Fossil teeth are a commonly preserved part of ancient animals due to their resilient composition of calcium fluorophosphates. This material is also known as apatite and is chemical-resistant and difficult to break down under much use. The apatite is covered with another very strong coat of enamel. For these reasons, fossil teeth are usually very well preserved and can be used to uncover valuable information about the lifestyles of extinct animals. Fossil teeth can also be compared to the teeth of living relatives to determine how species have evolved. Sometimes, scientists will reconstruct an ecosystem simply using the fossil teeth found in a geological deposit. In order to do this, scientists typically look at fossil teeth to determine whether an animal was a carnivore or an herbivore. Often, the shape of the fossil teeth will give it away but sometimes it is necessary to analyze the isotopic composition of the teeth to determine the nutritional components of the animal’s diet.