Vertebrate fossils have been recovered from the Cypress Hills Formation since 1883, producing a wealth of material for study. The largest bones and teeth come from brontotheres; some of the skulls are almost four feet (1.2 m) long. There are also bones of entelodonts (the so-called giant pigs or hell pigs), hornless members of the rhinoceros family, small camels, antelopes, oreodonts, anthracotheres, and several genera of horses including Mesohippus, Parahippus, and Hypohippus. Carnivores include small canids, medium sized sabre-toothed cats, and bear-like Hemipsalodons. Small mammals, represented primarily by teeth and jaw fragments, include rabbits and many kinds of rodents, as well as proscalopid insectivores. Reptiles and amphibians include crocodilians, turtles, boid snakes, burrowing toads, and spadefoot toads. There are also bones of freshwater fish such as catfish and bowfins.