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 extremely rare. Here we present a new fossil haplochromine from the upper Miocene site Waril (9–10 million years) in Central Kenya. Comparative morphology, supported by Micro-CT imaging, reveals that it bears a unique combination of characters relating to dentition, cranial bones, caudal skeleton and meristic traits. Its most prominent feature is the presence of exclusively unicuspid teeth, with canines in the outer tooth row. †Warilochromis unicuspidatus gen. et sp. nov. shares this combination of characters solely with members of the Haplochromini and its lacrimal morphology indicates a possible relation to the riverine genus Pseudocrenilabrus. Due to its fang-like dentition and non-fusiform body, †W. unicuspidatus gen. et sp. nov. might have employed either a sit-and-pursue or sit-and-wait hunting strategy, which has not been reported for any other fossil haplochromine cichlid. The age of the fossil (9–10 MYA) is incompatible with the ‘out of Tanganyika’ hypothesis, which postulates that the divergence of the Haplochromini began only 5–6 MYA. The presence of this fossil in an upper Miocene palaeolake in the Central Kenya Rift, as well as its predatory lifestyle, indicate that Haplochromini were already an important component of freshwater drainages in East Africa at that time.

中文翻译：

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来自肯尼亚中部中新世上部（9-10 MYA）的新单倍丽慈鲷。

被称为“坦噶尼喀湖辐射”的多样化过程催生了非洲丽鱼科物种最丰富的分支。坦噶尼喀湖、马拉维湖和维多利亚湖中发现的几乎所有丽鱼科鱼种（总共由 12-16 个部落组成）都属于这个分支。引人注目的是，后两个湖中的所有物种都是单染色体部落的成员，其起源尚不清楚。“来自坦噶尼喀”的假说认为，单染色体与坦噶尼喀湖的其他慈鲷部落和谱系同时出现，大概是在 5-600 万年前 (MYA)，并且它们今天存在于马拉维湖和维多利亚湖以及非洲其他地方是由于后来的迁移。相比之下，“坦噶尼喀熔炉假说”假设，单染色体在坦噶尼喀湖形成之前就出现在非洲，并且它们的分歧可能开始于大约 17 MYA。单倍体化石可能会解决这一争论，但此类化石极为罕见。在这里，我们展示了来自肯尼亚中部中新世上部遗址瓦里尔（9-1000 万年）的新单倍色素化石。在显微 CT 成像支持下的比较形态显示，它具有与牙列、颅骨、尾骨和分枝特征相关的独特特征组合。它最显着的特征是仅存在单尖牙，犬齿位于外齿排。†Warilochromis unicuspidatus gen. 等 十一月 仅与单染色体成员共享这种特征组合，其泪腺形态表明可能与河流拟肾属有关系。由于其尖牙状齿列和非梭形体，†W。独尖齿根 等 十一月 可能采用了“坐追”或“坐等”狩猎策略，目前还没有任何其他单倍丽丽鱼化石报道过这种策略。该化石的年龄（9-10 MYA）与“来自坦噶尼喀”的假说不相容，该假说假设单染色体的分化只开始于 5-6 MYA。在肯尼亚中部裂谷的中新世上游古湖中发现的这块化石，以及它的掠食性生活方式，表明单染色体已经是当时东非淡水排水系统的重要组成部分。