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Synapsida [a] is a diverse group of tetrapod vertebrates that includes all mammals and their extinct relatives. It is one of the two major clades of the group Amniota, the other being the more diverse group Sauropsida (which includes all extant reptiles and birds).
Tetrapoda includes three living classes: amphibians, reptiles, and mammals. Overall, the biodiversity of lissamphibians, [23] as well as of tetrapods generally, [24] has grown exponentially over time; the more than 30,000 species living today are descended from a single amphibian group in the Early to Middle Devonian.
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.
Animals range in size from 8.5 millionths of a metre to 33.6 metres (110 ft) long and have complex interactions with each other and their environments, forming intricate food webs. The study of animals is called zoology .
The list below largely follows Darrel Frost's Amphibian Species of the World (ASW), Version 5.5 (31 January 2011). Another classification, which largely follows Frost, but deviates from it in part is the one of AmphibiaWeb , which is run by the California Academy of Sciences and several of universities.
The decline in amphibian and reptile populations has led to an awareness of the effects of pesticides on reptiles and amphibians. [176] In the past, the argument that amphibians or reptiles were more susceptible to any chemical contamination than any land aquatic vertebrate was not supported by research until recently. [ 176 ]
Reptiles are tetrapod animals in the class Reptilia, comprising today's turtles, crocodilians, snakes, amphisbaenians, lizards, tuatara, and their extinct relatives. The study of these traditional reptile orders, historically combined with that of modern amphibians, is called herpetology.
Biology of the Reptilia is an online copy of the full text of a 22-volume 13,000-page summary of the state of research of reptiles. HerpMapper is a database of reptile and amphibian sightings; Amphibian and Reptile Atlas of Peninsular California, San Diego Natural History Museum; A Primer on Reptiles and Amphibians; Field Herp Forum