Sahelanthropus tchadensisTimespan: 7 – 6 mya

Region: Western Africa (Chad)

Specimens: 2

Discovered: Brunet, 2002

Holotype: TM 266-01-060-1

Lineage: Unknown

Environment: Uknown

Diet: Unknown

Speculation/theories: • Unclear if ancestor to later hominids, gen assumed on hominin lineage (Brunet) but

suggestion that may be ancestor to gorillas (Senut) • Pre or contemp with chimp/human divergence• foramen magnum positioned near back of skull, so head held forward; uncertain if habitual

biped, but capable• Enormous brow-ridges: unlike Australopthecines, not seen again until H. erectus• lacks significant facial prognathism (even less than A. afarensis)

D I A G N O S T I C F E AT U R E S

cranium• orthognathic face w/ weak subnasal prognathism• upper part of the face wide relative to narrow short lower face• supraorbital torus continuous, large, thick; orbits separated by a very wide interorbital pillar;

flat frontal squama w/marked postorbital constriction but w/out supratoral sulcus• small sagittal crest & large nuchal crest• flat, rel large nuchal plane w/ large external occipital crest• large mastoid process & small occipital condyles• basiooccipital short, anteriorly narrow' petrous temporal 308° rel to sagittal plane• biporion line touches basion • round external auditory porus; broad glenoid cavity w/ large post-glenoid process• mandibular corpus short & robust w/ wide extramolar sulcus• mental forarmen large, anteriorly opening

dentition• large canine fossa • small, narrow U-shaped dental arch• rel small incisors• small upper canines (male), • upper & lower canines w/ extensive apical wear

• cheek teeth small wi/in range of Ar. ramidus & A. afarensis

• enamel thickness of cheek teeth intermediate btwn chimp and Austro

• canine relatively small, not dramatically projecting• small apically-worn canines: tip worn down consistent with lack of

apelike shearing complex & upper canine occludes with lower premolar w/out overlapping (no evidence of honing)

• vertical symphysis• weakly-developed transverse torus

• small braincase, long and narrow basicanium• Canine within size range of variation for living apes• Nearly horizontally-oriented braincase, little or no hint of forehead• truncated triangular basioccipital bone, petrous portion of the

temporal bone oriented 60° to bicarotid chord

affinities w/

hominids &

differences from apes {

Similarities to apes {

K E Y S P E C I M E N S

• TM 266-01-060-1 “Toumai” (male) – fragmented cranium (heavily distorted from crushing but nearly complete), small portion of mandible, isolated teeth.

360-370cc.

Tip of canine worn down (unlike ape).

• TM 292-02-01 – partial mandible containing the left canine and P4

M A J O R S I T E S• Toros-Menalla, Chad – single quarry western Djurab Desert, northern Chad:

specimens found in perilacustrine sandstone

B I B L I O G R A P H Y

Brunet, M., et al (2002) A new hominid from the Upper Miocene of Chad, central Africa. Nature: 418(6894), 145-151

Brunet, M., et al (2005) New material of the earliest hominid from the Upper Miocene of Chad. Nature 434(7034), 752-755.

Guy, F. et al (2005) Morphological affinities of the Sahelanthropus tchadensis (Late Miocene hominid from Chad) cranium, Proceedings of the National Academy of Sciences

Lebatard, A. et al (2008) Cosmogenic nuclide dating of Sahelanthropus tchadensis and Australopithecus bahrelghazali: Mio-Pliocene hominids from Chad, Proceedings of the National Academy of Sciences

Senut, B. et al (2006) An Ape or the Ape: Is the Toumaï Cranium TM 266 a Hominid?, Paleoanthropology Journal

Wood B. (2002): Hominid revelations from Chad. Nature 418:133-5.

Zollikofer, C. (2005) Virtual cranial reconstruction of Sahelanthropus tchadensis, Nature