Computed tomographic analysis of the dental system of three Jurassic ceratopsians and implications for the evolution of tooth replacement pattern and diet in early-diverging ceratopsians.

Abstract

The dental system of ceratopsids is among the most specialized structure in Dinosauria by the presence of tooth batteries and high-angled wear surfaces. However, the origin of this unique dental system is poorly understood due to a lack of relevant knowledge in early-diverging ceratopsians. Here, we study the dental system of three earliest-diverging Chinese ceratopsians: <i>Yinlong</i> and <i>Hualianceratops</i> from the early Late Jurassic of Xinjiang and <i>Chaoyangsaurus</i> from the Late Jurassic of Liaoning Province. By micro-computed tomographic analyses, our study has revealed significant new information regarding the dental system, including no more than five replacement teeth in each jaw quadrant; at most one replacement tooth in each alveolus; nearly full resorption of the functional tooth root; and occlusion with low-angled, concave wear facets. <i>Yinlong</i> displays an increase in the number of maxillary alveoli and a decrease in the number of replacement teeth during ontogeny as well as the retention of functional tooth remnants in the largest individual. <i>Chaoyangsaurus</i> and <i>Hualianceratops</i> have slightly more replacement teeth than <i>Yinlong</i>. In general, early-diverging ceratopsians display a relatively slow tooth replacement rate and likely use gastroliths to triturate foodstuffs. The difference in dietary strategy might have influenced the tooth replacement pattern in later-diverging ceratopsians.