Corybas obscurus is a
terrestrial,
perennial herb with a single reniform (kidney-shaped) or cordiform (heart-shaped) leaf born on a
petiole that is 5.1–40.8 mm long. The leaf itself is 5.8–18.2 × 9.6–26.7 mm and has a
mucronate apex. The single flower is held on a peduncle with a small floral bract. The dorsal
sepal arches over the
labellum and is broad at the apex; it ranges from dark crimson to nearly black. The lateral sepals range from crimson to dark red and are filiform (thread-like), between 11.7 and 20.6 mm long. The
petals resemble the lateral sepals but are longer, between 27.3 and 57.2 mm long. The labellum, around 10 mm wide, is
auriculate at the base and is strongly curved downwards. It folds inwards and forms a central groove; its margins are very slightly cupped. The inner surface of the labellum is covered with
trichomes ending with a compact head (glandular). It is curved at its base, forming a cylindrical opening with a flared, highly fimbriate (toothed) mouth. The surface of the posterior half of the labellum has many hair-like structures that are curved backwards. The labellum is dark crimson or nearly black with a pale green center. The ovary is 3.0–8.4 mm long. The
column is 1.6 mm long and curved, and the
stigma is flanked with two notched winglike structures. Flowering occurs from October to November. When not in flower,
Corybas obscurus can be confused with other species in the
C. trilobus species complex, whose members all share auriculate leaves. In flower, it is similar to
Corybas confusus, particularly in terms of the lip color. However,
C. obscurus has a short dorsal sepal firmly pressed against the upper border of the labellum and a reniform to cordiform leaf.
C. obscurus may be distinguished from
C. trilobus by its dark flower coloration and opacity. == Taxonomy ==