Gobisaurus 

Genus: Gobisaurus Vickaryous, Russell, Currie, & Zhao, 2001

Classification: Dinosauria - Ornithischia - Thyreophora - Ankylosauria - Ankylosauridae - Shamosaurinae 

Etymology: Gobi, refers to the geographic locale.

Synonyms: none 

Type species: G. domoculus Vickaryous, Russell, Currie, & Zhao, 2001

Other Species: none 

Diagnosis: Large ankylosaurid with orbits 20% of cranial length and external nares 23% of cranial length; robust basipterygoid processes not fused to main pterygoid body; elongate premaxillary processes of vomers visible in palatal view. Similar to Shamosaurus in having delta-shaped dorsal profile, with premaxillae forming narrow apex. Differs from Shamosaurus in that cranium longer than wide; lacks discernible cranial sculpturing over antorbital area; maxillary tooth row length compared to overall cranium length relatively shorter; maximum premaxillary rostrum width greater than distance between the posteriormost maxillary teeth; reduced supraorbital bosses; and anterior surface of pterygoid vertically oriented (Vickaryous, Russell, Currie, & Zhao, 2001). 

Species: Gobisaurus domoculus Vickaryous, Russell, Currie, & Zhao, 2001

Etymology: domo to subjugate; and oculus, the eye.

Synonyms: none 

Holotype: IVPP V12563, virtually complete skeleton with skull. 

Referred Specimens: none

Time: Lower Cretaceous (Aptian–?Albian).

Horizon: Ulanhushao (Suhongtu) Formation.

Location: IVPP V12563 is believed to have been collected from the same general locality as the large theropod Chilantaisaurus maortuensis, approximately 60 km north of Chilantai (Jilantai; 39 45 N, 105 45E), on the east side of ChilantaibSalt Lake (Chilantaiyen Chih), Maortu, Alashan Desert, Nei Mongol Zizhique (Inner Mongolia), China.

Total length: 5-7 m, skull length 45.7 cm. 

Mass: ~ 2000 kg. 

Diagnosis: as for the genus. 

Comments: Amongst the fossil material collected by the Sino-Soviet Expeditions (1959–1960) to the Alshan Desert, China, was a large, virtually complete ankylosaur skeleton. Gobisaurus domoculus closely resembles Shamosaurus scutatus, but is distinct in having an unfused basipterygoid–pterygoid contact and elongate premaxillary processes of the vomers. Although it is difficult to make a definitive taxonomic assignment without considering postcranial material, a preliminary phylogenetic analysis places Gobisaurus as the sister taxon of Shamosaurus, clustered as one of several successive outgroups of the Ankylosaurinae (Vickaryous, Russell, Currie, & Zhao, 2001). 

Shamosaurus, from the Early Cretaceous (Aptian–Albian) of Mongolia and Gobisaurus share a similar temporal and geographic distribution, in addition to demonstrating a number of congruent morphological features. Included amongst these are a delta-shaped dorsal profile; a narrow premaxillary rostrum; rounded squamosal and quadratojugal bosses; and large and prominent rostrolaterally oriented orbits and external nares (in Shamosaurus, the orbits and external nares represent approximately 18% and 19%, respectively, of the overall cranial length). Previous taxonomic work on ankylosaurs suggests that concordant morphology and overlapping temporal–geographic distribution are unremarkable amongst members of this clade (e.g., Edmontonia and Panoplosaurus). Both Shamosaurus and Gobisaurus may be diagnosed by a suite of unique apomorphic and plesiomorphic character state combinations. Furthermore, each taxon may be defined on the basis of one or more autapomorphies (Shamosaurus reportedly has a maxillary tooth row approximately 50% of the overall cranium length; Gobisaurus has elongate premaxillary processes of the vomers visible in palatal view) (Vickaryous, Russell, Currie, & Zhao, 2001). 

Illustrations:

Cranium of Gobisaurus domoculus gen. et sp. nov. in dorsal (A), ventral (B), right lateral (C), and occipital (D) views. IVPP V12563, holotype. Scale bar represents 100 mm (modidied from Vickaryous, Russell, Currie, & Zhao, 2001). 

 

Gobisaurus domoculus classification (modidied from Vickaryous, Russell, Currie, & Zhao, 2001). 

 

References:

Vickaryous, M. K., A. P. Russell, P. J. Currie, & Zhao X., 2001. A new ankylosaurid (Dinosauria: Ankylosauria) from the Lower Cretaceous of China, with comments on ankylosaurian relationships. Canadian Journal of Earth Sciences , 38: 1767-1780.