Open Paleo

Deltadromeus

Sereno et al., 1996 DEL-ta-DROHM-ee-us

From Greek delta ('river delta' or 'change') + dromos ('runner'), meaning 'river delta runner' or 'change runner', possibly referring to the Nile River delta region where related material was found.

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

Deltadromeus is an extinct genus of controversial theropod dinosaur that lived in present-day Morocco during the mid-Cretaceous period. It was described by American paleontologist Paul Sereno and colleagues in 1996. The genus contains a single species, D. agilis, named based on an incomplete postcranial skeleton, the holotype specimen. However, some fossils from the Bahariya Formation of Egypt that were formerly referred to the theropod Bahariasaurus have been suggested to belong to Deltadromeus. The holotype specimen of Deltadromeus was unearthed by a joint expedition by the University of Chicago and the Service Géologique du Maroc in Errachidia Province, eastern Morocco in rock layers coming from the Gara Sbaa Formation of the Kem Kem Beds. This indicates that these fossils date to the Cenomanian stage of the Cretaceous period, 100-95 million years ago.

Under dispute

The affinities of Deltadromeus are deeply contested, spanning both major averostran lineages. On the ceratosaur side, Carrano and Sampson (2008) recovered it as a basal ceratosaur (explicitly rejecting the earlier noasaurid interpretation). On the tetanuran side, the describing paper (Sereno and colleagues, 1996) recovered a basal coelurosaur, Apesteguía and colleagues (2016) a neovenatorid allosauroid (sister to Gualicho), Motta and colleagues (2016) a megaraptoran, and Delcourt and colleagues (2025) an ornithomimosaur. A synonymy with Bahariasaurus has also been proposed but is not adopted. Averostra is the least-inclusive clade all these hypotheses accept.

Diagnosis

  1. Anterior caudal vertebrae with broad quadrangular neural spines
  2. Coracoid and acromion broadly expanded anteroposteriorly, with shallow notch in anterior margin
  3. Ischial midshaft dorsoventrally compressed
  4. Femur with accessory trochanter on distal shaft and medial distal condyle with anterior extension
  5. Metatarsal IV distal condyles reduced
  6. Large deep fossa occupying majority of the medial aspect of the proximal end of the fibula

Species

Deltadromeus agilis Sereno et al., 1996

Type species

From Greek 'agilis' meaning 'agile', referring to the cursorial proportions of the animal's hindlimbs.

Holotype
SGM-Din 2 , Service Géologique du Maroc, Ministére de l’Energie et des Mines
Material
Incomplete postcranial skeleton: dorsal ribs, gastralia, caudal vertebrae, chevrons, scapulocoracoid, forelimbs, pelvis, hindlimbs, pedes
Horizon
upper Gara Sbaa Formation, Cenomanian, Late Cretaceous , 100.5–93.9 million years ago
Locality
Aferdou N'Chaft, Draa-Tafilalet, Morocco

References

  1. Sereno, P. C.; Dutheil, D. B.; Iarochene, M.; Larsson, H. C. E.; Lyon, G. H.; Magwene, P. M.; Sidor, C. A.; Varricchio, D. J.; Wilson, J. A. (1996). Predatory Dinosaurs from the Sahara and Late Cretaceous Faunal Differentiation. Science 272(5264): 986-991. American Association for the Advancement of Science (AAAS). doi:10.1126/science.272.5264.986

    Describing paper; recovered Deltadromeus as a basal coelurosaur.

    sereno1996a
  2. Ibrahim, N.; Sereno, P. C.; Varricchio, D. J.; Martill, D. M.; Dutheil, D. B.; Unwin, D. M.; Baidder, L.; Larsson, H. C. E.; Zouhri, S.; Kaoukaya, A. (2020). Geology and paleontology of the Upper Cretaceous Kem Kem Group of eastern Morocco. ZooKeys 928: 1-216. doi:10.3897/zookeys.928.47517

    Places the holotype at Aferdou N'Chaft, and identifies the "Er Remlia" of the original description as the village nearest a different locality, Iferda N'Ahouar.

    ibrahim2020a
  3. Carrano, M. T.; Sampson, S. D. (2008). The Phylogeny of Ceratosauria (Dinosauria: Theropoda). Journal of Systematic Palaeontology 6(2): 183-236. doi:10.1017/S1477201907002246

    Recovered Deltadromeus as a basal ceratosaur near Elaphrosaurus, explicitly rejecting a noasaurid position (12 extra steps).

    carrano2008a
  4. Rauhut, O. W. M.; Carrano, M. T. (2016). The theropod dinosaur Elaphrosaurus bambergi Janensch, 1920, from the Late Jurassic of Tendaguru, Tanzania. Zoological Journal of the Linnean Society 178(3): 546-610. Oxford University Press (OUP). doi:10.1111/zoj.12425

    Recovered Deltadromeus among basal ceratosaurs in their Elaphrosaurus revision.

    rauhut2016b
  5. Apesteguía, S.; Smith, N. D.; Juárez Valieri, R. D.; Makovicky, P. J. (2016). An Unusual New Theropod with a Didactyl Manus from the Upper Cretaceous of Patagonia, Argentina. PLOS ONE 11(7): e0157793. Public Library of Science (PLoS). doi:10.1371/journal.pone.0157793

    Recovered Deltadromeus as a neovenatorid allosauroid, sister to Gualicho.

    apesteguía2016a
  6. Motta, M. J.; Aranciaga Rolando, A. M.; Rozadilla, S.; Agnolín, F. L.; Chimento, N. R.; Brissón Egli, F.; Novas, F. E. (2016). New theropod fauna from the Upper Cretaceous (Huincul Formation) of northwestern Patagonia, Argentina. Cretaceous Period: Biotic Diversity and Biogeography 71: 231-253. New Mexico Museum of Natural History and Science.

    Grouped Deltadromeus with Bahariasaurus and Aoniraptor as megaraptoran theropods (proposed Bahariasauridae).

    motta2016a
  7. Delcourt, D.; Grillo, O. N.; Hendrickx, C.; Kellermann, M.; Langer, M. C. (2025). The coelurosaur theropods of the Romualdo formation, early Cretaceous (Aptian) of Brazil: Santanaraptor placidus meets Mirischia asymmetrica. The Anatomical Record ar.70085. Wiley. doi:10.1002/ar.70085

    Recovered Deltadromeus within Ornithomimosauria, alongside Gualicho.

    delcourt2025a