Fissidens celticus

The species holotype was from Hustyn Wood, St Breock, Cornwall,[6] and it is common throughout the western parts of the United Kingdom.[3] In the United Kingdom, F. celticus often associates with Calypogeia arguta,[3] Diplophyllum albicans,[3] Dicranella heteromalla,[6] Dicranella rufescens,[3][7] Epipterygium tozeri,[3] F. bryoides,[3] Pellia epiphylla,[3] Pohlia lutescens,[3] and Pseudotaxiphyllum elegans.[3]

Fissidens celticus is most commonly found in South West England, but is also present in the south east and north west.[3]

There are records of F. celticus from Cornwall,[6] Devon,[8] Gloucestershire,[9] Kent,[10] and Sussex.[11] On the Isle of Wight, it is present in Parkhurst Forest,[12] and at Briddlesford Nature Reserve.[13] As of 2001, the only known record in Lancashire was on the River Lune Biological Heritage Site.[14]

The species can be found all across western Wales,[3][15] including on Anglesey.[16]

Fissidens celticus is present in much of western Scotland.[3] The Tayvallich Juniper and Fen SSSI (near Tayvallich, Argyll and Bute) is noted for its oceanic bryophytes, including F. celticus.[17]

In Northern Ireland, the only known location for F. celticus is in Ness Wood ASSI in County Londonderry.[18]

Fissidens celticus has been recorded in many other countries in Europe:

• Germany: in the Leuscheid associating with F. bryoides, Dicranella heteromalla, and Diplophyllum albicans.[19]
• Ireland: one specimen the Slieveardagh Hills, County Tipperary and two in County Cork near Kilworth; associating with F. bryoides and F. taxifolius.[20]
• Spain: in the Aiako Harriak Natural Park associating with F. viridulus.[21]
• Switzerland: in the cantons of Bern, St. Gallen, and Ticino.[5]

In 2019, it was first reported in Turkey (and therefore in Asia).[22] It was found in Bozyazı, Mersin Province, associating with Bartramia stricta, Bryum dichotomum, Didymodon tophaceus, Targionia hypophylla and Timmiella barbuloides.[22]