Chapter 4: Teeth Everywhere

As I continue reading into this book, it has become apparent that I have become less interested with Shubin's life and more interested in his discoveries. I knew this chapter would only be another link to our ancestors since teeth preserve in fossils the best and gave a strong clue to a creature's diet. After stating the structural differences between reptiles and mammals (in which reptiles lack occlusion and replace teeth consistently and mammals have honed jaw lines with only one extra pair of teeth) I knew he would lead into the analysis of a creature that fused both these traits in order to show a common ancestry. This creature was the reptile known as tritheledont. Predicting that an ancestor with both traits would be mentioned as I read, I wasn't surprised. What did surprise me is how Ostracoderms had an armor of bone for its head made of teeth. Before, I believed that bones were the origin of tooth, but the ostracoderm completely reversed my assumption by showing that its production of teeth transformed to form armor for the head. Hence, this was an interesting eye-opening chapter in my perspective.