The protoconid, metaconid, hypoconid
and entoconid are organized into two distinct lobes with rounded corners separated from each other by a well-developed median valley.
The p4 has a strongly developed posterior cuspid, m1 with strong and voluminous metaconid, m2 big with reduced to absent paraconid, narrow talonid almost completely occupied by the hypoconid
The m1 has the labial and lingual cusps alignment alternate rather than opposite (as in the uppers), the metaconid is anteriorly positioned with respect to the protoconid, and the entoconid is anteriorly positioned with respect to the hypoconid
. The murids are ridgelike and longitudinally oriented along the midline of the tooth.
Pit hypoplasia occurred most frequently, with most defects located on the hypoconid
of the first lower molar.
The ml (MBLUZ-P-3.990, MBLUZ-P-5.896, MBLUZ-P-4.690; Table I; Figure 2f) has an anteriorly projected paraconid without enamel band; a metaconid enamel band is present; meta-entoconid fold shallow and reflected 45[degrees] anteromesialy; ento-hypoconid fold deeper and less inclined (85[degrees]) anteromesialy than meta-entoconid fold; hypoconid
buccolingually broad, looks like a trigonid size; anterior facet of the trigonid convex; the lingual enamel band extends to the metaconid to the anterolingual side of the hypoconid
, without covering it totally; buccal enamel fold deeper; buccal enamel band covering the anteromesial protoconid facet through posteromesial hypoconulid facet; hypoconid
lingually projected; buccal enamel broader than lingual enamel.
A well developed furrow separates the hypoconid
from the strong protoconid on the buccal side.
geismarianus is characterized by an m I with a low, short trigonid with the metaconid slightly more posterior than the protoconid, a large talonid, subequal entoconid and hypoconid
, compressed m2 trigonid with an anterobuccal cingulid, and a very small paraconid SDSM 8640 differs from N geismarianus in that the length of the ml is not as reduced and has a lesser degree of trigonid compression on the m2.
Predominantly, these facets were found on the mesiobuccal aspect of the protoconids and were manifest as cusp-tip facets, although Phase II facets on the hypoconid
were viewed on a few specimens that had poorly preserved protoconids.
Its M3 has only a paracone and protocone, m2 and m3 are nearly the same size, with distinct metaconid, protoconid, posterolophid and hypoconid
elements, and all mandibular teeth (m1-m3) have a posterocrista.
Enamel is missing on the posterior face of the protoconid and mesiobuccal corner of the protoconid, and the posterior half of the hypoconid
The ectostylid is joined to the protoconid and hypoconid
. The basal cingulum is well developed and the median valley is deep with strong ectostylid.
The ectostylid lies towards the hypoconid
. The hypoconid
covers more area than the protoconid.