Cranial anatomy of Shunosaurus, a basal sauropod dinosaur from the Middle Jurassic of China Author Chatterjee, Sankar Author Zheng, Zhong text Zoological Journal of the Linnean Society 2002 2002-09-30 136 1 145 169 https://academic.oup.com/zoolinnean/article-lookup/doi/10.1046/j.1096-3642.2002.00037.x journal article 10.1046/j.1096-3642.2002.00037.x 0024-4082 5436845 GENUS SHUNOSAURUS DONG ET AL ., 1983 Diagnosis. The following cranial features are unique to Shunosaurus among sauropods: (1) tooth morphology is a combination of cylindrical and spatulate form; (2) pterygoid is extremely slender and small; (3) pterygoid has a fossa on the dorsal aspect; (4) quadrate ramus of the pterygoid is forked; (5) external nares are at the level of the orbit; (6) emargination of the ventral margin of the maxilla/jugal bar behind the tooth row; (7) vomers do not participate in the formation of the choanae; (8) quadratojugal participates in the articulation of the jaws; (9) the basisphenoid recess is extremely deep; (10) trochlear (IV) nerve has two exits; (11) basipterygoid process is not wrapped by the caudal process of the pterygoid; (12) postorbital contains a lateral pit; (13) occlusal level of the maxillary tooth row is convex downward, whereas that of the dentary is concave upward, like a pair of garden shears; (14) replacing tooth invades on the labial side of the functional tooth; (15) dentary tooth count 25 or more. Type species. Shunosaurus lii Dong, Zhou & Zhang, 1983 .