Sahelanthropus tchadensis

Sahelanthropus tchadensis is an extinct hominin species known from fossils found in Chad and dated to roughly seven million years ago. Its anatomy, especially its skull and teeth, informs debates about early hominin evolution and bipedalism.

Hominini: Hominini is the primate tribe comprising humans and extinct species more closely related to humans than to chimpanzees. This classification frames the disputed question of whether Sahelanthropus belongs on the human lineage.
Foramen magnum: The foramen magnum is the opening at the skull base through which the spinal cord passes. Its position in the skull has been used to assess whether Sahelanthropus held its head above an upright body.
Toumaï: Toumaï is the nickname for the nearly complete cranium that serves as the principal fossil of Sahelanthropus tchadensis. This skull supplies most of the anatomical evidence used to describe the species.
Orrorin tugenensis: Orrorin tugenensis is an extinct hominin species known from fossils in Kenya dated to about six million years ago. Its thigh-bone evidence offers a different basis for evaluating early bipedalism.
Human evolution: Human evolution is the biological history of humans and their extinct relatives. Sahelanthropus may document an early stage in this history, but its exact position remains contested.
Hominidae: Hominidae is the great-ape family, including orangutans, gorillas, chimpanzees, and humans. Sahelanthropus belongs within the wider ape family from which hominins emerged.
Bipedalism: Bipedalism is habitual locomotion on two legs. The species' possible upright posture is central to claims about early hominin behavior.
TM 266: TM 266 is the fossil locality in Chad where the principal Sahelanthropus remains were discovered. The locality links the species' fossils to their geological and environmental context.
Ardipithecus kadabba: Ardipithecus kadabba is an extinct early hominin species known from Ethiopian fossils dated to roughly 5.8 to 5.2 million years ago. Its later fossils provide another candidate for tracing early hominin anatomy.
Cladistics: Cladistics classifies organisms by shared derived traits and represents their relationships as branching lineages. Different choices about which anatomical traits count can alter Sahelanthropus' placement.

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