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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
- 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.
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Apr 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 into fins.
The hunt for the ancestors of living birds began with a specimen of Archaeopteryx, the first known bird, discovered in the early 1860s. Like birds, it had feathers along its arms and tail, but unlike living birds, it also had teeth and a long bony tail. Furthermore, many of the bones in Archaeopteryx ‘s hands, shoulder girdles, pelvis, and ...
The return to the sea: The evolution of marine mammals. : : : Both morphological and molecular data tell us that the ancestors of the marine mammals were terrestrial, and that their various marine lifestyles have evolved independently at least seven times! Each lineage shows shared as well as unique evolutionary solutions to the challenges of ...
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) 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.
Nov 4, 2023 · The resulting disruption of marine and terrestrial ecosystems caused a mass extinction called the end-Triassic extinction that impacted numerous plant and animal species and, in another important event in the evolution of birds, the only archosaurs that survived into the Jurassic were crocodylomorphs from the crocodile line and pterosaurs and ...
