Page 7 - whistler1967

The infraorbital foramen is paired with a smaller
foramen lying posterior to and slightly below the principal
infraorbital foramen.
No adult mandibles are represented in the sample of this
species. The juvenile mandibles, LACM 1829, bear no apophy-
sis below the condyle as is found in the subgenus Metoreodon
Schultz and Falkenbach.
Dentition: The type is the only adult available for study,
and the specimen bears only the molars. No permanent p2, p3,
p4, incisors or inferior canine are available for study.
However, pl and the superior canine erupt early and are
present in two juvenile specimens, LACM 1829 and 1384. These
teeth do not differ markedly from. those in !1• (!1.) calaminthu~
or !1• (!1.) crabilli. The mandibles of the juvenile LACM 1829
bear early wear M1-2 and an unerupted M3. These teeth seem
to be narrower in relation to length than any other described
species of the genus Merychyus.
Deciduous dentition: Both referred specimens bear deciduous
dentitions which permit a unique opportunity for study of
these less commonly described teeth. The dP4 is molariform
and square in outline. It bears a well-developed parastyle,
mesostyle, and metastyle. In addition, it appears to bear
a small protoconule and hypoconule as low distinct cusps on
the labial margins of the fossettes. The posterior loph of
the dp3 is also molariform, except that it lacks the styles.
There is also a small hypoconule on the labial margin of the
fossette in this tooth. The anterior loph is somewhat
reduced,.but bears two shallow, anteriorly opening fossettes.
The dP 2 is two-lophed, as long as the dP3, but only as broad
as the anterior loph of the latter. The labial surface bears
no styles, and any fossettes that may have been present are
completely worn away.
The dP2 and dP3 do not differ markedly from the
permanent P2 and P 3 in !1• (!1.) crabilli, except for smaller
size. The dP4 is three-lophed with an increase in loph size
from the anterior to the posterior loph. There is no lingual
cingulum, but weakly developed labial cingula are present at
the base of the crown between the lophs.
Figure 2 is a ratio diagram of selected characters in
the skull and superior and inferior dentitions of M.
(Merychyus) crabilli, !1• (Merychyus) minimus Schultz and
Falkenbach, ~- (Merychyus) calaminthus, and M. (Merychyus)

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