Open Paleo

Acheroraptor

Evans et al., 2013 ah-SHEH-ro-RAP-tuh

From Greek 'Acheron' (the underworld river) and Latin 'raptor' meaning 'thief' or 'plunderer'; meaning 'underworld thief'

72.2–66.0 million years ago Maastrichtian, Late Cretaceous
Late Cretaceous stages

Acheroraptor is an extinct genus of dromaeosaurid theropod dinosaur that lived in present-day Montana in the United States during the Maastrichtian stage of the Late Cretaceous period. It was described by Canadian paleontologists David Evans, Derek Larson, and Philip J. Currie in 2013. The genus contains a single species, A. temertyorum, named on an isolated maxilla with teeth. An incomplete dentary found nearby was also assigned to the species. These fossils were initially discovered by fossil poachers, though they were later sold to the Royal Ontario Museum, in layers belonging to the Hell Creek Formation. This indicates that these fossils date to the upper Maastrichtian stage, 67.2-66 million years ago.

Under dispute

The subfamily placement of Acheroraptor is contested. It was described as a basal velociraptorine (Evans and colleagues, 2013) with Asian affinities, a placement followed by Jasinski and colleagues (2020), but Powers and colleagues (2022) instead recover it within Saurornitholestinae, as the sister of Atrociraptor. Known mainly from jaw material, it is placed at Eudromaeosauria incertae sedis.

Diagnosis

  1. Extensive, posteriorly projected postantral wall that is visible laterally through the antorbital fenestra
  2. Maxillary fenestra positioned low in the antorbital fossa and almost reaching its ventral margin, situated directly posterior to the promaxillary fenestra
  3. Relatively small anterior region of the antorbital fossa (region between anterior borders of the antorbital fenestra and fossa)
  4. Maxillary dentition with prominent apicobasal ridges on both labial and lingual surfaces, consistently close to the anterior margins of each side

Species

Acheroraptor temertyorum Evans et al., 2013

Type species

Named for James and Louise Temerty — James being chairman of Northland Power and the Royal Ontario Museum Board of Governors — who have supported the museum for many years.

Holotype
ROM 63777 , Royal Ontario Museum
Material
Almost complete right maxilla, missing only the posterior portion of the jugal ramus, and an associated maxillary tooth complete with root.
Horizon
Hell Creek Formation, Maastrichtian, Late Cretaceous , 72.2–66.0 million years ago
Locality
45 km southwest of Jordan, Montana, United States

References

  1. Evans, D. C.; Larson, D. W.; Currie, P. J. (2013). A new dromaeosaurid (Dinosauria: Theropoda) with Asian affinities from the latest Cretaceous of North America. Naturwissenschaften 100(11): 1041-1049. Springer Science and Business Media LLC. doi:10.1007/s00114-013-1107-5 evans2013a
  2. Paul, G. S. (2024). The Princeton Field Guide to Predatory Dinosaurs. Princeton University Press.

    Source of the appearance features.

    paul2024b
  3. Jasinski, S. E.; Sullivan, R. M.; Dodson, P. (2020). New Dromaeosaurid Dinosaur (Theropoda, Dromaeosauridae) from New Mexico and Biodiversity of Dromaeosaurids at the end of the Cretaceous. Scientific Reports 10(1). Springer Science and Business Media LLC. doi:10.1038/s41598-020-61480-7

    Followed prior placement of Acheroraptor as having Asian dromaeosaurid affinities.

    jasinski2020a
  4. Powers, M. J.; Fabbri, M.; Doschak, M. R.; Bhullar, B. A. S.; Evans, D. C.; Norell, M. A.; Currie, P. J. (2022). A new hypothesis of eudromaeosaurian evolution: CT scans assist in testing and constructing morphological characters. Journal of Vertebrate Paleontology 41(5). doi:10.1080/02724634.2021.2010087

    Analyzed Acheroraptor phylogenetics within eudromaeosaurian framework using computed tomography

    powers2022a
  5. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Theropods. Princeton University Press.

    Illustrated by E. Viola.

    jones2026c