182 AFRICA
no more than a tiny fovea. Lingual side of crown
hardly slopes. Small paraconule lies at mesial base of
paracone. M2s closely resemble Mls, except lingual
slope less pronounced and metacone much smaller
than paracone; small metaconule is associated with
postprotocrista.Mandible
Virtually complete, with all erupted teeth present.
M3s not yet erupted.
Corpus relatively shallow s/i, but thick m/l. Front of
jaw somewhat backwardly sloping, with slight subalveo-
lar depression. Short, low keel lies in midline, just below
alveolar margin; otherwise, front of symphysis is
smoothly curved, featureless. Tooth rows long, slightly
divergent. Front of jaw narrow, arced across. Internally
there is a very tight curve. Small tubercle situated
between small, indistinct digastric fossae; at midline
there is a minimal elevation of inferior surface. Seen
from below, bone of mandible is much thinner at sym-
physis than to either side of it. Postincisal plane is long
and moderately sloping, and is undercut by a moderately
sized genial pit. Below pit bone is slightly thickened. On
the L, a moderately sized mental foramen lies between
P1 and 2; on the R, two mental foramina of equal size
lie at front and back of P2. Gonial angle rounded,
reflected inward slightly; it is smooth externally, but
bears small pterygoid markings low down internally.
Ramus relatively broad, deep, inclined slightly back-
ward. Coronoid process broad; rises above level of
condyle. Sigmoid notch deepest centrally. Sigmoid
notch crest terminates at lateral part of condyle. Fairly
stout pillar descends in midline of coronoid process in-
ternally; runs into a ridge of bone proceeding posteriorly
from lingual side of alveolar crest. Pillar internally on
condylar neck is faint; fades out before reaching a low
swelling where lingula would have been. Mandibular
foramen incomplete (not roofed over). Mylohyoid line
indistinct. Submandibular fossae quite long a/p, shallow.
All Is moderately high crowned; 12s longer m/d
than 11s. 11s straight sided; distal edges of 12s more
flared. I2 lingual surfaces only slightly more concave
than 11s. C crowns not completely erupted; less
robust than upper Cs. Lingually Cs bear distinct
mesial and distal margocristids, and a central pillar
running down from apex. Apical pillars slightly offset
distally Ps compressed buccolingually, like upper
counterparts. P1, and particularly P2, quite round in
occlusal outline. P1 protoconid is rather centrally
placed; crest runs from it down to a small swelling in
region of metaconid. Anterior fovea longer m/d than
posterior fovea, which is wider b/l; both are quite
deep. P2 protoconid more mesially positioned;
connected by stout crest to subequally sized, equally
forward metaconid (hence anterior fovea much
smaller than posterior).
M1 and 2 enamel slightly wrinkled. Both Ms
relatively narrow b/l, long m/d; bear relatively large,
centrally positioned hypoconulids and distinct if low
paracristids. Talonid basins quite narrow, constricted.
On Ml, but not M2, hypoconid extends lingually
beyond midline of crown. On both teeth there is a
wedge-shaped metastylid between metaconid and
small entoconid. On Ml there is a distinct notch
between hypoconid and hypoconulid; M2 is more
rounded distally.
See also Koobi Fora entry (KNM-ER 1813).REFERENCES
Brown, F. and C. Feibel. 1985. Stratigraphic notes on the
Okote Tuff Complex at Koobi Fora. Nature 316:
794-797.
Brown, F. and I. McDougall. 1993. Geologic setting and
age. In: A. Walker and R. Leakey (eds), The Nariokotome
Homo erectus skeleton. Cambridge, MA, Harvard
University Press, pp. 9-20.
Brown, F. et al. 1985. Early Homo erectus skeleton from west
Lake Turkana, Kenya. Nature 316: 788-792.
Harris, J. et al. 1988. Geology and paleontology of Plio-
Pleistocene deposits west of Lake Turkana. Contrid. Sci.Holloway, R. 2000. Brain. In: E. Delson et al. (eds), Ency-
clopedia of Human Evolution and Prehistory. New York,
Garland Publishing, pp. 141-149.
McDougall, I. et al. 1985. K-Ar and 40Ar/39Ar dating of the
hominid-bearing Plio-Pleistocene sequence at Koobi
Fora, Lake Turkana, northern Kenya. Bull. Geol. Soc. Am.kghtmire, P. 1990. Tbe Evolution of Homo erectus.
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Schwartz, J. H. and I. Tattersall. 2000. What constitutes
Homo erectus2Acfa. Antbropol. Sin. Suppl. 19: 18-22.
Smith, B. H. 1993. The physiological age of KNM
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