The anatomy of a troodontid tooth from the Late Cretaceous in Jiayin, Heilongjiang Province, China
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Abstract
The anatomical characteristics of troodontid teeth have remained largely unexplored. This study employs high-resolution computed tomography data to reconstruct and describe the morphology of a new troodontid tooth from the Upper Cretaceous Yuliangzi Formation, located in the Sunwu-Jiayin Basin of Jiayin, Heilongjiang, Northeast China. The reconstruction reveals previously unrecognized anatomical features and presents the first three-dimensional visualization of the pulp cavity of troodontid teeth. Notably, the ratio of enamel thickness at the base of the crown to the crown height is 1.9%. The enamel thickness on the labial side exceeds that on the lingual side in the distal denticles, a phenomenon observed in theropod teeth for the first time. The pulp cavity is distinctly narrow in the labiolingual dimension, tapering sharply towards the apex, and exhibiting a distal curvature, and displays nine distinct projections along basal half of its distal margin. Additionally, the presence of a wear facet supports the hypothesis of tooth-to-tooth occlusion in troodontids, similar to that observed in tyrannosaurids. Comparative morphological analysis identifies the specimen as a Troodon-morphotype tooth, thereby providing further evidence for faunal exchange between North America and Asia via Cretaceous Beringia. Moreover, the only theropods that have been definitively identified from the Yuliangzi Formation are tyrannosaurids and troodontids. In addition, the comparison of various dinosaur faunal assemblages within Maastrichtian deposits in China indicates that all of them contain tyrannosaurids.
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ARPHA Preprints
https://doi.org/10.3897/arphapreprints.e195849 (16 Apr 2026)
https://doi.org/10.3897/arphapreprints.e195849 (16 Apr 2026)
Submitted to Swiss Journal of Palaeontology
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doi:
10.3897/arphapreprints.e195849
First posted
16 Apr 2026
Authors
Yin Yalei
- Corresponding author
Center for Vertebrate Evolutionary Biology, Yunnan University, Kunming, China
College of Paleontology, Shenyang Normal University, Shenyang, China
Key Laboratory of Evolutionary Systematics of Vertebrates, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, China
Zhang Honggang
- Corresponding author
Paleontological Museum of Liaoning, Shenyang Normal University, Shenyang, China
Shenzhou Dinosaur Museum, Jiayin Dinosaur National Geological Park, Yichun, China
Shenzhou Dinosaur Museum, Jiayin Dinosaur National Geological Park, Yichun, China
Center for Vertebrate Evolutionary Biology, Yunnan University, Kunming, China
Conflict of interest
The authors have declared that no competing interests exist.
Supporting agencies
The Key Laboratory of Stratigraphy and Paleontology of the Ministry of Natural Resources (SP202502)
National Natural Science Foundation of China (42402018, 42372031)
Yunnan Revitalization Talent Support Program (202305AB350006)
Taishan Scholar Program of Shandong Province (tstp20240514)
Liaoning Provincial Natural Science Foundation (2025-BSLH-371, 2025-MSLH-621)
Open Fund of the Observation and Research Station of Stratigraphy, Paleontology and Environmental Geology in Chaohu, MNR (SPEG-2025-KF02)
Fundamental Research Funds for the Liaoning Universities (LJ202410166031)
This is an open access preprint distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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