Gyrocarpus americanus is a flowering plant in the Hernandiaceae family, with a wide pantropical distribution. It is commonly and variously known as the helicopter tree, propeller tree, whirly whirly tree, stinkwood or shitwood.
Gyrocarpus americanus is a slender, deciduous tree with smooth, grey bark, growing to about 12 m in height. The leaves are spirally arranged, crowded near the ends of the branches, up to 150 × 120 mm in size. They are ovate, often 3-lobed, dark green above, paler and greyer below, with velvety surfaces, 3-veined from the base. The veins are yellowish and the stalk up to 90 mm long. The cream to yellowish-green flowers grow in compact heads and have an unpleasant smell. The fruit is a woody nut with two long thin wings that help wind dispersal. The winged fruit and the smell of the flowers have given the tree its various common names.
- G. a. africanus Kubitzki (Africa)
- G. a. americanus Jacq. (East Africa, India, Malesia, northern Australia, Melanesia, Polynesia, and South and Central America)
- G. a. glaber Kubitzki (Madagascar)
Several other subspecies have been described. Kubitzki distinguished eight – three in Madagascar, one each in tropical West and East Africa, one in tropical Australia, and one in Malesia, with the eighth being the typical subspecies G. a. americanus originating in the Palaeotropics and reaching the Neotropics by trans-Pacific dispersal. Most of these are rarely collected or are not recognised. Moreover, the monophyly of G. americanus remains unclear; the African species G. angustifolius and G. hababensis may lie within it.
- "The Plant List: A Working List of All Plant Species". Retrieved 12 June 2015.
- Flowers of India, retrieved 1 March 2016
- Michalak et al. (2010).
- Michalak, Ingo; Zhang Li-Bing; Renner, Susanne S. (2010-05-11). "Trans-Atlantic, trans-Pacific and trans-Indian Ocean dispersal in the small Gondwanan Laurales family Hernandiaceae". Journal of Biogeography. 37 (7): 1214–1226. doi:10.1111/j.1365-2699.2010.02306.x.
- "Helicopter Tree". Flowers of India. Retrieved 2010-11-16.
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