Pseudotaxiphyllum richardsii Ireland 1991

Pseudotaxiphyllum richardsii

Pseudotaxiphyllum richardsii (E. B. Bartram) Ireland, Caldasia 16(78): 267. 1991. Isopterygium richardsii E. B. Bartram, Bryologist 44: 64. 1941. Type: Mexico, Sonora, Imuris, along Río de los Alisos, Richards & Drouet 757 (holotype: F!; isotypes: DUKE!, F!, FH!, MICH!, NY!).

Plants in thin mats, somewhat glossy to dull, light green to yellowish green. Stems to 1 cm long, 1–2 mm wide, simple or irregularly branched. Asexual reproductive bodies lacking. Leaves 0.5–1.0 mm long, 0.3–0.5 mm wide, flaccid, close, erect, indistinctly complanate when dry, more noticeably so when moist, concave, smooth, ovate to ovate-lanceolate, symmetric, acute to short-acuminate; margins plane or strongly involute when dry, serrate to serrulate nearly to base; costa weak, short and double; median cells 47–75 × 5–9 µm, smooth; apical cells smooth; alar cells distinctly differentiated, numerous

quadrate to short-rectangular cells present. Autoicous. Setae 0.6–0.7 cm long, reddish; capsules ˜1 mm long, inclined, nearly straight, ellipsoid, not or scarcely contracted below the mouth when dry; operculum high-conic; annulus not seen. Spores and calyptra not seen.

Distribution and ecology: Rare; endemic to Mexico, where it is known only from the states of Nayarit and Sonora (Figure 27); occurring on soil over rock in ravines and near rivers, ˜1300 m.

Discussion: This species is recognized by the combination of small (0.5–1.0 mm long), ovate to ovate-lanceolate, acute to short-acuminate leaves with serrate to serrulate margins that are strongly involute when dry; broad median leaf cells; distinctly differentiated alar regions

composed of numerous quadrate to short-rectangular cells; and autoicous sexual condition.

Specimens examined: MEXICO. Nayarit: Mpio. Acaponeta, near Labra along trail W of Jesús Maria, Norris & Taranto 14132 (MICH, TENN). Sonora: 15.2 km NE of Baviácora, Richards, Drouet & Lockhart 676 (F, FH, MICH, TENN, US); canyon 24.8 km SW of Cumpas, Richards, Drouet & Lockhart 722 (F, FH, MICH, NY, US); on side of Cerro Agua Caliente, along Río de los Alisos, near Imuris, Richards & Drouet 749 (F, FH, MICH, NY, TENN, US); on side of mountain just W of Alamos, Richards & Drouet 780 (F, MICH, US); Cañon de Huépari, N of Aribabi, 1310 m, Harvey 1669a (MICH); Cajón de la Higuera, near Moctezuma, White 349, 362, 366a, 367, 376, 390 (MICH); Río Moctezuma, Moctezuma, White 328, 329, 331, 348, 349 (MICH); Arroyo el Sance, near Moctezuma, White 318 (MICH).

Pseudotaxiphyllum richardsii là một loài Rêu trong họ Plagiotheciaceae. Loài này được (E.B. Bartram) Ireland miêu tả khoa học đầu tiên năm 1991.