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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 · Marine Mammal Diversity. Living groups of marine mammals vary greatly in their diversity. Rice (1998; Table 1 therein) reports that living Cetacea include 83 species in 39 genera; living Pinnipedia include 36 species in 21 genera; and Recent Sirenia include 5 species in 3 genera. Since then, several new species of cetaceans have been described ...
- Mark D. Uhen
- 2007
People also ask
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Apr 16, 2009 · Cetaceans (whales, dolphins, and porpoises) are an order of mammals that originated about 50 million years ago in the Eocene epoch. Even though all modern cetaceans are obligate aquatic mammals, early cetaceans were amphibious, and their ancestors were terrestrial artiodactyls, similar to small deer. The transition from land to water is documented by a series of intermediate fossils, many of ...
- J. G. M. Thewissen, Lisa Noelle Cooper, Lisa Noelle Cooper, John C. George, Sunil Bajpai
- 2009
Oct 18, 2012 · University of California Press, Berkeley, CA. 2012. 205 pp., $49.95 (cloth), $25.62 (Kindle). ISBN 9780520270572. Annalisa Berta leads readers through a vast range of topics regarding the evolution of marine mammals in Return to the Sea: The Life and Evolutionary Times of Marine Mammals. In this volume geared towards non-specialists (one might ...
- Mark D. Uhen
- muhen@gmu.edu
- 2013
Whales evolved massive bodies to not only store large quantities of energy but also to push aside the water for effective long-distance travel. At the same time that baleen whales were growing to massive proportions feeding on tiny crustaceans, another marine mammal, Desmostylia, was grazing on kelp and seagrass in the shallows.
High-speed swimming, remarkable breath-hold capabilities and an enormous gastro-intestinal tract combine to make marine mammals elite eating machines. But these voracious appetites have come at a cost. Many marine mammals are currently endangered or threatened; many others are in direct conflict with the human desire for seafood.
Nov 15, 2019 · Abstract. Early Cetacea are classified as Archaeoceti (six families), and their fossils reveal the morphological and functional evolution of early, terrestrial Artiodactyla to fully aquatic Cetacea over 15 million years during the Eocene (~52 Mya). The evolution of modern Cetacea (Neoceti: Mysticeti and Odontoceti) began in the late Eocene (~37 ...
