Monolophosaurus jiangi

Brusatte, Stephen L., Benson, Roger B. J., Currie, Philip J. & Xijin, Zhao, 2010, The skull of Monolophosaurus jiangi (Dinosauria: Theropoda) and its implications for early theropod phylogeny and evolution, Zoological Journal of the Linnean Society 158 (3), pp. 573-607 : 574-575

MONOLOPHOSAURUS JIANGI ZHAO & CURRIE, 1993

Holotype: IVPP 84019 , a complete skull and partial postcranial skeleton comprising the pelvis and axial column from the atlas to the sixth caudal vertebra.

Type locality and horizon: Middle Jurassic Shishugou Formation ( Eberth et al., 2001), 34 km northeast of Jiangjunmiao in the Jiangjunmiao Depression within the Junggar Basin, Xinjiang, China. Monolophosaurus was collected from low in the Shishugou Formation section north of the now-abandoned village of Jiangjunmiao and east of Gui Hua Mu Yuan (Silicified Wood Park). Based on radiometric ages from overlying tuffs and biostratigraphic data from within and below the Shishugou Formation, Monolophosaurus is regarded as no younger than late Callovian (D. A. Eberth, Royal Tyrrell Museum of Palaeontology, Drumheller, Alberta, Canada, pers. comm., 2009).

Diagnosis: Basal tetanuran theropod possessing the following autapomorphies of the cranium: nasal process of premaxilla bifurcating posteriorly at its contact with the nasal; lateral surface of premaxilla with deep groove leading from the subnarial foramen to a foramen on the base of the nasal process; raised crest on nasal with straight dorsal margin that is nearly parallel to the alveolar margin of the maxilla; two enlarged and equal-sized pneumatic fenestrae in the nasal; lacrimal with discrete tab-like process projecting dorsally above the preorbital bar; associated frontals that are rectangular and much wider than long (width to length ratio of 1.67).