Open Paleo

Iani

Zanno et al., 2023 YAN-ee

Named after Ianus (Janus), the two-faced Roman god of transitions and change, symbolizing the transitional nature of this dinosaur at a time of major faunal change

100.5–93.9 million years ago Cenomanian, Late Cretaceous
Late Cretaceous stages

Iani is an extinct genus of rhabdodontomorph iguanodontian dinosaur from the Late Cretaceous Cedar Mountain Formation of Utah, United States. The genus contains a single species, I. smithi, known from a partial skeleton including the skull. Its describers interpret it as a link between the genus Tenontosaurus and the Rhabdodontidae.

Under dispute

Iani was described as the earliest-diverging member of a clade with Tenontosaurus, within Rhabdodontomorpha (Zanno and colleagues, 2023), a placement Fonseca and colleagues (2024) and Czepiński and Madzia (2025) recover in Tenontosauridae. Dieudonné and colleagues (2026) instead place Iani and Tenontosaurus among the thescelosaurines, outside Iguanodontia, and Rotatori and colleagues (2026) find its position dependent on the method of analysis.

Diagnosis

  1. Three premaxillary teeth
  2. Distinct oval fossa on the caudomedial aspect of premaxillary lateral process
  3. Hatchet shaped postorbital facet on frontal with rostrally convex caudal and straight rostral margins
  4. Distinct, triangular caudomedial prong projecting off the caudal aspect of the palatine forming part of postpalatine foramen margin
  5. Distinct u-shaped notch in ectopterygoid between the palatine and jugal process forming part of postpalatine foramen
  6. Basioccipital with sharp midline lamina bordered contralaterally by two basioccipital foramina housed entirely within depressed fossa on rostroventral surface
  7. Caudally projecting conical tubercle on midline of rostroventralmost tip of basioccipital
  8. Angular occipital condyle on basioccipital with flattened ventral and caudal aspects and sharp rostrally projecting lip

Species

Iani smithi Zanno et al., 2023

Type species

Named for Joshua Aaron Smith and Smith's paleontological contributions.

Holotype
NCSM 29373 , North Carolina Museum of Natural Sciences
Material
Partial skeleton of a skeletally immature individual
Horizon
lower Mussentuchit Member, Cedar Mountain Formation, Cenomanian, Late Cretaceous , 100.5–93.9 million years ago
Locality
Fortunate Son, Utah, United States

References

  1. Zanno, L. E.; Gates, T. A.; Avrahami, H. M.; Tucker, R. T.; Makovicky, P. J. (2023). An early-diverging iguanodontian (Dinosauria: Rhabdodontomorpha) from the Late Cretaceous of North America. PLOS ONE 18(6): e0286042. Public Library of Science (PLoS). doi:10.1371/journal.pone.0286042

    Named Iani and recovered it with Tenontosaurus within Rhabdodontomorpha on two matrices.

    zanno2023a
  2. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Ornithischians. Princeton University Press.

    Source of the body length, mass, and hip height estimates.

    jones2026a
  3. 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 Iani in Tenontosauridae, within Rhabdodontomorpha.

    fonseca2024a
  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

    Recovered Iani in Tenontosauridae.

    czepiński2025a
  5. Dieudonné, P.; Becerra, M. G.; Zanesco, T.; Tortosa, T.; Cruzado-Caballero, P.; Stein, K.; Torcida Fernández-Baldor, F. (2026). Foskeia pelendonum, a new rhabdodontomorph from the Lower Cretaceous of Salas de los Infantes (Burgos Province, Spain), and a new phylogeny of ornithischian dinosaurs. Papers in Palaeontology 12(1). Wiley. doi:10.1002/spp2.70057

    Recovered Iani with Tenontosaurus in Thescelosaurinae, outside Iguanodontia.

    dieudonné2026a
  6. Rotatori, F. M.; Chiarenza, A. A.; Fanti, F.; Moreno-Azanza, M. (2026). The early origin of Iguanodontia: new insights into the macroevolution, diversity and biogeography of the clade. Palaeontology 69(2): e70057. doi:10.1111/pala.70057

    Recovered Iani with rhabdodontids under parsimony, and outside them in the non-clock Bayesian analysis.

    rotatori2026a