Open Paleo

Protoceratops

Granger & Gregory, 1923 PROH-toh-SERR-uh-tops /ˌproʊtoʊˈsɛrətɒps/

From Greek protos (first) and keratops (horned face); meaning "first horned face", chosen by Granger and Gregory to reflect their interpretation of the genus as an early, pre-ceratopsid member of the horned-dinosaur lineage.

83.6–72.2 million years ago Campanian, Late Cretaceous
Late Cretaceous stages

Protoceratops is a genus of small protoceratopsid dinosaurs that lived in Asia during the Late Cretaceous, around 75 to 71 million years ago. The genus Protoceratops includes two species: P. andrewsi and the larger P. hellenikorhinus. The former was described in 1923 with fossils from the Mongolian Djadokhta Formation, and the latter in 2001 with fossils from the Chinese Bayan Mandahu Formation. Protoceratops was initially believed to be an ancestor of ankylosaurians and larger ceratopsians, such as Triceratops and relatives, until the discoveries of other protoceratopsids. Populations of P. andrewsi may have evolved into Bagaceratops rozhdestvenskyi through anagenesis.

Diagnosis

  1. Skull broadly triangular in dorsal view, with wide lateral crests formed mainly by posteriorly and ventrally expanded jugals.
  2. Orbits very large and not surmounted by supraorbital horns.
  3. Hornless skull (or with at most an incipient nasal horn-core in adult males formed by upwardly arched nasals).
  4. Two premaxillary teeth present.
  5. Parietosquamosal frill fenestrated and supporting a strong median parietal crest; frill length increases continuously through ontogeny and can exceed basal skull length in mature adults.
  6. Ectopterygoid large and extensively exposed on the palate, in contact with the jugal — a primitive condition lost in later ceratopsians.
  7. Sacrum elongate and narrow, with the sacral vertebra count rising from seven in young individuals to eight in fully adult animals.
  8. Forelimb scarcely more than half the length of the hindlimb, with the femur shorter than the tibia and a relatively large pes bearing a compact metatarsus.

Species (2)

Protoceratops andrewsi Granger & Gregory, 1923

Type species

Named for Roy Chapman Andrews, leader of the AMNH Central Asiatic Expedition that recovered the holotype.

Holotype
AMNH 6251 , American Museum of Natural History
Material
Skull lacking the occiput, with mandible and dentition preserved; about 160 mm long from premaxilla to posterior margin of the jugal.
Horizon
Bayn Dzak Member, Djadokhta Formation, Campanian, Late Cretaceous , 83.6–72.2 million years ago
Locality
Bayan Zag, Ömnögovi, Mongolia

Protoceratops hellenikorhinus Lambert et al., 2001

From Greek 'hellenikos' (Grecian) and 'rhis' (nose), referring to the elevated, angular snout resembling a Greek profile.

Holotype
IMM 95BM1/1 , Inner Mongolia Museum, Hohhot
Material
Nearly complete skull of a male individual, missing only the rostralmost premaxillae/rostral bone, the caudal basioccipital, and the frill's median parietal ridge; no postcranial elements.
Horizon
Bayan Mandahu Formation, Campanian, Late Cretaceous , 83.6–72.2 million years ago
Locality
Bayan Mandahu, Inner Mongolia, China
Diagnosis
  1. Ventral edge of the dentary straight (curved in adult P. andrewsi).
  2. Caudal edge of the angular forming a caudally facing triangular surface for insertion of the depressor mandibulae.
  3. Long ventral projection of the squamosal contacting the quadratojugal at the caudoventral corner of the infratemporal fenestra (not observed in P. andrewsi).
  4. Longitudinal ridge on the maxilla straight and strongly reduced, discontinuous with the ventral margin of the jugal (well-marked, curved, and continuous with the jugal in P. andrewsi).
  5. Nasal horns bordered rostrally by a distinct concavity and more individualized than the incipient, regularly convex horns of P. andrewsi.

Notable specimens

  • “Fighting Dinosaurs”

    MPC-D 100/512 Paleontological Center, Mongolian Academy of Sciences Found 1971 iconic

    The Protoceratops half of the famous "Fighting Dinosaurs" specimen, fossilized in combat with a Velociraptor (MPC-D 100/25), giving direct evidence of predator-prey behavior. Found 3 August 1971 at the Tugriken Shire locality on a Polish-Mongolian expedition.

    Barsbold (1974)

  • MPC-D 100/1021

    Paleontological Center, Mongolian Academy of Sciences reproductive

    An embryo-bearing egg clutch reported in 2017 from the Ukhaa Tolgod locality, comprising at least 12 eggs and embryos with 6 preserving nearly complete skeletons; remains around the eggs indicate a soft-shelled composition.

    Erickson et al. (2017)

  • MPC-D 100/530

    Paleontological Center, Mongolian Academy of Sciences ontogeny

    A Protoceratops nest containing 15 articulated juveniles, collected from the Tugriken Shireh locality by Mongolian-Japanese expeditions and reported in 2011, documenting early growth stages of the genus.

    Fastovsky et al. (2011)

  • AMNH 6418

    American Museum of Natural History Found 1923 exceptional preservation

    A nearly complete skeleton collected in 1923 at the Flaming Cliffs in a rolled-up position, its skull preserving a thin, wrinkled, skin-like layer interpreted as possible skin impressions; the right side of the skull reportedly still retains this layer.

    Brown & Schlaikjer (1940)

  • ZPAL Mg D-II/3

    Institute of Paleobiology, Polish Academy of Sciences Found 1965 trace association

    An articulated subadult skeleton collected in 1965 at Bayan Zag; during preparation a four-toed digitigrade footprint cast was found below its pelvic girdle, one of the first finds of a dinosaur footprint associated with an articulated skeleton and the first for Protoceratops.

    Niedźwiedzki et al. (2012)Słowiak et al. (2019)Tereshchenko (2021)

References

  1. Barsbold, R. (1974). Poyedinok dinozavrov [Dueling dinosaurs]. Priroda 2: 81-83. barsbold1974a
  2. Erickson, G. M.; Zelenitsky, D. K.; Kay, D. I.; Norell, M. A. (2017). Dinosaur incubation periods directly determined from growth-line counts in embryonic teeth show reptilian-grade development. Proceedings of the National Academy of Sciences 114(3): 540-545. doi:10.1073/pnas.1613716114 erickson2017a
  3. Fastovsky, D. E.; Weishampel, D. B.; Watabe, M.; Barsbold, R.; Tsogtbaatar, K.; Narmandakh, P. (2011). A nest of Protoceratops andrewsi (Dinosauria, Ornithischia). Journal of Paleontology 85(6): 1035-1041. doi:10.1666/11-008.1 fastovsky2011a
  4. Niedźwiedzki, G.; Singer, T.; Gierliński, G. D.; Lockley, M. G. (2012). A protoceratopsid skeleton with an associated track from the Upper Cretaceous of Mongolia. Cretaceous Research 33(1): 7-10. doi:10.1016/j.cretres.2011.07.001 niedźwiedzki2012a
  5. Słowiak, J.; Tereshchenko, V. S.; Fostowicz-Frelik, Ł. (2019). Appendicular skeleton of Protoceratops andrewsi (Dinosauria, Ornithischia): comparative morphology, ontogenetic changes, and the implications for non-ceratopsid ceratopsian locomotion. PeerJ 7: e7324. doi:10.7717/peerj.7324 słowiak2019a
  6. Tereshchenko, V. S. (2021). Axial skeleton of subadult Protoceratops andrewsi from Djadokhta Formation (Upper Cretaceous, Mongolia). Paleontological Journal 55(7): 1408-1457. doi:10.1134/S0031030121120030 tereshchenko2021a
  7. Granger, W.; Gregory, W. K. (1923). Protoceratops andrewsi, a pre-ceratopsian dinosaur from Mongolia. American Museum Novitates 72: 1-9.

    Erects the genus and the type species on AMNH 6251 from the Djadokhta Formation; collected on the AMNH Central Asiatic Expedition.

    granger1923a
  8. Brown, B.; Schlaikjer, E. M. (1940). The structure and relationships of Protoceratops. Annals of the New York Academy of Sciences 40(3): 133-266. doi:10.1111/j.2164-0947.1940.tb00068.x

    Foundational AMNH monograph describing the full ontogenetic series (eggs through aged adults) and arguing for a transitional, near-bipedal pelvic structure in the genus.

    brown1940a
  9. Maryańska, T.; Osmólska, H. (1975). Protoceratopsidae (Dinosauria) of Asia. Palaeontologia Polonica 33: 133-182.

    Polish-Mongolian Expedition monograph; reports six P. andrewsi skulls from Bayan Zag smaller than those known to Brown and Schlaikjer, and erects Bagaceratops rozhdestvenskyi.

    maryańska1975a
  10. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Ornithischians. Princeton University Press.

    Source of the hip height estimate, and the appearance features.

    jones2026a
  11. Lambert, O.; Godefroit, P.; Li, H.; Shang, C. Y.; Dong, Z. M. (2001). A new species of Protoceratops (Dinosauria, Neoceratopsia) from the Late Cretaceous of Inner Mongolia (P. R. China). Bulletin de l'Institut Royal des Sciences Naturelles de Belgique, Sciences de la Terre 71(supplement): 5-28.

    Original description of Protoceratops hellenikorhinus on a male skull from the Bayan Mandahu Formation of Inner Mongolia.

    lambert2001a