History
George Gaylord Simpson, using traditional taxonomic techniques, in 1945 succeeded in grouping these spectacularly diverse mammals in the superorder he named Paenungulata ("almost ungulates"). But there were many loose threads in unravelling their genealogy. For example, hyraxes in his Paenungulata had some characteristics suggesting they might be connected to the odd-toed ungulates (Perissodactyla, such as horses and rhinos). Indeed, early taxonomists placed the Hyracoidea closest to the rhinoceroses, because of their dentition, and even some recent evidence suggested a possible affinity of Hyracoidea to Perissodactyla rather than to the rest of the Paenungulata. This would mean that paenungulates are not a clade.
Later, genetic techniques were developed for inspecting amino acid differences among haemoglobin sequences. The most parsimonious cladograms depicted Simpson's Paenungulata as an authentic clade and as one of the first groups to diversify from the basal placental mammals (Eutheria). The amino acid sequences do not support a connection with perissodactyls (odd-toed ungulates).
Read more about this topic: Paenungulata
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