Final answer:
Sahelanthropus tchadensis is known from a single skull found in Chad and has characteristics suggesting it existed around 7 million years ago, possibly during the divergence of human and chimpanzee lineages. Its distribution is confined to Chad, and while the fossil record is limited, it provides significant information on early hominins.
Step-by-step explanation:
Distribution of Sahelanthropus tchadensis:
The distribution of Sahelanthropus tchadensis, known from the discovery of its cranium, is currently restricted to Chad in Central Africa. Unearthed by French paleoanthropologist Michel Brunet and his team in 2002, it represents one of the earliest potential hominids, living approximately 7 million years ago. The skull exhibits a blend of primitive ape-like traits and advanced characteristics, such as a smaller cranial capacity akin to that of a chimpanzee and a pronounced brow ridge. Nevertheless, the position of the foramen magnum has sparked debate on whether Sahelanthropus was bipedal, as it suggests a non-upright head posture more in line with quadrupedal locomotion.
The fossil record of this species is sparse, with only one significant specimen known, the iconic 'Toumai' skull. Despite this, Sahelanthropus is crucial to our understanding of early hominins, as it existed during the time frame when genetic studies suggest human and chimpanzee lineages diverged. As such, while its exact place in the human lineage is unclear, it provides valuable insight into the morphology of potential ancestral species.
Sahelanthropus is part of a broader context of hominin discoveries, such as Ardipithecus, Orrorin, and various species of Australopithecus and Paranthropus, all contributing to the complex puzzle of human evolution.