Taxonomic and nomenclatural history of Neckera (Bryophyta, Neckeraceae), including reinstatement of Rhystophyllum, the correct name for a segregate of this genus

The complex taxonomic history of the moss genus <i>Neckera</i>, whose name was conserved at the Paris Congress in 1954, is reviewed. The issue of typifications of moss generic names by W. Ph. Schimper in 1860 is examined in detail and it is concluded that these typifications comply with the provisions of the "<i>International Code of Nomenclature for algae, fungi and plants</i>". Schimper was the first to typify <i>Neckera</i> with <i>N. pennata</i>, so it is unnecessary to treat this as a conserved type. The unitary designations of moss species proposed by Jakob Friedrich Ehrhart in his exsiccata "<i>Phytophylacium Ehrhartianum</i>", published between 1780 and 1785, are reviewed. It is concluded that two of these designations, <i>Diphyscium</i> and <i>Paludella</i>, are currently in use, having been validly published in the early nineteenth century. The same applies to <i>Rhystophyllum</i>, another of Ehrhart's unitary designations, which was validated as a subsection of <i>Neckera</i> by C. Müller in 1850 and, subsequently, first elevated to the rank of section by Mitten in 1869, rather than Braithwaite in 1905 as listed in "<i>Index muscorum</i>". Finally, E. Britton raised this infrageneric taxon to the rank of genus in 1904. <i>Rhystophyllum</i> is here reinstated from obscurity, since it is homotypic with the generic name <i>Exsertotheca</i> that was recently introduced for a segregate of <i>Neckera</i>. Accordingly, three new combinations are proposed: <i>Rhystophyllum crispum</i>, <i>Rh. intermedium</i> and <i>Rh. baeticum</i>. Neckera subsect. Leiophyllum is regarded as a heterotypic synonym of <i>Alleniella</i>, another recent segregate of the formerly broadly circumscribed genus <i>Neckera</i>.