Figure 4.

Images of a Hydrochoerus hydrochaeris (Rodentia, Caviomorpha) tooth used to obtain superficial enamel acid etch samples. Images were made with photograph cameras (A,B) and with a Scanning Electron Microscope using Back-scattered-electrons (BSE) mode (C–E). Rectangles are always amplified in the next figure of the series. (A), tooth picture taken with magnification lens showing the circular etched area inside the black rectangle. Bar = 0.5 cm. (B), details of the rectangle depicted in (A). Circular transparent spots with a diameter of ≈200 $\mathsf{\mu }$m can be observed. Bar = 1 mm. (C), amplification of the rectangle shown in (B). The circular area was etched with acid. The circular spots are superficial, having disappeared in the etched area, and have a composition with less dense elements (suggesting an organic composition) than the Ca and P that compose the hydroxyapatite of the enamel. Bar = 500 $\mathsf{\mu }$m. (D), amplification of the rectangle shown in (C). Bar = 100 $\mathsf{\mu }$m. (E)., amplification of the rectangle shown in (D). Prismatic enamel is seen on the left (asterisk) in the etched area. Bar = 50 $\mathsf{\mu }$m.