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  • Essay / Tetrapods - 1093

    The Lower Devonian period is widely considered to be a world of great diversity of lobe-finned fishes, including lungfishes, coelacanths and bony fishes. Over time, vertebrates made evolutionary advances that allowed them to travel on land. Coelacanths developed a single-boned shoulder girdle, lungfish developed paired fins, and sauriptera developed the major arm structures (humerus, radius, and ulna). As these developments progressed and environmental pressures increased in aquatic environments, vertebrates began to venture onto land. Sometimes it was for short excursions, sometimes a little longer. A major step in vertebrate evolution was the advancement of the tetrapod, a vertebrate animal with four appendages or legs. Buettneria, one of the first tetrapods, was primarily an aquatic animal with very short legs that was used for brief adventures on land. Over time, tetrapods made longer terrestrial excursions and developed more substantial terrestrial life. As a result, they developed different types of limbs that evolved for various uses. Some limbs were more suited to grasping, others to swimming, flying or walking. By the end of the Devonian, the oldest aquatic clades separated from tetrapods. Tetrapods continued to evolve over time. There are four classes of tetrapods: amphibians, reptiles, birds and mammals. They also evolved in this order. Within the four classes, the members of the different groups changed and adapted in order to fit their environment. This led to many different morphologies of tetrapods, which allowed some tetrapods to evolve toward terrestrial lifestyles, others toward aquatic environments, and others toward aerial existences. Amphibians, semi-aquatic animals, a...... middle of paper ...... as a force powerful enough to move vertebrates on land. To do this, four members allowing movement and radiation in the terrestrial world were developed. The fossil record and extant animals provide a cladistic map of how fish evolved into tetrapods and how tetrapods split into amphibians, reptiles, birds, and mammals. Works Cited Blount, Kitty and Maggie Crowley, eds. Encyclopedia of dinosaurs and prehistoric life. New York: Dk Publishing, Inc., 2008. Accessed November 29, 2011, http://books.google.com/books?id=a8bQxpPqmQgC&dq=Encyclopedia+of+Dinosaurs+and+Prehistoric+Life++By+Dorling+ Kindersley&source=gbs_navlinks_s.Feduccia, Alan. The origin and evolution of birds. New Haven: Yale University Press, 1999. Accessed November 29, 2011, http://books.google.com/books/about/The_origin_and_evolution_of_birds.html?id=8QRKV7eSqmIC.