Synthetoceras tricornatus is a large, extinct protoceratid, endemic to North America ( Nebraska ) during the Late Miocene, 10.3—5.3 Ma, existing for approximately 5 million years.

[1] With a length of 2 m (6.6 ft) and a mass of 150–200 kg (330–440 lb), Synthetoceras was the largest member of its family.

[2][3] It was also the last, and had what is considered to be the protoceratids' strangest set of horns.

Only males had this strange horn, and they probably used it in territorial fights.

This prehistoric even-toed ungulate-related article is a stub.