the teeth in the upper and lower jaw differ both in morphology as well as in tooth replacement. the teeth of the upper jaw tend to be larger (5-9mm) than those of the lower jaw (<5mm) and are serrated on the anterior edge while the lower jaw has serrations on the posterior edge. although it was originally thought that e. bathystoma had several rows of teeth on the upper jaw, it was later discovered that the tips of the teeth from the lower jaw had been left behind in the upper jaw. now it is known that the upper teeth are roughly positioned into a single row. the entire row is moved posteriorly so that the anterior portion of the premaxilla contains no teeth but the most posterior portion still holds two teeth. the teeth are also situated internally to the edge of the maxilla.