A small cichlid species flock from the Upper Miocene (9–10 MYA) of Central Kenya (original) (raw)
Related papers
New haplochromine cichlid from the upper Miocene (9–10 MYA) of Central Kenya
BMC Evolutionary Biology, 2020
Background The diversification process known as the Lake Tanganyika Radiation has given rise to the most speciose clade of African cichlids. Almost all cichlid species found in the lakes Tanganyika, Malawi and Victoria, comprising a total of 12–16 tribes, belong to this clade. Strikingly, all the species in the latter two lakes are members of the tribe Haplochromini, whose origin remains unclear. The ‘out of Tanganyika’ hypothesis argues that the Haplochromini emerged simultaneously with other cichlid tribes and lineages in Lake Tanganyika, presumably about 5–6 million years ago (MYA), and that their presence in the lakes Malawi and Victoria and elsewhere in Africa today is due to later migrations. In contrast, the ‘melting pot Tanganyika hypothesis’ postulates that Haplochromini emerged in Africa prior to the formation of Lake Tanganyika, and that their divergence could have begun about 17 MYA. Haplochromine fossils could potentially resolve this debate, but such fossils are extrem...
Scientific Reports
A new genus and species of fossil cichlid fishes of middle Miocene age (12.5 Ma) is described from the Ngorora fish Lagerstätte (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. Cichlid fishes (Cichliformes) represent one of the most diverse vertebrate families, comprising about 220 genera and over 1700 recognised species 1,2. They are widely distributed in tropical freshwater environments, with some species entering brackish or alkaline habitats (e.g. 3-5). Their evolutionary success has been attributed to numerous morphological and behavioural adaptations, such as the occurrence of both oral and pharyngeal jaws with specialised dentition, diverse mating systems, different modes of parental care (e.g. mouthbrooding), and visual sensitivity to nuptial male colouration (see 6-8). Cichlidae have been classified into four subfamilies, i.e. the Etroplinae (limited to Madagascar, Sri Lanka and India), the Ptychochrominae (restricted to Madagascar), the Cichlinae (found only in the Neotropics), and the Pseudocrenilabrinae (widely distributed in Africa and the Middle East) 9-14. In light of their current geographic distribution and their phylogenetic relationships, the first cichlids could have emerged in the Late Jurassic or Early Cretaceous, i.e. prior to the fragmentation of Gondwana (e.g. 13,15-18). On the other hand, recent palaeontological and molecular-clock-based time calibrations indicate a Late Cretaceous or early Cenozoic date of origin 19-22. Of the four cichlid subfamilies, the Pseudocrenilabrinae (African and Middle East cichlids) form the largest clade, with approximately 150 genera and 1100 species (e.g. 1,23). Within the Pseudocrenilabrinae, the haplotilapiines constitute the most diverse subclade (refs 24,25 ; Fig. 1). While extant haplotilapiines can be clearly defined by molecular genetics, their members share only one morphological apomorphy, namely the presence of tricuspid inner teeth in the oral jaws 24. Haplotilapiine cichlids are divided into 22 tribes (Fig. 1). Thirteen of these represent the clade that encompasses the members of the Lake Tanganyika radiation, also termed the East African Radiation (EAR), which includes the numerous species endemic to the Great Lakes of the East African Rift Valley
New Cichlid Fossils from the Middle-Late Miocene Alkaline Lakes of Africa
Journal of Vertebrate Paleontology
The African Cichlidae Oreochromis (Alcolapia) and Oreochromis amphimelas can survive in extremely alkaline environments and represent the only known modern alkaliphilic cichlid fish found in Africa. The presence of fossil cichlids from the Miocene of central Kenya (Tugen Hills) that are morphologically similar to Oreochromis (Alcolapia) has been noted in previous works, but the conclusions remained tentative. The purpose of this study is to examine newly discovered fossil cichlids from the Tugen Hills and to compare their osteology with that of extant Oreochromis (Alcolapia). This is performed based on a comprehensive collection of comparative material, using microscopy and computed microtomography (μCT). We provide a revised diagnosis for the genus †Rebekkachromis, and revise its systematic relationships by assigning it to the Oreochromini (rather than to the Etiini). Two new species of †Rebekkachromis are described, i.e., †R. valyricus, sp. nov., and †R. vancouveringae, sp. nov., and a morphologically diverse assemblage of cooccurring †Rebekkachromis specimens is documented. Moreover, we found that †Rebekkachromis had three sensory canal pores (instead of four) on the lower arm of the preopercle, a feature that distinguishes both the modern Oreochromis (Alcolapia) and our fossil specimens from almost all other modern African cichlid fish. Our new data indicate that alkaliphile cichlids similar to Oreochromis (Alcolapia) were present in Central Kenya about 10-13 Ma ago and that the ability of African cichlid fishes to thrive in highly alkaline waters had already developed by that time.
The Impact of the Geologic History and Paleoclimate on the Diversification of East African Cichlids
International Journal of Evolutionary Biology, 2012
The cichlid fishes of the East African Great Lakes are the largest extant vertebrate radiation identified to date. These lakes and their surrounding waters support over 2,000 species of cichlid fish, many of which are descended from a single common ancestor within the past 10 Ma. The extraordinary East African cichlid diversity is intricately linked to the highly variable geologic and paleoclimatic history of this region. Greater than 10 Ma, the western arm of the East African rift system began to separate, thereby creating a series of rift basins that ...
Miocene cercopithecoidea from the Tugen Hills, Kenya
Journal of human evolution, 2010
Miocene to Pleistocene fossiliferous sediments in the Tugen Hills span the time period from at least 15.5 Ma to 0.25 Ma, including time periods unknown or little known elsewhere in Africa. Consequently, the Tugen Hills deposits hold the potential to inform us about crucial phylogenetic events in African faunal evolution and about long-term environmental change. Among the specimens collected from this region are a number of discoveries already important to the understanding of primate evolution. Here, we describe additional cercopithecoid material from the Miocene deposits in the Tugen Hills sequence, including those from securely dated sites in the Muruyur Beds (16e13.4 Ma), the Mpesida Beds (7e6.2 Ma) and the Lukeino Formation (w6.2e5.7 Ma). We also evaluate previously described material from the Ngorora Formation (13e8.8 Ma). Identified taxa include Victoriapithecidae gen. et sp. indet., cf. Parapapio lothagamensis, and at least two colobines. Specimens attributed to cf. Pp. lothagamensis would extend the species’ geographic range beyond its type locality. In addition, we describe specimens sharing derived characters with modern African colobines (Tribe: Colobina), a finding that is congruent with previous molecular estimates of colobine divergence dates. These colobine specimens represent some of the earliest known members of the modern African colobine radiation and, in contrast to previous hypotheses, suggest that early African colobines were mainly arboreal and that semi-terrestrial Late Miocene and Plio-Pleistocene colobine taxa were secondarily derived in their locomotor adaptations.
2012
The cichlid fishes of the East African Great Lakes are the largest extant vertebrate radiation identified to date. These lakes and their surrounding waters support over 2,000 species of cichlid fish, many of which are descended from a single common ancestor within the past 10 Ma. The extraordinary East African cichlid diversity is intricately linked to the highly variable geologic and paleoclimatic history of this region. Greater than 10 Ma, the western arm of the East African rift system began to separate, thereby creating a series of rift basins that would come to contain several water bodies, including the extremely deep Lakes Tanganyika and Malawi. Uplifting associated with this rifting backponded many rivers and created the extremely large, but shallow Lake Victoria. Since their creation, the size, shape, and existence of these lakes have changed dramatically which has, in turn, significantly influenced the evolutionary history of the lakes' cichlids. This paper reviews the geologic history and paleoclimate of the East African Great Lakes and the impact of these forces on the region's endemic cichlid flocks.
Systematic Biology, 2002
Lake Tanganyika, the oldest of the East African Great Lakes, harbors the ecologically, morphologically, and behaviorally most complex of all assemblages of cichlid shes, consisting of about 200 described species. The evolutionary old age of the cichlid assemblage, its extreme degree of morphological differentiation, the lack of species with intermediate morphologies, and the rapidity of lineage formation have made evolutionary reconstruction dif cult. The number and origin of seeding lineages, particularly the possible contribution of riverine haplochromine cichlids to endemic lacustrine lineages, remains unclear. Our phylogenetic analyses, based on mitochondrial DNA sequences of three gene segments of 49 species (25% of all described species, up to 2,400 bp each), yield robust phylogenies that provide new insights into the Lake Tanganyika adaptive radiation as well as into the origin of the Central-and East-African haplochromine faunas. Our data suggest that eight ancient African lineages may have seeded the Tanganyikan cichlid radiation. One of these seeding lineages, probably comprising substrate spawning Lamprologus-like species, diversi ed into six lineages that evolved mouthbrooding during the initial stage of the radiation. All analyzed haplochromines from surrounding rivers and lakes seem to have evolved within the radiating Tanganyikan lineages. Thus, our ndings contradict the current hypothesis that ancestral riverine haplochromines colonized Lake Tanganyika to give rise to at least part of its spectacular endemic cichlid species assemblage. Instead, the early phases of the Tanganyikan radiation affected Central and East African rivers and lakes. The haplochromines may have evolved in the Tanganyikan basin before the lake became a hydrologically and ecologically closed system and then secondarily colonized surrounding rivers. Apparently, therefore, the current diversity of Central and East African haplochromines represents a relatively young and polyphyletic fauna that evolved from or in parallel to lineages now endemic to Lake Tanganyika. [Adaptive radiation; Cichlidae; Lake Tanganyika; mitochondrial DNA sequences; molecular phylogeny; species ock.]
Miocene fossil cercopithecoids from Kenya
American Journal of Physical Anthropology, 1986
Fossil cercopithecoid material from Ngeringerowa, Ngorora, and Nakali, dated at between 8.5 and 10.5 m.y., is described. The specimens are the only cercopithecoid remains dated between 15 and 6 m.y. from sub-Saharan Africa. The mandible of asmall colobine from Ngeringerowa (similar in size to Colobus verus) is assigned to a new genus and species, Microcolobus tugenensis. Unlike other colobine genera, the symphysis of Microcolobus lacks an inferior transverse torus. A colobine lower M1 or 2 from Nakali is longer and narrower than molars of M. tugenensis, indicating that it may belong to a distinct taxon. A P4 from Ngorora cannot be assigned confidently to subfamily, due to its unique metaconid morphology. The relationship between the new genus and other Miocene monkeys is considered.