Rebekkachromis nov. gen. from the middle–upper Miocene (11 MYA) of Central Kenya: the oldest record of a haplotilapiine cichlid fish

The fossil record of cichlids is sparse, and every new discovery can provide new insights into the evolutionary history of this speciose freshwater fish family. In this article, we describe † Rebekkachromis gen. nov. from the middle-to-late Miocene (c. 11 MYA) of the Central Kenya Rift within the East African Rift system. † Rebekkachromis is represented by two species that differ from all other fossil and extant African cichlids, except Etia , in possessing the unique character combination of two supraneural bones and a set of robust tricuspid oral teeth in the outer row of the dentition. Furthermore, † Rebekkachromis exhibits the only proposed morphological synapomorphy of the Haplotilapiini, namely the presence of tricuspid teeth in the inner row of the oral dentition. We show that † Rebekkachromis constitutes the oldest reliably identified fossil record of a haplotilapiine. The evolution of cichlid fishes possessing tricuspid teeth in the rivers and lakes of the Central Kenya Rift during the middle-to-late Miocene could have been facilitated by volcanic activity, as repeated ash falls may well have fostered the growth of algae and in particular diatoms. These fishes could thus have had a major advantage, because they could exploit the newly available, rich food resources.