Regnellidium is a monotypic genus of

fern A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes except t ...

s 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 The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

deposits of the eastern

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territo ...

. 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.

References

Other sources

* Mabberley, D. J. (1997). ''The Plant-Book''. Cambridge University Press. Salviniales Flora of Brazil Monotypic fern genera Plants described in 1904 {{Polypodiidae-stub