Scleropodium tourettii or Cirriphyllum crassinervium

This was an interesting one as this sample was identified in the field by a professional bryologist as Cirriphyllum crassinervium so in theory it should have been straight forward to key out. However, after running through the key it became apparent that it doesn't key to Cirriphyllum crassinervium. The leaf tip was the first problem being obtuse and not abruptly contracting to leave a short apiculus. This avenue led me then to chose between Rhynchostegium and Scleropodium. The key says that Scleropodium has differing sizes in stem and branch leaves whereas Rhynchostegium has them all the same size. I could see varying leaf sizes so opted for Scleropodium. This group only has two species which can be separated by habit when wet and dry plus S.tourettii has much more concave leaves than S.cespitans looking more like Pseudoscleropodium purum. This species can be eliminated by the long pinnate growth unlike the bushy matted like habit of S.tourettii. So we have an ID but look again the the thick costa in the basal half, this is typical of C.crassinervium and with the concave leaves with the flattened border we find out that it is C.crassinervium after all. As a postscript it is worth mentioning that Rhynchostegium murale is a similar looking plant and should be considered when identifying in the field perhaps.

Cirriphyllum crassinervium