What it is
A squat amphibian with a broad, flat head and short legs that sprawl out to the sides. It is shown at the rim of a drying swamp pool, about 305 million years ago, when the tropics were drying and the coal forests were breaking up. It stands for the coal-swamp amphibians in general, not one named kind.
Tied to water
An amphibian's skin has to stay damp, and its eggs have no shell, so they have to be laid in water. What hatches out of them is a swimming larva with gills. A frog still lives this way today. So when the swamps dried, amphibians had more to lose than animals that laid shelled eggs on land.
Why it matters
What happened to the animals when the swamp forest broke is still argued. A study in 2010 found amphibians hit hard, and the survivors cut off in islands of forest. But a second team, in 2018, corrected for where fossils happen to be collected. They looked for those islands and did not find them.