In contrast to dentine, the enamel was frequently fissured. Enamel is a hard but brittle material that may readily crack both during burial and sample preparation (cutting, polishing and volume changes upon drying of the embedding media). The enamel was furthermore frequently affected by superficial staining and etching.
In two teeth, human and cattle, morphological features observed within the enamel may be the result of post-mortem microbial activity (Figures 58, 59, 60, 61 and 62). Similar features have, to our knowledge, never been described before, indeed nor has any microbial boring within the enamel. On the contrary, several authors note that even in cases of severe bioerosion in dentine and cementum, the enamel is not attacked (Bell et al. 1991; Kierdorf et al. 2009; Kalthoff et al. 2011). This is also what we have observed in the majority of severely bioeroded teeth; the attack stops by the dentino-enamel border. Thus, further investigation is needed to confirm the nature of these features. Boring within the enamel close to the dentine is not unimaginable since the tufts, stretching out into the enamel from the dentino-enamel border contain greater concentration of proteins than the rest of the enamel (Nanci 2003). Underwood et al. (1999) note the occurrence of borings in the enamel of severely attacked fossil fish teeth, but limited to the area around the crown-root junction where the enamel is thin. Furthermore, bioerosion is frequently found in mollusc shells, consisting of between 90-95% calcium carbonate and less than 5% protein (Zhang and Zhang 2006), where the destruction has been observed both as caries-like pitting and branching tunnels (Hook and Golubic 1993; Raghukumar et al. 1989).