brontotherium
Bron`to*the"ri*um, n. Etym: [NL., fr. Gr. (Paleon.) Defn: A genus of large extinct mammals from the miocene strata of western North America. They were allied to the rhinoceros, but the skull bears a pair of powerful horn cores in front of the orbits, and the fore feet were four-toed. See Illustration in Appendix.