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Complex Dental Structure and Wear Biomechanics in Hadrosaurid Dinosaurs

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Science  05 Oct 2012:
Vol. 338, Issue 6103, pp. 98-101
DOI: 10.1126/science.1224495

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  1. Fig. 1

    Dental comparisons. (A) Hadrosaurid skeleton (Edmontosaurus). (B) Dental battery showing developing teeth (lingual view). (C) Edmontosaurus dental battery showing the progression of developing teeth and the grinding surface with teeth in various wear stages. (D) Ungulate grinding molars showing four-tissue composition. (E) Hadrosaurid outgroup condition (Camptosaurus) possessing individual shearing teeth at each position.

  2. Fig. 2

    Hadrosaurid dental organization. (A) Two-tissue model, frontal section of jaws depicting just enamel (red) and dentine (yellow) tooth composition (3, 4), with no enamel layers across the lower chewing surface. The upper (maxillary) teeth and lower (dentary) teeth were drawn at various angles across one another (1). The blue arrow depicts the movement of the upper teeth across the lower ones. The lower teeth may have been simultaneously drawn in the opposite direction. Tooth developmental stages are numbered in the upper (M#) and lower (D#) jaws. [Worn teeth were shed every 45 to 80 days from each column (7), up to 1880/year in total (17).] (B) Unexplained chewing surface features. (C) Hadrosaurus tooth with a Y-shaped ridge (arrow). (D) Sections through Edmontosaurus teeth showing tissues. Their presence and configurations vary throughout individual teeth. For instance, the roots (E), which become exposed, lack giant tubules. Coronal cementum (arrows) is present on the chewing surface and sides of a crown.

  3. Fig. 3

    Wear and hardness characterization. (A) Planarized Edmontosaurus tooth with wear track (left). (B) Profilometry of scratched tissues in AMNH 5896. Secondary dentine was not tested owing to its negligible footprint. (C) Mean and standard deviation from nanoindentation experiments on wear-relevant tissues in ungulates and hadrosaurids. The fossil bison absolute hardness values appear to be elevated from the degradation of elastic collagen, but the preservation of relative hardness, which is critical for understanding wear, is evident. Tissue-specific hardnesses in extant ungulate grinding teeth are highly variable among taxa. An exact match between values for the bison or horse and the analogous Edmontosaurus tissues is not expected. (D) Mean wear rates and standard deviation versus mean hardness and standard deviation for AMNH 5896 tissues.

  4. Fig. 4

    Tribological modeling of the AMNH 5896 dental battery. (A) Tissue distribution and measured wear rates used in the simulation. (B) Schematic of the computational framework and simulation procedure. An initially flat composite is exposed to abrasive wear under uniform pressure. The progression of wear depth and contact pressure are linked, leading to uniform recession only at a steady state. (C) Equilibrium profile following computational wear modeling of an initially planar composite surface of varying tissue types assigned fossilized wear-rate values.