辽宁早白垩世义县组一原始鸟脚类恐龙

初步记述了采自辽西地区早白垩世义县组新的原始鸟脚类恐龙化石材料，并依此建立一新属新种上园热河龙（Jeholosaurus shangyuanensis gen. et sp. nov.）。化石产于北票市上园镇陆家屯义县组下部第一段灰白色凝灰质砂岩中，同一层位产出过大量鹦鹉嘴龙化石。上园热河龙的主要鉴定特征包括6个前上颌齿，鼻骨背面发育小孔，前齿骨约为前上颌骨主体长度的1.5倍、未发育股骨前髁间沟、骨不在一平面上，第三趾趾节中第四节最长。上园热河龙具有一些真鸟脚类恐龙的近裔性状，比如眶前孔小，方骨孔大，位于方颧骨侧面，外下颌孔缺失。另外，上园热河龙的股骨近端形态非常接近进步的鸟脚类恐龙。但是上园热河龙发育有6个前上颌齿，上下颌关节处与齿列位于同一水平线，前上颌齿列与上颌齿列位于同一水平线，这些原始特征未见于已知鸟脚类恐龙。上园热河龙确切系统分类位置需要进一步确定。 上园热河龙是义县组中发现的第二种鸟臀类恐龙，增加了这类恐龙在热河生物群中的分异度。

A PRIMITIVE ORNITHOPOD FROM THE EARLY CRETACEOUS YIXIAN FORMATION OF LIAONING

A new ornithopod dinosaur is named and described on the basis of two specimens from the Early Cretaceous Yixian Formation at Lujiatun Locality, Liaoning Province, China. Diagnostic features of this new ornithopod include six premaxillary teeth, a few foramina on the dorsal surface of the nasal, a large quadrate foramen on the lateral side of the quadratojugal, lack of external mandibular fenestra, predentary about 1.5 times as long as the premaxillary main body, anterior intercondylar groove of the femur absent, metatarsals not in the same plane, pedal phalanx III-4 longer than other phalanges of pedal digit III. The discovery of a new ornithopod from the Yixian Formation increases the diversity of the Jehol fauna.