The typification and status of Leptophytum (Corallinaceae, Rhodophyta)

The status of the genus Leptophytum Adey has been uncertain, because the location of the nomenclatural type, Lithophyllum laeve Stromfelt nom. illeg., was unknown for years. In order to solve the problem of the missing type, new material was collected at the type locality of Lithophyllum laeve, Eyrarbakki, South Iceland. Part of the holotype has recently been found but does not show any diagnostic characters. The material collected at the type locality agrees well with Stromfelt's description of Lithophyllum laeve, and an epitype is designated. The epitype is found to be conspecific with Phymatolithon lenormandii (Areschoug in J. Agardh) Adey. Leptophytum laeve Adey, the type species of Leptophytum, therefore becomes a nomenclatural synonym of P. lenormandii and Leptophytum a nomenclatural synonym of Phymatolithon Foslie. The status of the genus Leptophytum and the features distinguishing the genus from Phymatolithon are discussed. Leptophytum laeve must be renamed however, because Adey's concept of it is taxonomically different from P. lenormandii. The lectotype of Lithothamnion tenue Rosenvinge is therefore designated and redescribed. Adey's concept of Leptophytum laeve is in full accordance with the lectotype of Lithothamnion tenue, which belongs to the genus Phymatolithon Foslie, and the new combination Phymatolithon tenue (Rosenvinge) Duwel et Wegeberg is proposed. The holotype of Lithothamnion foecundum Kjellman has been examined, and the new combination Phymatolithon foecundum (Kjellman) Duwel et Wegeberg is also proposed.