 Simpson established the grouping on the basis of morphological criteria, but this traditional understanding of Ferungulata has been challenged by a more recent classification, relying upon genetic criteria.These studies separated his ungulate orders into two distinct placental groups, within Afrotheria and Laurasiatheria, respectively.The 'true' ungulates, Perissodactyla and Artiodactyla, along with the whales, are included in the revised group, along with the Carnivora, and with the addition of pangolins (Pholidota), but the Tubulidentata and paenungulates are excluded.