(1666) Proposal to conserve the name Pseudocrossidium revolutum ( Pottiaceae , Bryophyta) with a conserved type

Two of the most widely distributed Pseudocrossidium R. S. Williams species in Europe are known as Ps. hornschuchianum (Schultz) R. H. Zander and Ps. revolutum (Schrad. ex Brid.) R. H. Zander. According to the main European floras (Nyholm, Ill. Fl. Nord. Mosses: 102–103. 1989; Cortini-Pedrottii, Flora dei muschi d’Italia. Sphagnopsida, Andreopsida, Bryopsida (I Parte): 362-364. 2001; Smith, Moss Flora of Britain & Ireland, ed. 2: 295. 2004) the differences between the two taxa are found in the shape of the leaf, shape and size of the upper laminal cells, the leaf apex and the presence or absence of gemmae on the adaxial part of the nerve. The former, Ps. hornschuchianum, includes plants which have lanceolate to triangular leaves, with acuminate apex, upper laminal cells quadrate, 10–14 μm wide, nerve with 2(3) guide cells at midleaf and absence of gemmae and is distributed in Europe, Macaronesia, North Africa, Southwest Asia and has also been recorded in North America, South Africa and Australia. The latter, Ps. revolutum, includes plants which have oblong-lanceolate, lingulate or linear-lingulate leaves, with rounded to obtuse apex, upper laminal cells quadrate-rounded, 8-10 μm wide, 4 guide cells and frequently with gemmae and it occurs widely in Europe, Macaronesia, North Africa and Southwest Asia. Although species delimitation in the genus Pseudocrossidium is in some cases difficult, the identity of both taxa have never been questioned. Also, they have been consistently accepted and widely used in bryological literature since its inception, e.g., by Schimper (Syn. Musc. Eur., ed. 2: 211–213. 1876), Limpricht (Laubm. Deutschl. 1: 620–623. 1888), Monkemeyer (Laubm. Eur.: 281. 1927), Podpera (Consp. Musc. Eur.: 212. 1954), Demaret & Castagne (Fl. Gén. Belgique, Bryoph. 2(1): 293–296. 1959), Bilewsky (in Nova Hedwigia 9: 368–369. 1965), Agnew & Vondráèek (in Feddes Repert. 86: 363–364. 1975), Corley & al. (in J. Bryol. 11: 621. 1981), Zander (in Bull. Soc. Nat. Sci. 32: 1–378. 1993), Frey & al. (in Gams, Kleine Kryptogamenfl. 4, ed. 6: 202. 1995), Crosby & al. (Checkl. Mosses: 206. 1999). In preparing the manuscript of the genus Pseudocrossidium R. S. Williams for the “Flora Briofítica Ibérica” project, it was found that Barbula revoluta Schrad. ex Brid. was not typified. In the protologue, Bridel (in J. Bot. (Schrader) 1800(1): 299. Apr. 1801) accepted this name but did not provide any description or mention of original material. However, the name was validly published, because Bridel indirectly referred to the previously effectively published, but pre-starting date “Barbula revoluta Schraderi” (Art. 32.1(c), Greuter & al., Regnum. Veg. 138: 53. 2000). In Schrader (Syst. Samml. Krypt. Gew 1 n.o 54. 1796) the text reads: “54. T. revoluta, furculo innovationibus ramoso, foliis lanceolatis carinatis margine revolutis: perichaetialibus acuminatis, capsulis oblongis. Hab. in rupibus, muris, locis siccis”. Schrader’s Exsiccata: Syst. Samml. Krypt. Gew. 1 no 54. 1796 is deposited in various herbaria, but only the material deposited in GOET and LE [according to Stafleu & Cowan (Regnum. Veg. 112: 316. 1985), the original herbarium is deposited in the latter herbarium] was loaned for this study. Both specimens have lanceolate leaves, with revolute margins from the apex to the base, acuminate apex, quadrate upper laminal cells and a transverse section of the costa semicircular, with 2(3) guide cells and lack of gemmae. Therefore, the original material is identified as Ps. hornschuchianum. On the other hand, the protologue of Barbula hornschuchiana Schultz (in Syll. Pl. Nov. 1: 35. 1822) includes a diagnosis and reference to the locality: “Germania, in collibus arenosis apricis Duc. Megapol. Stargard”. A search in the herbaria where Schultz specimens are kept (B and ROST) was unsuccessful. Therefore in order to fix the usage of this name, a neotype has to be designated.