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Fig. 9 | BMC Evolutionary Biology

Fig. 9

From: Synchrotron imaging of dentition provides insights into the biology of Hesperornis and Ichthyornis, the “last” toothed birds

Fig. 9

Synchrotron x-ray microtomographic images of Hesperornis tooth dentine increment lines (YPM.1206.B). a Parasagittal basal-apical section of the Hesperornis regalis isolated tooth YPM.1206.B, showing its dentine increment lines. b Higher magnification of the apex of the tooth from the same section. Regular incremental lines are observed throughout the dentine (white arrows), and are interpreted as daily lines. They are counted from the dentine horn to the incremental line corresponding to crown completion (dashed line). c Higher magnification of the series of incremental lines observed in the dentine and interpreted as daily increments. d Higher magnification at the cervix level of the area near the cementum-dentine junction (CDJ) in the root, for quantifying the tooth root extension rate. d, direction of the daily rate of dentine secretion (DSR); angle I, angle the dentine tubules make with the root surface; angle D, angle between an incremental line and the root surface. Scale bars a 0.5 mm, c 0.05 mm

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