492 Asr,\, EASTERN AND CENTRAL
of protoconid, creating small basin. Longer cristid
runs back from metaconid and turns buccally to run
to distal side of protoconid, enclosing larger basin. Ms
long, increase in relative length from Ml-M3. Buccal
sides bulbous; become increasingly so posteriorly. Lin-
gual cusps quite peripherally placed. On Ml-M3,
bases of protoconid and metaconid contact each other,
thereby delineating in front of them an m/d long
plane if not basin, and behind them a relatively trun-
cated talonid basin.
Sangirun 5 (“Pithecanthropus dubius”). Fragment of
R side of lower jaw from near midline through M2;
contains what have traditionally been identified as
damaged P2 and less damaged Ml and M2.
Corpus very thick and tall, would have been broad
across front. Postincisal plane would have been some-
what sloping. Shallow sulcus divides internal surface
horizontally and asymmetrically; taller surface lies above
(mylohyoid fossa?). Mental foramen large; lies under
anterior preserved partial tooth. Shallow, slightly down-
wardly sloping sulcus lies below foramen. Below
anterior root of M2 is a flexure in external surface of
corpus that appears to reflect a change in angle of the
corpus behind it. Mandibular canal runs far lingual to
midline of corpus.
P2 appears to have two long, “fused” roots that arc
gently distally (as crown would have). Ml very worn;
its roots diverge quite close to neck. There was proba-
bly a hypoconulid, aligned with other buccal cusps. M2
also very worn, but crown had been thickly and fairly
profusely crenulated, with crenulations on either side
of a structure that might be large protostylid. Apices of
buccal cusps quite centrally placed, and those of lingual
cusps placed more peripherally. Hypoconulid lies just
buccal to midline of crown. Talonid basin long and
somewhat constricted b/l. No paracristid discernible.
Mesial to apparent P2 is single large alveolus; mesial to
that is a series of small, irregularly arranged alveolae. If
these real, they suggest that the apparent P2 is poste-
rior root of a molar (presumably Ml). In front of small
alveolae is a large vacuity that may represent a single
alveolus. On M1, roots bifurczte right below neck, and
on M2, somewhat lower.
Sangirun 6 (holotype of “Meganthropus palaeojavan-
icus”). R mandibular fragment from symphysis to just
behind M1. P1-Ml present.
Massive in all dimensions, with very strong exter-
nal swelling and continuous curve around inferior
border. Internal curve at front of jaw probably tight.
Internally, there is a very long, steep postincisal plane,
probably with a genial pit just below the preserved
fragment of midline scar (if so, pit is very high up
symphysis). Postincisal plane does not extend to infe-
rior border and is undercut inferiorly (symphyseal
cross-section is thus angled forward at bottom).
Mandibular canal runs just lingual to midline of cor-
pus. Large mental foramen lies just below region be-
tween P2- M1; shallow horizontal sulcus runs below.
P1 and 2 similar in having bulbous buccal sides
and straighter lingual sides. Roots obliquely oriented
on m/b-d/l axis; crowns similarly skewed. P1 and 2
protoconid and slightly smaller metaconid lie quite
mesially; short cristid between them encloses a small,
deep mesial basin, and a stouter distal cristid encloses
a slightly larger deep basin. Buccal side of P1 bears
mesial and distal vertical grooves; only a faint mesial
groove present on buccal surface of P2. In outline, P1
is slightly more wedge shaped than P2. P2 wider b/l
mesially and more expanded distally. Groove on mesi-
olingual side of P1 root becomes deeper inferiorly. M1
very worn and very elongate; was apparently crenu-
lated occlusally. Some grooves on buccal surface delin-
eate a cingulid-like structure in protostylid region.
Hypoconulid rather buccally placed. Stout paracristid
encloses narrow basin. Roots very wide b/l; bifurcate
right at neck. In front of P1 is a large alveolus (C?).
Sungimn 7-70. Fragment of upper part of L man-
dibular corpus with partial M1 and very worn M2
and 3.
Fairly massive bone. Ramus begins to rise below
mesial root of Ml; would have obscured M3. Crowns
of M1 and 2 essentially featureless, but buccal sides of
M2 and 3 clearly preserve horizontal grooves that de-
lineate cingulid-like structure in region of protostylid.
Both M2 and 3 somewhat elongate; M3 is propor-
tionately wider b/l. Neither tooth seems to have had
trigonid basin. On M2, hypoconulid is just buccal to
midline; may not have been present on M3. Occlusal
morphology was probably always quite flat. Roots of
all molars bifurcate quite close to neck.
Sungirun 8 (“Meganthropus” B). Partial mandible
lacking rami. Runs from region of LMl around to
RM3. Badly crushed and weathered. Preserves base of
crown of M1 and moderately worn, weathered M3.
Also fragments of other tooth roots, although I region
missing.
Apparently very short jaw a/p, very narrow across
front, with quite strongly divergent tooth rows. Front