The tail is often lost, because it fractures easily, which may help it to escape from predators. Echimyids are ratlike in general appearance, with pointed or somewhat truncate noses and moderate-sized eyes and ears. The rounded or bluntly pointed ears extend beyond the pelage. The limbs are of moderate length. The cheek teeth are flat-crowned and rooted.
Spiny rats inhabit forests or clearings, often near water.
They are often common and the most abundant mammal in parts of their range, but most genera are little known. They may dig their own burrows or seek shelter beneath stumps, logs, or rocks. Several genera live in the hollows of trees, and Euryzygomatomys is apparently fossorial. Thrichomys has been noted in captivity leaping on its hind legs, but the other genera are climbing or scampering animals. Echimyids are reported to be good swimmers.