Geographic distribution: Supposedly endemic to Papua New Guinea (Hattori & Pippo 1986) (Fig. 7.1).
Affinities, differentiation & variation: Hattori (1972c) suggested that F. baladina from New Caledonia and F. incumbens from New Zealand were possibly closely related to F. errans and its variety var. angulistipula. However, it is contended here that a closer relationship may lie with F. fugax than with F. incumbens. Morphologically, F. errans and F. fugax appear to share the following similarities: small plant size; lateral margins of the underleaves entire or variously toothed with a single tooth on each shoulder, triangular, often blunt or obsolete; comparatively long lobules; and the potential to abundantly produce gemmae and propagula. Frullania errans also appears morphologically similar to F. baladina and F. campanulata.
Notes: Hattori (1972c) noted that the type does not have gemmae, but that another specimen determined by Verdoorn has gemmae abundantly dispersed on the dorsal surface of the leaf- and bract-lobes. This species is only known from scant material and collections, and more study is required to assess morphological variability and its relationship with other taxa, especially with F. baladina and F. errans var. angulistipula.