The oldest fossil cichlids (Teleostei : Perciformes): indication of a 45 million-year-old species flock

Five closely related species of fossil cichlids collected from an Eocene si te in Tanzania, East Africa, represent the oldest known cichlids. The speci mens are whole-body articulated fishes that are extremely well preserved an d, therefore, have the potential to add to our knowledge of the history of this family. Modern cichlids are particularly well known for the numerous s pecies flocks of the East African Great Lakes. A great deal of research is ongoing regarding all aspects of the fishes in these flocks, including thei r evolutionary history. The new collection of fossils reported here is inte rpreted as representing a species flock that arose in a small crater lake. These fossils indicate that cichlids' ability to form species flocks evolve d early in the history of this family.