Fig. 1
X-ray microtomographic views of the studied teeth or dentary fragments with teeth of Hesperornis regalis, Ichthyornis dispar, and Ichthyornithiformes indet. a Isolated tooth of Hesperornis regalis YPM.1206B, complete tooth. From left to right: lingual, mesial, labial and distal views, and apical part showing fluted ornamentation. b Virtually extracted tooth TH2 from Hesperornis regalis dentary YPM.1206A, lingual (left) and labial (right) views. Isolated teeth of Ichthyornis dispar: c YPM.1460, damaged tooth tip fragment, four views; d UAM_PV93.2.133_1, nearly complete tooth, from left to right: lingual, mesial and labial views; e UAM_PV93.2.133_2, nearly complete tooth, from left to right: lingual, mesial and labial views (small arrow shows level of horizontal section in i). Incomplete dentaries of: f Hesperornis regalis YPM.1206A, right dentary mesial portion, from top to bottom: lingual, occlusal and labial views; g Ichthyornis dispar YPM.1775, right dentary portion, from top to bottom: lingual, occlusal and labial views. h Isolated tooth of Ichthyornithiformes, NHMM/RD271, from left to right: labial, distal and lingual views; small arrow shows level of horizontal section in i. i comparison of crown horizontal section shapes of Ichthyornis dispar UAM_PV93.2.133_2 (left) and Ichthyornithiformes indet. NHMM/RD271 (right). All x-ray microtomography external views (synchrotron microtomography except d, e and (I,left) (conventional microtomography), and (H) (digital photography). Scale bars, a, b, c, d, e, h and i 0.5 mm, f 2.5 mm, g 0.75 mm