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The origins and evolutionary relationships between the three main groups of amphibians (apodans, urodeles and anurans) is a matter of debate.A 2005 molecular phylogeny, based on rDNA analysis, suggested that the first divergence between these three groups took place soon after they had branched from the lobe-finned fish in the Devonian (around 360 million years ago), and before the breakup of ...
This is a list of official U.S. state, federal district, and territory amphibians. State amphibians are designated by tradition or the respective state legislatures. [1] As of 2023, only 28 states and one territory have a state amphibian.
The District of Columbia lacks a state reptile although it does have an official tree, flower, bird, [92] fish, [93] amphipod, [94] and bat, [95] and an amphibian is under consideration. [96] None of the organized territories of the United States have state reptiles, although all four have designated official flowers.
This is a list of amphibians found in the United States. A total of 306 amphibian species have been recorded in the United States , [ 1 ] 2 of which are now extinct. [ 2 ] This list is derived from the database listing of Amphibian Species of the World .
[160] [161] Marine fish of many species are caught commercially for food. A smaller number of species are farmed commercially . [ 160 ] [ 162 ] [ 163 ] Humans and their livestock make up more than 90% of the biomass of all terrestrial vertebrates, and almost as much as all insects combined.
Hagfish form a class of about 20 species of eel-shaped, slime-producing marine fish. They are the only known living animals that have a skull but no vertebral column. Lampreys form a superclass containing 38 known extant species of jawless fish. [311] The adult lamprey is characterized by a toothed, funnel-like sucking mouth.
The vertebrates include mammals, birds, amphibians, and various classes of fish and reptiles. The fish include the jawless Agnatha, and the jawed Gnathostomata. The jawed fish include both the cartilaginous fish and the bony fish. Bony fish include the lobe-finned fish, which gave rise to the tetrapods, the animals with four
The evolution of tetrapods began about 400 million years ago in the Devonian Period with the earliest tetrapods evolved from lobe-finned fishes. [1] Tetrapods (under the apomorphy-based definition used on this page) are categorized as animals in the biological superclass Tetrapoda, which includes all living and extinct amphibians, reptiles, birds, and mammals.