四川自贡肉食龙一新种

YANGCHUANOSAURUS HEPINGENSIS —— A NEW SPECIES OF CARNOSAUR FROM ZIGONG, SICHUAN

和平永川龙(Yongchuanosaurus hepingensis sp. nov.)为四川盆地发现的又一相当完整肉食龙新材料,本文对它进行了记述.

A new species of Yangchuanasaurs, namely, Y. hepingensis is described.The material, a complaete skeleton, came from Heoing, Zigong, Sichuan Basin. Theropoda Marsh, 1881 Carnosauria Huene, 1920 Megalosauridae Huxley, 1869 Yangchuanosaurus Dong, Zhang, Li et Zhow, 1977 Yangchuanosaurus hepingensis sp. nov. Horizon Shangshaximiao Formation, Upper Jurassic. Diagnosis A big megalosaur, 8m in length. Skull large and moderately high, 1040 mm in length, 595 mm in height; the ratio of length to height of skull (comprising lower jaw) about 1.75. Two antorbital fenestra, the first is antero-posteriorly elongate and isosceles triangle in outline, the second is sinall and quadrilateral in outline. Frontal and prefrontal are not contributes to upper border of the orbita opening. The wing-like plates of parietal well developed. Supraoccipital small and narrow. Dentary thick andd relatively high Mandibular faramen large. Teeth relatively small, maxillary teeth relatively thin. Dental formula: Pm. 4, M. 13-14, D. 16. 9 opisthocoelous cervicals; 14 amphiplatyan dorsals, vertebrae relatively shorter than neural spines plate-like; 5 sacrals, with firmly co-ossified centra; more than 35 caudals, distal caudals with elongate prezygapophyses. Scapular shaft wide. Ilium high; pubis distal, foot-like, process short and wide; ischium distal expand. Discussion The material (ZDM0024) with typical traits of megalosaur: Relatively larger form. Skull large and moderately high. Lower ramus of squamosa^1 inclined steeply downward, post-orbital bar relatively slender. Mandible massive, with mandibular foramen. In section of teeth is lenticular, serrations on both fornt and back borders. Genus Yangchuanosaurus was erected by Dang, Zhang, Li et Zhow in 1977. Up to now there are 3 known species in Yangchuanosaurus; Y. shangyuensis, Y. magnus and the new species Y. hepingensis. Both Y. shangyuensis and Y. magnus was discovered in Shangshaximian Formation (Jurassic) of Yongchuan county. The 3 species belonged to the same age. From Zigong city to Yongchuan town only 120 km in distance. The material (ZDM 0024) is similar to genus Yangchuanosaurust in mos characters: Skull large and moderately high. 6 pairs external opening in skull. External nares oval. Lateral temporal fenestra moderately large, widest anter-posteriorly a^t the middle. Frontal with parietal co-ossified. Mandibular foramen large. Pm 4, no more than 15 maxillary teeth. Cervical vertebra opisthocoelous; dorsals amphiplatyan, dorsal spines plate-like, relatively high;5 sacrals, with firmly co-ossified centra; anterior caudal vertebrae with neural spines high. Pelvie girdle firm; shaft of pubis and ischium co-ossified; pubis distal, foot-like, process generally developed. Hence it is reasonable to assign the material (ZDM0024) to genus Yangchuanosaurus. Comparison of Y. hepingensis with Y. shangyuensis: Although these two species of Yangchuanosaurus are similar in most characters, some differences are present. See table 1, they are not one species. Table 1 The differential diagnosis for the two species Comparison of Y. hepingensis with Y. magnus, the differential diagnosis for these two species: Maxillary low and long, maxilla concave is long elliptical in outline; first antorbital fenestra is antero-posteriorly elongate and isosceles triangle in outline, second antorbital fenestra is quadrilateral in outline; teeth relatively smaller, maxillary teeth relatively thiner; ilium relatively higher and shorter; femur relatively slender and longer in Y. hepingensis. On the contrary, maxillary high, maxilla concave is triangle in outline; first antorbital fenestra is not antero-posteriorly elorngate, second antorbital fenestra is triangle in outline; teeth massive, maxillary teeth thick; ilium long and narrow; femur relatively massive and short in Y. magnus. Besides the preserved material of Y. magnus is incomplete to compare in every bone elements with that of Y. hepingensis.