What it is
A slim hunter with a long, narrow head, small sharp teeth, long thin legs and a very long tail. It looks a little like a monitor lizard, but it is no lizard. Varanopids are usually placed among the synapsids, on the same branch of the family tree as mammals.
Why it matters
About 289 million years ago, small animals and the hunters that ate them washed into caves at Richards Spur, in what is now Oklahoma. Scientists studying a little reptile there, Captorhinus, found its tail was built to snap off. They named the hunters it was most likely escaping: bigger amphibians, synapsids, varanopids among them, and possibly bigger relatives of Captorhinus itself.
Top of the food chain
Varanopids are the most common synapsids found at Richards Spur. One of them, Varanops, was big enough that scientists think it was one of the top predators there.