The term ‘siphuloid’ is introduced for a suite of distinct lichen genera with a superficially similar foliose to fruticose morphology, notably Siphula, Siphulella, Siphulopsis, Parasiphula and Knightiellastrum. Three new species are described: Parasiphula squamosa Kantvilas (from Tasmania and New Zealand), characterized by a whitish grey, squamulose or minutely foliose thallus lacking lichen substances or containing traces of atranorin; Siphula capensis Kantvilas (from southern Africa), containing baeomycesic and squamatic acids, and characterized by robust, broadly flattened, rounded lobes with thickened apices; and S. crittendenii (from the Caribbean but with an outlying collection from Queensland, Australia), an epiphytic species containing thamnolic acid, with fragile, flattened lobes mostly to 10 mm long and 1−5 mm wide, with ragged or much-divided apices. Salient features of the species of Parasiphula are summarized and a first key for this genus is presented. Infrageneric problems in Siphula are also discussed briefly. Caribbean islands, Coccotremataceae, Icmadophilaceae, new species, southern Africa, Tasmania, taxonomy