From the Greek hypnon (a kind of moss), adopted in the 18th century for a group of pleurocarpous mosses, and dendron (a tree), referring to the tree-like habit of the plants.

Plants medium-sized to tall, erect or projecting obliquely from the substratum. Distal innovations absent or weak. Stipe tomentose at the base only, occasionally with a few scattered tufts of tomentum. Frond palmate to subumbellate, occasionally pinnate or umbellate. Branches mostly strongly complanate. Stipe leaves mostly appressed to obliquely spreading, smooth; base not decurrent; apex acute to shortly acuminate; margin entire to coarsely serrate; costa ending in apex to short-excurrent; laminal cells smooth to distinctly prorate; marginal cells similar to the inner ones; alar cells usually indistinct. Branch leaves mostly glossy, anisomorphous, asymmetrical, smooth, mostly ovate-oblong; apex mostly acute to weakly acuminate; margin serrate; costa usually percurrent; lamina cells mostly prorate; submarginal cells often indistinctly elongated; alar cells indistinct.

Male gametoecia scattered. Capsule thecae costate to sulcate, strongly inclined to horizontal, occasionally cernuous; operculum bluntly rostrate. Spores 10–19 μm diam.

Hypnodendron (Müll.Hal.) Lindb. ex Mitt., in B.C. Seemann, Flora Vitiensis: 401 (1873); Hypnum Hedw. sect. Hypnodendron Müll.Hal., Synopsis Muscorum Frondosorum 2: 496 (1851) (excl. subsect. Flabellaria Müll.Hal.); Isothecium Brid. sect. Hypnodendron (Müll.Hal.) Wilson, in J.D. Hooker, Flora Novae-Zelandiae  2: 105 (1854). Type: H. junghuhnii (Müll.Hal.) A.Jaeger

Hypnodendron arcuatum (Hedw.) Lindb. ex Mitt., Transactions and Proceedings of the Royal Society of Victoria 19: 90 (1882); Hypnum arcuatum Hedw., Species Muscorum Frondosorum: 245 (1801).

This species occurs in New Zealand, Campbell Island and perhaps Norfolk Island. All Australian reports checked relate to either H. vitiense subsp. australe or H. spininervium subsp. archeri.

Hypnodendron menziesii (Hook.) Paris, Index Bryologicus: 604 (1895); Hypnum menziesii Hook., Musci Exotica 1: 33 (1818); Sciadocladus menziesii (Hook.) Lindb. ex Broth., in H.G.A. Engler & K.A.E. Prantl, Naturlichen Pflanzenfamilien I, 3(2): 1168 (1909).

Widespread in New Zealand. Single 19th century collections are known from Norfolk Island (Gunn s.n.) and Tasmania (Cunnningham s.n.), but both are most likely mislabelled.

Hypnodendron planifrons Müll.Hal., Hedwigia 37: 170 (1898).

This is a heterotypic synonym of H. spininervium subsp. spininervium which has been reported erroneously from Australia by E.G. Paris, Index Muscorum 2nd edn, 2: 374 (1904).

Hypnodendron spininervium var. pumilum Müll.Hal. ex Müll.Hal. & Broth., Abhandlungen Herausgegeben vom Naturwissenschaftlichen Verein zu Bremen 16: 509 (1900), nom. nud.

Erroneously treated as validly published in H. Streimann & J. Curnow, Catalogue of mosses of Australia and its external territories: 197 (1989).

Hypnodendron whiteleggei Müll.Hal. ex A.Burges, Proceedings of the Linnean Society of New South Wales 60: 84 (1935), nom. nud.

Erroneously treated as validly published in H. Streimann & J .Curnow, Catalogue of mosses of Australia and its external territories: 198 (1989).

Ramsay, H.P. (1987). Cytological and other studies on the Hypnodendraceae. Memoirs of the New York Botanical Garden 45: 135–153.

Touw, A. (1971). A taxonomic revision of the Hypnodendraceae (Musci). Blumea 19: 211–354.

Touw, A. (2012). Australian Mosses Online 22. Hypnodendraceae. (Australian Biological Resources Study: Canberra). Version 18 May 2012.

Touw, A. (2012). Australian Mosses Online 22. Hypnodendraceae. (Australian Biological Resources Study: Canberra). Version 18 May 2012.