Why Plagiothecium sylvaticum (Brid.) Schimp. (Plagiothecium, Plagiotheciaceae) has priority over P. platyphyllum Mönk.?

Abstract

Re-assessment of the lectotype of Hypnum sylvaticum Brid. (≡ Plagiothecium sylvaticum (Brid.) Schimp.) (B 31 0915 01) showed that this specimen is characterised by dense, 6–10 cm long stems, pale green, yellowish-green to dark green and dull foliage; with complanate, ovate, not imbricate and not julaceous, 2.0–3.0 × 1.0–1.6 mm leaves; acute and denticulate, often eroded apices; 75.0–160.0 × 12.5–20.0 μm laminal cells at mid-leaf, which form diagonal rows, and decurrencies of 3–4 rows of rectangular to square, inflated cells, forming distinct auricules. Thus, this specimen represents the characteristics of the taxon currently referred to as Plagiothecium platyphyllum Mönk. Taking into account the above and the fact that the name H. sylvaticum was published first, the correct name for the species is Plagiothecium sylvaticum. Whereas the later one (P. platyphyllum) is a synonym. Additionally, in this article for the name P. platyphyllum, a lectotype is designated and a new synonym (Plagiothecium ruthei f. submersum) is proposed for the resurrected P. sylvaticum.