Megalodacne reaches a maximum length of only 12 mm, Megalodacne are large beetles but its elytra does not cover the whole abdomen.
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. 
Species of the genus Megalodacne very closely resembles members of the genera Episcapha and Episcaphula (some members of which were formerly classified under Megalodacne). The best way to tell them apart is by size, as sap beetles are generally small, ranging from 2 to 12 mm (0.08 to 0.47 in) in length. An example of which is the sap beetle (Nitidulidae) genus Glischrochilus. 
