Telaranea is the third largest genus of Lepidoziaceae, after Bazzania (over 450 species) and Lepidozia (over 300 species). In this monograph, 98 species of Telaranea are recognized, 62 of which are extra-Australasian. Included are 11 new species, 2 new varieties, 27 new combinations (25 species and one variety), and one new name. New taxa are fully described and illustrated. Two subgenera of Telaranea are recognized (subg. Acrolepidozia, subg. Telaranea), and 7 sections within subg. Telaranea (sect. Neolepidozia (Fulf. & J. Tayl.) Engel & Merr. comb. nov., sect. Cancellatae Engel & Merr., sect. Ceraceae Engel & Merr. sect. nov., sect. Tricholepidozia (Schust.) Engel & Merr. comb. nov., sect. Transversae Engel & Merr., sect. Telaranea, sect. Tenuifoliae (Schust.) Engel & Merr. comb. nov.).

A major part of this work is devoted to a phylogenetic study of the genus Telaranea, with a discussion of character evolution in the genus and a reconstruction of ancestral character states. An ancestral area analysis was also undertaken, using phylogeny to trace the geographical history of members of the genus. Differing concepts of phylogeny as applied to leafy hepatics are also briefly considered. The phylogenetic analysis included 56 taxa and 32 characters, with representative species of Lepidozia, Kurzia, and Arachniopsis as out-groups. Cladograms obtained from parsimony analyses of the full data set and subsets of taxa, as well as distance (NJ) trees, were strikingly similar in topology. Monophyly of Telaranea is supported by the possession of a hyaloderm (enlarged, usually hyaline stem cortical cells) and an undivided first branch underleaf. Progressive reduction in morphological complexity as a central evolutionary tendency in the genus is strongly supported. The phylogeny indicates that Kurzia, as defined by the presence of Microlepidozia-type branching, is polyphyletic, and 6 species previously assigned to Kurzia are transferred to Telaranea. No support was found for maintaining Arachniopsis as a distinct genus, and 6 species of the genus are transferred to Telaranea. The new genus Amazoopsis Engel & Merr. is described, with 3 species: A. diplopoda (Pócs) Engel & Merr. comb. nov., A. dissotricha (Spruce) Engel & Merr. comb. nov., and A. gracilis Engel & Merr. sp. nov. The status of Monodactylopsis (Schust.) Schust. is discussed; the genus includes M. monodactyla (Spruce) Schust. and M. minima Schust. ex Engel & Merr., sp. nov. Paracromastigum vastilobum (Steph.) Engel & Merr. is a new combination. Keys to the subgenera and sections of Telaranea, the Australasian species, as well as the southern South American species of Telaranea, an