Open Paleo

Fukuivenator

Azuma et al., 2016 foo-KOO-ee-VEN-uh-tuh

From Fukui (Fukui Prefecture, Japan, where it was found) + Latin venator (hunter): 'hunter of Fukui Prefecture'.

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

Fukuivenator is an extinct genus of maniraptoran theropod dinosaur from the Early Cretaceous Kitadani Formation of Japan.

Under dispute

The affinities of Fukuivenator are disputed. Its original description (Azuma and colleagues, 2016) recovered it as a basal maniraptoran of uncertain position that could not be referred to any known coelurosaurian subgroup, and Hartman and colleagues (2019) placed it near the base of Maniraptora. A CT-based osteological restudy by the same group (Hattori and colleagues, 2021) instead recovered it as the basalmost member of Therizinosauria, citing therizinosaurian synapomorphies such as a subotic recess, eleven or more cervical vertebrae, and anterior humeral condyles, though the authors caution that support for this position is weak. Cau and Madzia (2021) instead recover it at the base of Paraves. Maniraptora is the least-inclusive clade all these hypotheses accept.

Diagnosis

  1. Unusually large external naris slightly smaller than antorbital fenestra in dorsoventral height; large premaxillary fenestra subequal in size to maxillary fenestra.
  2. Highly heterodont dentition with robust unserrated teeth: small spatulate anterior teeth, large posteriorly curved middle teeth, and small nearly symmetrical posterior teeth.
  3. Anterior and middle cervical vertebrae with transversely bifid neural spines, a feature unknown in any other theropod.
  4. Dorsoventrally bifurcated sacral ribs, a feature previously unreported in any other theropod.
  5. Middle caudal vertebrae with distally bifid prezygapophyses, not reported in any dinosaur previously.
  6. Caudal zygapophyseal facets expanded to be substantially wider than the zygapophyseal processes.

Species

Fukuivenator paradoxus Azuma et al., 2016

Type species

From Latin 'paradoxus' meaning 'paradoxical', referring to the unusual combination of primitive and advanced traits exhibited by the species.

Holotype
FPDM-V8461 , Fukui Prefectural Dinosaur Museum
Material
Disarticulated but closely associated skeleton within 50x50 cm area: skull elements, 8 cervical + 10 dorsal + 5 sacral + 30 caudal vertebrae, ribs, gastralia, chevrons, nearly complete scapulas/coracoids, most of both forelimbs, portions of both pubes, partial left ischium, nearly complete hindlimbs.
Horizon
Kitadani Formation, Aptian, Early Cretaceous , 121.4–113.2 million years ago
Locality
Kitadani Dinosaur Quarry, Fukui, Japan The coordinate is the quarry's, given to the second by Azuma and colleagues (2016); earlier papers state it only to the minute.

References

  1. Azuma, Y.; Xu, X.; Shibata, M.; Kawabe, S.; Miyata, K.; Imai, T. (2016). A bizarre theropod from the Early Cretaceous of Japan highlighting mosaic evolution among coelurosaurians. Scientific Reports 6(1). Springer Science and Business Media LLC. doi:10.1038/srep20478 azuma2016a
  2. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Theropods. Princeton University Press.

    Source of the hip height estimate, and the appearance features.

    jones2026c
  3. 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

    Paravian phylogeny analysis placing Fukuivenator near the base of Maniraptora.

    hartman2019a
  4. Hattori, S.; Kawabe, S.; Imai, T.; Shibata, M.; Miyata, K.; Xu, X.; Azuma, Y. (2021). Osteology of Fukuivenator paradoxus: a bizarre maniraptoran theropod from the Early Cretaceous of Fukui, Japan. Memoir of the Fukui Prefectural Dinosaur Museum 20: 1-82.

    CT-based restudy recovered Fukuivenator as the basalmost therizinosaurian based on new synapomorphies

    hattori2021a
  5. Cau, A.; Madzia, D. (2021). The phylogenetic affinities and morphological peculiarities of the bird-like dinosaur Borogovia gracilicrus from the Upper Cretaceous of Mongolia. PeerJ 9: e12640. PeerJ. doi:10.7717/peerj.12640

    Recovered Fukuivenator as the earliest paravian.

    cau2021a