Open Paleo

Hesperonyx

Rotatori et al., 2023 hes-PERR-ON-iks

Western claw; from Greek hesperos (western) and onyx (claw)

154.8–149.2 million years ago Kimmeridgian, Late Jurassic
Late Jurassic stages

Hesperonyx is an extinct genus of dryomorphan ornithopod dinosaur from the Late Jurassic Lourinhã Formation of Portugal. The genus contains a single species, Hesperonyx martinhotomasorum, known from bones of the fore- and hindlimbs.

Under dispute

Hesperonyx martinhotomasorum is of uncertain position within Dryomorpha. Rotatori and colleagues (2023), describing the genus, recovered it among the non-dryosaurid dryomorphans under parsimony and at the base of Dryosauridae in a time-calibrated Bayesian analysis, which they attributed probably to long-branch attraction, and concluded it is a dryomorphan of uncertain affinities. Later analyses remain split: Bertozzo and colleagues (2025a) recovered it within Dryosauridae under implied weighting, and Huang and colleagues (2026) paired it with Draconyx in a clade they labeled Dryosauridae, while Bertozzo and colleagues (2025b) placed it outside Dryosauridae as the sister of the ankylopollexian clade. No author argues for either position; the disagreement is between analyses, not between published interpretations. It is placed at Dryomorpha.

Diagnosis

  1. Cnemial crest of tibia laterally oriented
  2. Inner condyle of tibia forms 90° angle with cranio/caudal axis of proximal tibia
  3. Fibula and tibia articulation tightly interlocked
  4. Fibula has protruding process overhanging fibular condyle cranially
  5. Distal fibular shaft develops high crest and marked twist
  6. Reduced metatarsal I
  7. Claw-like pedal ungual phalanges

Species

Hesperonyx martinhotomasorum Rotatori et al., 2023

Type species

Named for Micael Martinho and Carla Alexandra Tomás, honoring their efforts in fossil curation and preparation at the Museu da Lourinhã.

Holotype
ML 2700 , Museu da Lourinhã
Material
Isolated carpal elements including ungual phalanx, left ulnare and left metacarpal fragment; partial left hind limb including tibia, fibula, complete metatarsals I-II, partial metatarsal III, proximal metatarsal IV, five phalanges, three pedal unguals.
Horizon
Praia da Amoreira-Porto Novo Member, Lourinhã Formation, Kimmeridgian, Late Jurassic , 154.8–149.2 million years ago
Locality
Praia de Porto Dinheiro, Lisbon, Portugal

References

  1. Rotatori, F. M.; Ferrari, L.; Sequero, C.; Camilo, B.; Mateus, O.; Moreno-Azanza, M. (2023). An unexpected early-diverging iguanodontian dinosaur (Ornithischia, Ornithopoda) from the Upper Jurassic of Portugal. Journal of Vertebrate Paleontology 43(4). Informa UK Limited. doi:10.1080/02724634.2024.2310066

    Erected Hesperonyx; its Bayesian analysis recovers it at the base of Dryosauridae and its parsimony analyses among non-dryosaurid dryomorphans.

    rotatori2023a
  2. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Ornithischians. Princeton University Press.

    Treats Hesperonyx as an early iguanodontian, likely a dryosaurid.

    jones2026a
  3. Bertozzo, F.; Camilo, B.; Araújo, R.; Manucci, F.; Kullberg, J. C.; Cerio, D. G.; de Carvalho, V. F.; Marrecas, P.; Figueiredo, S. D.; Godefroit, P. (2025). Cariocecus bocagei, a new basal hadrosauroid from the Lower Cretaceous of Portugal. Journal of Systematic Palaeontology 23(1). doi:10.1080/14772019.2025.2536347

    Its implied-weighting analysis recovers Hesperonyx within Dryosauridae; its equal-weighting analysis leaves it unresolved within Iguanodontia.

    bertozzo2025a
  4. Bertozzo, F.; Niu, K.; Vallée Gillette, N.; Godefroit, P. (2025). Anatomical description and digital reconstruction of the skull of Jeholosaurus shangyuanensis (Dinosauria, Ornithopoda) from China. PLoS ONE 20(1): e0312519. Public Library of Science (PLoS). doi:10.1371/journal.pone.0312519

    Recovers Hesperonyx outside Dryosauridae as the sister of a clade of Camptosaurus, Draconyx and Iguanodon.

    bertozzo2025b
  5. Huang, J.; Wu, W.; Mao, L.; Bertozzo, F.; Dhouailly, D.; Robin, N.; Pittman, M.; Kaye, T. G.; Manucci, F.; He, X.; Wang, X.; Godefroit, P. (2026). Cellular-level preservation of cutaneous spikes in an Early Cretaceous iguanodontian dinosaur. Nature Ecology & Evolution 10(2): 203-210. Springer Science and Business Media LLC. doi:10.1038/s41559-025-02960-9

    Recovers Hesperonyx as the sister of Draconyx in a clade labeled Dryosauridae.

    huang2026a