Open Paleo

Iguanodon

Mantell, 1825 i-GWAH-nuh-don /ɪˈɡwɑːnədɒn/

From the modern lizard 'Iguana' and Greek 'odous/odontos' (tooth); meaning 'iguana tooth', referring to Mantell's original recognition that the fossil teeth resembled those of living iguanas at much larger scale.

125.8–113.2 million years ago Barremian–Aptian, Early Cretaceous
Early Cretaceous stages

Iguanodon is one of the original three genera that Owen used to found Dinosauria in 1842 (alongside Megalosaurus and Hylaeosaurus) and is among the earliest dinosaurs ever scientifically described. Gideon Mantell erected the genus in 1825 on isolated teeth from the Tilgate Forest beds of Whiteman's Green, near Cuckfield in Sussex, recognizing their similarity to the teeth of living iguanas at vastly greater scale; Mantell originally designated I. anglicus as the type species. The discovery in 1878 of more than thirty articulated skeletons in a coal mine at Bernissart in Belgium produced the first reliable picture of the animal's anatomy and underpinned Louis Dollo's classic restorations. Because Mantell's anglicus syntype teeth proved too fragmentary to anchor the genus, ICZN Opinion 1947 (2000) set aside all prior type-species fixations under plenary power, designating Iguanodon bernissartensis Boulenger in Beneden, 1881 as the new type species and skeleton Q (RBINS 1534) as its lectotype. Subsequent taxonomic revisions by Paul (2008) and Norman (2010) split many of the species historically referred to Iguanodon into separate genera — including Mantellisaurus (atherfieldensis), Barilium (dawsoni), Hypselospinus (fittoni, hollingtoniensis), and Dakotadon (lakotaensis) — leaving I. bernissartensis as essentially the only currently valid species and the genus as a Barremian-Aptian ankylopollexian of Western Europe.

Diagnosis

  1. Skull bearing 29 maxillary and 25 dentary tooth positions with an accessory palpebral bone above the orbit.
  2. Scapula broad with a dorsally-placed acromion process.
  3. Manus massive with a large conical thumb (digit I) ungual modified into a defensive 'thumb spike'; phalanx 1 of digit I retained.
  4. Sacrum of eight fused vertebrae with mediolaterally compressed dorsal centra.
  5. Prepubic process shallow with a long posterior acetabular body of the pubis.
  6. Adult body size on the order of 8-10 m and 3-4 metric tons, larger than most contemporaneous Wealden iguanodontians.

Species

Iguanodon bernissartensis Boulenger, 1881

Type species

From 'Bernissart', the village in Hainaut Province, Belgium, where the celebrated coal-mine bonebed was discovered in 1878.

Lectotype
RBINS 1534 , Royal Belgian Institute of Natural Sciences
Material
Articulated skeleton ('skeleton Q').
Horizon
Sainte-Barbe Clays Formation, Barremian–Aptian, Early Cretaceous , 125.8–113.2 million years ago
Locality
Bernissart coal mine, Hainaut, Belgium

Synonyms of the genus

Name Type Reason
Iguanodon anglicus nomen rejectum The original 1825 type species, based on isolated and diagnostically inadequate teeth from Tilgate Forest. ICZN Opinion 1947 (2000) set aside all prior type-species fixations under plenary power, replacing it with I. bernissartensis. Not formally placed on the Official Index, but its type-species status is fully superseded.
Iguanosaurus junior objective Proposed by Ritgen (1828) for the animal Mantell had named Iguanodon three years earlier. Carrying the same type, it is an objective synonym; Norman (1986) and Weishampel and colleagues (2004) both list it as such.
Therosaurus junior objective Fitzinger (1843) renamed Mantell's genus in the Systema Reptilium. Carrying the same type, it is an objective synonym; Norman (1986) lists it as one, and Olshevsky (1991) carries it in the Iguanodon synonymy.

Notable specimens

  • CMP-11/8

    Museu Temps de Dinosaures pathology

    Right tibia with a smooth, swollen growth covering about a sixth of its length. CT scanning showed thickened bone beneath the surface, pointing to a long-standing infected skin ulcer rather than a healed break or a tumor — the first such infection reported in a dinosaur.

    Salas-Herrera et al. (2026)

ICZN cases

References

  1. Mantell, G. (1825). Notice on the Iguanodon, a newly discovered fossil reptile, from the sandstone of Tilgate Forest, in Sussex. Philosophical Transactions of the Royal Society of London 115: 179-186. Royal Society of London. doi:10.1098/rstl.1825.0010

    Erects Iguanodon on isolated tooth material from Whiteman's Green, Sussex. Mantell's original type species (I. anglicus) was later superseded by I. bernissartensis under ICZN Opinion 1947.

    mantell1825a
  2. Boulenger, G. A. (1881). Sur l'arc pelvien chez les dinosauriens de Bernissart [On the pelvic arch in the dinosaurs of Bernissart]. Bulletins de l'Académie Royale de Belgique 1(5): 1-11.

    In French, series 3. Establishes Iguanodon bernissartensis; the name was proposed by G. A. Boulenger in a report by P.-J. van Beneden.

    boulenger1881a
  3. Paul, G. S. (2008). A revised taxonomy of the iguanodont dinosaur genera and species. Cretaceous Research 29(2): 192-216. Elsevier BV. doi:10.1016/j.cretres.2007.04.009

    Initiates the modern split of Iguanodon by erecting Mantellisaurus and Dakotadon, restricting Iguanodon to I. bernissartensis.

    paul2008a
  4. Norman, D. B. (1986). On the anatomy of Iguanodon atherfieldensis (Ornithischia: Ornithopoda). Bulletin de l'Institut Royal des Sciences Naturelles de Belgique, Sciences de la Terre 56: 281-372.

    Gives the genus synonymy, listing Iguanosaurus and Therosaurus as objective junior synonyms and Streptospondylus and Cetiosaurus as subjective ones.

    norman1986a
  5. Olshevsky, G. (1991). A revision of the parainfraclass Archosauria Cope, 1869, excluding the advanced Crocodylia. Mesozoic Meanderings 2: 1-196.

    Carries Therosaurus and Sphenospondylus in the Iguanodon synonymy.

    olshevsky1991a
  6. Norman, D. B. (2010). A taxonomy of iguanodontians (Dinosauria: Ornithopoda) from the lower Wealden Group (Cretaceous: Valanginian) of southern England. Zootaxa 2489(1): 47-66. Magnolia Press. doi:10.11646/zootaxa.2489.1.3

    Splits the lower Wealden iguanodontians, removing dawsoni to Barilium and fittoni/hollingtoniensis to Hypselospinus.

    norman2010a
  7. International Commission on Zoological Nomenclature (2000). Opinion 1947. Iguanodon Mantell, 1825 (Reptilia, Ornithischia): Iguanodon bernissartensis Boulenger in Beneden, 1881 designated as the type species. Bulletin of Zoological Nomenclature 57(1): 61-62. International Trust for Zoological Nomenclature.

    Resolves Case 3037 (Charig and Chapman, 1998). Designates I. bernissartensis as the type species and skeleton Q (RBINS 1534) as lectotype under plenary power. Vote 21-0.

    iczn2000a
  8. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Ornithischians. Princeton University Press.

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

    jones2026a
  9. Van Beneden, P. J. (1881). Sur l'arc pelvien chez les dinosauriens de Bernissart [On the pelvic arch in the dinosaurs of Bernissart]. Bulletins de l'Académie royale des Sciences, des Lettres et des Beaux-Arts de Belgique 1: 600-608.

    Report containing Boulenger's naming of Iguanodon bernissartensis, the designated type species.

    vanbeneden1881a
  10. Salas-Herrera, J.; Gasulla, J. M.; Marco Domenech, S. F.; Tosca-Segura, R.; Ortega, F.; Escaso, F. (2026). First occurrence of polymicrobial ulcer in dinosaurs. Royal Society Open Science 13(8). The Royal Society. doi:10.1098/rsos.261293

    Diagnoses the tibia CMP-11/8 from the Mas de la Parreta quarry near Morella, eastern Spain, as an adult I. bernissartensis with a skin ulceration that reached the periosteum.

    salas-herrera2026a
  11. Weishampel, D. B.; Dodson, P.; Osmólska, H. (eds.) (2004). The Dinosauria, Second Edition. University of California Press, Berkeley. weishampel2004a
  12. Ritgen, F. A. (1828). Versuchte Herstellung einiger Becken urweltlicher Thiere [Attempted reconstruction of the pelvises of some prehistoric animals]. Nova Acta Physico-Medica Academiae Caesareae Leopoldino-Carolinae Naturae Curiosorum 14: 281. ritgen1828a
  13. Fitzinger, L. (1843). Systema Reptilium. Fasciculus Primus. Amblyglossae. 106 pp. Braumüller und Seidel. fitzinger1843a
  14. Charig, A. J.; Chapman, S. D. (1998). Case 3037. Iguanodon Mantell, 1825 (Reptilia, Ornithischia): proposed designation of Iguanodon bernissartensis Boulenger in Beneden, 1881 as the type species, and proposed designation of a lectotype. Bulletin of Zoological Nomenclature 55: 99-104. charig1998a