Plants very small, to 5 mm tall, tufted, pale to glaucous green above, yellow to brown below. Stems erect, rarely branched. Leaves erect-spreading, ovate-lanceolate to linear-lanceolate, acuminate, 0.22–0.60 mm long, 0.115–0.200 mm wide; margin entire to bluntly denticulate above; costa failing below apex; laminal cells short-rectangular, losing shape towards apex and margin, thick-walled, smooth, 12–60 × 7–6 µm.

Setae erect, to 10 mm long. Capsules erect to pendulous, globose to oblong, rarely urceolate, wrinkled or occasionally slightly furrowed; operculum convex, umbonate. Peristome absent. Spores globose, densely papillose, 44–70 µm diameter.

Endemic.

This minute, endemic species occurs in Western Australia, South Australia, Victoria and Tasmania. It has been reported from New South Wales (Scott & Stone, 1976), but no specimens could be examined to confirm this; however, its occurrence there is not unlikely.

Philonotis australiensis grows on moist soils in sheltered habitats.

Glyphocarpa pusilla Hook.f. & Wilson, London J. Bot. 3: 544 (1844); Bartramia pusilla (Hook.f. & Wilson) Müll.Hal., Syn. Musc. Frond. 1: 480 (1848); Bartramidula pusilla (Hook.f. & Wilson) Paris, Index. Bryol. 116 (1894); Philonotis australiensis D.G.Griffin & W.R.Buck, Bryologist 92: 376 (1989). 
Type: Tas., D.Lyall; holo: BM? n.v.

Taxonomic synonyms

Bartramidula weymouthii Broth., Pap. & Proc. Roy. Soc. Tasmania 1902: 115 (1903); Bartramidula pusilla var. weymouthii (Broth.) Rodway, Pap. & Proc. Roy. Soc. Tasmania 1913: 194 (1914).
Type: on roadside bank, Port Cygnet, Lymington, Tas., Sept. 1889, W.A.Weymouth; holo: H-BR n.v.

W.A.: Preston River, D.H.Norris 25667 (CANB).

S.A.: 13 km NE of Cleve, H.Streimann 54692 [Musci Australas. Exsicc. 380] (CANB).

Vic.: Teddys Lookout, Lorne, W.W.Watts 1080 (NSW).

Tas.: Mt Wellington, W.A.Weymouth 550 (CANB).

D.G.Catcheside, Mosses of South Australia 286, fig. 171 (1980), as Bartramidula pusilla; D.Meagher & B.Fuhrer, Field Guide to the Mosses and Allied Plants of Southern Australia 165 (2003).

Scott, G.A.M. & Stone, I.G. (1976).The Mosses of Southern Australia: 322–341. (Academic Press: London).

Gilmore, S.R. (2012). Australian Mosses Online 42. Bartramiaceae. Australian Biological Resources Study, Canberra. Version 9 June 2012. http://www.anbg.gov.au/abrs/Mosses_online/42_Bartramiaceae.html

First published as: Gilmore, S.R. (2006). Bartramiaceae, in McCarthy, P.M (ed.) Flora of Australia 51: 248–270. (Australian Biological Resources Study, Canberra & CSIRO Publishing, Melbourne.)