For over thirty years, science called this a reptile. Then gills showed up on its cousins.
It was a sturdy land animal, found near Seymour, Texas, and named Seymouria.
From nineteen eleven, papers ranked it a reptile, and in nineteen eighteen, the most primitive one known.
Even its champions saw amphibian features in its skull. Still, in nineteen thirty-nine, the label held.
But doubts grew. By nineteen forty-seven, the crucial point was how an animal grows up.
A reptile, by definition, lays an egg that skips the larva, a young stage spent in water.
That year, Seymouria was moved out of the reptiles, onto the amphibian side.
Five years later, gills were first seen on fossils of its cousins, from what is now the Czech Republic.
Their young had bushy gills behind the head, and stayed larvae until about six years old.
Those cousins lived millions of years earlier, far from Texas. No larva of Seymouria has been found.
So Seymouria was not a reptile. It was a land animal near the line that led to reptiles, from a family that grew up in water.
The same animal sits on the same card. Only the label has changed.
