{{Short description|Species of moss}} {{Use dmy dates|date=June 2024}} {{Speciesbox | image = | status = CR | status_system = IUCN2.3 | status_ref =<ref name=iucn>{{cite iucn |author=Bryophyte Specialist Group |date=2000 |title=''Fissidens hydropogon'' |volume=2000 |article-number=e.T39170A10172325 |doi=10.2305/IUCN.UK.2000.RLTS.T39170A10172325.en |access-date=15 November 2021}}</ref> | display_parents = 4 | genus = Fissidens | species = hydropogon | authority = Spruce ex Mitt. | synonyms = *''Octodiceras hydropogon'' <small>(Spruce ex Mitt.) A. Jaeger</small> *''Conomitrium hydropogon'' <small>(Spruce ex Mitt.) Paris</small> | synonyms_ref =<ref name=WFO>{{cite web |title=''Fissidens hydropogon'' Spruce ex Mitt. |url=https://wfoplantlist.org/taxon/wfo-0001193532-2023-12 |website=WFO Plant List |publisher=World Flora Online |access-date=1 June 2024 |archive-date=1 June 2024 |archive-url=https://web.archive.org/web/20240601125449/https://wfoplantlist.org/taxon/wfo-0001193532-2023-12 |url-status=live }}</ref> }}

'''''Fissidens hydropogon''''' is a species of moss in the family Fissidentaceae. It is a critically endangered species endemic to Ecuador.<ref name=iucn/>

==Taxonomy and history== ''Fissidens hydropogon'' was first validly described by English bryologist William Mitten in 1869, placing it in ''Fissidens'' sect. ''Octodiceras'' and attributing it to Richard Spruce, the collector of the holotype.<ref>{{cite journal |last1=Mitten |first1=William |author1-link=William Mitten |year=1869 |title=Musci Austro-Americani, sive Enumeratio Muscorum omnium Austro-Americanorum mihi hucusque cognitorum, eorum præcipue in terris Amazonicis Andinisque Ricardo Spruceo lectorum |journal=The Journal of the Linnean Society. Botany |publisher=Linnean Society of London |volume=12 |page=585 |url=https://www.biodiversitylibrary.org/page/224831 |via=Biodiversity Heritage Library}}</ref> A 1988 revision placed ''F. hydropogon'' in ''Fissidens'' subgenus ''Sarawakia'' alongside ''F. beccarii'' and ''F. acacioides'', though this subgenus would later be reduced to section status under ''Fissidens'' subgenus ''Fissidens'' in 2004.<ref name=revision/><ref>{{cite journal |last1=Pursell |first1=Ronald A. |last2=Bruggeman-Nannenga |first2=Maria A. |year=2004 |title=A Revision of the Infrageneric Taxa of ''Fissidens'' |journal=The Bryologist |volume=107 |issue=1 |pages=1–20 |doi=10.1639/0007-2745(2004)107[1:AROTIT]2.0.CO;2 |jstor=3244563}}</ref>

==Distribution and habitat== ''Fissidens hydropogon'' was initially only known from one site, submerged in a river in Pastaza Province, Ecuador at {{cvt|450|m}} above sea level.<ref name=revision>{{cite journal |last1=Pursell |first1=R. A. |last2=Bruggeman-Nannenga |first2=M. A. |last3=Allen |first3=B. H. |year=1988 |title=A Taxonomic Revision of ''Fissidens'' Subgenus ''Sarawakia'' (Bryopsida: Fissidentaceae) |journal=The Bryologist |volume=91 |issue=3 |page=206 |doi=10.2307/3243220|jstor=3243220 }}</ref><ref name=FN>{{cite journal |last1=Pursell |first1=Ronald A. |year=2007 |title=Fissidentaceae |journal=Flora Neotropica |volume=101 |pages=117–120 |jstor=4393959}}</ref> In 2008 it was discovered growing on the vegetation of ''Cuphea bombonasae'' on the periodically flooded shore of the River Nangaritza, {{cvt|950|m}} above sea level in Zamora-Chinchipe Province, {{cvt|500|km}} southwest of the type location.<ref name=BG2011>{{cite journal |last1=Benitez |first1=Angel |last2=Gradstein |first2=S. Robbert |year=2011 |title=Adiciones a La Flora De Briófitas Del Ecuador |journal=Cryptogamie, Bryologie |language=es |volume=32 |issue=1 |page=73 |doi=10.7872/cryb.v32.iss1.2011.065}}</ref><ref name=IUCNsp>{{cite book |author=International Union for the Conservation of Nature |year=2011 |title=Species on the Edge of Survival |publisher=HarperCollins Publishers |page=176 |isbn=978-0-00-741914-2}}</ref>

==Description== ''Fissidens hydropogon'' is an irregularly branched moss with few rhizoids. The overlapping leaves are lanceolate with bluntly pointed tips, each measuring approximately {{cvt|2.5|mm}} long. Old growth is brown or black with eroded leaves. This species is monoicous, with perichaetia and perigonia arising from the same stems. Sporophytes are limited to one per perichaetium, with very short setae measuring {{cvt|0.5|mm}} or less. The capsules are egg-shaped, measuring {{cvt|0.5-0.9|mm}} long, with pointed calyptrae that cover only the tip of the capsule. The spores are smooth and measure {{cvt|22-27|um|mm}}.<ref name=revision/>

==Conservation status== ''Fissidens hydropogon'' is listed as critically endangered on the International Union for the Conservation of Nature's Red List under criteria B1 and B2c, based on the small area in which it occurs and the decline of its habitat.<ref name=iucn/>

==References== {{Reflist}}

{{Taxonbar|from=Q5455222}}

Category:Fissidentaceae Category:Endemic flora of Ecuador Category:Critically endangered flora of South America Category:Taxonomy articles created by Polbot Category:Plants described in 1869 Category:Aquatic plants Category:Taxa named by William Mitten