New World porcupines are stout animals, with blunt, rounded heads, fleshy, mobile snouts, and coats of thick, cylindrical or flattened spines.

[1] They are distinguished from the Old World porcupines in that they have rooted molars, complete collar bones, entire upper lips, tuberculated soles, no trace of first front toes, and four teats.

Their diets consist mainly of bark, leaves, and conifer needles, but can also include roots, stems, berries, fruits, seeds, nuts, grasses, and flowers.

[1] They include three genera, of which the first is represented by the North American porcupine (Erethizon dorsatum), a stout, heavily built animal, with long hairs almost or quite hiding its spines, four front and five hind toes, and a short, stumpy tail.

Genus Chaetomys, distinguished by the shape of its skull and the greater complexity of its teeth, contains the bristle-spined rat (C. subspinosus), a native of the hottest parts of Brazil.