1. Agnatha
"In addition to the absence of jaws, modern agnathans are characterized by absence of paired fins; the presence of a notochord both in larvae and adults; and seven or more paired gill pouches." (Wikipedia: Agnatha, 8.2.21 UTC 22:47)
2. Amphibia
"[Amphibia] inhabit a wide variety of habitats, with most species living within terrestrial, fossorial, arboreal or freshwater aquatic ecosystems... Traditionally, the class Amphibia includes all tetrapod vertebrates that are not amniotes." (Wikipedia: Amphibian, 8.14.21 UTC 22:444)
3. Aves
"Birds are a group of warm-blooded vertebrates constituting the class Aves, characterized by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered hear, and a strong yet lightweight skeleton." (Wikipedia: Birds, 8.4.21 UTC 21:49)
4. Chondrichthyes
"Chondrichthyes is a class that contains the cartilaginous fishes that have skeletons primarily composed of cartilage Chondrichthyes are jawed vertebrates with paired fins, paired nares, scales, and a heart with its chambers in series." (Wikipedia: Chondrichthyes, 7.13.21 UTC 17:22)
5. Mammalia
"Mammals... are characterized by the presence of mammary glands... a neocortex, fur or hair and three middle ear bones." (Wikipedia: Mammal, 8.8.21 UTC 07:22)
6. Osteichthyes
"Osteichthyes, popularly referred to as the bony fish, is a diverse taxonomic group of fish that have skeletons primarily composed of bone tissue. They can be contrasted with the Chondrichthyes, which have skeletons primarily composed of cartilage." (Wikipedia: Osteichthyes, 7.3.21 UTC 15:56)
7. Reptilia
"Reptiles are... a paraphyletic grouping comprising all amniotes except synapsids (mammals and their extinct relatives) and Aves (birds). The class comprises turtles, crocodilians, snakes, amphisbaenians, lizards, tuatara and their extinct relatives." (Wikipedia: Reptile, 8.14.21 UTC 20:48)
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