吉林省中部早白垩世泉头组-原始鸟脚类恐龙

A PRIMITIVE ORNITHOPOD FROM THE EARLY CRETACEOUS QUANTOU FORMATION OF CENTRAL JILIN, CHINA

报道了在松辽盆地白垩纪沉积中首次发现的原始鸟脚类恐龙化石,并根据其头部特征建立一新属新种——娇小长春龙(Changchunsaurus parvus gen.etsp.nov.)。化石产于吉林省公主岭市刘房子镇山前泉头组上部紫红色含砾泥质砂岩中,同一层位还产有兽脚类、鳄类、恐龙蛋、哺乳类等化石。娇小长春龙是一种混合了原始的和衍生性状的小型鸟脚类恐龙。它具有某些比多数鸟脚类和头饰龙类要原始的特征,例如,5颗前上颌齿、前上颌骨吻部只有很短一段齿缺、前上颌骨与上颌齿之间的间隙较小、颊齿两侧的釉质对称、前上颌骨腹侧边缘与上颌骨腹侧边缘基本处于同一水平线等。同时,娇小长春龙也具有一些与真鸟脚类类似的进步特征,比如眶前孔小、外下颌孔缺失。娇小长春龙具有颧骨突,这在鸟脚类恐龙中较为罕见,它的颧骨突表面具有鲕状构造,这一特征未见于其他已知鸟脚类。娇小长春龙的前齿骨形态与角龙类接近,腹支明显长于侧支,前齿骨与齿骨的愈合方式同角龙类相似。娇小长春龙的确切系统分类位置需要进一步的工作来确定。

Summary A new ornithopod (Changchunsaurus parvus gen. et sp. nov.) dinosaur is named and described on the basis of a specimen from the Early Cretaceous Quantou Formation at Liufangzi locality , Jilin Province, China. The specimen represents the first primitive ornithopod taxon from the Cretaceous deposits in the Songliao Basin. Changchunsaurus is an interesting ornithopod in having a combination of primitive and derived characters. It shares with some ornithopod autopomorphies: paroccipital process is crescent-shaped, the jaw articulation offsets ventral to the maxillary tooth row. It shares with euornithopods the following synapomorphies: antorbital fenestra small, external mandibular fenestra absent. However, It is believed that Changchunsaurus is also more primitive than most of ornithopods and marginocephalians in having five premaxillary teeth, a short edentulous anterior portion of premaxilla, a short diastema between premaxillary and maxilla teeth, the enamel on crowns of maxilla teeth and dentary teeth distribute symmetrically, and the premaxillary bill margin with that of the maxilla. Its jugal boss projects lateral face of the jugal. There is nubble structure on the lateral expansion of jugal, which is not described in other ornithopods. Changchunsaurus has a long predentary, which suggests it might have an immobile mandibular symphysis as in ceratopsians, and the predentary ventral process is longer than the lateral process. It is similar to derived ornithopods in the morphology of the predentary with bilobate ventral process end. Further work is needed to give precise phylogenetic relationship of the new ornithopod.