[5] Members of the order Polydesmida are also known as flat-backed millipedes, because on most species, each body segment has wide lateral keels known as paranota.

[5] Many of the larger species show bright coloration patterns which warn predators of their toxic secretions.

One striking and unique deviation occurs in adult males of the species Aenigmopus alatus, which retain 31 pairs of walking legs and feature no gonopods.

Millipedes in other orders usually continue to molt as adults, developing through either euanamorphosis or hemianamorphosis.

[11][17] Millipedes in this order typically develop through a series of eight stages, hatching with only 7 segments (including the telson) and 3 pairs of legs, then molting seven times.

[11][3] Polydesmids are very common in leaf litter, where they burrow by levering with the anterior end of the body.

[18] The species of Polydesmida are variously classified into four suborders (names ending in "-idea"), and 29 families, the largest (numerically) including Paradoxosomatidae, Xystodesmidae, and Chelodesmidae.