Deltadromeus

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Deltadromeus
Temporal range:
Ma
↓
Mounted skeleton cast with reconstructed skull
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Theropoda
Clade: †Noasauridae (?)
Genus: †Deltadromeus
Sereno et al., 1996
Species:
†D. agilis
Binomial name
†Deltadromeus agilis
Sereno et al., 1996
Synonyms

Deltadromeus (meaning "delta runner") is a genus of

theropod dinosaur from the Aoufous Formation of Morocco.[1]

It had long, unusually slender hind limbs for its size, suggesting that it was a swift runner.

Kem Kem Beds, which date to the mid-Cretaceous Period (mid-Cenomanian age), about 95 million years ago. It may be a junior synonym of the contemporary Bahariasaurus.[2] The classification of Deltadromeus has been in flux since its original description. In 2016, a South American theropod known as Gualicho shinyae was found to possess many similarities with Deltadromeus. Depending on the phylogenetic position of Gualicho, Deltadromeus may have been a neovenatorid carnosaur, a tyrannosauroid, or a basal coelurosaur if its close relation to Gualicho is legitimate.[3][4][5] Other studies have considered it a ceratosaurian, more specifically a member of the family Noasauridae.[6][7][8][9]

Description

sauropod

The holotype of Deltadromeus agilis (museum catalogue number SGM-Din2) is a partial skeleton of an animal which is estimated to have measured 8 metres (26 ft) long. The weight of the living animal was estimated to have been around 1,050 kilograms, slightly more than an imperial ton.[10]

Size of the holotype, speculatively restored as a noasaurid, compared to a human

A number of specimens (catalogued under IPHG 1912 VIII) were originally considered by

Tyrannosaurus rex.[1] However, the referral of the coracoid, pubes and hindlimb material catalogued under IPHG 1912 VIII to Deltadromeus has been questioned because the remains came from different horizons and localities in the Bahariya Formation, and actually exhibit notable differences from the holotype of Deltadromeus.[12]

The Deltadromeus skeleton has been found in the same formation as those of the giant theropods Carcharodontosaurus, Spinosaurus and Bahariasaurus, which may be synonymous with Deltadromeus. No skull material has been found for either Deltadromeus or Bahariasaurus, and though carnivore teeth labelled as "Deltadromeus" are sold in rock shops, there is no way of knowing if they actually come from this animal.[2]

Classification

Diagrams showing holotype remains (A) and size of a lost femur (B)
Pectoral and forelimb

As a ceratosaur

Many studies published since the original description of Deltadromeus have considered it to be a

ceratosaur, although different studies disagree on what kind of ceratosaur. One 2003 study suggested it was a member of the Noasauridae,[6] though others have found it to be more primitive, possibly related to the primitive ceratosaurs Elaphrosaurus and Limusaurus.[13][14] A more comprehensive study of noasaurid relationships published in 2016 found that both of these interpretations were essentially correct, with Deltadromeus, Limusaurus and Elaphrosaurus all found to be within the Noasauridae.[7] A 2017 paper describing ontogenetic changes in Limusaurus and the effect of juvenile taxa on phylogenetic analyses placed Deltadromeus as a noasaurid in every analysis regardless of which Limusaurus specimen was used, although the analyses did not include Gualicho or Aoniraptor. According to the writers of the paper, resolving the phylogenetic positions of Gualicho, Aoniraptor, Deltadromeus and megaraptorans is one of the most critical issues presently facing theropod systematics.[8] Deltadromeus was also considered a noasaurid in a 2020 review of the Kem Kem Group geology and fauna.[9]

The cladogram below follows a 2016 analysis by Oliver Rauhut and Matthew Carrano.[7]

Abelisauroidea 

As an avetheropod

The original description of Deltadromeus in 1996 found that it was a fairly basal coelurosaur, only slightly more advanced than the Late Jurassic genus Ornitholestes.[1]

Cast with alternate skull reconstruction

In 2016, an analysis of

tyrannosauroids different from the Megaraptoridae.[4] A 2018 study by Porfiri et al. has supported the idea that Gualicho and megaraptorans were basal coelurosaurs, outside of both Neovenatoridae and Tyrannosauroidea. However, this study did not include Deltadromeus.[5]

The cladogram below follows the 2016 Gualicho analysis by Sebastián Apesteguía, Nathan D. Smith, Rubén Juarez Valieri and Peter J. Makovicky.[3]

Allosauroidea 

References

  1. ^
    S2CID 39658297
    .
  2. ^ a b Holtz, Thomas R. Jr. (2008) Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages Supplementary Information
  3. ^
    PMID 27410683
    .
  4. ^ a b Matías J. Motta; Alexis M. Aranciaga Rolando; Sebastián Rozadilla; Federico E. Agnolín; Nicolás R. Chimento; Federico Brissón Egli & Fernando E. Novas (2016). "New theropod fauna from the Upper Cretaceous (Huincul Formation) of northwestern Patagonia, Argentina". New Mexico Museum of Natural History and Science Bulletin. 71: 231–253.
  5. ^
    S2CID 134117648
    .
  6. ^ a b Wilson, Jeffrey A.; Sereno, Paul; Srivastava, Suresh; Bhatt, Devendra K.; Khosla, Ashu; Sahni, Ashok (2003). "A new abelisaurid (Dinosauria, Theropoda) from the Lameta Formation (Cretaceous, Maastrichtian) of India". Contr. Mus. Palaeont. Univ. Mich. 31: 1–42.
  7. ^
    doi:10.1111/zoj.12425
  8. ^
    S2CID 441498
    .
  9. ^
    PMID 32362741
    .
  10. S2CID 53446536
    .
  11. ^ Stromer (1934). "Ergebnisse der Forschungsreisen Prof. E. Stromers in den Wüsten Ägyptens." II. Wirbeltierreste der Baharije-Stufe (unterstes Cenoman). 13. Dinosauria. Abh. Bayer. Akad. Wiss., Math.-Nat. Abt., (n. s.) 22 1-79, 3 pls.
  12. ^ Mortimer, Mickey (September 17, 2014). "No giant Egyptian Deltadromeus". The Theropod Database Blog.
  13. S2CID 30068953
    .
  14. S2CID 4358448
    .
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