Cross references:   Labyrinthodonts   Reptiles   Mammals    
Permian Discontinuity     Subcortical Brain         

Amphibian (Wiki)   

Amphibians are members of the class Amphibia, a group of vertebrates whose living forms include frogs, toads, salamanders, newts and caecilians. They are characterized as non-amniote, ectothermic tetrapods, meaning their eggs are not surrounded by membranes, they are cold-blooded, and they have four limbs. Most amphibians lay their eggs in water and the larvae undergo metamorphosis from a juvenile form with gills to an adult air-breathing form with lungs. Some, however, are paedomorphs that retain the juvenile water-breathing form throughout life.

The earliest amphibians evolved in the Devonian Period from Sarcopterygians, fish that had lungs and bony fins,[3] features that were helpful in adapting to dry land. They diversified and became dominant during the Carboniferous and Permian periods,[4] but were later displaced by reptiles and other vertebrates.

Genome size, secondary simplification, and the evolution of the brain in salamanders.
    "Compared to other vertebrates, even including lampreys and hagfishes in some respects, salamanders exhibit a relatively simple organization of brain and sense organs"
    "Phylogenetic analysis shows that the most parsimonious interpretation of these data is that the simple organization of the brain and sense organs of salamanders was derived secondarily from a more complex ancestral state."
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