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Aquatic Rhynchostegium Moss - Rhynchostegium aquaticum
Other Names:  Eurhynchium riparioides, Platyhypnidium riparioides, Platyhypnidium aquaticum

Species of Concern
Native Species

Global Rank: GNR
State Rank: S1

Agency Status


External Links

General Description
Taxonomists have often differentiated the aquatic species of Rhynchostegium (Family Brachytheciaceae) as the distinct genus, Platyhypnidium (Family Amblystegiaceae). The FNA (Volume 28) treatment includes these aquatic species in (the broad sense of) Rhynchostegium as they have been shown phylogenetically to have originated several times. Additionally, the American-Asian-Australian populations of Rhynchostegium ripariodes have different origins than the European-African populations. The widespread population in North America is regarded by FNA as R. aquaticum.

Plant: Mats. Dark-green becoming brown when old. Stems are 4-10 cm tall, usually with a few branches, but occasionally simple.

Leaf: Leaves imbricate to somewhat spreading, 1.4-2.4 x 0.8-2.0 mm, broadly ovate to suborbicular, usually concave, not plicate, and not decurrent. Leaves widest at about the middle. The apex is acute to broad and almost rounded or occasionally apiculate. Margins plane, distinctly serrate to the base or nearly so. Costa is variable, ½ or ¾ the length of leaf and usually ends with a spine; sometimes the costa reaches the apex and rarely it is forked.

Leaf Cells: Median cells long and narrow, 40-75 x 4-5 µm. Cells shorter at the base and apex. Alar cells are a little differentiated, often hyaline and sometimes somewhat inflated.

Range Comments
Canada: BC, MB, NB, NL, NS, ON, QC; USA: AL, AZ, AR, CA, CT, DE, GA, ID, IL, IN, KY, ME, MD, MA, MI, MN, MO, MT, NH, NJ, NM, NY, NC, OH, OK, OR, PA, SC, TN, TX, UT, VT, VA, WA, WV, WI; Mexico; Central America; South America; e Asia; Pacific Islands; Australia (FNA 2014). In Montana: Flathead and Sanders Counties (Elliott 2016).

Observations in Montana Natural Heritage Program Database
Number of Observations: 4

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density



(Observations spanning multiple months or years are excluded from time charts)

Aquatic, attached to stones in or at the edges of streams and springs with running water (Elliott 2016). Widespread, but never abundant in the Pacific Northwest.

Reproductive Characteristics
Autoicous. Seta 1.0-1.5 cm long, smooth. Capsules shrunken under the mouth when dry and 1.6-2.0 mm long.

  • Literature Cited AboveLegend:   View Online Publication
    • Elliott, J.C. and A.K. Pipp. 2018. A Checklist of Montana Mosses (1880-2018). Updated 3 January, 2020. Montana Natural Heritage Program, Helena, Montana. 73 pp.
    • Flora of North America Editorial Committee, eds. 2014. Flora of North America North of Mexico. Volume 28. Bryophytes: Mosses, Part 2. Oxford University Press, Inc., NY. xxi + 702 pp.
  • Additional ReferencesLegend:   View Online Publication
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    • Elliot, J. C. 1993. Second checklist of Montana mosses. Unpublished report. U.S. Forest Service, Region 1. Missoula, MT. 45 pp.
    • Lawton, E. 1971. Keys for the Identification of the Mosses on the Pacific Northwest. Reprinted from 'Moss Flora of the Pacific Northwest'. Published as Supplement No. 2 of the Journal of the Hattori Botanical Laboratory. Nichinan, Miyazaki, Japan. 66 pp.
    • Lawton, E. 1971. Moss Flora of the Pacific Northwest. Hattori Botanical Laboratory. Japan: Yamabuki-cho, Shinjuku-ku, Tokyo. 362 pages plus appendices.
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Citation for data on this website:
Aquatic Rhynchostegium Moss — Rhynchostegium aquaticum.  Montana Field Guide.  .  Retrieved on , from