Evolution of amphibians

The first ever group of amphibians was Icthyostegalia, a series of giant, salamander-like amphibians (Labyrinthodonts) appearing in the Early Devonian 400,000,000 BCE. These creatures laid out the blueprint for the lungs of every vertebrate that has lungs. They were fiercely dependent on water to reproduce and to soak up their thin skin that dried out in minutes. They lived in a world where they had to avoid giant fish like Dunkleosteus, Gorgonichthyes, and Hyneria.

Then, in the Carboniferous, roughly 350,000,000 BCE, three more kinds of amphibians appeared. The Reptiliomorphs, the Anthracosaurs, and the Temnospondyls. The Reptiliomorphs were a group of amphibians living near the water but not quite as dependently as the Icthyostega. The reptiliomorphs had reptile-like characteristics that may link them to having evolved into reptiles, including Dinosaurs. The Temnospondyls are suspected to have evolved into modern amphibians, the Lissamphibians. The appear to have various lissamphibian-like characteristics, and appear to look the most like Salamanders of any of the Labyrinthodonts. Anthracosaurs were the giants among these giants, and included vicious predators like Proterogyrinus and Gephyrostegus.

By the time of the Permian, starting 300,000,000 BCE, new groups like Seymouria, Rhinesuchus, and the largest Labyrinthodont that ever lived, Prionosuchus. This crocodile-shaped beast measured over 9 meters (30 feet) from nose tip to tale tip. It may likely have preyed on smaller everything, including Pelycosaurs like Edaphosaurus and Sphenacodon, as well as little creatures like Gerobatrachus, the "frogamander". These "frogamanders" were the precursors to lissamphibians, and just as well, the amniotes had a precursor of their own,

In 250,000,000 BCE, almost every Labyrinthodont species that was neither a frogamander nor the reptiliomorph equivalent was exterminated by volcanoes exploding (as opposed to erupting), carbon monoxide, desertification, extreme heat, dehydration, earthquakes, sandstorms, and ash-storms. 95% of life in general was obliterated by these disasters, collectively known as the Permian Mass Extinction. So began the Triassic.

At roughly 249,000,000 BCE, these two specimens evolved into the frogs and the first mammals, as well as newer, more successful reptiles than the ones that first appeared in the Carboniferous and Permian. The new order Anura contained no modern-day species at this time, except for perhaps the True frogs (ranids) and the Tree Frogs.

The Jurassic Period (starting 208,000,000 BCE) saw the evolution of the first toad family (the midwife toads), as well as the first salamanders, newts, and caecilians. The caecilians are basically snake-like amphibians. At this time, the reptiles, especially the dinosaurs, were the dominant life form. Therefore, the amphibians were confined to swamps and mucky area of dirt (i.e. the midwife toads).

The Cretaceous Period, beginning 145,000,000 BCE, saw the first fire-bellied toads and the first poison dart frogs. Reptiles were still the norm at this time, so amphibians still lived in confined areas. Mammals and birds were beginning to take over, and a meteor landed 65,000,000 BCE clearing out the dinosaurs and 65% of species in general.

The Cenozoic Era, the Age of Mammals, started with the Paleogene Period, which started with the Paleocene epoch. About around year 57,000,000 BCE, the first bufonids, or true-toads, appeared. These included large specimens by modern frog standards, some recent species the size of lunchboxes. These amphibians were the best adapted amphibians in zoological history to life on land, for they had (and still have) dry, leathery skin covered in tubercles (wart-like structures that do not give off any infections of any kind), and fingers for burrowing. Granted, they still needed to return to the water for drinking (by absorbing it through their underbellies) and for laying their shell-less, water-dependent eggs.