| transverse sections of various fossil shark teeth |
| transverse section and sagittal section |
| Isurus oxyrinchus (a; transverse section, b; sagittal section), Carcharodon carcharias (c; transverse section, d; sagittal section) |
| Cosmopolitodus hastalis (a; transverse section, b; sagittal section), Isurus planus (c; transverse section, d; sagittal section) |
| Otodus megalodon (a; transverse section, b; sagittal section), Squalicorax pristodontus (c; transverse section, d; sagittal section) |
| scale bar; 0.5 mm |
| Analysis of Enameloid Microstructure Teeth were embedded in transparent polyester resin prior to sectioning, and were cut in cross- or longitudinal section using a diamond blade. Following the initial cut, the surface of the resin block to be observed was ground, until the desired plane of section was reached, using 600-, 1500-, 3000-, and 5000-grit silicon carbide abrasive paper. Ground sections were then etched for 10 s in 5 % HC‚Œ. |
| Enameloid Microstructure of |
| a: lingual surface; showing surface shiny-layered enameloid (SLE) b: slightly ground lingual surface; parallel-bundled enameloid (PBE) of the cutting edge c: ground lingual surface; tangled-bundled enameloid (TBE) and a part of the dentine |
| 1. Surface shiny-layered enameloid (SLE) of Carcharhinus brachyurus |
| 2. parallel-bundled enameloid (PBE) of Carcharodon carcharias |
| 3. tangled-bundled enameloid (TBE) & parallel-bundled enameloid (PBE) of Carcharodon carcharias (a,b; TBE., c,d;TBE/PBE boundary |
| SEM Analysis of Enameloid Microstructure Teeth were ground, until the desired plane of section was reached, using 600-, 1500-, 3000-, and 5000-grit silicon carbide abrasive paper. Ground sections were then etched for 10 s in 5 % HCl. Prior to SEM analysis, ground sections were coated with gold. Analysis and photography of ground sections was carried out on a Hitachi S-3500N scanning electron microscope with an acceleration voltage of 10 kV. |
| Specimens 1. Squalicorax pristodontus: Cretaceus (Maastrichitien), Oued ergita 2. Isurus oxyrinchus: Senhata Formation,Late Miocene, Chiba Prefecture, Japan 3. Isurus planus: Hokuriku G.Sekinohana, Middle Miocene, Ishikawa Prefecture, Japan 4. Cosmopolitodus hastalis: Senhata Formation,Late Miocene, Chiba Prefecture, Japan 5. Carcharodon carcharias Naarai Formation, Pliocene, Choshi-shi Chiba Prefecture, Japan 6. Otodus megalodon: Aoso Formation, Miocene, Miyagi Prefecture, Japan 7. Carcharhinus brachyurus: Senhata Formation,Late Miocene, Chiba Prefecture, Japan |
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