Tetraceratops BW
Life reconstruction of Tetraceratops insignis, by Nobu Tamura
Scientific classification
Kingdom: Animalia
Phylum: Chordata
clade: Synapsida
Order: ?Therapsida
Genus: Tetraceratops
Matthew, 1908

Tetraceratops insignis ("four-horned face emblem") is a species of synapsid from the early Permian of Texas. It was one of the first synapsids. While often considered a therapsid,[1] some studies suggest that it is actually a more basal sphenacodontian.[2][3]


Tetraceratops is known solely from a skull, one which appears to possess a mosaic of both non-therapsid and therapsid characteristics.[3] The skull is badly crushed, so the horn pair of the angular processes was initially overlooked, hence the name.[4] The premaxilla and prefrontal horns were known from the beginning, and are obvious on the skull. The teeth at the tip of the premaxilla are obviously large, but their true shape and function cannot be determined as a result of its fragmentary nature.[3] The robust morphology of the horns is proposed to serve a function in combat or a fossorial lifestyle, being analogous to the horns of Ceratogaulus and Peltephilus, and may have been used for defence when the head was exposed at the entrance of the burrow.[3]


On the basis of its percieved two pairs of horns (now known to be three), Tetraceratops' name means "four-horned face".[5] The specific epithet insignis translates to "emblem", in reference to its intricate structure.[5]


Tetraceratops was initially considered by William Diller Matthew to be most comparable to Dimetrodon, though he did not refer it to any specfic 'pelycosaur' family.[5] Some early studies suggested a sphenacodontid placement, though Alfred Romer and Llewellyn Ivor Price, in their book Review of the Pelycosauria, considered it a more basal animal, part of the Eothyrididae.[6] Some studies suggested a placement near the base of the Therapsida[1], but the most recent study suggests that Tetraceratops is actually a relatively basal synapsid.[3]


  1. 1.0 1.1 Amson, E.; Laurin M. (2011). "On the affinities of Tetraceratops insignis, an Early Permian synapsid". Acta Palaeontologica Polonica. 56 (2): 301–312. doi:10.4202/app.2010.0063.
  2. Conrad, J.; Sidor, C. A. (2001). "Re-evaluation of Tetraceratops insignis (Synapsida: Sphenacodontia)". Journal of Vertebrate Paleontology. 21: 42A. doi:10.1080/02724634.2001.10010852. S2CID 220414868.
  3. 3.0 3.1 3.2 3.3 3.4 Spindler, Frederik (2020). "The skull of Tetraceratops insignis (Synapsida, Sphenacodontia)". Palaeovertebrata. 43 (1): e1. doi:10.18563/pv.43.1.e1.
  4. Laurin, M.; Reisz. R. R. (1996). "The osteology and relationships of Tetraceratops insignis, the oldest known therapsid". Journal of Vertebrate Paleontology. 16 (1): 95–102. doi:10.1080/02724634.1996.10011287.
  5. 5.0 5.1 5.2 Matthew, W. D., 1908. A four-horned Pelycosaurian from the Permian of Texas. Bulletin of the American Museum of Natural History XXIV, 183-185
  6. "Price, A., Price, L. W. (1940). "Review of the Pelycosauria".