[1] Adult beetles of the genus Megalodacne range in size from 9 to 22 millimetres (0.35 to 0.87 in), making them among the larger members of the family.

[2][3] Distinguishing characteristics of the genus along with other members of the subfamily Megalodacninae include large eyes and a lack of depressions in the club joint of the antennae.

[7][9] The elytra of the sap beetles which most resemble Megalodacne also do not cover the whole abdomen and leave the last abdominal segment(s) exposed.

[10] Megalodacne species feed on harder bracket fungi than smaller members of the family.

In others, the larvae feed alongside adults by gnawing out shallow depressions on the fruiting bodies of fungi.