[D] Xixiposaurus suni [sG] [T]
Saurischia Sauropodomorpha Prosauropoda Plateosauridae
Lower Lufeng Formation, Lufeng of Yunnan Province, China
A new prosauropod dinosaur Xixiposaurus suni gen. et sp. nov. from the lower Lufeng Formation of lower Jurassic in Lufeng of Yunnan, China is reported. The diagnostic characters are as follows: steep slant of the skull roof in lateral view; the maximum height of the mandible larger than twice of minimum height of the dentary; the 4th cervical centrum being longest in cervicals; minimum width of the pubic apron wider than width of the pubic peduncle; the fourth trochanter having a V-shape notch in lateral view. The phylogenetic analysis shows that it is one of the most derived forms among Chinese prosauropods.
Xixipo-, occurred village in Lufeng County. Sun-, honoring Professor Sun Ge, Jilin University, China.
Diagnostic characters include: steep slant of the skull roof in lateral view; the maximum height of the mandible larger than twice of minimum height of the dentary; the 4 th cervical centrum being longest in cervicals; minimum width of the pubic ap ron wider than width of the pubic peduncle; the fourth trochanter having a V-shape notch in lateral view.
The astragalus is from the Lower Lufeng Formation, Lufengosaurus hunei Young 1941, Yunnanosaurus huangi Young 1942, and Jingshanosaurus xinwaensis Zhang & Yang 1994 were also occurred. Xixiposaurus does not possess autapomorphies of these taxa which emended by Barrett et al. ( 2005, 2007) and Upchurch et al. (2004). Lü et al. ( 2007) described Yunnanosaurus youngi based on diagnosis including: the sixth cervical vertebra is the longest among the vertebral column; the neural spines of posterior cervical vertebrae are short with expanded distal end, which is wider than its anteroposterior length; ischium longer than pubis; distal end of the pubis isround. The ischium of Xixiposaurus is longer than pubis, although, this character is shared with Coloradisaurus from Triassic of Argentine. Furthermore, the longest cervical vertebra is the fourth in Xixiposaurus the posterior cervical neural sp ines are longer than wide.
Although Mussaurus is the sister taxon of Xixiposaurus, compared to this genus, Xixiposaurus has several differences. Caudal rim of the narial fossa lies rostral to the cranial edge of the antorbital fenestra; profile of the rostral end ofmaxilla slopes continuously towards the rostral tip in Mussaurus antorbital fossa of Mussaurus is longer than that of orbital; dentary of Xixiposaurus does not possess the lateral lamina; the deltopectoral crest is visible from posterior view in Mussaurus; the olecranon p rocess is developed in Xixiposaurus; the fourth trochanter of Mussaurus is positioned at the center of posterior surface, though that of Xixiposaurus is at the medialmost part of posterior surface.