OMO KIBISH 239
In addition to portions of coronal suture lateral
to bregma, parts of sagittal and lambdoid sutures are
preserved. Coronal suture is open, fairly well inter-
digitated. Sagittal and lambdoid sutures shallowly
denticulate; at least the sagittal appears not to have
been segmented.
Internally, frontal bears a long section of what
would have been an extraordinarily long, fairly thick,
but not excessively prominent frontal crest. As pre-
served on L, frontal lobe, although tall, did not extend
fully over orbital cones. Parietal marked by profusion of
arborizing meningeal grooves. Sagittal sinus not visible
on preserved bone. Midline of occipital bears low,
broad crest separating large, deep impressions for R oc-
cipital lobe from the much smaller, shallower, more su-
periorly situated impression for L occipital lobe. Mid-
line occipital crest swells into modest internal occipital
protuberance, below which was a short, low, broad ex-
ternal occipital crest. L transverse sinus originates just
above protuberance; is quite tall s/i, although shallow, as
it runs between impressions for occipital and cerebellar
lobes. L transverse sinus fades out further laterally,
before reaching occipitomastoid suture. A very low,
thin crest emanates from R side of internal occipital
protuberance, separating impressions for cerebellar and
occipital lobes; it rapidly fades out. Impression for L
cerebellar lobe is deeper than, but not as expansive as,
the R. As seen on the R, preserved part of sigmoid
sinus is deep, wide. No sign of superior petrous sinus on
fragment of petrosal preserved on the R.
The two mandibular fragments may not be asso-
ciated, since the ramal portion indicates a shallower
jaw than the more anterior piece, which shows full
depth of specimen. For its apparent size, anterior
piece shows a relatively short jaw that is also relatively
tall s/i, but not very thick m/l, by level of M1. Tooth
rows were fairly divergent. Internal and external
curves at front of jaw were broad, more or less parallel.
From above, bone across symphysis essentially uni-
formly thick from side to side, with only the merest
hint of a bulge in midline externally. In profile, pre-
served part of symphyseal region shows outward slope
before curving down into inferior margin. Preserved
bone across symphyseal region essentially smooth, al-
though with a faint localized swelling lower down. No
keel and no depressions. Below regions of Cs, close to
inferior border on both sides, is another low swelling
of bone just above inferior border. As seen hlly on the
L, mental foramen is large. On both sides, foramen
lies below level of P2, about midway down. Internally,
postincisal plane would have been short, probably ver-
tical, as the bone is lower down. Genial ridges produce
a low protrusion. In the midline, above inferior mar-
gin, is a vertical central scar, with a long, thin genial
crest on either side. Digastric fossae poorly defined, as
indicated on the R, where fossa is small and faces
backward.
Larger L portion of corpus preserves a faint, essen-
tially horizontal mylohyoid line, situated halfway up
bone. Surface of bone below is shallowly concave (but
no real submandibular fossa). Small foramen penetrates
bone low down under region of P1. R ramus fragment
preserves an inferior border extending anteriorly under
molar region. Superiorly, there is no indication of molar
roots (suggesting either huge retromolar space or loss of
molars posteriorly). In profile, preserved anterior root
of ramus is fairly strongly inclined posteriorly (suggests
that ramus could not have been very long a/p, although
it was relatively tall s/i). Posterior border of ramus was
also strongly inclined backward. Gonial area smoothly
curved with smooth external surface. Just forward of
angle is a small upward indentation in inferior margin.
Condyle chewed by scavenger; was not very m/l wide.
Upper condylar surface slopes slightly forward, laterally.
Thick vertical crest runs down from medial margin of
condyle for a short distance. Triangular posterior sur-
face of condyle flat, strongly narrowing inferiorly. Sig-
moid notch crest thick; terminating on anterior face of
condyle, lateral to its midline. Sigmoid notch was prob-
ably not very deep. Internal margin of gonial region
bears five distinct tubercles (ranging from very small to
large) well separated from each other. Apparently no
pillar on inside of coronoid process, at least anteriorly.
Portion of mandibular nerve (or cast of inside of its
canal) preserved.OmoIII
Three crushed, weathered fragments of skull. Two
quite thin boned, shallowly curved, but uninformative
cranial vault pieces; third is part of a glabellar region
(probably not hominid).REFERENCESButzer, K. 1969. Geological interpretation of two Pleis-
tocene hominid sites in the Lower Omo Basin. Nature
222: 1133-1135.
Butzer, K. 1976. The Mursi, Nkalabong and lbish Forma-
tions, Lower Omo Basin, Ethiopia. In: Y. Coppens et al.