Plants robust, brownish to reddish in distal part, black and frequently defoliated below. Stems 5-10 cm, central strand absent. Stem leaves straight appressed when dry, erectopatent when moist, lanceolate, 2.7--3.5 × 0.5--0.75 mm, sharply keeled distally, margin narrowly reflexed on both sides, awns terete, firm and short, denticulate, costa 70-120 µm wide at base, channeled distally, projecting on dorsal side; distal laminal cells 1-stratose, apex and margins 2-stratose; medial laminal cells elongate with extremely thick and nodulose lateral walls; basal juxtacostal laminal cells linear with extremely thick, slightly porose walls; basal marginal laminal cells in a few rows short-rectangular, thin-walled. Gemmae absent. Sexual condition dioicous. Seta cygneous, 3--4 mm. Capsule sporadically present, exserted, yellowish-brown, ovoid, smooth, exothecial cells thin-walled with incrassate corners, annulus present, operculum rostrate, peristome teeth orange, 40-60 µm wide at base, split and perforated, smooth proximally, papillose distally. Calyptra not seen.

Loose tufts on dry boulders; of conservation concern; 0--1000 m; B.C.; Alaska, Wash.

This northwestern North American endemic G. attenuata resembles forms of the extremely variable Racomitrium heterostichum, and because G. N. Jones (1933) mentioned five varieties of this latter species, it is not surprising that in some herbaria, e.g. NY, all specimens of G. attenuata have been filed as varieties of R. heterostichum. N. C. Kindberg (1897) realized that his species was not a Racomitrium, but a Grimmia, and he wrote: "Habit of G. elatio." In spite of Kindberg's correct transfer to Grimmia, T. C. Frye (1918) synonymized it with R. macounii. The confusion was enlarged when H. Möller (1929) synonymized it with Grimmia elatior, and J. Muñoz (1999b) published it as G. arcuatifolia Kindberg, which is a synonym of G. lisae De Notaris. There is some resemblance to G. austrofunalis, which is characterized by robust, scarcely branched stems, reddish distally, and blackish and frequently defoliated basally. In G. austrofunalis, however, the costa is 30--60 µm wide, the leaves are ovate-lanceolate, 2--2.5 mm, curved and shiny when dry, there is only one leaf margin recurved, the distal areolation is 1-stratose and the awns are smooth and longer. Grimmia elatior is characterized by ellipsoid striate capsules, only one leaf margin broadly recurved, and an opaque 2-stratose distal lamina with rounded usually mammillose to papillose cells, the mid leaf cells quadrate to short-rectangular with slightly sinuose, thick walls.