Clepsydrops was a primitive amniote from the early Late Carboniferous that was related to Archaeothyris and the synapsids—the ancestors of mammals. Like many other terrestrial early amniotes, it had the diet of insects and smaller animals. It also laid eggs on land rather than in the water, as most of its ancestors did. Its jaws were slightly more advanced than Paleothyris, and Hylonomus.