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Apr 16, 2015 · April 16, 2015. The oceans are teeming with tetrapods—“four-legged” birds, reptiles, mammals and amphibians—that have repeatedly transitioned from the land to the sea, adapting their legs ...
- 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
- 144
- 2007
- 21 May 2007
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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
Mar 21, 2012 · When did scientists first propose that marine mammals evolved from land-living mammals? What findings led to this conclusion?
4,000 Years of Marine History through the Eyes of a Seabird. A Hawaiian petrel flies over part of its North Pacific feeding grounds.(Photo courtesy of Jim Denny) by Anne Wiley. Most people have never heard of the Hawaiian petrel, an endangered, crow-sized seabird that spends the majority of its life searching for food over the North Pacific Ocean.
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. The lineage leading to today's mammals split up in the Jurassic; synapsids from this ...
