Much of what has been named and reported from Australia as A. acuminata (especially crenate-denticulate, falcate-leaved material) is A. acutifolia. The two species can be readily distinguished when sporophytes are present; A. acuminata has turgid spores of c. 16-25 µm, while A. acutifolia has turgid spores that are mostly at least 32-50 µm. In the absence of capsules identification can be uncertain since leaf characters can vary within species. Typical A. acuminata has straight, panduriform leaves 2-3 times as long as wide and often widest above or at the sinus; apices are ±abruptly formed, occupy c. a quarter of the length of the leaf, and distal cells are often triangular and wider than long from near the sinus to the apex. Andreaea acutifolia often has falcate and secund, indistinctly to obviously panduriform leaves that are clearly broadest near the insertion. The leaves tend to taper distally from the sinus, but when abruptly narrowed that distal portion tends to occupy about a third of the length of the leaf. The leaves of A. acutifolia have distal laminal cells that are usually (but not always) longer than wide.
Stems 10-20 mm long. Leaves ±panduriform, 0.25-0.40 mm wide, equally wide in base and mid-leaf, 2-3 times as long as wide; blade rarely falcate, usually not secund, not flexuose; apex mostly slightly reflexed, narrowly acute or acuminate, not rounded, often with a ±abrupt terminal triangular area occupying a quarter (rarely more) of the length of the leaf; sinus strongly contracted; margin incurved, usually proximally crenate or toothed; base distinctly sheathing; costa absent; laminal cells heterogeneous, distally papillose and unistratose, proximally marginally mostly rectangular, often mostly oblique. Perigonial paraphyses absent. Perichaetial bracts convolute and sheathing. Capsule base shorter than valves. Turgid spores 16-25 µm diam.; shrivelled spores (14-) 16-21 µm diam.