Dimetrodon tooth biomechanics + Psittacosaurus complex dental microanatomy + Late Cretaceous troodontid tooth anatomy
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Ben Creisler
May 9, 2026, 2:49:34 PM (7 days ago) May 9
to DinosaurMa...@googlegroups.com
Ben Creisler
Free pdf:
Yin Yalei, Buyu Wu, Zixian Sui, Junwei Xing, Qi Zhao, Shuai Shao & Xing Xu (2026)
High-resolution tomographic analysis reveals complex dental microanatomy in Psittacosaurus.
ARPHA Preprints
doi: https://doi.org/10.3897/arphapreprints.e197963
https://preprints.arphahub.com/article/197963/list/9/
Psittacosaurus is known as the genus with the greatest number of species, among non-avian dinosaurs, with hundreds to thousands of specimens discovered throughout Asia. Nevertheless, the anatomical characteristics of Psittacosaurus teeth have not been thoroughly examined in previous research, limiting our understanding of its taxonomy. This study employs high-resolution computed tomography data to reconstruct and analyse the morphology of a left dentary tooth of Psittacosaurus discovered from the Lower Cretaceous Jiufotang Formation in Longcheng, Chaoyang, western Liaoning, China, which represents a new fossil site for psittacosaurs within the Jehol Biota. The reconstruction has revealed varied features of Psittacosaurus dentary teeth. These features include a distally angled bulbous primary ridge, secondary ridges present on the primary ridge of the crown, a median labial depression extending to the base of the crown, and a cingulum restricted on the distal lobe. Importantly, the reconstruction provides the first high-fidelity, three-dimensional visualization of a ceratopsian pulp cavity, which is characterized by a chisel-shaped pulp chamber and a columnar pulp canal. Our findings highlight the potential of non-destructive, high-resolution tomographic methods to uncover hidden anatomical complexity in well-studied fossil groups.
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Free pdf:
Yin Yalei, Wu Buyu, Pei Rui, Zhang Honggang, Zhang Xin, Shen Fengbin & Xing Xu (2026)
The anatomy of a troodontid tooth from the Late Cretaceous in Jiayin, Heilongjiang Province, China
ARPHA Preprints 7: e195849 (preprint)
doi: https://doi.org/10.3897/arphapreprints.e195849
https://preprints.arphahub.com/article/195849/
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.
Recent papers:
Adam J. Snyder, Eric Snively & Kirstin S. Brink (2026)
Tooth biomechanics of the non-mammalian synapsid Dimetrodon using two and three-dimensional finite element analysis
Journal of Experimental Biology jeb.251898.
doi: https://doi.org/10.1242/jeb.251898
https://journals.biologists.com/jeb/article-abstract/doi/10.1242/jeb.251898/371644/Tooth-biomechanics-of-the-non-mammalian-synapsid
Major changes in tooth morphology can be tracked throughout the evolutionary history of the Early Permian non-mammalian synapsid, Dimetrodon (295-270 MA). Teeth changed from the ancestral condition of folded roots (plicidentine) and crowns with smooth cutting edges (carinae) to a morphology with elongate roots and blade-like ziphodont crown morphology with serrated denticulate carinae, typical of other extinct apex predators. We created virtual models of individual teeth to investigate the functional differences between these morphological conditions through a combination of 2D and 3D Finite Element Analyses (FEA). Material properties based on extant values of enamel, dentine, and bone were imported on models loaded with point forces directed at the tooth tips. Results show that in the crowns, denticles convey energy non-homogenously, funneling stress and strain to the thinnest enamel layers between the denticles. Increased surface area of the expanded tooth roots resulted in lower stress values than present in the crowns. Similar areas in a short, folded root did not significantly alter energy transmitted to the cortical bone when compared to elongated, smooth roots. FEA results support the hypothesis that denticles and elongated, non-folded roots were all adaptations that would assist Dimetrodon in the oral processing of larger prey items.
Journal of Experimental Biology jeb.251898.
doi: https://doi.org/10.1242/jeb.251898
https://journals.biologists.com/jeb/article-abstract/doi/10.1242/jeb.251898/371644/Tooth-biomechanics-of-the-non-mammalian-synapsid
Major changes in tooth morphology can be tracked throughout the evolutionary history of the Early Permian non-mammalian synapsid, Dimetrodon (295-270 MA). Teeth changed from the ancestral condition of folded roots (plicidentine) and crowns with smooth cutting edges (carinae) to a morphology with elongate roots and blade-like ziphodont crown morphology with serrated denticulate carinae, typical of other extinct apex predators. We created virtual models of individual teeth to investigate the functional differences between these morphological conditions through a combination of 2D and 3D Finite Element Analyses (FEA). Material properties based on extant values of enamel, dentine, and bone were imported on models loaded with point forces directed at the tooth tips. Results show that in the crowns, denticles convey energy non-homogenously, funneling stress and strain to the thinnest enamel layers between the denticles. Increased surface area of the expanded tooth roots resulted in lower stress values than present in the crowns. Similar areas in a short, folded root did not significantly alter energy transmitted to the cortical bone when compared to elongated, smooth roots. FEA results support the hypothesis that denticles and elongated, non-folded roots were all adaptations that would assist Dimetrodon in the oral processing of larger prey items.
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PREPRINTS
Free pdf:
Yin Yalei, Buyu Wu, Zixian Sui, Junwei Xing, Qi Zhao, Shuai Shao & Xing Xu (2026)
High-resolution tomographic analysis reveals complex dental microanatomy in Psittacosaurus.
ARPHA Preprints
doi: https://doi.org/10.3897/arphapreprints.e197963
https://preprints.arphahub.com/article/197963/list/9/
Psittacosaurus is known as the genus with the greatest number of species, among non-avian dinosaurs, with hundreds to thousands of specimens discovered throughout Asia. Nevertheless, the anatomical characteristics of Psittacosaurus teeth have not been thoroughly examined in previous research, limiting our understanding of its taxonomy. This study employs high-resolution computed tomography data to reconstruct and analyse the morphology of a left dentary tooth of Psittacosaurus discovered from the Lower Cretaceous Jiufotang Formation in Longcheng, Chaoyang, western Liaoning, China, which represents a new fossil site for psittacosaurs within the Jehol Biota. The reconstruction has revealed varied features of Psittacosaurus dentary teeth. These features include a distally angled bulbous primary ridge, secondary ridges present on the primary ridge of the crown, a median labial depression extending to the base of the crown, and a cingulum restricted on the distal lobe. Importantly, the reconstruction provides the first high-fidelity, three-dimensional visualization of a ceratopsian pulp cavity, which is characterized by a chisel-shaped pulp chamber and a columnar pulp canal. Our findings highlight the potential of non-destructive, high-resolution tomographic methods to uncover hidden anatomical complexity in well-studied fossil groups.
====
Free pdf:
Yin Yalei, Wu Buyu, Pei Rui, Zhang Honggang, Zhang Xin, Shen Fengbin & Xing Xu (2026)
The anatomy of a troodontid tooth from the Late Cretaceous in Jiayin, Heilongjiang Province, China
ARPHA Preprints 7: e195849 (preprint)
doi: https://doi.org/10.3897/arphapreprints.e195849
https://preprints.arphahub.com/article/195849/
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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