Marine biology gannets, and auks. Although they spend most of their lives in the ocean, species such as gulls can often be found thousands of miles inland. There are five main types of marine mammals, namely cetaceans (toothed whales and baleen whales); sirenians such as manatees; pinnipeds including seals and the walrus; sea otters; and the polar bear. All are air-breathing, and while some such as the sperm whale can dive for prolonged periods, all must return to the surface to breathe. Marine habitats can be divided into coastal and open ocean habitats. Coastal habitats are found in the area that extends
Saber-toothed cat cats can be viewed as examples of convergent evolution. This convergence is remarkable due not only to the development of elongated canines, but also a suite of other characteristics, such as a wide gape and bulky forelimbs, that is so consistent that it has been termed the "saber-tooth suite." Of the feliform lineages, the family Nimravidae is the oldest, entering the landscape around 42 mya and becoming extinct by 7.2 mya. Barbourofelidae entered around 16.9 mya and were extinct by 9 mya. These two would have shared some habitats. The different groups of saber-toothed cats evolved their saber-toothed characteristics entirely