Mesonyx measured about 1.5 m (5 ft) long not including the tail, and weighted an estimated 22.7–34 kg.[2][unreliable source?] It was a fast predator from the Middle Eocene of Wyoming, and it probably hunted hoofed plant eaters, moving lightly on its toes. However, instead of claws, Mesonyx's toes ended in small hooves. Its long skull had a relatively large sagittal crest above the braincase to anchor large jaw muscles and give it a powerful bite.