Open Paleo

Convolosaurus

Andrzejewski et al., 2019 kon-vuh-luh-SAWR-us /ˌkɒnvələˈsɔːrəs/

From Latin convolo ('to flock together') + Greek sauros ('lizard'), meaning 'flocking lizard', in reference to the concentration of juvenile fossils found together at the discovery site.

121.4–113.2 million years ago Aptian, Early Cretaceous
Early Cretaceous stages

Convolosaurus is a genus of basal ornithopod dinosaur from the Twin Mountains Formation from Proctor Lake in Comanche County, Texas. The type and only species is Convolosaurus marri.

Under dispute

Convolosaurus was described as a basal ornithopod just outside Iguanodontia, crownward of Hypsilophodon (Andrzejewski and colleagues, 2019), and Dieudonné and colleagues (2020, 2026) and Tykoski and colleagues (2023) recover it in a similar position. Fonseca and colleagues (2024) and Czepiński and Madzia (2025) instead recover it as the earliest-diverging tenontosaurid, within Rhabdodontomorpha.

Diagnosis

  1. Four premaxillary teeth each with a proximodistally oriented sulcus on the buccal surface, unique among ornithopods.
  2. Opisthocoelous cervical vertebrae.
  3. Sacral neural spines twice the height of the sacral centra.
  4. Proximal caudal neural spines 1.5 times the height of the centrum.
  5. Curved maxillary tooth roots (curved medially in anteroposterior view).
  6. Laterally compressed prepubic process.

Species

Convolosaurus marri Andrzejewski et al., 2019

Type species

Named for Dr. Ray H. Marr, who propagated the Society of Vertebrate Paleontology at Southern Methodist University.

Holotype
SMU 72834 , Shuler Museum of Paleontology, Southern Methodist University
Material
Skull and partial articulated skeleton with 9 cervical, 15 dorsal, 6 sacral, 23 caudal vertebrae; scapulae; coracoids; humeri; left ulna and radius; partial left manus; articulated pelvis; femora; proximal tibiae; proximal left fibula.
Horizon
lower Twin Mountains Formation, Aptian, Early Cretaceous , 121.4–113.2 million years ago
Locality
Proctor Lake, Texas, United States

References

  1. Andrzejewski, K. A.; Winkler, D. A.; Jacobs, L. L. (2019). A new basal ornithopod (Dinosauria: Ornithischia) from the Early Cretaceous of Texas. PLOS ONE 14(3): e0207935. Public Library of Science (PLoS). doi:10.1371/journal.pone.0207935

    Named Convolosaurus and recovered it outside Iguanodontia, crownward of Hypsilophodon.

    andrzejewski2019a
  2. Paul, G. S. (2024). The Princeton Field Guide to Dinosaurs (3rd ed.). Princeton University Press.

    Source of the mass estimate.

    paul2024a
  3. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Ornithischians. Princeton University Press.

    Source of the hip height estimate.

    jones2026a
  4. 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 Convolosaurus as the earliest-diverging tenontosaurid, within Rhabdodontomorpha.

    fonseca2024a
  5. 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 Convolosaurus within Rhabdodontomorpha as a tenontosaurid.

    czepiński2025a
  6. 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 Convolosaurus outside Iguanodontia.

    dieudonné2020a
  7. Tykoski, R. S.; Contreras, D. L.; Noto, C. (2023). The first small-bodied ornithopod dinosaur from the Lewisville Formation (middle Cenomanian) of Texas. Journal of Vertebrate Paleontology 43(2). Informa UK Limited. doi:10.1080/02724634.2023.2257238

    Recovered Convolosaurus among hypsilophodont-grade ornithopods, near Hypsilophodon.

    tykoski2023a
  8. 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 Convolosaurus near Hypsilophodon, outside Iguanodontia.

    dieudonné2026a