Flora of North America species comparison

Of conservation concern.

Previous to its discovery in Iceland, as Grimmia grisea (H. C. Greven 1998), G. reflexidens was known from only the Southern Hemisphere. It had previously been collected east of East Bay, Newfoundland, now the only known locality in North America, but was not recognized as G. reflexidens. The latter is similar to G. asperitricha Dixon & Sainsbury of New Zealand, and the two species have been confused by G. O. K. Sainsbury (1945) as well as by R. Ochyra (1993). J. Muñoz (1998b) synonymized G. reflexidens with G. sessitana. However, the former is readily separated from the latter by: (1) enlarged perichaetial leaves, (2) decurrent awns, (3) non-bulging laminal cells, and (4) dioicous sexual condition. Capsules are unknown from Northern Hemisphere material, but G. reflexidens lacks stomata while they are present for G. sessitana. Although G. reflexidens and G. teretinervis both have decurrent awns they are easily separated by a number of characters: G. reflexidens grows in compact cushions, has long awns, and a semicircular costa; G. teretinervis grows in loose clumps, is hyaline-tipped to short-awned, and has a unique costa that is distally almost completely circular in transverse section.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

As reported by R. R. Ireland (1982b), 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, Hastings proposed that the distribution of G. teretinervis in North America is largely correlated with the boundaries of ancient epicontinental seaways. These deposits have 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 this species and, until reported by Ireland, antheridial plants also were 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 awns that are none-the-less often long-decurrent. These features give the plants a blackish brown, shiny thread-like appearance.

(Discussion copyrighted by Flora of North America; reprinted with permission.)