Open Paleo

Elasmaria

Calvo et al., 2007

Its genera lived 137.1–66.0 million years ago Early Cretaceous–Late Cretaceous
Early Cretaceous and Late Cretaceous stages

Elasmaria is a clade of small to medium-sized ornithopod dinosaurs known from Cretaceous deposits across the former supercontinent of Gondwana, including South America, Antarctica, Australia, and possibly Africa. It groups together many lightly built, bipedal ornithopods that were once loosely lumped as "hypsilophodonts." Originally erected to unite just Macrogryphosaurus and Talenkauen, the clade was later found to be far more inclusive, drawing in a variety of Southern Hemisphere forms such as the Antarctic Morrosaurus and Trinisaura, as well as Anabisetia. Its members are distinguished chiefly by thin, mineralized plates arranged along the ribs, together with gracile, cursorial hindlimbs suited to running. Elasmaria represents a major southern radiation of ornithopods that persisted through much of the Cretaceous.

Under dispute

The position of Elasmaria is contested. Analyses on the matrix of Dieudonné and colleagues recover it within Iguanodontia, as the sister of Dryomorpha (Dieudonné and colleagues, 2020; Rotatori and colleagues, 2023) or, most recently, within Dryosauridae (Dieudonné and colleagues, 2026a, 2026b), and Fonseca and colleagues (2024) place it in Euiguanodontia. Madzia and colleagues (2017), Herne and colleagues (2019) and Cruzado-Caballero and colleagues (2019) instead recover it within Ornithopoda but outside Iguanodontia, Bertozzo and colleagues (2025) leave its members unresolved against Iguanodontia, and Boyd (2015) placed it outside Ornithopoda, among the thescelosaurines.

Diagnosis

  1. Thin, plate-like mineralized intercostal plates on the dorsal ribs (where preserved)
  2. Gracile, cursorial hindlimb proportions
  3. Anterolaterally projecting preacetabular process of the ilium
  4. Retention of a small, slender pedal digit I

Genera placed directly in Elasmaria

  • Anabisetia Coria & Calvo, 2002 Turonian (93.9–89.8 Ma)Argentina
  • Atlascopcosaurus Disputed Rich & Vickers-Rich, 1989 Barremian–Albian (125.8–100.5 Ma)Australia
  • Chakisaurus Nogueira et al., 2024 Cenomanian–Turonian (100.5–89.8 Ma)Argentina
  • Diluvicursor Herne et al., 2018 Albian (113.2–100.5 Ma)Australia
  • Fostoria Bell et al., 2019 Cenomanian (100.5–93.9 Ma)Australiaunder dispute
  • Galleonosaurus Herne et al., 2019 Barremian (125.8–121.4 Ma)Australia
  • Gasparinisaura Coria & Salgado, 1996 Campanian (83.6–72.2 Ma)Argentina
  • Isasicursor Novas et al., 2019 Maastrichtian (72.2–66.0 Ma)Argentina
  • Leaellynasaura Rich & Vickers-Rich, 1989 Aptian–Albian (121.4–100.5 Ma)Australia
  • Macrogryphosaurus Calvo et al., 2007 Coniacian (89.8–85.7 Ma)Argentina
  • Mahuidacursor Cruzado-Caballero et al., 2019 Santonian (85.7–83.6 Ma)Argentina
  • Morrosaurus Rozadilla et al., 2016 Maastrichtian (72.2–66.0 Ma)Antarctica
  • Muttaburrasaurus Bartholomai & Molnar, 1981 Albian–Cenomanian (113.2–93.9 Ma)Australiaunder dispute
  • Notohypsilophodon Martínez, 1998 Cenomanian (100.5–93.9 Ma)Argentinaunder dispute
  • Qantassaurus Rich & Vickers-Rich, 1999 Barremian (125.8–121.4 Ma)Australiaunder dispute
  • Sektensaurus Ibiricu et al., 2019 Campanian–Maastrichtian (83.6–66.0 Ma)Argentina
  • Talenkauen Novas et al., 2004 Campanian (83.6–72.2 Ma)Argentina
  • Tietasaura Bandeira et al., 2024 Valanginian–Hauterivian (137.1–125.8 Ma)Brazil
  • Trinisaura Coria et al., 2013 Campanian (83.6–72.2 Ma)Antarctica

References

  1. Calvo, J. O.; Porfiri, J. D.; Novas, F. E. (2007). Discovery of a new ornithopod dinosaur from the Portezuelo Formation (Upper Cretaceous), Neuquén, Patagonia, Argentina. Arquivos do Museu Nacional, Rio de Janeiro 65(4): 471-483. doi:10.5281/zenodo.13461915

    Named Elasmaria.

    calvo2007c
  2. 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

    Provides a modern phylogenetic delimitation of Elasmaria within Iguanodontia.

    fonseca2024a
  3. Rozadilla, S.; Agnolín, F. L.; Novas, F. E.; Aranciaga Rolando, A. M.; Motta, M. J.; Lirio, J. M.; Isasi, M. P. (2016). A new ornithopod (Dinosauria, Ornithischia) from the Upper Cretaceous of Antarctica and its palaeobiogeographical implications. Cretaceous Research 57: 311-324. Elsevier BV. doi:10.1016/j.cretres.2015.09.009

    Nested Elasmaria within Euiguanodontia in their phylogenetic analysis of Gondwanan ornithopods.

    rozadilla2016a
  4. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Ornithischians. Princeton University Press.

    Describes Elasmaria as one of the earliest-diverging ornithopod branches, with its internal relationships ill-defined.

    jones2026a
  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

    Recovers Elasmaria within Dryosauridae in an analysis of ornithischian relationships.

    dieudonné2026a
  6. Dieudonné, P. E.; Paulina-Carabajal, A.; Cruzado-Caballero, P. (2026). A redescription of the holotype skull of the ornithischian dinosaur Gasparinisaura cincosaltensis (Dryosauridae, Dysalotosaurinae clade nov.) and phylogenetic implications. Cretaceous Research 189: 106478. doi:10.1016/j.cretres.2026.106478

    Recovers Elasmaria within Dryosauridae, with Gasparinisaura in a polytomy with its specifiers.

    dieudonné2026b
  7. Boyd, C. A. (2015). The systematic relationships and biogeographic history of ornithischian dinosaurs. PeerJ 3: e1523. PeerJ. doi:10.7717/peerj.1523

    Ornithischian phylogenetic analysis bearing on the placement of Elasmaria.

    boyd2015a
  8. Madzia, D.; Boyd, C. A.; Mazuch, M. (2017). A basal ornithopod dinosaur from the Cenomanian of the Czech Republic. Journal of Systematic Palaeontology 16(11): 967-979. Informa UK Limited. doi:10.1080/14772019.2017.1371258

    Recovered Elasmaria within Ornithopoda, outside Iguanodontia.

    madzia2017a
  9. Herne, M. C.; Nair, J. P.; Evans, A. R.; Tait, A. M. (2019). New small-bodied ornithopods (Dinosauria, Neornithischia) from the Early Cretaceous Wonthaggi Formation (Strzelecki Group) of the Australian-Antarctic rift system, with revision of Qantassaurus intrepidus Rich and Vickers-Rich, 1999. Journal of Paleontology 93(3): 543-584. Cambridge University Press (CUP). doi:10.1017/jpa.2018.95

    Recovered Elasmaria as the sister of Clypeodonta, within Ornithopoda.

    herne2019a
  10. Cruzado-Caballero, P.; Gasca, J. M.; Filippi, L. S.; Cerda, I. A.; Garrido, A. C. (2019). A new ornithopod dinosaur from the Santonian of Northern Patagonia (Rincón de los Sauces, Argentina). Cretaceous Research 98: 211-229. Elsevier BV. doi:10.1016/j.cretres.2019.02.014

    Recovered Elasmaria in a polytomy sister to Iguanodontia.

    cruzado-caballero2019a
  11. Dieudonné, P. E.; Cruzado-Caballero, P.; Godefroit, P.; Tortosa, T. (2020). A new phylogeny of cerapodan dinosaurs. Historical Biology 33(10): 2335-2355. doi:10.1080/08912963.2020.1793979

    Recovered Elasmaria within Iguanodontia, with Eousdryosaurus as the sister of Dryomorpha.

    dieudonné2020a
  12. 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

    Recovered Elasmaria within Iguanodontia, as the sister of Dryomorpha.

    rotatori2023a
  13. 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

    Recovered elasmarians in a polytomy with Iguanodontia.

    bertozzo2025a
  14. Coria, R. A.; Cerda, I. A.; Escaso, F.; Baiano, M. A.; Bellardini, F.; Braun, A.; Coria, L. M.; Gutierrez, J. M.; Pino, D.; Windholz, G. J.; Currie, P. J.; Ortega, F. (2024). First Valanginian (Early Cretaceous) ornithopod (Dinosauria, Ornithischia) from Patagonia. Cretaceous Research 166. Elsevier BV. doi:10.1016/j.cretres.2024.106027

    Did not recover Elasmaria as a clade.

    coria2024a