Desert millipedes out of Texas, New Mexico and northern Mexico, and unusual for the group in being genuinely arid-adapted.
O. ornatus reaches six inches or so and tolerates conditions that would kill most millipedes. That does not mean bone dry. They need a humid retreat within a drier enclosure, which is a more nuanced setup than either extreme, and getting it wrong is the common failure.
Wild-collected seasonally in volume, so prices are very low and availability follows the warm months. They are also long lived, which means a wild adult may have many years left or very few, and the listing will not tell you. Captive breeding is uncommon and slow.