After the dinosaurs became extinct 65 million years ago, the mammals grew to adjust to the wide range of habitats left vacant by the extinct reptiles. Once shrew-like in appearance and lifestyle teh mammals quickly expanded into different life forms and environments to become the dominant group of land-dwelling vertibrates as well as a major part of aquatic life. There are 4000 species of mammals. These beautiful playing cards, illustrated by artist Cecelia Fitzsimons, bring to life the vibrant diversity of 54 familiar animals of the North American Continent.