Véra Eisenmann

Monodactyl Equids of East Turkana : Tables

2017-07-19T16:29:07Z

Methods of measurements may be found at this web side inside the chapter "Tools".

Summary

2017-07-19T16:29:03Z

1. In East Turkana, at Koobi Fora, inside levels about 1.9 My old, were found remains of a very large Allohippus : A. koobiforensis. The patterns of its upper and lower cheek teeth were different from usual Allohippine patterns.

At the same time there lived at Koobi Fora a smaller monodactyl equid, probably an Allohippus because of its short protocones, usual in this genus. The gracility of the limb bones referred to this ?Allohippus sp. and their similarities with extant E. africanus suggest adaptation to dry conditions.

2. Inside levels about 1.5 My old, were found fossils resembling Allohippus koobiforensis but much smaller.

From the same levels were collected a few upper cheek teeth possibly belonging to the ?Allohippus sp. of old levels.

Other fossils of the same age remain incertae sedis. Some resemble Asses, many - small Grevy zebras.

3. Inside younger levels (MC zone, around 1My ago) were found two very different forms : one resembling Sussemiones by the marked plications of the teeth enamel, the other resembling ?Allohippus sp. or Wild Asses.

4. From the Guomde Formation come very plicated teeth, possibly indicating humid conditions.

5. The associated upper and lower cheek teeth from the Galana Boi Formation could belong to an extant E. grevyi or E. burchelli.

6. A large E. burchelli was possibly present in the MA zone. E. burchelli was certainly present in the MC zone.

Equus cf. burchelli from MA and MC zones

2017-07-19T16:17:45Z

Tibia
KNM ER 1277 is a perfectly preserved Tibia (Fig. 59, 60) resembling a large E. burchelli.
Fig. 59
Fig. 60
â€œAssociatedâ€ First Phalanges
The association of KNM ER 2678 Ph1 (MC zone, Sub Chari, Area 6 A) is certainly wrong (Fig. 61). In an Equus individual, Anterior Ph1 are never shorter than the Posterior.
Fig. 61
Simpson's Ratio diagrams indicate that both Ph1 probably belonged to an E. burchelli albeit not to the same animal (Fig. 62).
Fig. 62

- Monodactyl Equids from East Turkana

Equus from Galana Boi

2017-07-19T16:13:16Z

Associated Upper and Lower Cheek teeth
KNM ER 4055, Galana Boi, (Fig. 58). The pattern of the upper cheek teeth is compatible with extant Equus burchelli and Equus grevyi. The size is intermediate. The lower premolar has a very high stem and reminds of Asses and some teeth from Garba IV at Melka Kunturé. The depth of the vestibular groove of the molars, however, is not an Asinine character.
Fig. 58

- Monodactyl Equids from East Turkana

Monodactyl Equids from Guomde

2017-07-19T16:10:49Z

KNM ER 2658 are associated one upper premolar and two lower premolars (Fig. 56). The enamel is very plicated like in the Sussemione-like teeth of Figure 54. The protocone is long and indented, like in A. koobiforensis (Fig. 4).
Fig. 56
Surprisingly enough, from the Guomde Formation, Area 105-109, a lower P2-M1 series (P4 and M1 were sectioned, Fig. 58) has the same pattern as A. koobiforensis (Fig. 6).
Fig. 57

- Monodactyl Equids from East Turkana

Monodactyl Equids from MC Zone

2017-07-19T16:07:58Z

Associated Upper and Lower Cheek Teeth
KNM ER 2652 are an upper right Premolar and the mesial half of a left Premolar (Fig.53).
Fig. 53
Both are very plicated thus differing strongly from all the Koobi Fora specimens younger than NS zone. The pli caballin is wide at its base. Both teeth remind of Sussemiones .

Other Upper Cheek Teeth
Unlike the precedent, the teeth belonging to the fragment of palate KNM ER 1457 (Fig. 54) are not plicated. Post-protoconal valleys are shallow, protocones are short, symmetrical and lingually grooved.
Fig. 54
They may belong to the larger form described and referred to ?Allohippus sp. above (see KNM ER 2691 from MA zone in Fig. 31). If the post-protoconal grooves were deeper, they would look like Ass teeth. One isolated premolar, KNM ER 2684, Area 6A, has indeed a deep groove (Fig. 55). FS 101, without origin, has a similar pattern. But on the molar KNM ER 2066, the groove is shallow.
Fig. 55

Lower Cheek Teeth
There are no other lower cheek teeth than the specimen illustrated on Fig. 54.

Incertae sedis from MA zone

2017-07-19T16:00:13Z

Upper Cheek Teeth
Some teeth from MA zone resemble A. koobiforensis by long and indented protocones but differ by shallow post-protoconal grooves and smaller size (Fig. 32).
Fig. 32

Lower Cheek Teeth (Fig. 33)
Both teeth from MA zone are very probably molars because of their elongated hypoconulids. In both the vestibular groove is shallow although not as much as it would be in premolars. This shallow groove added to a symmetrical double knot with rounded metaconid and metastylid is a character found in extant Asses. The lower premolar or molar FS 17 has no origin but belonged certainly to the same form.
Fig. 33

Associated Limb bones
The MC KNM ER 2069 B-C is associated with two first phalanges (Fig. 34).
Fig. 34
Among the extant Equus I have been unable to find a closer fit to this MC than the much larger E. grevyi (Fig. 35).
Fig. 35
The associated Ph1 KNM ER 2069 D and 2069 E resemble E. grevyi although they are smaller (Fig. 36).
Fig. 36
Radius
KNM ER 2055 (Fig. 36) is similar to the minimum of extant E. grevyi (Fig. 37).
Fig. 37
Fig. 38

Metacarpals
Most are damaged and altogether they do not form an homogeneous group (Fig. 39, 40).
Fig. 39
Fig. 40
– KNM ER 1275 L (Fig. 29) has as wide a proximal epiphysis as KNM ER 1276 from NS zone (Fig. 16).
– KNM ER 1274 ( Fig. 41) is slender and would fit with Wild Asses or very small E. grevyi if not the development of its distal keel (measure 12) not found in E. africanus nor E. grevyi (Fig. 42) but found in the more robust KNM ER 2069 (Fig. 35, 36).
Fig. 41
Fig. 42
– KNM ER 1297, 103-0235/9 is much smaller but looks alike KNM ER 1276 from NS zone (Fig. 43, 44).
Fig. 43
Fig. 44
– KNM ER 2050 (Fig. 45) is damaged but some approximate dimensions can still be used for comparisons (Fig. 46).
Fig. 45
The closest fit I could find is the MC of one extant Poitou donkey (BM 81-1338).
Fig. 46
– The damaged KNM ER 1431, 1717, and the juvenile 2215 are not very informative (Fig. 39).

Tali (Fig. 47)
KNM ER 1275 J, associated with MT and other limb bones, was referred to ?Allohippus sp. The other are smaller.
Fig. 47
– KNM ER 685 A, 1296, 2048, 1385 (06A-0309, MA) and 2049 have the proportions and size of E. hydruntinus and the proportions of the extant E. grevyi ;
– KNM ER 661 A, 1290, and 2047 (123, AssHom 1811) have the proportions of extant E. hemionus (Fig. 48).
Fig. 48

Metatarsals
The specimens are few and fragmentary (Fig. 49)
Fig. 49
KNM ER 2057 has a rather deep proximal epiphysis not unlike some extant E. grevyi (Fig. 50).
Fig. 50

First Phalanges
From MA zone, Chari-, Area 06A-0301, there is an anterior phalanx (Fig. 52)
Fig. 51
which very probably belongs to a Wild Ass (Fig. 53).
Fig. 52

?Allohippus sp. from MA zone

2017-07-19T15:35:52Z

Upper Cheek Teeth
Morphologies similar to ?Allohippus sp. from NS zone are found in MA zone : KNM ER 2688, 2691, and 4025 ; the decidual FS 75 2 has no origin (Fig. 28).
Fig. 28

Associated Limb bones
KNM ER 1275 are associated MC, MT, phalanges, and Tarsals (Fig. 29).
Fig. 29
– The fragmentary MC could belong to ?Allohippus sp. (Fig. 16).
– The MT is slender, smaller but similar to KNM ER 5358 and 4052 (Fig. 20) referred to ?Allohippus sp.
– The Ph1P is slender (measures 1-3), with a deep proximal diameter (5). It resembles Ph1P of contemporaneous European Equids (Venta Micena and Cueva Victoria) and also extant Wild Asses (Fig. 30).
Fig. 30
– The Talus resembles those of extant large donkeys (Fig. 29, 31).
Fig. 31

?Allohippus sp. from MA zone

2017-07-19T15:35:35Z

Upper Cheek Teeth
Morphologies similar to ?Allohippus sp. from NS zone are found in MA zone : KNM ER 2688, 2691, and 4025 ; the decidual FS 75 2 has no origin (Fig. 28).
Fig. 28

Allohippus cf. koobiforensis from MA and MC zones

2017-07-19T15:25:42Z

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

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

Mandible
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 â€“ 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).