Spiny Rats: Echimyidae

The physical characteristics of spiny rats vary greatly from species to species, from rat-sized to the size of a small cat. Their head and body length is from 4.13 to 18.9 inches (10.5 to 48 centimeters) and a tail length of 0.2 to 16.6 inches (0.5 to 42 centimeters). They weigh from 0.46 to 2.9 pounds (210 to 1,300 grams). In appearance, most species of spiny rat are rat-like, with pointed noses, although several species have blunt noses and resemble squirrels. Their front feet have four toes while their hind feet have five.

Spiny rats got their name because most species have spiny or bristly fur, most noticeably on their backs and rumps. The spiny qualities vary between species: the armored rat has well-developed spines, spiny rats, or casiragua, have broad and stiff hair, and the punaré has soft fur with no hint of spines.

Fur color also varies greatly between species, with upper body fur being gray or various shades of brown, and white or cream on their undersides. Several species, including the toro and the white-faced arboreal spiny rat have black-and-white or white faces.