Bryum callistomum H.Philib. Dataset GBIF Backbone Taxonomy Rank SPECIES Classification kingdom Plantae phylum Bryophyta class Bryopsida order Bryales family Bryaceae genus Ptychostomum species Ptychostomum arcticum Name Homonyms Bryum callistomum H.Philib. Bryum callistomum Dicks. ex With. Bryum callistomum Dicks.