Planera

Planera is a genus of flowering plants with a single living species, Planera aquatica, the planertree or water elm. The genus has an extensive fossil record dating back to the Cretaceous and spanning the northern hemisphere, with a few southern hemisphere records as well. The living species is found in the southeastern United States, it is a small deciduous tree 10–15 m tall, closely related to the elms but with a softly, prickly nut 10–15 mm diameter, instead of a winged seed. It grows, as the name suggests, on wet sites. Despite its common English name, this species is not a true elm, although it is a close relative of the elms (species of the genus Ulmus). It is also subject to Dutch elm disease, a disease which affects only members of the Ulmaceae. It is native to most of the southeast United States. It is hardy down to Zone 7.

Species

 * Planera aquatica

Fossil species

 * †Planera antiqua Heer, 1883 (Santonian-Campanian; Paatuut Formation, Greenland)
 * †Planera aquaticiformis Hollick, 1936 (Paleocene/Eocene; "Berg Lake flora", Alaska)
 * †Planera australis Ettingshausen, 1887 (Late Cretaceous; Otago, New Zealand)
 * †Planera chankaensis Pavlyutkin, 2005 (Miocene; Novokachalinsk, Russia)
 * †Planera crenata Newberry, 1883 (jr homonym, replacement name P. lingualis)
 * †Planera cretacea Berry, 1907 (Cretaceous; North Carolina)
 * †Planera dubia Lesquereux, 1859 (Eocene, Chuckanut Formation, Washington)
 * †Planera emarginata (Göppert) Heer, 1856 (Tortonian, Poland)
 * †Planera ezoana Ôishi & Huzioka, 1954 (Eocene; Hokkaido, Japan)
 * †Planera hebridica Simpson, 1961 ("Cenozoic"; Isle of Mull, Scotland)
 * †Planera knowltoniana Newberry, 1896 (Cenomanian; Raritan Formation, Virginia)
 * †Planera mullensis Simpson, 1961 ("Cenozoic"; Isle of Mull, Scotland)
 * †Planera myricifolia (Lesquereux) Cockerell, 1908 (Priabonian; Florissant Formation, Colorado)
 * †Planera parvula Saporta, 1888 (Oligocene; France)
 * †Planera subkeaki (Rérolle) Saporta, 1888 (Tortonian; La Cerdagnya, France)
 * †Planera thompsoniana Traverse, 1955 (Burdigalian; Brandon lignite, Vermont)
 * †Planera ulmifolia Schloemer-Jäger, 1958 (Paleocene; Brøgger peninsula, Spitsbergen)
 * †Planera variabilis Newberry, 1883 (Ypresian; Green River Formation, Wyoming)

Species formerly included in Planera

 * †Abelicea ungeri (Kováts ex Ettingshausen) Holmboe
 * †Cedrelospermum nervosum (Newberry) Manchester
 * †Chaetoptelea microphylla (Newberry) Hickey
 * †Fagopsis longifolia Lesquereux