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Temporal range: Middle-Late Miocene
Synthetoceras BW.jpg
Scientific classification edit
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Family: Protoceratidae
Genus: Synthetoceras
S. tricornatus
Binomial name
Synthetoceras tricornatus
Stirton, 1932

Synthetoceras tricornatus is a large, extinct protoceratid artiodactyl, endemic to North America from the Miocene epoch, 13.6—5.33 Ma, existing for approximately 8.27 million years.[1]


Skull of S. tricoronatus

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).[2][3][4][5]


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.[6]

Body mass[edit]

Three fossil specimens of Synthetoceras were measured by M. Mendoza, C. M. Janis, and P. Palmqvist for body mass.[7] The specimens were determined to weigh:

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

Fossil distribution[edit]

Fossils have been recovered from:


  1. ^ PaleoBiology Database: Poabromylus, basic info
  2. ^ R. A. Stirton. 1932. University of California Publications, Bulletin of the Department of Geological Sciences 21(6)
  3. ^ J. T. Thurmond and D. E. Jones. 1981. Fossil Vertebrates of Alabama 1-244
  4. ^ R. L. Carroll. 1988. Vertebrate Paleontology and Evolution. W. H. Freeman and Company, New York 1-698
  5. ^ D. R. Prothero and J. A. Ludtke. 2007. Family Protoceratidae. in D. R. Prothero and S. Foss (eds.), The Evolution of Artiodactyls 169-176
  6. ^ Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 273. ISBN 1-84028-152-9.
  7. ^ M. Mendoza, C. M. Janis, and P. Palmqvist. 2006. Estimating the body mass of extinct ungulates: a study on the use of multiple regression. Journal of Zoology 270(1):90-101
  • Prothero D.R., 1998. Protoceratidae. pp. 431–438 in C.M. Janis, K.M. Scott, and L.L. Jacobs (eds.) Evolution of Tertiary Mammals of North America Cambridge University Press, Cambridge.