Cyclophyllideans usually have a scolex with four acetabula and many, but not all, possess a circle of hooks on a rostellum. Some of the largest of all Cyclophyllidean tapewrorms are those in the family Taeniidae, although members of the genus Echinococcus represent a notable exception. Members of the Taeniidae utilize mammals as both intermediate and definitive hosts. In the intermediate host, larval stages are bladder worms (i.e. cysticercus, coenurus, hydatid cysts) and for some species significant morbidity and even mortality can occur in the intermediate host. Adult worms are intestinal and usually cause little serious pathology. The scolex on the left is a Choanotaenia sp. (Dilepididae).