Welcome back! We hope that you enjoyed the first lesson of the Ancient Marine Reptiles mini MOOC. In lesson one, we discussed a variety of modern and extinct groups of aquatic amniotes. Some of these groups would have been familiar to you, and some you had probably never heard of before. We also explored some of the many differences between living in water and living on land, and we gave examples of how some amniote groups have overcome these challenging differences. As you may have already seen, some of the solutions to the different aspects of the aquatic problem were solved in the same way by unrelated groups- a phenomenon called convergence. The next three lessons will build on your understanding of the aquatic problem as we investigate it more detail in three extinct groups of marine reptiles: the ichthyopterygians, sauropterygians, and mosasauroids. Each lesson will follow the same general outline. First, we will introduce you to the group and some of its diversity. The second part of each lesson will focus on how that group adapted to solve the aquatic problem, and how this resulted in specializations for feeding, locomotion and reproduction. Finally we will give you an overview of the evolutionary history of the group through time and space, as well as presenting some important fossils and localities from Canada and around the world. In lesson two, we will study the first of the three major groups of extinct marine amniotes: the ichthyopterygians. The ichthyopterygians were highly specialized animals. Most of the later members looked something like a dolphin or a tuna, a great example of convergent evolution. These reptiles were probably among the fastest aquatic creatures that ever lived. They were found all over the world, from the early Triassic to the mid-Cretaceous, a span of 150 million years. By the end of this lesson, you should be familiar with the history and diversity of this group, and be able to appreciate some of their impressive specializations to solve the aquatic problem.