Temporal range: Late Miocene
An artist's illustration of Synthetoceras tricornatus
Synthetoceras tricoronatus.jpg
A skull of Synthetoceras tricornatus
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Family: Protoceratidae
Genus: Synthetoceras
Stirton, 1932
Species: S. tricornatus
Binomial name
Synthetoceras tricornatus
Stirton, 1932
Synthetoceras is a large, extinct protoceratid endemic to North America from the Miocene epoch, 13.6—5.33 Ma, existing for approximately 8.27 million years.


Synthetoceras was named by Stirton (1932). It is the type genus of Synthetoceratinae, Synthetoceratini. It was assigned to Protoceratidae by Stirton (1932), Thurmond and Jones (1981) and Carroll (1988); to Synthetoceratinae by Hulbert and Whitmore (2006); and to Synthetoceratini by Webb (1981), Prothero (1998), Webb et al. (2003) and Prothero and Ludtke (2007).


With a length of 2 m (6 ft 8 in), Synthetoceras was the largest member of its family. It was also the last, and had what is considered to be the protoceratids' strangest set of horns. The two horns above its eyes looked fairly normal and similar to those of many modern horned mammals, but on its snout it had a bizarre, long horn with a forked tip that gave it a Y shape. Only males had this strange horn, and they probably used it in territorial fights.

Body mass

Three fossil specimens of Synthetoceras were measured by M. Mendoza, C. M. Janis, and P. Palmqvist for body mass. The specimens were determined to weigh:

  • Specimen 1: 332.4 kg (730 lb)
  • Specimen 2: 228.3 kg (500 lb)

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