Orthoporus ornatus is a North American species of millipede in the family Spirostreptidae that can be found in the U.S. states of Arizona, New Mexico and Texas, and as far south as the Mexican state of San Luis Potosí. Individuals on average are 4 inches (10 cm) in length, but can either be as small as 3 inches (76 mm), or exceed up to 6 inches (150 mm) in length. They are dark brownish coloured, but can sometimes be yellow. In fact, in every state the species look different. The antennae are located near the organs of Tömösváry. The species feed on both living and dead organic material. The species prefer sunshine, but can be seen on summer rainy days as well. A disturbed Orthoporus ornatus may curl into a coil and release a toxic substance that is located on all sides of its body. The species can live more than 10 years. The species feed on shrubs of Ephedra, which grows in Jornada del Muerto, and on Salsola that grows in Albuquerque.