Calypogeia fissa (L.) Raddi, Jungermanniogr. Etrusca: 33. 1818.

Bakalin, Vadim A., Klimova, Ksenia G. & Nguyen, Van Sinh, 2020, A review of Calypogeia (Marchantiophyta) in the eastern Sino-Himalaya and Meta-Himalaya based mostly on types, PhytoKeys 153, pp. 111-154 : 111

Calypogeia fissa (L.) Raddi, Jungermanniogr. Etrusca: 33. 1818.

Basionym.

Mnium fissum L., Sp. Pl. 1: 1114. 1753. nom. conserv. Original material: Great Britain, Surrey, Dorking; not seen.

Remarks.

Calypogeia fissa is one of the oldest names in Calypogeia , and several taxa were split from the original C. fissa s.l. The species seems to be restricted to Europe. Within North America and the northwestern amphi-Pacific (Commanders, Kamchatka, Kurils, Sakhalin), C. fissa is substituted by C. neogaea (R.M. Schust.) Bakalin. Stotler and Crandall-Stotler (2017: 591) noted that C. fissa "likely does not occur in North America and specimens identified as such likely belong to C. neogaea ". In an older time, C. fissa was recorded in Japan, although it was doubted as early as Hattori (1952) and then was never mentioned for the Japanese flora. The nearest morphological ally of C. fissa in temperate East Asia is C. tosana .

Nevertheless, Calypogeia fissa was several times recorded even at a relatively recent time for the East Asian mainland: Singh and Nath (2007a) recorded it for the East Khasi Hills and West Khasi Hills as well as (presumably based on other literature records, unfortunately not cited in l.c.) for Sikkim and Darjeeling. Bapna and Kachroo (2000) described its wide distribution in India. Wang et al. (2011) mentioned it for Taiwan; Fang et al. (1998), for Jiangxi. The records of the species for Yunnan and Hunan are based on Nicholson et al. (1930). Presumably, the vast majority of records of C. fissa may be based on misidentifications of C. tosana (if so, the latter is much more widely distributed on the Asian mainland than would be obvious if only available publications were taken into account). We hypothesize that ‘true’ Calypogeia fissa should be restricted to Europe from where the only accessions were confirmed by Buczkowska et al. (2018), and that the species should be excluded from the Sino-Himalayan Calypogeia flora. Moreover, even in Europe, Calypogeia fissa is represented by two genetically well-separated taxa ( Buczkowska et al. 2011) that probably require taxonomic revision.