Véra Eisenmann

Allohippus cf. koobiforensis from MA and MC zones

mercredi 19 juillet 2017

Cranial fragment
KNM ER 1211 (Area 01, MA) belonged to a young adult.
Fig. 22
Although it is crushed some dimensions can be measured or estimated. Clearly this specimen is much smaller than A. koobiforensis but, as much as can be seen, has similar proportions (Fig. 23).
Fig. 23

KNM ER 1239 belonged to an old male (Fig. 24). The incisor’s arcade is rounded as in browser species.
Fig. 24

The mandible KNM ER 1582 (Fig. 25) seems a little different from KNM ER 5361 from NS zone (Fig. 10, 11). Its muzzle is as long (137mm) but wider (63mm) probably because the animal was younger. It would correspond to a cranium muzzle about 150 mm long and 68 mm wide – approximately the same size as the muzzle above.
Incisors are moderately worn. All infundibula are closed.
Fig. 25

Upper Cheek teeth (Fig. 26)
All from MA zone.
Like in A. koobiforensis from NS zone, the protocones are lingually concave, the postprotoconal grooves are deep, and plis caballins are present, at least on premolars.
Fig. 26

Lower Cheek Teeth
The enamel pattern of KNM ER 1582 resembles that of KNM ER 5360 and 5361 from NS zone (Fig. 14 and 12) but the series is longer (Fig. 27).
Fig. 27
The presence of a pli protostylid on the decidual dP2 KNM ER 1245 could indicate its belonging to A. koobiforensis although the tooth seems too small and mesially too blunt. The postfossette of KNM ER 2652 (MC zone) is very plicated as in A. koobiforensis. KNM ER 4023 resembles KNM ER 4046 from NS zone (Fig. 7).

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