ABSTRACT Psittacosaurus is the most speciose nonavian dinosaur genus, represented by at least 10 (and possibly as many as 19) species uncovered over a wide geographic range. Here, we report a new species of large-bodied Psittacosaurus from the Ondai Sayr locality in central Mongolia, which has hitherto produced only one other Psittacosaurus specimen. This new species is characterized by: (1) an elongate snout, with a gently inclined rostronasal margin, (2) a cranium dorsally convex rather than flat, (3) a subtemporal length less than 40% of total skull length, (4) a maxillary lamina that cups the posterior toothrow, (5) five premaxillary foramina arrayed in an arc, (6) an antorbital fossa as long as it is wide, and (7) a palpebral with a well-developed posterior tonguelike process. Psittacosaurus amitabha is resolved as the most basal member of the genus Psittacosaurus in our phylogenetic analysis. This taxon expands our knowledge of the already-speciose genus Psittacosaurus as well as our understanding of the Ondai Sayr fauna, which is poorly known in comparison to other Mongolian Early Cretaceous localities.

中文翻译：

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阿弥陀佛鹦鹉嘴龙是蒙古中部翁代赛尔地区角龙类恐龙新种

摘要鹦鹉嘴龙是最特殊的非鸟类恐龙属，在广泛的地理范围内发现了至少 10 个（可能多达 19 个）物种。在这里，我们报告了一种来自蒙古中部 Ondai Sayr 地区的大型鹦鹉龙新种，该物种迄今为止仅产生了一个其他鹦鹉龙标本。这个新物种的特点是：（1）细长的鼻子，鼻尖边缘略微倾斜，（2）颅骨背凸而不是平坦的，（3）颞下长度小于颅骨总长度的 40%，（4）一个上颌骨板覆盖后牙托，(5) 五个上颌前孔排列成弧形，(6) 一个宽的眶前窝，以及 (7) 具有发达的后舌状突起的睑板。在我们的系统发育分析中，鹦鹉嘴龙被确定为鹦鹉嘴龙属的最基础成员。这个分类群扩展了我们对已经特异的鹦鹉嘴龙属的了解，以及我们对翁代赛尔动物群的了解，与其他蒙古早白垩世地区相比，温代赛尔动物群知之甚少。