''Claytosmunda'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

fern The ferns (Polypodiopsida or Polypodiophyta) are a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. They differ from mosses by being vascular, i.e., having specialized tissue ...

. It has only one extant species, ''Claytosmunda claytoniana'' (

synonym A synonym is a word, morpheme, or phrase that means precisely or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are a ...

''Osmunda claytoniana''), the interrupted fern, native to

Eastern Asia East Asia is a geocultural region of Asia. It includes China, Japan, Mongolia, North Korea, South Korea, and Taiwan, plus two special administrative regions of China, Hong Kong and Macau. The economies of China, Japan, South Korea, and Taiwan ...

Eastern United States The Eastern United States, often abbreviated as simply the East, is a macroregion of the United States located to the east of the Mississippi River. It includes 17–26 states and Washington, D.C., the national capital. As of 2011, the Eastern ...

, and

Eastern Canada Eastern Canada (, also the Eastern provinces, Canadian East or the East) is generally considered to be the region of Canada south of Hudson Bay/ Hudson Strait and east of Manitoba, consisting of the following provinces (from east to west): Newf ...

. The

specific epithet In Taxonomy (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin gramm ...

is named after the English-born Virginian botanist

John Clayton John Clayton may refer to: Arts and entertainment Writing *John Clayton (architect) (died 1861), English architect and writer *John Clayton (sportswriter) (1954–2022), American sportswriter and reporter *John Bell Clayton and Martha Clayton, Joh ...

. "Interrupted" describes the gap in middle of the blade left by the fertile portions after they wither and eventually fall off. The plant is known from

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

s to have grown in

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

, showing a previous

circumboreal The Circumboreal Region in phytogeography is a floristic region within the Holarctic Kingdom in Eurasia and North America, as delineated by such geobotanists as Josias Braun-Blanquet and Armen Takhtajan. It is the largest floristic region in ...

distribution. Fragmentary foliage resembling ''Claytosmunda'' has been found in the fossil record as far back as the

Triassic The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is t ...

Description

OFH-018 Osmunda claytoniana fertile frond

''Claytosmunda claytoniana''

frond A frond is a large, divided leaf. In both common usage and botanical nomenclature, the leaves of ferns are referred to as fronds and some botanists restrict the term to this group. Other botanists allow the term frond to also apply to the lar ...

s are

bipinnate The following terms are used to describe leaf morphology in the description and taxonomy of plants. Leaves may be simple (that is, the leaf blade or 'lamina' is undivided) or compound (that is, the leaf blade is divided into two or more leaflets ...

, tall and broad, the blade formed of alternate segments forming an arching blade tightening to a pointed end. The lower end is also slightly thinner than the rest of the frond because the first segments are shorter. Three to seven short, cinnamon-colored fertile segments are inserted in the middle of the length, giving the plant its name. In their absence, the plant in all its stages appears similar to '' Osmundastrum cinnamomeum'' (cinnamon fern). The base of the segments distinguishes the two species: where ''O. cinnamomeum'' has typical felt-like

hairs Hair is a protein filament that grows from follicles found in the dermis. Hair is one of the defining characteristics of mammals. The human body, apart from areas of glabrous skin, is covered in follicles which produce thick terminal and fin ...

, the few hairs present on ''C. claytoniana'' are extremely short, usually requiring a

magnifying glass A magnifying glass is a convex lens—usually mounted in a frame with a handle—that is used to produce a magnified image of an object. A magnifying glass can also be used to focus light, such as to concentrate the Sun's radiation to create ...

to see well. Like other species in the family Osmundaceae, it grows a very large

rhizome In botany and dendrology, a rhizome ( ) is a modified subterranean plant stem that sends out roots and Shoot (botany), shoots from its Node (botany), nodes. Rhizomes are also called creeping rootstalks or just rootstalks. Rhizomes develop from ...

, with persistent stipe bases from previous years. It forms small, dense

colonies A colony is a territory subject to a form of foreign rule, which rules the territory and its indigenous peoples separated from the foreign rulers, the colonizer, and their '' metropole'' (or "mother country"). This separated rule was often or ...

, spreading locally through its rhizome, and often forming

fairy ring A fairy ring, also known as fairy circle, elf circle, elf ring or pixie ring, is a naturally occurring ring or arc of mushrooms. They are found mainly in forested areas, but also appear in grasslands or rangelands. Fairy rings are detectable by ...

Taxonomy

The species was first described by

Carl Linnaeus Carl Linnaeus (23 May 1707 – 10 January 1778), also known after ennoblement in 1761 as Carl von Linné,#Blunt, Blunt (2004), p. 171. was a Swedish biologist and physician who formalised binomial nomenclature, the modern system of naming o ...

in 1753, as ''Osmunda claytoniana''. In 2005, it was recognized as being somewhat different from other species in the genus by being placed in a separate subgenus, ''Osmunda'' subgenus ''Claytosmunda''. In 2016, the subgenus was raised to a new genus, ''Claytosmunda'', as part of the

Pteridophyte Phylogeny Group The Pteridophyte Phylogeny Group (PPG) is an informal international group of systematic botanists who collaborate to establish on the classification of pteridophytes ( lycophytes and ferns) that reflects knowledge about plant relationships discove ...

classification (PPG I). The change of genus is recognized in some taxonomic databases. Others place the species in the genus ''

Osmundastrum ''Osmundastrum'' is genus of leptosporangiate ferns in the family Osmundaceae with one living species, ''Osmundastrum cinnamomeum'', the cinnamon fern. It is native to the Americas and eastern Asia, growing in swamps, bogs and moist woodlands. I ...

''. The oldest known species of ''Claytosmunda'' is ''C. beardmorensis,'' from the

Middle Triassic In the geologic timescale, the Middle Triassic is the second of three epoch (geology), epochs of the Triassic period (geology), period or the middle of three series (stratigraphy), series in which the Triassic system (stratigraphy), system is di ...

of Antarctica. ''Claytosmunda'' when considering fossils is

paraphyletic Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...

, as some of the fossils are likely to be more closely related to modern ''

Osmunda ''Osmunda'' is a genus of primarily temperate-zone ferns of family Osmundaceae. Five to ten species have been listed for this genus. They have existed since the Early Cretaceous. Description Completely dimorphic fronds or pinnae (hemidimorphic ...

'' and ''

Plenasium ''Plenasium'' is a genus of ferns in the family Osmundaceae. It is recognized in the Pteridophyte Phylogeny Group The Pteridophyte Phylogeny Group (PPG) is an informal international group of systematic botanists who collaborate to establish on ...

'' than they are to the modern ''C. claytoniana.''

Extinct species

After * †''C. beardmorensis'' (J.M.Schopf, 1978) (Middle Triassic: East Antarctica). * †''C. chengii'' Blomfleur et al. 2017 (Middle Jurassic: Liaoning, China). * †''C. johnstonii'' (Tidwell, Munzing & M.R.Banks, 1991) (?Early Jurassic: Tasmania, Australia). * †''C. embreii'' (Stockey & S.Y.Sm., 2000) (Early Cretaceous: California, USA). * †''C. liaoningensis'' (Wu Zhang & Shao-Lin Zheng, 1991) (Middle Jurassic: Liaoning, China). * †''C. nathorstii'' (C.N.Mill., 1967) (Palaeogene: Svalbard). * †''C. plumites'' (N.Tian & Y.D.Wang 2014 (Middle Jurassic: Liaoning, China). * †''C. preosmunda'' (Y.M.Cheng, Yu F.Wang & C.S.Li, 2007) (Middle Jurassic: Liaoning, China). * †''C. sinica'' (Y.M.Cheng & C.S.Li, 2007) (Middle Jurassic: Liaoning, China). * †''C. tekelili'' (E.I.Vera, 2012) (Early Cretaceous: West Antarctica). * †''C. wangii'' (N.Tian & Y.D.Wang, 2014 (Middle Jurassic: Liaoning, China). * †''C. wehrii'' (C.N.Mill., 1982) (Miocene: Washington, USA). *†''C. zhangiana'' Tian et al, 2021. (Middle Jurassic, Liaoning, China)

Distribution

North America

In eastern North America it occurs in: the

Great Lakes region The Great Lakes region of Northern America is a binational Canadian– American region centered on the Great Lakes that includes the U.S. states of Illinois, Indiana, Michigan, Minnesota, New York, Ohio, Pennsylvania, and Wisconsin and the Ca ...

; eastern Canada – in southern

Manitoba Manitoba is a Provinces and territories of Canada, province of Canada at the Centre of Canada, longitudinal centre of the country. It is Canada's Population of Canada by province and territory, fifth-most populous province, with a population ...

Ontario Ontario is the southernmost Provinces and territories of Canada, province of Canada. Located in Central Canada, Ontario is the Population of Canada by province and territory, country's most populous province. As of the 2021 Canadian census, it ...

Quebec Quebec is Canada's List of Canadian provinces and territories by area, largest province by area. Located in Central Canada, the province shares borders with the provinces of Ontario to the west, Newfoundland and Labrador to the northeast, ...

(north to

tree line The tree line is the edge of a habitat at which trees are capable of growing and beyond which they are not. It is found at high elevations and high latitudes. Beyond the tree line, trees cannot tolerate the environmental conditions (usually low ...

); and east to

Newfoundland Newfoundland and Labrador is the easternmost province of Canada, in the country's Atlantic region. The province comprises the island of Newfoundland and the continental region of Labrador, having a total size of . As of 2025 the population ...

; eastern United States – upper

New England New England is a region consisting of six states in the Northeastern United States: Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, and Vermont. It is bordered by the state of New York (state), New York to the west and by the ...

south through the

Appalachian Mountains The Appalachian Mountains, often called the Appalachians, are a mountain range in eastern to northeastern North America. The term "Appalachian" refers to several different regions associated with the mountain range, and its surrounding terrain ...

and Atlantic seaboard, into the

Southeastern United States The Southeastern United States, also known as the American Southeast or simply the Southeast, is a geographical List of regions in the United States, region of the United States located in the eastern portion of the Southern United States and t ...

Georgia Georgia most commonly refers to: * Georgia (country), a country in the South Caucasus * Georgia (U.S. state), a state in the southeastern United States Georgia may also refer to: People and fictional characters * Georgia (name), a list of pe ...

and

Alabama Alabama ( ) is a U.S. state, state in the Southeastern United States, Southeastern and Deep South, Deep Southern regions of the United States. It borders Tennessee to the north, Georgia (U.S. state), Georgia to the east, Florida and the Gu ...

; and west across the

Southern United States The Southern United States (sometimes Dixie, also referred to as the Southern States, the American South, the Southland, Dixieland, or simply the South) is List of regions of the United States, census regions defined by the United States Cens ...

Mississippi River The Mississippi River is the main stem, primary river of the largest drainage basin in the United States. It is the second-longest river in the United States, behind only the Missouri River, Missouri. From its traditional source of Lake Ita ...

, and back up the

Mississippi embayment The Mississippi embayment is a physiographic feature in the south-central United States, part of the Mississippi Alluvial Plain. It is essentially a northward continuation of the fluvial sediments of the Mississippi River Delta to its conflu ...

through the

Midwestern United States The Midwestern United States (also referred to as the Midwest, the Heartland or the American Midwest) is one of the four census regions defined by the United States Census Bureau. It occupies the northern central part of the United States. It ...

to the Great Lakes.

Asia

In eastern Asia, the fern is found in the

subtropical The subtropical zones or subtropics are geographical zone, geographical and Köppen climate classification, climate zones immediately to the Northern Hemisphere, north and Southern Hemisphere, south of the tropics. Geographically part of the Ge ...

and

temperate In geography, the temperate climates of Earth occur in the middle latitudes (approximately 23.5° to 66.5° N/S of the Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ran ...

Asia in: the

Eastern Himalaya ] The Eastern Himalayas extend from eastern Nepal across Northeast India, Bhutan, the Tibet Autonomous Region to Yunnan in China and northern Myanmar. The climate of this region is influenced by the monsoon of South Asia from June to September. It ...

South Central China South Central China, South-Central China or Central-South China ( zh, c = 中南, p = Zhōngnán, l = Central-South), is a List of regions of China, region of China. It consists of eight provincial administrative regions, namely Henan, Hubei, ...

and

Eastern China East China () is a geographical region in the People’s Republic of China, mainly consisting of seven province-level administrative divisions, namely the provinces (from north to south) Shandong, Jiangsu, Anhui, Zhejiang, Jiangxi, Fujian, a ...

Taiwan Taiwan, officially the Republic of China (ROC), is a country in East Asia. The main geography of Taiwan, island of Taiwan, also known as ''Formosa'', lies between the East China Sea, East and South China Seas in the northwestern Pacific Ocea ...

, the

Korean Peninsula Korea is a peninsular region in East Asia consisting of the Korean Peninsula, Jeju Island, and smaller islands. Since the end of World War II in 1945, it has been politically divided at or near the 38th parallel between North Korea (Dem ...

, the

Ryukyu Islands The , also known as the or the , are a chain of Japanese islands that stretch southwest from Kyushu to Geography of Taiwan, Taiwan: the Ryukyu Islands are divided into the Satsunan Islands (Ōsumi Islands, Ōsumi, Tokara Islands, Tokara and A ...

, and

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

Ecology

''Claytosmunda claytoniana'' is found in humid zones, mostly in forests, but also in more open

habitat In ecology, habitat refers to the array of resources, biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species' habitat can be seen as the physical manifestation of its ...

s and

biome A biome () is a distinct geographical region with specific climate, vegetation, and animal life. It consists of a biological community that has formed in response to its physical environment and regional climate. In 1935, Tansley added the ...

s, although rarely in

bog A bog or bogland is a wetland that accumulates peat as a deposit of dead plant materials often mosses, typically sphagnum moss. It is one of the four main types of wetlands. Other names for bogs include mire, mosses, quagmire, and musk ...

s. The interrupted fern is often found alongside

ostrich Ostriches are large flightless birds. Two living species are recognised, the common ostrich, native to large parts of sub-Saharan Africa, and the Somali ostrich, native to the Horn of Africa. They are the heaviest and largest living birds, w ...

cinnamon Cinnamon is a spice obtained from the inner bark of several tree species from the genus ''Cinnamomum''. Cinnamon is used mainly as an aromatic condiment and flavouring additive in a wide variety of cuisines, sweet and savoury dishes, biscuits, b ...

, and sensitive ferns.

Hybrids

''Osmunda'' × ''ruggii'', is a hybrid between ''C. claytoniana'' and '' O. spectabilis'' (American royal fern). The hybrid is considered important because it suggests a closer genetic relationship between ''C. claytoniana'' and ''O. spectabilis'' than between ''C. claytoniana'' and ''O. cinnamomeum'' (a fact which has led to moving ''O. cinnamomeum'' out of ''Osmunda'' and into its own genus ''Osmundastrum''). ''Osmunda'' × ''ruggii'' is sterile and is known from only about two natural populations, despite the many areas in which both ''C. claytoniana'' and ''O. spectabilis'' are found.

Uses

Medicinal

The

Iroquois The Iroquois ( ), also known as the Five Nations, and later as the Six Nations from 1722 onwards; alternatively referred to by the Endonym and exonym, endonym Haudenosaunee ( ; ) are an Iroquoian languages, Iroquoian-speaking Confederation#Ind ...

used the plant as treatment for blood disorders and venereal diseases.Univ. Mich.-Dearborn College of Arts, Sciences, and Letters: Native American Ethnobotany: ''Osmunda'' species
(scroll for ''O. claytoniana'') . accessed 12.1.2011

References

Flora of North America: ''Osmunda claytoniana''RangeMap:Flora of Taiwan: ''Osmunda claytoniana''
* * Phipps, C. J., Taylor, T. N., Taylor, E. L., Cuneo, N. R., Boucher, L. D., and Yao, X. (1998). ''Osmunda'' (Osmundaceae) from the Triassic of Antarctica: An example of evolutionary stasis. American Journal of Botany, 85: 888–895 {{Taxonbar, from1=Q30109404, from2=Q91257630, from3=Q2748623 Osmundales Ferns of the Americas Ferns of Asia Flora of China Flora of Japan Flora of Korea Flora of Taiwan Flora of the Northeastern United States Flora of the North-Central United States Flora of the Southeastern United States Flora of Eastern Canada Flora of Manitoba Edible plants Plants used in traditional Native American medicine Monotypic fern genera