaria mirabilis andAraucaria sphaerocarpa from the Middle Jurassic of Argentina and England respectively.[15] The oldest records of theWollemia-Agathis lineage from theCretaceous, includingEmwadea microcarpa from theAlbian agedWinton Formation of Australia[16] andWairarapaia mildenhallii from the Albian-Cenomanian of New Zealand.[17][12] The oldest fossils currently confidently assignable toAgathis are those ofAgathis immortalis from theSalamanca Formation of Patagonia, which dates to thePaleocene, approximately 64.67–63.49 million years ago.Agathis-like leaves are also known from the slightly olderLefipán Formation of the same region, which date to the very end of the Cretaceous.[18] Araucariaceae fossils are also known from the latest Oligocene or earliest Miocene of the southwesternmost tip of Africa.[19] Claimed records ofAgathis from the Eocene of Canada based on chemical analysis of amber are questionable.[20]
^abFu Liguo; Li Nan; Robert R. Mill (1999)."Araucariaceae"(PDF).Flora of China.4:9–10. Archived fromthe original(PDF) on May 24, 2011. Retrieved2011-11-19.
^Derived from papers by A. Farjon and C. J. Quinn & R. A. Price in the Proceedings of the Fourth International Conifer Conference,Acta Horticulturae 2003; 615
^Archibald, S. Bruce; Makarkin, Vladimir N. (February 2004)."New genus of minute Berothidae (Neuroptera) from Early Eocene amber of British Columbia".The Canadian Entomologist.136 (1):61–76.doi:10.4039/n03-043.ISSN0008-347X."Nuclear magnetic resonance (NMR) spectroscopy indicated that the amber was formed by resin from the genusAgathis (Araucariaceae) (Poinar et al. 1999); however, NMR spectroscopy indicating the origins of various Cretaceous ambers from Araucariaceae may be problematic (Grimaldi et al. 2000).
Kendall, Mabel W (1949). "A Jurassic member of the Araucariaceae".Annals of Botany. New Series.13 (50):151–161.doi:10.1093/oxfordjournals.aob.a083211.
Kershaw, Peter; Wagstaff, Barbara (2001). "The Southern Conifer Family Araucariaceae: History, Status, and Value for Paleoenvironmental Reconstruction".Annual Review of Ecology and Systematics.32:397–414.doi:10.1146/annurev.ecolsys.32.081501.114059.
Pye, Matthew G.; Henwood, Murray J.; 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):173–185.Bibcode:2009PSyEv.277..173P.doi:10.1007/s00606-008-0120-1.S2CID21846658.
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