New hippopotamid specimens recently collected at Kanapoi (ca. 4 Ma) are similar to the taxon previously recognized in this site and referred to aff. Hippopotamus protamphibius. Their examination provided the opportunity to reassess the taxonomic status of this taxon. It appears different from the late Miocene hippopotamids from the Turkana Basin (prominently Archaeopotamus harvardi), but also differs from the late Pliocene–early Pleistocene aff. Hip. protamphibius, which is smaller and displays more advanced features (notably canine expansion and orbit elevation). In contrast, the Kanapoi material appears very similar to the material from the Hadar Formation (3.4 Ma–2.9 Ma). However, the current confusion surrounding the taxonomic status of the Hadar specimens, previously attributed to various taxa that may be identical, does not allow attribution of a specific name to the Kanapoi material for now and, while waiting for the revision of Hadar hippopotamid diversity, it is referred here to aff. Hippopotamus cf. sp. Hadar. This contribution allows recognizing that a large hippopotamid, possibly a transitional form between the late Miocene species and Plio-Pleistocene species, was distributed from Afar to Turkana between 4.2 Ma and 2.95 Ma. The marked endemism of hippopotamids in the Pleistocene rift basins therefore initiated after 2.9 Ma.

最近在Kanapoi（约4 Ma）收集的新河马标本与以前在该地点识别并称为aff的分类单元相似。河马protamphibius。他们的检查为重新评估该分类单元的分类状态提供了机会。它似乎不同于图尔卡纳盆地的中新世晚期河马（主要是考古古生物），但也不同于上新世－更新世早期。时髦的。前两栖类，它较小，并且显示更高级的功能（尤其是犬的扩张和轨道高度升高）。相反，Kanapoi物质看起来与哈达尔组（3.4 Ma–2.9 Ma）的物质非常相似。但是，当前围绕Hadar标本状态的混淆（以前归因于可能是相同的各种分类单元），目前尚不允许在Kanapoi材料中使用特定名称，并且在等待修改Hadar河马肽多样性时，它在这里称为aff。河马cf. sp。哈达尔。这一贡献使人们认识到，大型的河马，可能是晚中新世物种和上新世物种之间的过渡形式，是从阿法尔到图尔卡纳地区分布在4.2 Ma至2.95 Ma之间。因此，更新世裂谷盆地中河马的显着特有性在2.9 Ma之后开始。