Schistidium teretinerve (Limpricht) Limpricht
Plants in loose tufts, green-brown to reddish-brown, shiny. Stems 2--3 cm, central strand strong. Stem leaves ovate-cordate to lanceolate, 0.6--1.2 × 0.2--0.5 mm, keeled, not plicate, margin plane, awn to 0.3 mm, often just hyaline tipped, commonly long-decurrent, costal transverse section prominent, circular distally; distal laminal cells 2-stratose, bulging, marginal cells 2-stratose, bulging; medial laminal cells rounded quadrate, thick-walled; basal juxtacostal laminal cells quadrate to short-rectangular, straight, thin to thick-walled; basal marginal laminal cells oblate to quadrate, straight, thick-walled, not hyaline. Perichaetial leaves unknown. Sexual condition dioicous. Seta unknown. Capsule unknown.
Moist calcareous sandstone, limestone and dolomite outcrops; 250--1700 m; Alta., B.C., N.W.T., Ont., Que., Yukon; Alaska, Ark., Col., Minn., Mo., Mont., Nev., Okla., Wis.; Europe.
As reported by R. R. Ireland (1982), Grimmia teretinervis is widely scattered across North America, but nowhere is it common. R. I. Hastings (2002) added several more Western collection locations to those reported by Ireland. Based on field observations and by correlating collecting localities with bedrock geology, R. I. Hastings (2002) proposed that the distribution of G. teretinervis in North America was largely correlated with the boundaries of ancient epicontinental seaways. These deposits had subsequently undergone faulting or were subjected to glacial-fluvial erosion. The ancient oceans provided the calcareous sediments and the faulting and erosion created the steep exposures preferred by G. teretinervis. Sporophytes have never been observed for Grimmia teretinervis and, until reported by Ireland (1982), antheridial plants were also unknown. Despite the lack of sporophytes, this species is readily identified by its unique costal structure, which is circular in transverse section. It commonly has thick-walled, bulging laminal cells and very short hair points that are none-the-less often long-decurrent. These features give the plants a blackish brown, shiny thread-like appearance.