[5][6] The shell of Avitelmessus was about 2.25 inches (5.7 cm) in length and was nearly ovular in shape, with a "rounded outline".

[3] The upper surface was marked by "broad, shallow grooves" which formed two attached diamond-like shapes, with the larger one closer to the front.

[3] The "fairly blunt" anterior edge of the carapace possessed a small, central rostrum, with orbits on either side.

[4] The colors are described as "a medium background, dark spots and blotches, and light lines".

The "near restriction" of Avitelmessus to the Mississippi embayment (and that of other Dakoticancridae members to other specific areas) suggest "provincialism" among the family.