The Ringbone Formation is a thick Campanian-age sequence of Late Cretaceous rocks in southwestern New Mexico, first identified near Ringbone Ranch in the Little Hatchet Mountains. About 7,500 feet thick, it records changing environments through conglomerate, dark shale, sandstone, black limestone, tuffaceous sandstone, and upper beds that include basalt and andesite breccia. It lies above the Mojado Formation and below the Hidalgo Formation. Its fossils, including Physa, Sabal, tyrannosaurs, hadrosaurs, and a hadrosaur tail skin impression, make it one of New Mexico’s dinosaur-bearing formations and an important geologic and paleontologic record.