Fig. 7
Synchrotron x-ray microtomographic images showing Hesperornis tooth implantation and replacement. a Basal-apical, transverse section of Hesperornis regalis isolated tooth YPM.1206.B showing the cementum and tooth attachment tissue on the root. Insert b at labial edge of the tooth root with the different cementum tissues: fine acellular cementum layer (ac) and the cellular cementum (cc) with large cementocyte lacunae (cl). Sharpey’s fibers (Sf) are also visible. Insert c at lingual edge of the tooth root showing cementum with numerous large cementocyte lacunae (cl) and Sharpey’s fibers (Sf). d–g Virtual sections of the tooth attachment in the dentary YPM.1206A. d Parasagittal section of the first tooth TH1 in YPM1206A. The tooth (dentine, d) is inserted via Sharpey’s fibers (Sf) into the jaw bone (jb). Some resorption holes (rh) confirm resorption of the jaw bone surrounding teeth during dental replacement. e Higher magnification of this region of implantation shows the cellular cementum directly attached to the jaw bone via Sharpey’s fibers. f Virtual transverse section through the fragmented tooth and cementum (THc) preserved in front of TH3 in the groove. The tooth is poorly preserved, with only some root dentine (d) still present. It is surrounded by the cementum. g Higher magnification on the cementum and jaw bone shows that the cementum is directly attached to bone tissue (asterisk) with Sharpey’s fibers. This tissue is separated by a space (possibly a diagenetic crack), from the rest of the groove bone wall, but it is histologically similar to this bone wall (with osteocyte lacunae). In e and g the white arrowheads point to the direction of visible Sharpey’s fibers that can be traced across the cementum-bone boundary. Scale bars a 0.5 mm, b c 0.1 mm, d 0.5 mm, e f g 0.25 mm