Cystodium sorbifolium

{{Short description|Species of fern}}

{{speciesbox

| display_parents = 3

| grandparent_authority = J.R.Croft 1986

| genus = Cystodium (plant)

| parent_authority = J.Sm. 1841

| species = sorbifolium

| authority = (Sm.) J.Sm.

| synonyms = {{tx|Cystodiopteris|Rauschert 1982[http://www.ars-grin.gov/cgi-bin/npgs/html/genus.pl?26532 Cystodiopteris] USDA-ARS Germplasm Resources Information Network (GRIN) 28 January 2010}}

}}

Cystodium is a fern in its own family, Cystodiaceae.{{cite journal |author=Christenhusz, Maarten |author2=Xian-Chun Zhang |author3=Harald Schneider |name-list-style=amp |year=2011 |title=A linear sequence of extant families and genera of lycophytes and ferns |journal=Phytotaxa |volume=19 |issue=18 Feb. 2011 |pages=7–54 |doi=10.11646/phytotaxa.19.1.2 |url=http://www.mapress.com/phytotaxa/content/2011/f/pt00019p054.pdf}} It contains a single species: Cystodium sorbifolium {{au|(Sm.) J.Sm. 1841}}. Because it looks like a small tree fern, it had previously been placed in the tree fern family Dicksoniaceae. Subsequent analysis had moved it to the Lindsaeaceae,{{cite journal|last1=Korall|first1=Petra|last2=Conant|first2=David S.|last3=Schneider|first3=Harald|last4=Ueda|first4=Kunihiko|last5=Nishida|first5=Harufumi|last6=Pryer|first6=Kathleen M.|year=2006|title=On the Phylogenetic Position of Cystodium: It's Not a Tree Fern – It's a Polypod!|journal=American Fern Journal|volume=96|issue=2|pages=45–53|doi=10.1640/0002-8444(2006)96[45:OTPPOC]2.0.CO;2|url=http://www.pryerlab.net/publication/fichier736.pdf|access-date=2012-02-02|archive-url=https://web.archive.org/web/20080820183641/http://www.pryerlab.net/publication/fichier736.pdf|archive-date=2008-08-20|url-status=dead}} but the most recent phylogenetic studies have placed it in its own separate family, Cystodiaceae, with a sister relationship to the current Lindsaeaceae.{{cite journal|last1=Lehtonen|first1=Samuli|last2=Tuomisto|first2=Hanna|last3=Rouhan|first3=Germinal|last4=Christenhusz|first4=Maarten J. M. |year=2010 |title=Phylogenetics and classification of the pantropical fern family Lindsaeaceae |journal=Botanical Journal of the Linnean Society |volume=163 |issue=3 |pages=305–359 |doi=10.1111/j.1095-8339.2010.01063.x|doi-access=free}} A fossil species of the genus Cystodium sorbifolioides is known from the Cenomanian aged Burmese amber in Myanmar.{{Cite journal|last1=Regalado|first1=Ledis|last2=Schmidt|first2=Alexander R.|last3=Appelhans|first3=Marc S.|last4=Ilsemann|first4=Bork|last5=Schneider|first5=Harald|last6=Krings|first6=Michael|last7=Heinrichs|first7=Jochen|date=December 2017|title=A fossil species of the enigmatic early polypod fern genus Cystodium (Cystodiaceae) in Cretaceous amber from Myanmar|url= |journal=Scientific Reports|language=en|volume=7|issue=1|pages=14615|doi=10.1038/s41598-017-14985-7|issn=2045-2322|pmc=5668433|pmid=29097728}}