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The evolution of cetaceans is thought to have begun in the Indian subcontinent from even-toed ungulates (Artiodactyla) 50 million years ago (mya) and to have proceeded over a period of at least 15 million years. [2] Cetaceans are fully aquatic marine mammals belonging to the order Artiodactyla and branched off from other artiodactyls around 50 mya. Cetaceans are thought to have evolved during ...
Feb 1, 2019 · Each taxonomic marine mammal group evolved from a different group of land mammals, whose ancestors separately ventured back into the ocean environment. Despite these different origins, many marine mammals evolved similar features — streamlined bodies, paddle-like limbs and tails — through convergent evolution.
Dec 1, 2010 · By the time the first mammals evolved 200 million years ago, however, dinosaurs were the dominant vertebrates.
Nov 15, 2019 · The story of Cetacea began with the evolutionary radiation of placental mammals after the extinction of the dinosaurs and most large marine reptiles at the end of the Cretaceous about 66 million years ago (hereafter written Mya) (Fig. 2.1 ). The Paleocene (66–56 Mya) was the first epoch of the Cenozoic, a time when many placental mammals were small (<10 kg; Godinot 1994; Alroy 1999; Hu et al ...
Apr 16, 2015 · Genomic studies are also helping to piece together the reasons marine animals with different land ancestors appear to have developed similar adaptations when they went into the ocean, according to ...
Sep 24, 2014 · They evolved to take advantage of ecological niches that were not filled by other organisms. This basic concept, evolving to fill available niches, is a common outcome of the evolutionary process. The of adaptation of cetaceans and other mammals to the oceans may be similar to that of the hippopotamus.
Flippered and charismatic, pinnipeds (which includes seals, sea lions, and walruses) are true personalities of the sea. Like whales, manatees, and sea otters, they are marine mammals, meaning millions of years ago their ancestors evolved from a life on land to a life at sea. Today, they remain creatures of both land and sea.
