Regnellidium Diphyllum

Regnellidium is a monotypic genus of ferns of family Marsileaceae.The single living species, Regnellidium diphyllum, the two-leaf water fern, is native to southeastern Brazil and adjacent regions of Argentina. It resembles its relatives from the genus Marsilea, but has 2-lobed leaves (rather than 4). This fern is sometimes grown in aquaria. A fossil assigned to the species Regnellidium upatoiensis has been found in Cretaceous deposits of the eastern United States.The genus name of Regnellidium is in honour of Anders Fredrik Regnell (1807–1884), a Swedish physician and botanist. It was first described and published in Ark. Bot. Vol.3 (Issue 6) on page 2 in 1904.

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