The long-leaved flapwort is a very rare native leafy liverwort. Liverworts are closely related to mosses and hornworts and together these are often referred to as lower plants. Superficially many liverworts look like flattened mosses. The long-leaved flapwort occurs on thin layers of soil overlying moist or wet sandstone rocks and stones. It is found on sheltered slopes and in or near flushes, streams and rivers in humid deciduous woodland to an altitude of 215m.
The Yorkshire Dales National Park (YDNP) is said to be a UK stronghold for this critically endangered liverwort which was only recorded three times between 1950 and 1999, two of those records being in the YDNP. These historical records relate to Twisleton Glen near Ingleton in the South West of the National Park.
Members of the Yorkshire Dales Biodiversity Forum, the British Bryological Society and other local bryologists started the systematic surveying of suitable habitat at historic sites in the Yorkshire Dales National Park in the Winter of 2012 to aid the conservation of this species. This work is on-going.