Fig. 2. Mesosaurid parareptile Stereosternum tumidum Cope, 1886 in Tooth microstructure of the Early Permian aquatic predator Stereosternum tumidum

Fig. 2. Mesosaurid parareptile Stereosternum tumidum Cope, 1886 from Passo do São Borja outcrop, Irati Formation, Lower Permian of the Paraná Basin; UFRGS-PV-0378-P. A. Composite photograph of a longitudinal cut of the anteriormost preserved tooth. B. Closer view of the distal extremity of the same tooth. The enamel layer is visible in a lighter color. Some dentinary tubules are indicated. C. Closer view of a section of the base of the same tooth, indicating the mixed composition of the dentinary wall. The crenulated boundary surface between the dentinary wall and the pulp is shown. Dashed lines indicate two denteons, and some vascular canalicles are also noted. Abbreviations: cs, crenulated surface of the pulp-dental boundary; igd, interglobular dentine; od, orthodentine; vc, vascular canalicle; vd, vasodentine.