Diagnosis:—Differing from all other species of the genus Entosthodon by its combination of narrowly oblong-obovate, aristate leaves, that are bordered and toothed in the upper ⅔ and its zygomorphic, peristomate capsules.

TYPE:— TANZANIA. South Uluguru Mts.: East edge of Lukwangule Plateau, 2350–2370 m, 9 June 1988, T. Pócs, R. Ochyra & H. Bednarek-Ochyra 88108/ V (BOL, holotype!; isotype EGR!).

Plants small, light-green. Stems reddish-brown, to 3 mm high, branching multiple times by sub-perigonial innovation; in cross-section with 1‒2 layers of thick-walled cortical cells, a hyalodermis and a central strand; rhizoids cerise. Leaves erect-spreading, contorted when dry, narrowly oblong-obovate, (0.75)1.2–1.6(1.9) × 0.4–0.6 mm, plane to slightly recurved, short-acuminate, serrate in upper ⅔, aristate, arista to 300 μm; cells of upper lamina quadrate to oblong-hexagonal, 37–63 × 15–25 μm; basal cells 50–125 × 20–30 μm; marginal cells longer and narrower, thicker-walled, forming a border one cell wide; costae ending below apex.

Polyoicous. Setae 5–13mm long, straight to curved, pale-yellow to reddish-brown. Capsules inclined to horizontal, gibbous, zygomorphic, oblong-obovoid, 1.4–2.5 × 0.5–1 mm, weakly constricted below the mouth when dry, yellow to reddish-brown at maturity, with a well differentiated neck ca. ½ the total length of the capsule; mouth slightly oblique, ca. ¾ the diameter of the capsule; exothecial cells 15–25 × 3–7 μm, in cross-section with thick, strongly cuneate anticlinal walls, 3–5 rows of oblate cells at mouth. Opercula plano-convex, cells twisted anti-clockwise from above. Peristome double; exostome teeth straight, regular in shape, orange, tapered to an acute apex, to 100 μm high, ca. 20 μm wide at base, smooth, striate, trabeculate; endostome teeth smooth, hyaline, to 40 μm high and 30 μm wide. Spores 30–35 μm, tetrahedral, verrucate-lirate to reticulate. Calyptrae cucullate, rostrate.

Etymology: The species is named in honour of Terry A.J. Hedderson, for his interest in, and extensive collecting of, Entosthodon in southern Africa and for his contribution towards African bryology.

Habitat and distribution: The species is known only from the type collection in the Uluguru Mountains of Tanzania. The type of E. heddersonii was collected at an elevation of ca. 2360 m along a rocky, peaty stream bank on the eastern edge of the Lukwangule Plateau.