Pinniped Missing Link
I think it is really exciting when there are recent discoveries that represent a major addition to the evolution of a group of animals. I just read about a 2007-2008 discovery in a former lakebed from Devon Island in the Canadian arctic of a missing link between a land-dwelling animal with legs, webbed feet and a streamlined body for swimming and the modern pinnipeds that include the modern seals, sea lions and walruses. This new species is named Puijila darwini, after Darwin who predicted that this species should exist and the Inuit word for young sea mammal. Previously, the earliest pinniped was Enaliarctos which already had fully formed flippers. The temperature that Puijila had lived in was similar to present day coastal New Jersey. As the seasonal temperatures became cooler, the freshwater lakes would freeze in the winter forcing the animals to travel over land and search for food in the sea. This fossil suggests that the Arctic may have played an important role in pinniped evolution.