Sahelanthropus tchadensis is an extinct hominid species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 that is dated to about . Whether it can be regarded as part of the Hominina

Hominina

The more anthropomorphic primates of the Hominini tribe are placed in the Hominina subtribe. Referred to as hominans, they are characterized by the evolution of an increasingly erect bipedal locomotion. The only extant species is Homo sapiens...

 tree is unclear; there are arguments both supporting and rejecting it. Another complication in its classification is that it is older than the human-chimpanzee divergence

Chimpanzee-human last common ancestor

The chimpanzee-human last common ancestor is the last species, a species of African apes, that humans, bonobos and chimpanzees share as a common ancestor....

 (estimated to ) seen in genetic data, and that there are few if any specimens other than the partial cranium known as Toumaï.
Existing fossils – a relatively small cranium nicknamed Toumaï ("hope of life" in the local Dazaga language of Chad), five pieces of jaw

Jaw

The jaw is any opposable articulated structure at the entrance of the mouth, typically used for grasping and manipulating food. The term jaws is also broadly applied to the whole of the structures constituting the vault of the mouth and serving to open and close it and is part of the body plan of...

 and some teeth–make up a head that has a mixture of derived and primitive features.