Open Paleo

Callovosaurus

Galton, 1980 cah-LO-vo-SOR-us

From Callovian (the Middle Jurassic geological age during which the animal lived, named after Kellaways/Callovium in England) + Greek sauros (σαῦρος) meaning 'lizard'; overall meaning 'Callovian lizard'.

165.3–161.5 million years ago Callovian, Middle Jurassic
Middle Jurassic stages

Callovosaurus is a genus of iguanodontian dinosaur known from most of a left thigh bone discovered in Middle Jurassic-age rocks of England. At times, it has been considered dubious or a valid genus of basal iguanodontian, perhaps a dryosaurid.

Under dispute

Callovosaurus leedsi, based only on a femur, was named as a camptosaurid (Galton, 1980) and is regarded as the earliest dryosaurid by Ruiz-Omeñaca and colleagues (2007), but its limited material leaves the assignment weakly constrained: McDonald and colleagues (2012) recovered it in an unresolved basal Iguanodontia polytomy.

Diagnosis

  1. Greater trochanter proportionally narrow
  2. Lesser trochanter expanded anteroposteriorly and flattened transversely, forming a thin sheet
  3. Distal end of femur unexpanded
  4. Anterior intercondylar groove shallow
  5. Fourth trochanter positioned more proximally than in Camptosaurus dispar
  6. Greater trochanter does not underlap the lesser trochanter, unlike Camptosaurus dispar

Species

Callovosaurus leedsi Galton, 1980

Type species

Named for Alfred Nicholson Leeds, the collector who found the type specimen.

Holotype
BMNH R1993 , Natural History Museum
Material
A left femur
Horizon
Peterborough Member, Oxford Clay Formation, Callovian, Middle Jurassic , 165.3–161.5 million years ago
Locality
Fletton brick pit, City of Peterborough, United Kingdom

References

  1. Galton, P. M. (1980). European Jurassic ornithopod dinosaurs of the families Hypsilophodontidae and Camptosauridae. Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen 160(1): 73-95. Schweizerbart. doi:10.1127/njgpa/160/1980/73

    Named Callovosaurus as a camptosaurid.

    galton1980a
  2. Ruiz-Omeñaca, J. I.; Pereda-Suberbiola, X.; Galton, P. M. (2007). Callovosaurus leedsi, the earliest dryosaurid dinosaur (Ornithischia: Euornithopoda) from the Middle Jurassic of England. Horns and Beaks: Ceratopsian and Ornithopod Dinosaurs 3-16. Indiana University Press, Bloomington.

    Reassessed Callovosaurus as the earliest dryosaurid dinosaur, on the basis of femoral characters.

    ruiz-omeñaca2007a
  3. McDonald, A. T.; Espílez, E.; Mampel, L.; Kirkland, J. I.; Alcalá, L. (2012). An unusual new basal iguanodont (Dinosauria: Ornithopoda) from the Lower Cretaceous of Teruel, Spain. Zootaxa 3595(1). Magnolia Press. doi:10.11646/zootaxa.3595.1.3

    Recovered Callovosaurus in an unresolved basal Iguanodontia polytomy in phylogenetic analysis

    mcdonald2012a
  4. Czepiński, Ł.; Madzia, D. (2025). Exploring the diversity and disparity of rhabdodontomorph ornithopods from the Late Cretaceous European archipelago. Scientific Reports 15(1). Springer Science and Business Media LLC. doi:10.1038/s41598-025-98083-z

    Rhabdodontomorph-focused ornithopod analysis that does not sample Callovosaurus.

    czepiński2025a
  5. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Ornithischians. Princeton University Press.

    Treats Callovosaurus as a valid dryosaurid.

    jones2026a