Eocene cichlid fishes from Tanzania, East Africa

A large collection of fishes from Tanzania, East Africa, includes represent atives of four or five families of fishes. The majority of specimens are ci chlids, with at least five species being represented, distinguished by oste ological characters such as the shape of the opercular bones, frontals, and supraoccipital crest. These species are all named and described in the sam e genus based on shared scale and squamation characters. The site, at Mahen ge in the Singida Region, was a crater lake about half a kilometer in diame ter. It has been dated as Eocene. about 46 Ma, based on radiometric techniq ues. The cichlid species, being very closely related, may have constituted a species flock, which would indicate that cichlids had the ability to form flocks as early as the Eocene.