Fissidens hydropogon is a species of moss endemic to the Bombonasa River in Ecuador’s Pichincha province at the foot of the Andes Mountains. It lives submerged in the flowing river at an altitude of 450 metres. The species is only known from two collections made by English botanist Richard Spruce between 1849 and 1860 and has not been observed since that time. It is categorised as critically endangered because its known habitat is less than 10km squared and there is a general decline in suitability of that habitat.