Parasaurolophus californii is a herbivore, mainly feeding on fruits, leaves, cycads, ferns, and horsetails, that walks both as a biped and as a quadruped. It is a hadrosaurid, part of a diverse family of Cretaceous dinosaurs known for their range of bizarre head adornments. This species is known for its large, elaborate cranial crest, which at its largest forms a long curved tube projecting upwards and back from the skull. Charonosaurus from China, which may be its closest relative, has a similar skull and a similar crest. Its crest is used for visual recognition of both species and sex, acoustic resonance, and thermoregulation. It is a herd-dwelling animal and lives in groups up to about 19 at a time.