Open Paleo

Oryctodromeus

Varricchio et al., 2007 or-ik-tow-drohm-ee-us

From Ancient Greek 'oruktēs' meaning 'digger' and 'dromaios' meaning 'runner'; translates as 'digging runner', reflecting its unique status as the first non-avian dinosaur with evidence of burrowing behavior.

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

Oryctodromeus is an extinct genus of small orodromine thescelosaurid dinosaur. Fossils are known from the Late Cretaceous Blackleaf Formation of southwestern Montana and the Wayan Formation of southeastern Idaho, USA, both of the Cenomanian stage, roughly 105-96 million years ago. A member of the small, presumably fast-running herbivorous family Thescelosauridae, Oryctodromeus is the first non-avian dinosaur published that shows evidence of burrowing behavior.

Under dispute

Oryctodromeus is recovered within Orodrominae by most analyses (Brown and colleagues, 2013; Boyd, 2015; Barta and Norell, 2021). Avrahami and colleagues (2024) instead recover it, with Fona, within Thescelosaurinae.

Diagnosis

  1. Long paraoccipital processes indicating skull with relatively broad proportions
  2. Basioccipital with steeply sided ventral box rostral to occipital condyle
  3. Sacrum incorporating seven vertebrae including two posterior dorsals
  4. Large scapula with sharply angled narrow acromion bearing thin-edged laterally projecting spine
  5. Distinct posterior bend to scapular blade
  6. Ilium with very short pre-acetabular and long post-acetabular portions
  7. Brevis shelf sloping mediolaterally, visible laterally throughout length
  8. Long prepubic process with transversely broad proximal portion and elongate ventral fossa

Species

Oryctodromeus cubicularis Varricchio et al., 2007

Type species

From Latin 'cubicularis' meaning 'of the lair' or 'of the chamber', referring to the burrowing lifestyle of the animal; together with the genus name it translates as 'digging runner of the lair'.

Holotype
MOR 1636a , Museum of the Rockies
Material
Fused premaxillae; posterior/occipital region of the braincase; three cervical, six dorsal, sacral and 23 caudal vertebrae; three dorsal ribs; scapulocoracoid; scapula; coracoid; humerus; ulna; radius; tibiae; distal fibula; metatarsal IV
Notes
Two juveniles preserved with the holotype in the burrow chamber are the paratype, MOR 1636b.
Horizon
upper Blackleaf Formation, Cenomanian, Late Cretaceous , 100.5–93.9 million years ago
Locality
Lima Peaks, Montana, United States

References

  1. Varricchio, D. J.; Martin, A. J.; Katsura, Y. (2007). First trace and body fossil evidence of a burrowing, denning dinosaur. Proceedings of the Royal Society B: Biological Sciences 274(1616): 1361-1368. The Royal Society. doi:10.1098/rspb.2006.0443 varricchio2007a
  2. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Ornithischians. Princeton University Press.

    Source of the hip height estimate.

    jones2026a
  3. Brown, C. M.; Evans, D. C.; Ryan, M. J.; Russell, A. P. (2013). New data on the diversity and abundance of small-bodied ornithopods (Dinosauria, Ornithischia) from the Belly River Group (Campanian) of Alberta. Journal of Vertebrate Paleontology 33(3): 495-520. Informa UK Limited. doi:10.1080/02724634.2013.746229

    Small-bodied ornithopod diversity study recovering Oryctodromeus within Orodrominae.

    brown2013a
  4. Avrahami, H. M.; Makovicky, P. J.; Tucker, R. T.; Zanno, L. E. (2024). A new semi-fossorial thescelosaurine dinosaur from the Cenomanian-age Mussentuchit Member of the Cedar Mountain Formation, Utah. The Anatomical Record 307(12): 3717-3781. Wiley. doi:10.1002/ar.25505

    New thescelosaurine description recovering Oryctodromeus within Thescelosaurinae.

    avrahami2024a
  5. Barta, D. E.; Norell, M. A. (2021). The Osteology of Haya griva (Dinosauria: Ornithischia) from the Late Cretaceous of Mongolia. Bulletin of the American Museum of Natural History 445(1): 1-112. doi:10.1206/0003-0090.445.1.1

    Recovered Oryctodromeus within Orodrominae in their Haya griva osteology phylogenetic analysis.

    barta2021a
  6. Boyd, C. A. (2015). The systematic relationships and biogeographic history of ornithischian dinosaurs. PeerJ 3: e1523. PeerJ. doi:10.7717/peerj.1523

    Recovered Oryctodromeus within Orodrominae.

    boyd2015a