The mammals were more primitive than those that lived in the younger Kaiparowits Formation. Trace fossils are relatively abundant in the Wahweap Formation, and suggest the presence of crocodylomorphs, as well as ornithischian and theropod dinosaurs. Evidence of invertebrate activity in this formation ranged from fossilized insect burrows in petrified logs to fossils of mollusks, large crabs, and a wide diversity of gastropods and ostracods.