G. subbasilare is dark green turf-forming terrestrial or log dwelling moss of wet forest and rainforest.

The leaves are unique in the family, having thin-walled and elongated lamina cells. The teeth on the leaf margins often occur in pairs, particularly near the leaf apex. When dry, the chloroplasts clump at the cell ends, giving the leaf a characteristic chequered pattern which can be discerned with a hand lens.

G. subbasilare may easily be mistaken for Pyrrhobryum mnioides but the latter is a larger and brighter green. G. subbasilare also has a softer and more delicate appearance.