Plants medium-sized, in thin, loose mats, yellow-green to green. Stems 2-4 cm, 2-3 mm wide. Leaves wide-spreading to squarrose, usually wrinkled and contorted when dry, ovate-lanceolate to ovate, 1-1.5 × 0.4-0.7 mm; margins plane to erect throughout, serrulate proximally, serrate to serrulate distally; alar cells short-rectangular to quadrate, 19-33 × 9-19 µm, region small, with 1 or 2 cells on margins; medial laminal cells often flexuose, linear-fusiform, 71-141 × 5-7 µm. Specialized asexual reproduction absent. [Seta brown to reddish, 2-3 cm. Capsule horizontal to pendulous, sometimes nearly erect, light brown to reddish, 1-1.5 mm; operculum obliquely short-rostrate. Spores 9-14 µm].

Capsules mature fall. Low sandstone bluffs along rivers; elevation unknown; Miss.; Mexico; West Indies; Central America; South America.

Isopterygium tenerifolium is known in the flora area from only one recent collection from Mississippi (Lauderdale County, eastern shore of Chunky River at Stukey Bridge, 32°15'N, 88°52'W, 30 September 1992, Buck 22129 CANM, NY). The species is morphologically close to I. tenerum, differing by the somewhat larger plants, stems often 2-4 cm, leaves 1-1.5 mm and usually wrinkled and contorted when dry, and seta 2-3 cm. The collection in CANM contains only one plant with an undeveloped sporophyte that has a seta of 2 cm; fully developed sporophytes remain unseen in the flora area. The species should be sought elsewhere in the Gulf Coast region where other populations likely occur.