In the UK, most of the D. tophaceus we find is ssp tophaceus. However in spring 2021, Didymodon tophaceus ssp sicculus was found by Peter Martin growing on Lundy Island off the North Devon coast. It is new to Britain and amongst other characters is distinguished from ssp tophaceus by its nerve being narrower and having shorter cells over the ventral surface.
Read the Field Guide account
The Bryophyte identification page under Resources contains several useful keys and other information on the genus Didymodon.
Bryophyte identification resources
