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 is missing.
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.
