Open Paleo

Geminiraptor

Senter et al., 2010 JEM-in-i-RAP-tor

Twin seizer; from Latin gemini (twins) and raptor (seizer), referring to the twin geologists Marina and Celina Suarez who discovered the fossil site

137.1–132.6 million years ago Valanginian, Early Cretaceous
Early Cretaceous stages

Geminiraptor is a genus of theropod dinosaur that lived in North America during the Early Cretaceous period. Geminiraptor was a small, ground-dwelling bipedal theropod. The type species of Geminiraptor is G. suarezarum.

Under dispute

Geminiraptor, known from a single maxilla, was described as a troodontid (Senter and colleagues, 2010), and later analyses disagreed on its position within Troodontidae (Hartman and colleagues, 2019, within Troodontinae; Kubota and colleagues, 2024, outside it). Freimuth and colleagues (2026) instead identify it as an early therizinosaurian: CT scans show replacement teeth like those of Falcarius, and their analyses recover it as the sister taxon of Falcarius utahensis, leading them to recombine it as Falcarius suarezarum. It is placed at Coelurosauria incertae sedis, the clade spanning both identifications.

Diagnosis

  1. Extensive pneumatization of the maxilla internal to the antorbital fossa, inflating the bone to a triangular cross-section
  2. Large, craniocaudally elongate maxillary fenestra
  3. Promaxillary fenestra visible in lateral view
  4. Craniocaudally narrow promaxillary strut and interfenestral strut
  5. Small, square dental alveoli with bony septa between them

Species

Geminiraptor suarezarum Senter et al., 2010

Type species

Named for twin geologists Drs. Marina and Celina Suarez, who discovered the Suarez site from which the fossil was recovered.

Holotype
CEUM 7319 , College of Eastern Utah Prehistoric Museum
Material
Maxilla
Notes
Senter and colleagues (2010) give the holotype as CEUM 7319; Freimuth and colleagues (2026) give CEUM 73719 throughout, without mentioning a renumbering.
Horizon
lower Yellow Cat Member, Cedar Mountain Formation, Valanginian, Early Cretaceous , 137.1–132.6 million years ago
Locality
Suarez Site, Utah, United States

Synonyms

  • Falcarius suarezarum reassigned

    Combination proposed by Freimuth and colleagues (2026), who reidentify the holotype maxilla and the Suarez Site bonebed material as an early therizinosaurian and the sister taxon of Falcarius utahensis.

References

  1. Senter, P.; Kirkland, J. I.; Bird, J.; Bartlett, J. A. (2010). A New Troodontid Theropod Dinosaur from the Lower Cretaceous of Utah. PLoS ONE 5(12): e14329. Public Library of Science (PLoS). doi:10.1371/journal.pone.0014329 senter2010a
  2. Hartman, S.; Mortimer, M.; Wahl, W. R.; Lomax, D. R.; Lippincott, J.; Lovelace, D. M. (2019). A new paravian dinosaur from the Late Jurassic of North America supports a late acquisition of avian flight. PeerJ 7: e7247. PeerJ. doi:10.7717/peerj.7247

    Recovered Geminiraptor within Troodontinae in paravian phylogenetic analysis.

    hartman2019a
  3. Kubota, K.; Kobayashi, Y.; Ikeda, T. (2024). Early Cretaceous troodontine troodontid (Dinosauria: Theropoda) from the Ohyamashimo Formation of Japan reveals the early evolution of Troodontinae. Scientific Reports 14(1). Springer Science and Business Media LLC. doi:10.1038/s41598-024-66815-2

    Placed Geminiraptor outside Troodontinae in troodontid phylogenetic analysis.

    kubota2024a
  4. Freimuth, W. J.; Lively, J. R.; Zanno, L. E. (2026). Reassessment of the Early Cretaceous North American "troodontid" Geminiraptor suarezarum as a therizinosaurian and mosaic evolution of coelurosaurian maxillae. PLOS ONE 21(9): e0356471. doi:10.1371/journal.pone.0356471

    Reidentifies the holotype as a therizinosaurian from CT-imaged replacement teeth and phylogeny, and recombines it as Falcarius suarezarum.

    freimuth2026a