Revision of the Original Material of Plagiothecium denticulatum var. obtusifolium (Turn.) Moore and New Synonyms for This Taxon

Hypnum denticulatum var. obtusifolium was described by Turner in the early nineteenth century. This taxon, now known as Plagiothecium denticulatum var. obtusifolium, has not been studied in detail or received a detailed description. During the revision in the Natural History Museum (herbarium BM), a specimen described there as a type (BM000890810) was found, but a careful analysis showed that it is currently not a type specimen. On the other hand, the conducted research showed that the holotype of this taxon is the figure attached by Turner to the newly described taxon. However, because the holotype does not contain all taxonomically significant features, the specimen found was used to designate the epitype of this name (BM000890810). Therefore, this paper provides the first complete description of the qualitative and quantitative characteristics of this taxon, which is today known as P. denticulatum var. obtusifolium. Forty qualitative and quantitative characteristics analyzed made it possible to make redescription of the examined taxon. Moreover, analysis of two morphologically similar, currently distinct taxa, P. sandbergii and P. denticulatum var. auritum, revealed no differences between them. Therefore, these taxa were proposed as new synonyms of P. denticulatum var. obtusifolium. Additionally, for both taxa mentioned above, lectotypes were proposed for P. denticulatum var. auritum, specimen PC0132639, and for P. sandbergii, specimen PC0132604, both from the Muséum National d’Histoire Naturelle, Paris, France (Herbarium PC).