New fossil cichlid from the middle Miocene of East Africa revealed as oldest known member of the Oreochromini

A new genus and species of fossil cichlid fishes of middle Miocene age (12.5 Ma) is described from the Ngorora fish Lagerstatte (Tugen Hills, Kenya) in the East African Rift Valley. Parsimony analysis of morphological characters using published phylogenetic frameworks for extant cichlids combined with the application of a comprehensive best-fit approach based on morphology was employed to place the new fossil taxon in the phylogenetic context of the African cichlids. The data reveal that the fossil specimens can be assigned to the tribe Oreochromini within the haplotilapiines. +Oreochromimos kabchorensis gen. et sp. nov. shows a mosaic set of characters bearing many similarities to the almost pan-African Oreochromis and the East African lake-endemic Alcolapia. As the striking diversity of present-day African cichlids, with 1100 recognised species, has remained largely invisible in the fossil record, the material described here adds significantly to our knowledge of the Miocene diversity of the group. It effectively doubles the age of a fossil calibration point, which has hitherto been used to calibrate divergence times of the East African cichlids in molecular phylogenetic investigations. Furthermore, the comparative dataset derived from extant cichlids presented here will greatly facilitate the classification of fossil cichlids in future studies

†<i>Tugenchromis pickfordi</i>, gen. et sp. nov., from the upper Miocene—a stem-group cichlid of the ‘East African Radiation’

<p>The highly diverse tropical freshwater fish family Cichlidae is sparsely represented in the fossil record. Here we describe the new cichlid †<i>Tugenchromis pickfordi</i>, gen. et sp. nov., from the Upper Miocene (9–10 Ma) of central Kenya. The new taxon possesses a unique combination of characters, including six lateral line foramina on the lacrimal, three lateral line segments, cycloid scales, and a low number of vertebrae (29), dorsal fin spines (13), and dorsal soft rays (9). Its lacrimal morphology and tripartite lateral line suggest an affinity with the present-day Lake Tanganyika tribes Ectodini and Limnochromini, and thus with members of the ‘East African Radiation’ among the African cichlids. To further elucidate the relationships of †<i>T. pickfordi</i>, we used a comprehensive comparative data set comprising meristic data from all present-day tribes of the ‘East African Radiation.’ Principal coordinates analyses support links between the fossil and Ectodini + Limnochromini, and additionally with modern Haplochromini. We conclude that †<i>T. pickfordi</i> could be an extinct lineage within the ‘most ancient Tanganyika tribes,’ or a stem lineage of the ‘ancient Tanganyika mouthbrooders.’ A direct relationship to the Haplochromini is unlikely because its members do not exhibit the derived characteristics of the lacrimal as seen in †<i>T. pickfordi</i>. Because Lake Tanganyika is located in the western branch of the East African Rift System, †<i>T. pickfordi</i> from the eastern branch supports the ‘melting-pot Tanganyika hypothesis,’ which posits that the cichlids of modern Lake Tanganyika are derived from riverine lineages that had already diversified prior to the lake formation.</p> <p>http://zoobank.org/urn:lsid:zoobank.org:pub:37520070-99B3-463C-B8E6-9452D1F62722</p> <p>SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at <a href="http://www.tandfonline.com/UJVP" target="_blank">www.tandfonline.com/UJVP</a>.</p> <p>Citation for this article: Altner, M., U. K. Schliewen, S. B. R. Penk, and B. Reichenbacher. 2017 . †<i>Tugenchromis pickfordi</i>, gen. et sp. nov., from the upper Miocene—a stem-group cichlid of the ‘East African Radiation’. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2017.1297819.</p