Sarmentypnum exannulatum, also known as ringless hook-moss, is a species of medium-sized wetland moss belonging to the family Amblystegiaceae.

[1] Sarmentypnum exannulatum is characterized by its medium-sized stature, ranging from green to yellowish, and occasionally exhibiting a reddish secondary pigment.

[1] The stem leaves of S. exannulatum are ovate or ovate-triangular in shape, gradually narrowing to the apex.

[1] 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.