KOOBI FOR,\ (INCLCDES Ezisr TURKI~NA, ILERET) 139
ER 1506 Morph from protoconid to base of metaconid. Thick, subdi-
KNM-ER 1506A. Fragment of R corpus with Ml
and 2. Corpus robust, although narrow compared to
its depth; uniformly thick down to inferior margin.
Root of ramus preserved; indicates M3 would have
been almost entirely hidden in side view. Ml and M2
somewhat worn but well preserved; crowns fairly low;
in occlusal outline, lingual sides relatively straight and
buccal sides quite crescentic. Both have small, deep
anterior and posterior foveae; large, wedge-shaped,
centrally placed hypoconulids; and m/d short
hypoconids that cross lingually beyond midline of
crown. Lingual cusps marginally placed and quite
compressed b/l compared to buccal cusps; latter have
internally placed apices and very long buccal slopes.
M2 bears small protostylid.
KNM-ER 1802 (A-D). Partial lower jaw lacking
rami, LP1-RC. Also kXM-ER 1802E, isolated
LM,; colored differently but apparently associated
with this individual.
In profile, upper part of symphysis is slightly for-
wardly displaced from curve defining its bottom; oth-
erwise, front of jaw is smoothly curved externally and
fairly smoothly retreating in side view. Cheek tooth
rows almost straight from behind C; diverge slightly
as they run posteriorly. From below, front of jaw has
slight bell-shaped curve, with hint of a keel in midline
of external symphysis. Large mental foramen under
P2. Root of ramus (visible on the L) indicates M3
would have been hidden (to some extent) in side view.
Alveoli of LIl-I2 preserved; roots were not small
and would have been somewhat laterally compressed.
Relatively large, ovoid RC root is preserved. As noted
on the R, P1 would have abutted d/l side of C. Pls
and P2s do not greatly resemble one another. As seen
on RP1, tall metaconid and lower protoconid lie op-
posite each other and are closely approximated. Thick
paracristid arcs widely forward between these cusps,
enclosing a relatively large, deep basin. Shelf-like
postprotocingulid somewhat subdivided; runs distally
from stylid-like projection at protoconid base, arcing
around to terminate in tiny stylid well down at meta-
conid base. Postprotocingulid lies lower on crown
than paracristid; somewhat distends d/l corner of
tooth, giving a somewhat oblique axis. P2 slightly
larger than Pl, especially m/d. Metaconid tall and pe-
ripherally placed; lies opposite the much lower but
also peripherally placed protoconid. Moderately thick
paracristid lies in front of these cusps and courses
vided postprotocingulid courses from protoconid
down to distinct cusp in d/l corner of tooth and en-
closes broad posterior basin.
Ml and 2 relatively large teeth; b/l wide and dis-
tinctly long m/d. Apices of buccal cusps slightly
internally placed; lingual cusp apices more marginal
(buccal side of crown slopes more than straighter lin-
gual side). Ml slightly shorter m/d than M2 and
about as wide b/l. On both, hypoconid extends lin-
gually beyond midline of tooth; hypoconulid moder-
ately large and somewhat buccally shifted. Both Ms
bear small but distinct metastylids, crenulated enamel
(more extensive and thick on M2). Ml anterior fovea
wedge-shaped; wider b/l and longer m/d than the
very tiny, pit-like fovea on M2. M1 bears a narrow but
deep posterior fovea situated lingual to hypoconulid.
On both M~s, a small cuspulid lies right within simi-
lar fovea; apex of the metaconid more internally
placed than on M1. Region of M2 hypoconulid not
expanded laterally, thus giving smooth curve to distal
margin of tooth.ER 1802E. LM,. Crown incomplete. Much more
thickly and deeply crenulated than M2; would have
had deep, possibly b/l wide anterior fovea. Hypoconid
extended lingually across midline of tooth. Lingual to
hypoconulid was a small stylid; lingual to stylid was a
small fovea. Lingual margin of tooth was subdivided
by a series of small fissures.WT 15000 Morph
(see also Nariokotome entry)KNM-ER 1813. Cranium reconstructed from
numerous fragments, lacking part of cranial base,
most of left orbital region, and nasal cavity structures.
Very small. Cranial bone not very thick. Some slight
distortion.
Braincase relatively long. Posttoral sulcus confined
to area between high points of R and L tori. In profile,
frontal rises quite steeply from posttoral sulcus; brain-
case probably reached maximum height around
bregma. From this point, profile shows possible indica-
tions of shallow postbregmatic depression, anterior to
which it descends in smooth curve to low, broad bulge
in region of external occipital protuberance. Nuchal
plane rather flat, forming a distinct angle with the
rounded occipital plane below the distinct superior
nuchal line (well preserved on L). Seen from above,