Howler monkey, (genus Alouatta), any of several tropical American monkeys noted for their roaring cries. Several species of howlers are widely distributed through Central and South America. These are the largest New World monkeys and generally attain lengths of about 40–70 cm (16–28 inches), excluding the 50–75-cm (20–30-inch) tail. Howlers are stoutly built bearded monkeys with a hunched appearance and thickly furred prehensile tails that are naked on the underside of the tip to afford a better grip. The hair is long and thick and, depending on species, is typically black, brown, or red. Howlers are characterized by expansion of the hyoid bone into a large shell-like organ in the throat that gives resonance to the voice. In connection with the enlarged hyoid, howlers have a large throat, protruding jaws, and high sloping faces.