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May 21, 2007 · Before exploring how the anatomical changes for life in water came about, one must know how marine mammals are related to one another, and particularly to their terrestrial relatives. A brief introduction to the phylogeny of each group of marine mammals is presented here, based on the latest studies using both morphological and molecular data.
- Mark D. Uhen
- 144
- 2007
- 21 May 2007
Sep 24, 2014 · If I understand evolutionary biology correctly, mammals first evolved on land as small, rodent-like creatures, in a time when reptiles were dominant on land. Eventually, they diversified into the species we know today.
A rigorous test for the evolution of marine mammals would use many more species and more characters. But the general result holds: mammals made the transition to water at least three times: in pinnipeds (seals and walruses), in whales, and also in sirenians (dugongs and manatees).
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The evolution of mammals has passed through many stages since the first appearance of their synapsid ancestors in the Pennsylvanian sub-period of the late Carboniferous period. By the mid- Triassic , there were many synapsid species that looked like mammals.
Marine mammals are mammals that rely on marine (saltwater) ecosystems for their existence. They include animals such as cetaceans ( whales , dolphins and porpoises ), pinnipeds ( seals , sea lions and walruses ), sirenians ( manatees and dugongs ), sea otters and polar bears .
A review of the broad outlines of what we know about the evolution of marine mammals from their fossil record, and then a focus on three discrete case studies that highlight important ecological transitions and evolutionary transformations that have occurred over the past 50 million years.
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First came the ancestors of antelope, cats, giraffes, and rhinos. Later, around ten million years ago, North American mammals—camels, horses, and dogs—began to arrive.
