Szechuanosaurus zigongensis

Rauhut, Oliver W. M., 2003, The interrelationships and evolution of basal theropod dinosaurs, Special papers in palaeontology 69, pp. 1-213 : 21-22

‘Szechuanosaurus' zigongensis Gao, 1993 ; metataxon

Age . Bathonian-Callovian.

Occurrence. Xiashaxiamo Formation, Sichuan, China.

Diagnosis. Differs from Gasosaurus and Xuanhanosaurus in the more rectangular deltopectoral crest and the proximal part of the humerus being less expanded transversely; from Monolophosaurus and Eustreptospondylus in the gradually sloping anterior rim of the maxilla and the lack of opisthocoelous cervical vertebrae; from Piatnitzkysaurus in the gradually sloping anterior rim of the maxilla and the less expanded proximal humerus; from Iliosuchus in the lack of a vertical ridge on the ilium; from Poekilopleuron in the more strongly pronounced olecranon process of the ulna and the lack of a medial process on the radius; from Metriacanthosaurus in the less steeply sloping posterodorsal rim of the ilium; from Proceratosaurus in the more massive and relatively shorter posterior part of the maxilla. There are no elements preserved that overlap with Megalosaurus or Piveteausaurus .

Remarks. ‘ Szechuanosaurus" zigongensis is one of five theropod taxa described from the Xiashaxiamo Formation of China. However, two of these taxa, Chuandongocoelurus primitivus and Kaijiangosaurus lini , are here regarded as nomina dubia, and there seem to be sufficient differences between ‘5.’ zigongensis and Gasosaurus and Xuanhanosaurus to regard the former species as a tentatively valid metataxon. It should be noted, however, that the discovery of more material might prove ‘S.9 zigongensis to be a junior synonym of Xuanhanosaurus qilixiaensis , since these two taxa are very similar in all comparable elements with the exception of the humerus.

It is rather unclear why ‘ Szechuanosaurus" zigongensis has been referred to the considerably younger genus Szechuanosaurus . The type material of this genus is not diagnostic, and the material referred to the type species by Dong et al. (1983) differs significantly from the type skeleton of ‘5.’ zigongensis . Thus, the latter species should be removed from Szechuanosaurus .