A neoceratopsian dinosaur from the early Cretaceous of Mongolia and the early evolution of ceratopsia

Congyu Yu,Zorigt Badamkhatan,Albert Prieto-Marquez,Mark Norell,Tsogtbaatar Chinzorig

doi:10.1038/s42003-020-01222-7

Abstract

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.

Highlights

IntroductionBeg 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 spaced tubercles on the lateral ridge of the surangular
Ceratopsia is a diverse dinosaur clade from the Middle Jurassic to Late Cretaceous with early diversification in East Asia
The holotype and only known specimen of Beg tse was collected near the town of Tsogt-Ovoo, Ömnögovi aimag (Province) in Mongolia during the 2015 Mongolian Academy of Sciences-American Museum of Natural History Joint Paleontological Expedition

Summary

Introduction

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 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. This species adds the diversity of ceratopsian dinosaurs around the Early/Late Cretaceous

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