This amphibian is still coming out of the water. The head came out first. Keep watching. The body keeps coming. That is two meters of animal, and in these swamps, it owned the water.
Its name is Eryops. It belongs to a group called the temnospondyls. For tens of millions of years, animals built like this one were the biggest hunters in the water here. The skull alone is about as long as your forearm. Flat, wide and heavy, with the eyes set high on top of it. That is a head built to rest low at the water's edge, and watch the surface.
But an amphibian is the wrong animal to find at the top of anything. Its 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. Every amphibian that has ever lived has been leashed to standing water at some point in its year.
And in the water, this one was the biggest hunter there was.
So how does it feed? Look at the mouth. There are teeth along the jaw, and a second set on the palate, the roof of the mouth. Nothing about that is built for chewing. It is built for holding. The animal grabs, lifts its head, throws it back, and lets the catch slide down. That only works where the prey cannot get away quickly, and in shallow water, almost nothing can.
The group tried other shapes too. In a lake in the tropics, a long way south of here, another temnospondyl went after fish. It grew a long, straight, narrow snout lined with small teeth. Its name is Prionosuchus. You will find a length quoted for it that makes it the largest amphibian that ever lived. That figure is scaled up from a broken skull, and the skull is most of what anyone has. It is a calculation, not a measurement. So here, it gets no number.
So why did any of this work? Because of the water. This land sat on the equator, wet the whole year round, and the water never went anywhere. Pools, channels, drowned forest floor, one running into the next for hundreds of kilometers. Being tied to water costs an animal nothing in a world where water is everywhere. For a very long time, it cost them nothing at all.
Then the ground moved. The last of the continents finished closing up into one mass. The wet belt that ran across the middle of it broke apart. Rain went seasonal. Pools that had held water all year started going dry between rains, and the mud at the bottom of them cracked into plates.
None of that kills a grown animal. A grown animal can walk to the next pool. It kills the eggs.
And something in the same swamp did not have the problem. Tens of millions of years earlier, a line of four-legged animals had started laying a different kind of egg. It had a shell on the outside and a membrane inside it, holding a private pond around the embryo. Lay one of those on dry ground, and it still works. No pool. No larva. No swimming stage at all.
That is the whole difference. Not a fight. Not a faster hunter. One line of animals needed an address with water in it, and one line did not. The world was about to run very short of addresses.
So go back to the waterline. The head comes out first, then the body, and then all of it goes back in. While the water was everywhere, that was never a weakness. The temnospondyls stayed on wherever it stayed wet, and some held out far longer than anybody expected. What they never got back was the run of the whole land.
