Fossils have generally been classified into "H. rudolfensis" due to large skull size, flatter and broader face, broader cheek teeth, more complex tooth crowns and roots, and thicker enamel compared to "H. habilis". Early "Homo" are characterised by larger teeth compared to later "Homo". The cheek teeth of KNM-ER 60000, a jawbone, in terms of size are on the lower end for early "Homo", except for the third molar which is within range. The molars increase in size towards the back of the mouth. The tooth rows of KNM-ER 1470, KNM-ER 60000, and KNM-ER 62000 are rectangular, whereas the tooth row of KNM-ER 1802 is U-shaped, which may indicate that these two morphs represent different species, or demonstrate the normal range of variation for "H. rudolfensis" jaws. In UR 501 from Uraha, Malawi—the oldest "H. rudolfensis" specimen dating to 2.5–2.3 mya—the tooth enamel thickness is the same as in other early "Homo", but the enamel on the molars is almost as thick as "Paranthropus" molars (which have some of the thickest enamel of any hominin). Such a wide variation in enamel thickness across the cheek teeth is not exhibited in KNM-ER 1802, which may indicate regional differences among "H. rudolfensis" populations.