Véra Eisenmann

Monodactyl Equids from Konso, Introduction

2017-10-03T10:47:54Z

This article is entirely based on the data kindly given to me by Hideo Nakaya many years ago. The raw measurements are Tables A and B.
In the following study I describe the fossils of Konso referring to the chronological order given by Gen Suwa et al., 2003 :

– Interval 1, KGA 4 loality, around 1.9 My old
– Interval 3, KGA 4HA locality, around 1.5 My old
– Interval 4, KGA 10, 11, and 7/8 M localities, around 1.4 My old
– KGA 7/8 U and 12 localities, around 1.3 My old
– KGA 20, around 1 My old.

Unfortunately, I do not know whether the specimens notes â€œ7/8â€ belong to Interval 4 or 5. They will be discussed separatedly

Monodactyl Equids from Konso, Interval 1

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Earlier Fauna, Interval 1, KGA 4 locality, around 1.9 My old

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Metacarpals
There are six fragments, KGA 4-359, KGA 4-1801, and KGA 4-2179 and (Fig. 1). The diaphysis of KGA 4-2179 is abnormally flat. Its distal dimensions as well as that of KGA 4-1801 are much smaller than in KGA 4-359.
As much as it is possible to guess, KGA 4-359 resembles KNM ER 1276 of Notochoerus scotti faunal zone (NS) at Koobi Fora referred to Allohippus sp. (in an article on this web-site) and FLK I 507-573 from Olduvai Bed I. Another fragment, KGA 10-698, could belong the same species but its age is much younger, only about 1.4 My. Among extant species, the closest in proportions is E. africanus (Fig. 2), but it is much smaller.
The other MC III are more flat in the diaphysis, a character usually associated with robustness.

Metatarsal
Three proximal fragments differ from each other (Fig. 3) .One of them, KGA 4-2381 seems similar to KNM ER 4052 and 5338 from NS zone at Koobi Fora (Fig. 4). These MT resemble those of extant Wild Asses. The other two have also relatively deep diaphyses.

Tali
The closest resemblance I could find for these two tali are two specimens from Olduvai Bed I (Fig. 5).

Calcanea
There are five specimens.

Phalanges
– There are two first phalanges (Ph1) one of which, KGA 4M-1537 has dimensions so bizarre that it cannot be of use. KGA 4M,CA7-2031 is a robust phalanx, possibly anterior, with a wide proximal end. It has the same proportions as Tih 630 of Tihodaà¯ne (Fig. 6).

– There is also a second posterior phalanx (Ph 2P), KGA 4M-2032,CA7, resembling one Ph2P of Tighenif â€“ probably E. mauritanicus (Fig. 7).

To summarize :
There is evidence for two forms of during Interval 1 : one reminding of Wild Asses ; the other with wider and flatter diaphyses and deep distal keels.

Monodactyl Equids from Konso, Interval 3

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Interval 3, KGA 4HA locality, around 1.5 My old
Two fragments of MC, KGA 4HA-1221 and 1227 are not informative.

- Monodactyl Equids from Konso, Southern Ethiopia

Monodactyl Equids from Konso, Interval 4

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Interval 4, KGA 10 and 11 localities, around 1.42 My old

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Metacarpals
Nine MC out from eleven are wide and flat in the diaphysis (measures 3 and 4), have large supra-articular widths (10), and relatively large maximal condylar depths (14-13). Some have also deep keels (12).
The only entire MC (KGA 10-904) seems smaller and less robust.
Its proportions are A. stenonis-like.
KGA 10-698 was commented above.

Metatarsals
One of the nine MT (KGA 10-1403-82) is very large. Another (KGA 10-1572) is narrower and relatively deeper in the diaphysis than the others.

Tali
One is very large and wide, probably associated with the MT KGA 10-1403-82. The rest belong to a more slender form. Two are probaly left and right of the same animal (KGA 10-2310 and 2410).

Calcanea
One (out of four) is very large and is probably associated with Talus KGA 10-1403.

First Posterior Phalanx
KGA 10-1403 looks like a very large E. burchelli granti (Fig. 11).

To summarize :
Like during Interval 1, there is evidence for at least two forms :
– one specimen (KGA 10-1572) with a deep diaphysis (usually associated with slenderness) ;
– the very large associated robust MT, Talus, Calcaneum, and Posterior Ph1 (KGA 10-1403 et al) ;
– the majority with wide and flat diaphyses (usually associated with robustness) similar but smaller than the precedent.

Monodactyl Equids from Konso, Interval 5

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Interval 5, KGA 12, around 1.3 My old

Metacarpals
Three specimens (Fig. 12) have relatively flat and wide diaphyses, wide suptra-articular breadths and deep keels..

Metatarsals
They are robust, with wide suptra-articular breadths, and deeper diaphyses than most of Konso metapodials. They are not unlike Olduvai Upper Bed II Metatarsals (Fig. 14).

Talus
KGA 12-256 resembles most Tali from Konso KGA 7 and 8 (Fig. 22).

First Phalanx
One posterior first phalanx resembles a specimen from Olduvai (Fig. 15).

Second Phalanx
An anterior Ph2 looks like a large E. mauritanicus one from Tighenif (Fig. 16).

To summarize :
Unlike in other Intervals, there is evidence for only one form. The fossils resemble Olduvai Upper Bed II specimens or E. mauritanicus.

Monodactyl Equids from Konso, Interval 4 or 5

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Interval 4 or 5, KGA 7/8 localities

Cranium
The data (Table A) and photographs of the cranium KGA 8-374 were kindly communicated by Dr Hideo Nakaya (Fig. 17).
The cranium (Basilar Length : 529mm) is about the size of E. grevyi, complete, and belonged to an adult male. The cheek (measure 32) is longer than the naso-incisival notch (31) as it always is in Equus unlike Allohippus.

The Simpson's ratio diagram (Fig. 18) shows an asinine character : the relative breadth of the muzzle between the crests (measure 17bis).

Upper Cheek Teeth
The post-protoconal valleys are not deep, the protocones are short with flat lingual faces and convex vestibular ones (Fig. 19).
Similar morphologies may be observed in teeth from Venta Micena, Spain and Ubeidiyeh, Israel (see articles on this web-site), and they are usually asociated with slender limb bones.

Metacarpals
There are a few specimens, with different morphologies (Fig. 20).
– KGA 7-215 of medium size and robustness and the deep proximal end like the Middle-Upper Pleistocene E. melkiensis of North Africa (Fig. 22) ;
– KGA 8-165 larger, very robust, with a deep keel ;
– KGA 8-418, very small.

Metatarsal
There is only one proximal fragment which looks like the MT from KGA 12.

Tali
Most (Fig. 22) have the usual proportions observed at Konso (and indeed in most extant Equus species).
But KGA 8-435 is unusual, somewhat resembling the talus of a Poitou Donkey (Fig. 23).

Posterior Second Phalanx
KGA 7-445 looks like Ph2 of E. mauritanicus (fig. 24).

To summarize :
Fossils from Interval 4 or 5, KGA 7/8 localities belong to two forms, one Ass-like, the other robust.

Monodactyl Equids from Konso, Interval 6

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Interval 6, KGA 20, around 1 My old
There is just one Talus resembling a large, fragmentary specimen from Olduvai Bed III-IV (Fig. 25).

- Monodactyl Equids from Konso, Southern Ethiopia

Monodactyl Equids from Konso, Discussion

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Discussion

Gen Suwa et al., 2003 distinguish an earlier fauna, with endemic bovids, prior to 1.7 Ma, followed by â€œan influx of external elementsâ€¦most likely related to a general East African trend of climatic dryingâ€ , resulting in â€œthe post-1.5 Ma characterized by newly occurring taxa and locally continued lineagesâ€ .

I have found evidence for two forms of during Interval 1 : one reminding of Wild Asses ; the other with wider and flatter diaphyses and deep distal keels.

The following observations can be made by pooling the data for the post-1.5 Ma equids.
1. The only evidence for the apparition of a new form is provided by the metatarsals of Konso 5, KGA 12. The only three MT inside the whole Konso sample to be entire were collected at KGA 12 (Fig. 26).
Moreover, all the MT of KGA 12 have similar proportions. One fragment from KGA 7 seems to belong to the same form. Metatarsals and Ph1 resemble fossils from Olduvai Bed II.
2. Apart from Interval 5, KGA 12, there is always evidence for two forms : one more or less Ass-like and one, much more frequent, apparently more robust.

Relation between Cranium and MC dimensions
Figure 27 shows the relation between basilar lengths and supra-articular MC widths in extant Equus, and how the basilar length of the cranium from Konso relates to the supra-articular widths of the MC.
It shows that almost all MC from Konso, whatever the Intervals, are compatible by their size with the cranium KGA 8-374.

Monodactyl Equids from Konso, Conclusions

2017-10-03T10:47:16Z

Conclusions

The material from Konso comprises one beautiful cranium and many limb bones most of which are unfortunately fragmentary. The whole is not homogeneous.

Most limb bones suggest the existence all through the sequence of a robust Equus. Only those from Interval 5, KGA 12 have definite resemblance to an African robust species â€“ probably E. oldowayensis of Bed II. Some limb bones have Asinine characters.

The cranial size is compatible with the other, more frequently represented form(s) but some cranial characters suggest an Asinine species to which I believe it belongs.

Reference

GEN SUWA, HIDEO NAKAYA, BERHANE ASFAW, HARUO SAEGUSA, AWOKE
AMZAYE, REIKO T. KONO, YONAS BEYENE, and SHIGEHIRO KATOH
Source : Journal of Vertebrate Paleontology, 23(4):901-916. 2003.