Open Paleo

Hypsilophodon

Huxley, 1870 hip-si-LOF-o-don /ˌhɪpsɪˈlɒfoʊdɒn/

From Greek 'hypsilophos' meaning 'high-crested' and 'odon' meaning 'tooth', hence 'high-crested tooth', referring to its distinctive tooth morphology.

125.8–121.4 million years ago Barremian, Early Cretaceous
Early Cretaceous stages

Hypsilophodon is a neornithischian dinosaur genus from the Early Cretaceous period of England. It has traditionally been considered an early member of the group Ornithopoda, but recent research has put this into question.

Diagnosis

  1. Premaxillary bones nearly entire and distinctly preserved (unique among Dinosauria at time)
  2. Incisor teeth in premaxilla distinctly different in shape from maxillary teeth, anterior premaxilla beak-like and edentulous
  3. Maxillary teeth lack serrations characteristic of Iguanodon, instead showing enamel ridges with sinuated free edge
  4. Metatarsus indicates four well-developed toes, unlike Iguanodon
  5. Tibia and fibula proportions different from Iguanodon: fibula 5+ inches with leg longer than femur

Species

Hypsilophodon foxii Huxley, 1870

Type species

Named for William Fox, the clergyman and fossil collector who discovered the holotype skull on the Isle of Wight.

Holotype
NHMUK PV R 197 , Natural History Museum
Material
Skull approximately 3.8-3.9 inches long with premaxillary bones nearly entire. Maxilla with ten teeth, mandible ramus visible. Vertebra centrum preserved.
Horizon
Hypsilophodon Bed Bed, Wessex Formation, Barremian, Early Cretaceous , 125.8–121.4 million years ago
Locality
about 210 yd east of Barnes High, Isle of Wight, United Kingdom Huxley (1870) names the Wealden formation and gives no site.

Notable specimens

  • NHMUK PV R 5829

    Natural History Museum largest individual

    The skeleton of a large animal and the largest known specimen, with a femur length of 202 millimeters; it anchors the genus's revised maximum known length of about 1.8 meters after a larger femur was reattributed to Valdosaurus.

    Galton (1974)Galton (2009)

  • NHMUK PV R 5830, NHMUK PV R 196, NHMUK PV R 196a

    Natural History Museum ontogeny

    Among the most significant specimens of the genus, these are skeletons of juvenile animals, documenting growth stages of the taxon.

    Galton (1974)

References

  1. Huxley, T. H. (1870). On Hypsilophodon Foxii, a new Dinosaurian from the Wealden of the Isle of Wight. Quarterly Journal of the Geological Society of London 26(1-2): 3-12. Geological Society of London. doi:10.1144/gsl.jgs.1870.026.01-02.07 huxley1870a
  2. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Ornithischians. Princeton University Press.

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

    jones2026a
  3. Galton, P. M. (1974). The ornithischian dinosaur Hypsilophodon from the Wealden of the Isle of Wight. Bulletin of the British Museum (Natural History), Geology 25: 1-152.

    Locates the holotype about 210 yd east of Barnes High, which the describing paper does not.

    galton1974a
  4. Galton, P. M. (2009). Notes on Neocomian (Lower Cretaceous) ornithopod dinosaurs from England - Hypsilophodon, Valdosaurus, "Camptosaurus", "Iguanodon" - and referred specimens from Romania and elsewhere. Revue de Paléobiologie, Genève 28(1): 211-273. galton2009a