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Journal of Paleontology 90(1):170–181
Table 1. Tooth measurements of the hypodigm of Nabotherium aegypticum n. gen. (length x width, in mm). Specimen
Canine
DPC 10527 –– DPC 10825 ––
DPC 8410 11.3× 8.9
Lower Dentition CGM 67201
DPC 10668 –– 10.3×5.2 DPC 10736 –– DPC 13424 ––
DPC 9048 DPC 10197
CGM 67202 –– – –
10.3× 9.7 12.5× 10.2
– 7.3×3.6
DPC 6473 –– DPC 8213 –– –
11.2× 8.6 P1
Upper Dentition NHM M8449 –– DPC 13442 –– CGM 67200
P2 P3 P4 7.2×4.2
11.5×7.6 –
–– 10.8×12.7 –
11.6×12.4 11.4×13.3
–– – –– 9.9×12.2 13.1×9.5 13.3×8.9
M1 –
15.3×15.8 14.6×14.9 –
–– 12.6×13.8 ––– –– 12.1×14.2
16.1×19.8 –
– –
– ––– 29.4×15.0 –
12.9×9.0 14.4×12.1 17.4×13.8 21.8×14.6
–– – –– 18.9×10.1
The postmetacristule runs distolabially and fuses with the distal cingulum; and the lingualmetacristule runsmesiolingually tomerge with the lingual cingulum. The occlusal pattern on M3 is similar to those observed on
M1 andM2.M3 is larger although with a relatively shorter distal margin, giving the tooth a somewhat trapezoidal occlusal outline. Also, the parastyle is less developed on M3 than on M2. A weakly developed preparacrista is present. The cingulum is continuous around the crown. The labial cingulum is well developed with respect to that of M2, in particular the portion labial to the paracone. Mandible: Nabotherium aegyptiacum has a robust mand-
ible with a relatively shallow horizontal ramus. Although CGM 67201 (Fig. 7) shows numerous fractures due to postmortem damage, three mental foramina are visible. The mesial mental foramen has a roughly oval outline and is situated below the mesial root of P2. The distal mental foramen is roughly the same size as the mesial one and is positioned between P3 and P4. The third mental foramen is situated below the mesial root of P3. The mandibular symphysis is fused in adults, U-shaped, and extends posteriorly back to the level of P2. Lower dentition: The anterior portion of the mandible in
CGM 67201 is distorted and the lower incisors are not preserved. However, DPC 9048 (Fig. 8) preserves this region (although not the incisors themselves) and makes clear that Nabotherium had three lower incisors on each side arranged in a shallow arc across the front of the mandible, and that I3 was not separated from the canine by a diastema. The canines are large, projecting, and oval in cross section. In CGM 67201, the alveolus of the left lower canine is
exposed, which reveals that the tooth root is very deep and curves dorsally to terminate beneath P1. DPC 9048 has both canines in place and shows that the mesial edge of the canine is sharply defined, and that a wear facet is present on the distal canine surface. Lower premolars: P1 is a small peg-shaped tooth with a
labiolingually compressed crown and an oval base, and is separated by a very short diastema from the lower canine. In CGM 67201(Fig. 7), the right P1 is well preserved and consists of one main cusp, from which run mesial and distal cristids, the distal one being longer than the mesial one. The tooth is single- rooted, convex laterally, concave medially, and curves distally.
13.3×8.5 –– 28.9×14.1 16.1×10.9 –– –
18.1×11.5
There is a short diastema between the P1 and P2, slightly larger than that between the P1 and the canine. The left P2 is well preserved in both CGM 67201 and DPC
9048 (Figs. 7.2, 8.1). The tooth is larger than P1, triangular in shape when viewed lingually, and double-rooted. The main cusp is tall and acutely pointed. A cristid runs mesially from the main cusp to terminate at the base of the crown. The distal cristid runs distally from the distal portion of the main cusp and bifurcates into two cristids, one of which runs lingually and the other continues distally to end at the base of the crown, meeting the small and shallow distal cingulid. The latter cristid courses around the distal margin of the tooth. There is no diastema between the P2 and P3. P3 is well-preserved on DPC 9408. It has a morphology
similar to that of P2, but it is larger with a more distinct and relatively longer mesial crest and a more distally extended posterior portion. P4, best observed on DPC 9048, is relatively more robust
and broader than the other premolars. The P4 protoconid is as high as those of P2–3 and is more robust. The mesial crest is slightly more curved than that of P3 and the lingual distal crest is stronger. The distal portion of the crown is relatively broader
than in the other premolars and a low shelf is formed by an expanded distal cingulid. Lower molars: M1 is relatively long and broad when
compared with P4 and shows appreciable wear compared to other cheek teeth. The second lower molar is well preserved in DPC 9048 and is a slightly longer and broader version ofM1 but with a broader (mesiodistally) hypoconulid shelf. M3 is the longest lower molar because it has an extended
hypoconulid lobe (Figs. 7.4, 8.1–8.2). The M3 trigonid and talonid are equally wide and have crenulations covering the occlusal surface. The mesial cingulid is moderately developed, runs around the mesial margin of the crown, and merges with the labial cingulid. There is a small spur on the mesial cingulid at the base of metaconid. The metaconid and protoconid are transversely placed and separated by a deep and narrow valley. The premetacristid slopes down from the mesial side of the metaconid and joins the preprotocristid near the middle of the mesial margin of the tooth, forming a U-shaped crest. The hypoconid is placed slightly mesial to the entoconid. The prehypocristid (cristid obliqua) is acute and curves
10.6×5.1 –– 15.9×10.9 –– – 12.7×6.8
10.3×5.3
– –––– 15.2×16.9
13.9×15.3
16.9×20.9 18.3×19.7 18.8×20.7 17.4×19.8
M2 –
M3
17.1×19.5 –
18.7×21.6 19.4×22.8 18.3×21.5
18.2×22.5
28.4×15.7 31.0×15.2 –
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