What it is
A cousin of Seymouria from the early Permian, found in what is now the Czech Republic. Almost every fossil of it is a young animal. Its adults are still unknown.
Why it matters
Some of its young kept bushy gills behind the head, on skulls up to about 32 millimeters long, and most kept the grooves of a lateral line, a sense organ for life in water. That showed Seymouria's family grew up in water, so they were not reptiles.
A slow childhood
Growth rings in its bones suggest it grew up like a salamander. It stayed a larva until about six years old, and probably could not breed before about nine or ten.