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Apr 16, 2009 · Around 34 million years ago, the first representatives of the modern groups of whales, odontocetes and mysticetes are found. It is now generally assumed that odontocetes and mysticetes (together called Neoceti) arose from a common Eocene cetacean ancestor and are thus monophyletic.
- J. G. M. Thewissen, Lisa Noelle Cooper, Lisa Noelle Cooper, John C. George, Sunil Bajpai
- 2009
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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- Bob Strauss
- Fish and Sharks. Between 500 and 400 million years ago, vertebrate life on earth was dominated by prehistoric fish. With their bilaterally symmetric body plans, V-shaped muscles, and notochords (protected nerve chords) running down the lengths of their bodies, ocean dwellers like Pikaia and Myllokunmingia established the template for later vertebrate evolution It also didn't hurt that the heads of these fish were distinct from their tails, another surprisingly basic innovation that arose during the Cambrian period.
- Tetrapods. The proverbial "fish out of water," tetrapods were the first vertebrate animals to climb out of the sea and colonize dry (or at least swampy) land, a key evolutionary transition that occurred somewhere between 400 and 350 million years ago, during the Devonian period.
- Amphibians. During the Carboniferous period, dating from about 360 to 300 million years ago, terrestrial vertebrate life on earth was dominated by prehistoric amphibians.
- Terrestrial Reptiles. About 320 million years ago, give or take a few million years, the first true reptiles evolved from amphibians. With their scaly skin and semi-permeable eggs, these ancestral reptiles were free to leave rivers, lakes, and oceans behind and venture deep into dry land.
May 21, 2007 · Mammals have entered the aquatic environment on at least seven separate occasions. The first to do so were the Cetacea and Sirenia, which both originated at approximately the same time in the late Early Eocene (Gingerich, 2005 b; Gheerbrant et al., 2005 a, b).
- Mark D. Uhen
- 146
- 2007
- 21 May 2007
Jan 5, 2014 · But looking at swimming in dogs afforded Fish the opportunity to investigate how swimming in marine mammals may have evolved from walking in their terrestrial ancestors.
Jan 11, 2024 · It was one of the biggest mysteries of evolution: how did four-legged land mammals evolve into whales? And how did a top team of paleontologists unravel this 50-million-year-old cold case?
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Nov 15, 2019 · Convergent morphological adaptations for an aquatic life (e.g., fusiform body shape, flukes and flippers) evolved separately in the three taxonomic orders of extant marine mammals (Artiodactyla [infraorder Cetacea], Carnivora [clade Pinnipedia and sea otters], and Sirenia).
