Typonym: Schistidium obtusifolium Irel. & Crum, Bryologist 87: 371. 1985. Type: CANADA. Quebec: Pare du Bic, Cap Enrage, pointe Ouest, 48°22' N, 68°46' W, on dry calcareous conglomerate, 15 Jun 1983, Zoladeski & Lutzoni 11201 (isotype: CANM!).
Brotherus (1924) treated Schistidium as a subgenus of Grimmia and recognized in it two groups including species with ochyrostomous capsules and species with more-or-less reduced peristomes. The latter group consists of five species including Grimmia flaccida (De Not.) Lindb., G. canariensis (Wint.) Broth, in Engl. & Prantl, G. aethiopica C. MülL, G. atrofusca Schimp. and G. antarctici Card. Of these, the former three are synonymous with Schistidium pulvinatum and obviously have nothing to do with S. steerei. On the other hand, S. atrofuscum (Schimp.) Limpr. is closely related to S. apocarpum, but differs in having peristome teeth mostly short, more-or-less truncate at apex but often very irregular there and variously cut. In addition, leaf margins are plane above and only recurved on one or both sides below, and these characters are sufficient enough to exclude any relationship of this species with S. steerei. Likewise, S. antarctici (Card.) Savicz-Lyub. & Smim., a species described from Antarctica by Cardot (1906), exhibits the same set of features in the leaf and peristome structure as S. atrofuscum does and is evidently diflferent from S. steerei. Bremer (1980b) reduced S. antarctici to synonymy with S. apocarpum, but this solution is debatable. As I suggested elsewhere (Ochyra et aL, 1986), populations that are commonly named S. apocarpum in the Southem Hemisphere appear to be specifically distinct, and I proposed tentatively the name S. chrysoneurum for austral plants and placed S. antarctici in synonymy with this species.
The geographic and floristic affiliation of S. steerei is obscure, as one or two collections from nearly the same place provide a wholly inadequate basis for phytogeographic consideration. Having examined all relevant type collections of austral species of Schistidium I a m sure that this species does not seem to have been described earlier under another name. O n the other hand, specimens of this species may very well exist misnamed in herbaria or in the pending files of other bryologists or collectors. Nevertheless, it has not yet been collected either on South Georgia (Bell, 1984), today one ofthe austral areas best known bryologically, or in southem South America.
Antarctica is not an area with a high level of moss endemism, if the occurrence of endemic moss taxa is possible there at all. This continent, including oflfshore archipelagos, was completely swept by continental glaciation during the Pleistocene, so that S. steerei perforce must have immigrated from elsewhere. The bryophyte flora that exists there at present consists of mainly several important floristic elements, including the truly South American temperate element, whose species representing it appear to be in majority. The species associated with S. steerei at the type locaUty, S. chrysoneurum, Ceratodon purpureus (Hedw.) Brid., Pohlia cruda (Hedw.) Lindb., Bryum pseudotriquetrum (Hedw.) Gaertn., Meyer & Scherb., Sanionia uncinata (Hedw.) Loeske, among others, are all characteristic and common inhabitants of moist gravelly soil over a vast expanse of the maririme antarctic, and so offer no significant insights into the possible geographical origin of the species. However, it seems likely that S. steerei originated from yet undiscovered popularion(s) in southem South America since, apart from some cosmopolitan and bipolar species, the majority of moss species in the Antarctic is also very widespread and common in this area. Hence, southem South America appears to be the most promising region where further populations of S. steerei might be discovered. This hypothesis seems to be best confirmed by the case of Sarconeurum glaciale (C. Müll) Card. & Bryhn in Card., a monotypic genus that was considered for a very long time as the best example of an antarctic endemic (Greene et al., 1970). However, this taxon was discovered in southem South America, including fertile plants that are unknown in the antarctic botanical zone (Greene, 1975; Matteri, 1982).