Open Paleo

Iguanodontia

Baur, 1891

Its genera lived 165.3–66.0 million years ago Middle Jurassic–Late Cretaceous

Iguanodontia is a major clade of derived ornithopod dinosaurs that includes the lineage leading up to the duck-billed hadrosaurs. While the most primitive ornithopods were small bipeds, advanced iguanodontians became quadrupedal and grew to large body size, so the group spans everything from modest cursorial forms to some of the largest plant eaters of their era. Members were traditionally lumped into a superfamily and family of "iguanodontids," but phylogenetic studies have shown that assemblage to be a paraphyletic grade rather than a natural cluster of close relatives (Poole, 2022). Larger, more derived iguanodontians were bulk feeders, able to subsist on tough, low-nutrition vegetation thanks to a long gut passage time and an increasingly sophisticated chewing apparatus. They were among the most successful and widespread herbivores of the Cretaceous.

Diagnosis

  1. Loss of the primitive ornithopod first premaxillary tooth
  2. Reduced or absent antorbital and surangular foramina
  3. Femoral fourth trochanter pendant in form
  4. Wide, ventrally flattened pedal unguals approaching a hoof-like form

Clades within Iguanodontia

Genera placed directly in Iguanodontia

  • Emiliasaura Coria et al., 2024 Valanginian (137.1–132.6 Ma)Argentinaincertae sedisunder dispute
  • Eucercosaurus Nomen dubium Seeley, 1879 Albian (113.2–100.5 Ma)United Kingdomincertae sedis
  • Kangnasaurus Disputed Haughton, 1915 Late Cretaceous (100.5–66.0 Ma)South Africa
  • Loncosaurus Nomen dubium Ameghino, 1899 Cenomanian–Coniacian (100.5–85.7 Ma)Argentinaincertae sedisunder dispute
  • Sphenospondylus Nomen dubium Seeley, 1883 Early CretaceousUnited Kingdomincertae sedis
  • Syngonosaurus Nomen dubium Seeley, 1879 Albian (113.2–100.5 Ma)United Kingdomincertae sedis
  • Tenontosaurus Ostrom, 1970 Albian–Cenomanian (113.2–93.9 Ma)United Statesincertae sedisunder dispute
  • Tichosteus Nomen dubium Cope, 1877 Kimmeridgian–Tithonian (154.8–143.1 Ma)United Statesincertae sedis

References

  1. Baur, G. (1891). Remarks on the reptiles generally called Dinosauria. American Naturalist 25: 434-454. doi:10.1086/275329

    Named Iguanodontia.

    baur1891a
  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 Iguanodontia.

    madzia2021a
  3. Poole, K. E. (2022). Phylogeny of iguanodontian dinosaurs and the evolution of quadrupedality. Palaeontologia Electronica 25(3): a30. doi:10.26879/702

    Analyzed iguanodontian phylogeny and the evolution of quadrupedality, reviewing how the traditional Iguanodontidae proved paraphyletic.

    poole2022a