Key to the species of Cryptoxyleborus of Thailand [modified from Smith et al. 2020]

1 Elytra without visible mycangial opening...................................................................2

– Elytra with mycangial opening on basal slope or near scutellum on dorsal surface.................................. 3

2 Smaller, stouter species, 1.4 mm long, 2.55× as long as wide; pronotum as long as wide; sides of tapering part of elytra convex in dorsal view......................................................................... percuneolus (Schedl)

– Larger, more elongate species, 2.1‒2.2 mm long, 3.0–3.3× as long as wide; pronotum 1.15 times longer than wide; sides of tapering part of elytra weakly concave in dorsal view.......................................... brevicauda sp. nov.

3 Mycangial openings located on elytral disc, comprised of two large subcircular pits; elytral apex attenuate; first elytral interstriae without distinct denticles.................................................................. subnaevus Schedl

– Mycangial openings located on anterior slope of elytral base, comprised of two transverse slits or four small circular pits; elytral apex tapering; first elytral interstriae with a row of distinct denticles............................................. 4

4 Mycangial openings in elytral base comprised of four small round pits............................ .. quadriporus Beaver

– Mycangial openings in elytral base comprised of two transverse slits..............................................5

5 Smaller; 2.35–2.6 mm; elytral vestiture uniseriate on all discal interstriae (except at base)........... stenographus (Schedl)

– Larger, 3.2–3.3 mm; elytral vestiture irregularly biseriate on discal interstriae 2–4.................. turbineus (Sampson)