Dilophosaurus wetherilli ( Welles, 1954 )

Rauhut, Oliver W. M., 2003, The interrelationships and evolution of basal theropod dinosaurs, Special papers in palaeontology 69, pp. 1-213 : 19

Dilophosaurus wetherilli ( Welles, 1954)

Age .?Sinemurian-Pliensbachian.

Occurrence. Kayenta Formation, Arizona, USA.

Diagnosis. Lacrimal with thickened dorsoposterior rim; cervical neural spines with a distinct central ‘cap ’ and an anterior and posterior ‘shoulder ’; scapular blade with squared distal expansion.

Remarks. Dilophosaurus wetherilli ( Text-fig. 5a ) was originally described as a new species of Megalosaurus by Welles in 1954, but it was not until 1984 that a detailed description of the holotype was published (Welles 1984). The most striking feature of the skull are the two large, very thin cranial crests, best preserved in a so-far undescribed skull (UCMP V6468). However, since similar crests have been reported for Syntarsus ( Rowe 1989) and another species from the Lower Jurassic of China [based on the presence of these crests, this species was originally referred to the genus Dilophosaurus as D. sinensis ( Hu 1993) , but this referral has recently been doubted ( Lamanna et al. 1998)], this character cannot be used to define the genus or species, but D. wetherilli shows enough other apomorphies to establish it as a valid genus and species.

Figures

text-fig. 5. Skull reconstructions of representatives of Jurassic OTUs in left lateral view, a, Dilophosaurus wetherilli, Early Jurassic (Sinemurian-Pliensbachian), Kayenta Formation, Arizona, USA; based on UCMP V 4214 and V 6468. B, Syntarsus rhodesiensis, Early Jurassic (Hettangian-Sinemurian), Forest Sandstone, Zimbabwe; composite reconstruction based on many isolated skull elements from the National Museum of Natural History in Harare (see Appendix), c, Magnosaurus oxoniensis, Middle Jurassic (Callovian), Oxford Clay, England; based on OUM J 13558, unpreserved elements shaded. D, Monolophosaurus jiangi, Middle Jurassic, Wucaiwan Formation, China; redrawn from Zhao and Currie (1993b). E, Allosaurus fragilis, Late Jurassic (Kimmeridgian-Tithonian), Morrison Formation, USA; based on MOR 693. f, basal bird Archaeopteryx sp., Late Jurassic (Tithonian), lithographic limestones of Solnhofen, Germany; based on Wellnhofer (1974), Elzanowski and Wellnhofer (1996), and the Berlin, Eichstätt, and Munich specimens. G, Ceratosaurus sp., Late Jurassic (Kimmeridgian-Tithonian), Morrison Formation, USA; based on USNM 4735 and UMNH VP 5278. H, Ornitholestes hermanni, Late Jurassic (Kimmeridgian-Tithonian), Morrison Formation, USA, based on AMNH 619. Abbreviations as in Text-figure 4, and: If, lacrimal fenestra; mf, maxillary fenestra; nf, nasal foramen; pmf, promaxillary fenestra. Scale bars represent 10 mm (b, f, h), 50 mm (c) and 100 mm (a, d, e, g).