This is Dimetrodon, the world's top predator about 270 million years ago. Living before the dawn of the dinosaurs, this striking creature was actual a distant ancestor of mammals like us. Now we've discovered the most complete Dimetrodon skeleton ever.
The skeleton was discovered by paleontologists from the Houston Museum of Natural Science. We've known about Dimetrodon since its initial discovery in 1878, but this is one of the best finds yet, and the first time we've found a skull for this particular subspecies. Even better, the skeleton is articulated, meaning all the fossilized bones are in the right place. This particular skeleton has been nicknamed Wet Willi, the former after its drainage ditch origins and the latter after local 19th century dinosaur expert Samuel Williston.
I'll let the museum's associate curator of paleontology Dave Temple explain the finding:
Dimetrodon ruled the planet for fifteen million years at the end of the Permian Period. About 265 million years ago, it fell victim to the Capitanian extinction, a massive extinction event that was still just a prelude to the Permian-Triassic event about ten million years later. As such, Dimetrodon lived a good ten to fifteen million years before the earliest dinosaurs emerged, despite the fact that its likeness is often including in sets of plastic dinosaurs.
The sail on its back was easily its most iconic feature, although we've only recently figured out its purpose. Early theories suggested the fin was a sort of inbuilt fan that it could use to cool itself down, but now paleontologists are fairly certain it was just used as a display of dominance with enemies and potential mates alike.
Dimetrodon did have one mammalian feature: its teeth. It was one of the first creatures to develop the differentiated teeth that mammals need to chew their foods. Reptiles have more uniform teeth and tend to just gulp down their food, Dimetrodon was able to break apart and chew its food, making it a precursor of sorts to modern mammals.