Coscinodon Sprengel, Einl. Stud. Kryptog. Gew. 281. 1804.
Greek, a sieve-toothed peristome
Authors: Roxanne I. Hastings
Plants small, 4.5--15 mm, olive green to dark black-green. Stem leaves oval to ovate-lanceolate, keeled distally, usually long awned, basal cells usually rectangular and smooth walled. Seta straight. Capsule with poorly differentiated annulus. Calyptra large, covering 1/2 to all of capsule, erose, becoming cucullate with age, campanulate, plicate.
Species 10 (5 in the flora): temperate to Arctic-alpine.
Species in the genus Coscinodon are widespread across North America but are largely absent from the interior Great Plains and along the west coast. They all prefer dry acidic rocks. The largely calcareous regions of the continental interior do not provide suitable habitat for these species.
Historically, North American authors have often considered Coscinodon to be a subgenus of Grimmia. Not until the 1980's did they follow the European approach distinguishing these two genera. The separation of these two genera is largely sporophytic. Coscinodon have large, campanulate, plicate calyptra that commonly cover the capsule, whereas Grimmia have smaller, non-plicate calyptra that are not campanulate. It is often stated that Coscinodon have very long awns compared to most Grimmia. This is true for the widespread species, C. calyptratus and C. cribrosus, and also C. yukonensis. But C. arctolimnius is muticous to short awned and C. hartzii has awns not much longer than most Grimmia.
Churchill, S. P. 1981. A phylogenetic analysis, classification and synopsis of the genera of the Grimmiaceae (Musci). In: V. A. Funk and D.R. Brooks, eds. 1981. Advances in Cladistics. New York. Pp. 127--144. Hastings, R. I. 1999. Taxonomy and biogeography of the genus Coscinodon (Bryopsida, Grimmiaceae) in North America, including a new species. Bryologist 102: 265--286. Hastings, R. I. and H. Deguchi. 1997. Taxonomy of Coscinodon arctolimnius (Bryopsida, Grimmiaceae) including a new subspecies from Asia. Bryologist 100: 50--55. Ireland, R. R. and H. Crum. 1976. Distribution of Grimmia cribrosa in North America. Bryologist 79: 355--357. Muñoz, J. 1998. Amended description of Coscinodon calyptratus (Grimmiaceae) and major range extensions into Eurasia and New Zealand. Bryologist 101: 89--92. Murray, B. M. 1992. Bryophyte flora of Alaskan steppes. Brybrothera 1: 9--33. Steere, W. C. 1978. The Mosses of Arctic Alaska. Brophyt. Biblioth. 14: 1--508. Steere, W.C. 1974. Grimmia (Coscinodon) arctolimnia, a new species from Great Bear Lake, Northwest Territories, Canada. Bryologist 77: 230--234.