Open Paleo

Hypsilophodontidae

Dollo, 1882 Type genus Hypsilophodon

Its genera lived 125.8–121.4 million years ago Early Cretaceous
Early Cretaceous stages

Hypsilophodontidae is a traditionally used family of small-bodied, bipedal ornithopod dinosaurs. Historically it functioned as a wastebasket for a wide range of lightly built ornithischians from around the world, spanning the Middle Jurassic to the Late Cretaceous, but this broad grouping is now generally regarded as an unnatural assemblage. Modern phylogenetic analyses have drastically restricted the family, moving most former members into groups such as Thescelosauridae and Elasmaria, so that only Hypsilophodon itself and one or two close relatives are retained. Some analyses recover it as the only non-iguanodontian ornithopods, the sister group of Iguanodontia (Boyd, 2015; Fonseca and colleagues, 2024), a result Fonseca and colleagues note contrasts with most other studies. Its restricted membership remains unsettled: alongside Hypsilophodon from the Barremian of the Isle of Wight, Longrich and colleagues (2024) add Vectidromeus, while Fonseca and colleagues (2024) add Gideonmantellia.

Diagnosis

  1. Accessory tooth-like ossification on the ascending process of the astragalus
  2. Straight articular surface of the femoral head
  3. Anterior (lesser) trochanter positioned anterior to the greater trochanter
  4. Small body size with gracile, cursorial bipedal limb proportions

Genera placed directly in Hypsilophodontidae

  • Hypsilophodon Huxley, 1870 Barremian (125.8–121.4 Ma)United Kingdom
  • Vectidromeus Longrich et al., 2024 Barremian (125.8–121.4 Ma)United Kingdomunder dispute

References

  1. Dollo, L. (1882). Première note sur les dinosaures de Bernissart. Bulletin du Musée Royal d'Histoire Naturelle de Belgique 1: 1-18.

    Listed and briefly diagnosed the family Hypsilophodontidae in his classification of the Ornithopoda.

    dollo1882a
  2. Madzia, D.; Arbour, V. M.; Boyd, C. A.; Farke, A. A.; Cruzado-Caballero, P.; Evans, D. C. (2021). The phylogenetic nomenclature of ornithischian dinosaurs. PeerJ 9: e12362. doi:10.7717/peerj.12362

    Provides the modern phylogenetic definition of Hypsilophodontidae.

    madzia2021a
  3. Boyd, C. A. (2015). The systematic relationships and biogeographic history of ornithischian dinosaurs. PeerJ 3: e1523. PeerJ. doi:10.7717/peerj.1523

    Recovered a restricted Ornithopoda of Hypsilophodon foxii plus Iguanodontia.

    boyd2015a
  4. Longrich, N. R.; Martill, D. M.; Munt, M.; Green, M.; Penn, M.; Smith, S. (2024). Vectidromeus insularis, a new hypsilophodontid dinosaur from the Lower Cretaceous Wessex Formation of the Isle of Wight, England. Cretaceous Research 154. Elsevier BV. doi:10.1016/j.cretres.2023.105707

    Described Vectidromeus as a hypsilophodontid, restricting the family to Hypsilophodon and Vectidromeus.

    longrich2024c
  5. Fonseca, A. O.; Reid, I. J.; Venner, A.; Duncan, R. J.; Garcia, M. S.; Müller, R. T. (2024). A comprehensive phylogenetic analysis on early ornithischian evolution. Journal of Systematic Palaeontology 22: 2346577. doi:10.1080/14772019.2024.2346577

    Recovered Hypsilophodontidae as Hypsilophodon and Gideonmantellia, the only non-iguanodontian ornithopods, noting this contrasts with most other studies.

    fonseca2024a