Ceratopsia is a diverse dinosaur clade from the Middle Jurassic to Late Cretaceous with early diversification in East Asia. However, the phylogeny of basal ceratopsians remains unclear. Here we report a new basal neoceratopsian dinosaur Beg tse based on a partial skull from Baruunbayan, Ömnögovi aimag, Mongolia. Beg is diagnosed by a unique combination of primitive and derived characters including a primitively deep premaxilla with four premaxillary teeth, a trapezoidal antorbital fossa with a poorly delineated anterior margin, very short dentary with an expanded and shallow groove on lateral surface, the derived presence of a robust jugal having a foramen on its anteromedial surface, and five equally spaced tubercles on the lateral ridge of the surangular. This is to our knowledge the earliest known occurrence of basal neoceratopsian in Mongolia, where this group was previously only known from Late Cretaceous strata. Phylogenetic analysis indicates that it is sister to all other neoceratopsian dinosaurs.

Ceratopsia 是一个多样化的恐龙进化枝，从中侏罗纪到晚白垩世，东亚的早期多样化。然而，基底角龙类的系统发育尚不清楚。在这里，我们报告了一种新的基础新角龙类恐龙Beg tse，它基于来自蒙古 Ömnögovi 伊马格的 Baruunbayan 的部分头骨。求通过原始和衍生特征的独特组合进行诊断，包括原始深的前上颌骨有四颗前上颌牙齿，一个梯形的眶前窝，前缘轮廓不清，很短的牙齿，侧面有一个扩大的浅槽，衍生的存在健壮的颈部在其前内侧表面有一个孔，在环的侧脊上有五个等距的结节。据我们所知，这是已知最早发生在蒙古的基底新角龙类，该组以前仅在晚白垩世地层中被发现。系统发育分析表明它是所有其他新角龙类恐龙的姐妹。