Open Paleo

Falcarius

Kirkland et al., 2005 fal-cuh-RYE-us

From Latin falcarius (sickle cutter or scythe-bearer): 'sickle cutter', likely alluding to its therizinosaur affinities and large curved claws.

125.8–121.4 million years ago Barremian, Early Cretaceous
Early Cretaceous stages

Falcarius is a genus of primitive therizinosaur dinosaur that lived during the Early Cretaceous period in what is now North America. Its remains were first collected in the Cedar Mountain Formation in 1999, with subsequent findings made during the 2000s. The genus is known from multiple specimens ranging from immature to fully-grown individuals.

Diagnosis

  1. Expansive, open pneumatic cavities in basioccipital and basisphenoid with basisphenoidal recess directed ventrally
  2. Extensive subcondylar pneumatic recesses lateral to the occipital condyle
  3. One enlarged tooth at anteriormost end of dentary (first alveolus hypertrophied, housing tooth with twice cross-sectional area of posterior teeth)
  4. Laterally deflected and biconcave apex of the deltopectoral crest
  5. Posterior tuberosity on distal end of humerus opposite the radial condyle
  6. Flexor tubercle of phalanx I-II with well-defined collateral pits on distal aspect

Species

Falcarius utahensis Kirkland et al., 2005

Type species

Named for Utah, the US state where the holotype and hundreds of associated specimens were recovered from the Cedar Mountain Formation.

Holotype
UMNH VP 15000 , Utah Museum of Natural History
Material
Partial braincase
Horizon
lower Yellow Cat Member, Cedar Mountain Formation, Barremian, Early Cretaceous , 125.8–121.4 million years ago
Locality
Crystal Geyser Quarry, Utah, United States

References

  1. Kirkland, J. I.; Zanno, L. E.; Sampson, S. D.; Clark, J. M.; DeBlieux, D. D. (2005). A primitive therizinosauroid dinosaur from the Early Cretaceous of Utah. Nature 435(7038): 84-87. Springer Science and Business Media LLC. doi:10.1038/nature03468 kirkland2005a
  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. 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

    Emends the genus diagnosis and proposes a second species, Falcarius suarezarum, for Geminiraptor suarezarum and the Suarez Site bonebed.

    freimuth2026a