Pyrospondyl - the lava dweller pokemon
Pyrospondyl is the evolved form of temnoclast, an ancient pokemon.
Upon evolving the pokemon loses its gills, so since this is the part of it that fossilises most easily, pyrospondyl fossils are considerably rarer than those of its pre-evolved form. This means that pyrospondyl cannot spend too much time in lava, as they need to come up for air, but their lungs are still suitably adapted for long periods of time under lava.
Pyrospondyl that have been revived from fossils have been observed digging the ground with their shovel-shaped heads in order to build nests, but this has only occurred in the hottest climates. The pokemon simply cannot survive in the cold for very long, which may have been another reason for their extinction.
Genetic analysis shows that the pokemon is closely related not only to wooper, but also to charmander, which can be seen as evidence that a pokemon’s typing is fluid and ever-changing.
[Hooray for getting better at drawing things! Temnospondyli are my favourite extinct amphibians.]