''Sarmentypnum exannulatum'', also known as ringless hook-moss, is a

species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...

of medium-sized wetland moss belonging to the family

Amblystegiaceae Amblystegiaceae is a family of mosses. It includes 20 to 30 genera with a total of up to 150 species. *'' Hypnites'' Ettingsh.1855 *'' Hypnobartlettia'' Ochyra1985 *'' Koponenia'' Ochyra1985 *'' Larrainia'' W.R. Buck2015 *''Leptodictyum'' (Schim ...

. It was first described by Wilhelm Philipp Schimper in collaboration with his brother Wilhelm Philippe Schimper in 1854.

Description

''Sarmentypnum exannulatum'' is characterized by its medium-sized stature, ranging from green to yellowish, and occasionally exhibiting a reddish secondary pigment. The stems of the plant have apices with branches and shoots. The epidermal cells of the stems typically widen, forming a partial hyalodermis. The axillary hairs have 1-4 distal cells, which are hyaline when young. The stem leaves of ''S. exannulatum'' are ovate or ovate-triangular in shape, gradually narrowing to the apex. They are often falcate but may also be straight. The leaves are concave and not decurrent at the base. The margins of the leaves are distinctly denticulate either proximally, distally, or both. The apex of the leaves is acuminate. The

costa Costa may refer to: Biology * Rib (Latin: ''costa''), in vertebrate anatomy * Costa (botany), the central strand of a plant leaf or thallus * Costa (coral), a stony rib, part of the skeleton of a coral * Costa (entomology), the leading edge of th ...

terminates at approximately 3/5 to nearly the entire length of the leaf. The alar region extends from the margins to the costa or nearly so. The shoots of ''S. exannulatum'' can reach a length of 20–30 cm, with leaves measuring 2.5–4 mm in length.

Distribution

''Sarmentypnum exannulatum'' can be found in North America,

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the souther ...

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Pacific Islands Collectively called the Pacific Islands, the islands in the Pacific Ocean are further categorized into three major island groups: Melanesia, Micronesia, and Polynesia. Depending on the context, the term ''Pacific Islands'' may refer to one of ...

, and Australia. It can be observed in intermediately mineral-rich fens, around springs, late snow beds, and even submerged in lakes. This species is known to occur in a range of elevations, from low to high, spanning from sea level up to 4200 meters.

References

{{Taxonbar, from=Q5486582 Hypnales Plants described in 1854