Ardipithecus ramidus 4.4 million years ago
Known from the Aramis in the Middle Awash study area and Gona, Afar rift, Ethiopia. The first fossils were discovered in 1992 and 1993, and are 4.4 to 4.5 million years old. At the same time of discovery (and announcement in 1994), it was the oldest known species of human ancestor. Ar. Ramidus is primitive in having large and robust canines, and somewhat ape-like molar and deciduous molar shapes. It is thought to be a primitive species ancestral to Australopeticus, and was given a new genus and species name. The meaning of Ardipithecus Ramidus is “root of the ground ape” after the Afar words “ardi” (“ground”) and “ramid” (“roots”). A partial skeleton of this species is under study and is expected to shed new light on how this species might have walked. A small fragment of baby mandible with deciduous molar and unerrupted permanent incisor. The deciduous molar of Ar. Ramidus is narrow, and differs from the shape in Australopethicus and Homo which is broader for crushing food. In this feature Ar. Ramidus resembles apes rather than Australopethicus or humans. However, its incisor is narrow, and unlike the broad incisors of modern apes like chimpanzees (who eat a lot of ripe fruit).
These 10 teeth comprise the holotype specimen (the standard specimen) of Ardipethicus ramidus. Front row: lower premolars. The upper canine is diamond-shaped, which makes it more advanced than in Ar.kadabba and more similar to Australopithecus or humans, but it is large and robust. The lower premolar that wears against the canine is tall and is intermediate between apes and Australopithecus.
Source: Authority for Research and Conservation of Cultural Heritage