Question: How many years ago did amphibians first live?
About the article "Evolution", section "Evolution of life".

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FAM149A diverged from amphibians around 400 million years ago, Birds 300 million years ago and mammals, not including primates, 94 million years ago.
Divergence from Primates last occurred around 5 million years ago. 
The superclass Tetrapoda is divided into four classes of vertebrate animals with four limbs.
Reptiles, birds and mammals are amniotes, the eggs of which are either laid or carried by the female and are surrounded by several membranes, some of which are impervious.
Lacking these membranes, amphibians require water bodies for reproduction, although some species have developed various strategies for protecting or bypassing the vulnerable aquatic larval stage.
They are not found in the sea with the exception of one or two frogs that live in brackish water in mangrove swamps.
On land, amphibians are restricted to moist habitats because of the need to keep their skin damp.
The smallest amphibian (and vertebrate) in the world is a microhylid frog from New Guinea ("Paedophryne amauensis") first discovered in 2012.
It has an average length of and is part of a genus which contains four of the world's ten smallest frog species.
The largest living amphibian is the Chinese Giant Salamander ("Andrias davidianus") but this is a great deal smaller than the largest amphibian that ever existed—the extinct "Prionosuchus", a crocodile-like temnospondyl dating to 270 million years ago from the middle Permian of Brazil.
The largest frog is the African Goliath frog ("Conraua goliath") which can reach and weigh .
Amphibians are ectothermic (cold-blooded) vertebrates that do not maintain their body temperature through internal physiological processes.
Their metabolic rate is low and as a result, their food and energy requirements are limited.
In the adult state, they have tear ducts and movable eyelids, and most species have ears that can detect airborne or ground vibrations.
They have muscular tongues, which in many species can be protruded.
Modern amphibians have fully ossified vertebrae with articular processes.
Their ribs are usually short and may be fused to the vertebrae.
Their skulls are mostly broad and short, and are often incompletely ossified.
Their skin contains little keratin and lacks scales, apart from a few fish-like scales in certain caecilians.
The skin contains many mucous glands and in some species, poison glands.
The hearts of amphibians have three chambers, two atria and one ventricle.
They have a urinary bladder and nitrogenous waste products are excreted primarily as urea.
Most amphibians lay their eggs in water and have aquatic larvae that undergo metamorphosis to become terrestrial adults.
Amphibians breathe by means of a pump action in which air is first drawn into the buccopharyngeal region through the nostrils.
These are then closed and the air is forced into the lungs by contraction of the throat.
They supplement this with gas exchange through the skin. 
Diadectes (meaning "crosswise-biter") is an extinct genus of large, very reptile-like amphibians that lived during the early Permian period (Cisuralian epochs, between 290 and 272 million years ago).
"Diadectes" was one of the very first herbivorous tetrapods, and also one of the first fully terrestrial animals to attain large size. 
"Tulerpeton" lived approximately 365 million years ago, in the Late Devonian period when the climate was fairly warm and there were no glaciers.
Land had already been colonized by plants.
During the Devonian period, the first truly terrestrial tetrapods – the ancestors of present day reptiles, birds, amphibians and mammals - first began to appear. 
 The underworld is what's left over from a thousand years ago.
Endless fields of decaying skyscrapers and apartment blocks, all abandoned for a thousand years or more.
It is unknown how many people if any live down here.