Unexpected finding of a new Equus species (Mammalia, Perissodactyla) belonging to a supposedly extinct subgenus in late Pleistocene deposits of Khakassia (southwestern Siberia)
Author
Eisenmann, Véra
Author
Sergej, Vasiliev
text
Geodiversitas
2011
2011-09-30
33
3
519
530
http://dx.doi.org/10.5252/g2011n3a5
journal article
10.5252/g2011n3a5
1638-9395
5373568
Equus
(
S.
)
ovodovi
n. sp.
HOLOTYPE
. — Palatal fragment, with P3/-M1/ of both sides (
IAES 21
).
ETYMOLOGY. — In honour of Professor N. D. Ovodov, of the Institute of Archeology and Ethnography (
Novosibirsk
) who excavated the Proskuriakova cave in 1973-1974.
MATERIAL EXAMINED. — Enumerated above and described below. Besides Proskuriakova cave, fossils possibly belonging to the same species were found in late Pleistocene alluvial deposits of “Pred-Altai plain” (Upper Ob) and in
Altai
caves where they can be traced up to the end of Pleistocene (
Vasiliev
et al.
2006
).
TYPE LEVEL
. — Late Pleistocene.
TYPE LOCALITY
. — Proskuriakova cave,
Khakassia
, western Siberia.
DIAGNOSIS
Slender
Equus
slightly larger than the extant
E.hemionus onager
;cheek teeth relatively small;shallow postprotoconal grooves on the upper cheek teeth; shallow lingual grooves, elongated double knots and metaconids on the lower cheek teeth; deep vestibular grooves on the lower molars; occasional presence of a pli protostylid on P/2; deep diaphyses on the MC and MT.
GENERAL DESCRIPTION
The Simpson’s ratio diagram (
Fig. 1
) where
E. hemionus onager
is the reference zero line, compares MT length, distal articular breadth, depth of the diaphysis (respectively MT1, MT11, MT4), size of P3/-P4/ (Psize),size of M1/-M2/ (Msize), protocone length of P3/-P4/ and of M1/-M2/ (Pprot.; Mprot.), in
E.
(
S.
)
ovodovi
n. sp.
of Proskuriakova to the same dimensions in
E. hemionus onager
(zero line), in
E.
(
S.
)
altidens
Reichenau, 1915 (Süssenborn)
, and in three forms of
E. hydruntinus
.
C D
FIG. 3. — Upper cheek teeth of
Equus
(
S.
)
ovodovi
n. sp.
, Proskuriakova Cave (Khakassia, Southwestern Siberia):
A
, M3/ (no. 15);
B
, M (no. 12);
C
, P (no. 11);
D
, M (no. 13);
E
, P2/ (no. 1);
F
, P (no. 5);
G
, P (no. 4);
H
, P (no. 14);
I
, P (no. 3);
J
, M (no. 8);
K
, M (no. 9);
L
, M (no. 10);
M
, P (no. 6);
N
, P (no. 7);
O
, P2/ (no. 2). Scale bar: 3 cm.
FIG. 4. — Upper cheek teeth:
A
, M of
E
. (
S.
) cf.
suessenbornensis
Reicheau, 1915
from Akhalkalaki (
Vekua 1962
) (AKHA 1290);
B
, P of
E.
(
S.
)
suessenbornensis
from Süssenborn (S 876);
C
, P3/ of
E
. (
Amerhippus
)
andium
Wagner-Branco, 1883
, Punin,Ecuador (FAM 11). Scale bar: 3 cm.
TABLE 2.— Measurements (in mm) of upper cheek teeth of
Equus
(
S.
)
ovodovi
n. sp.
, Proskuriakova cave (Khakassia,southwestern Siberia). Abbreviations:
Ht
, height of the crown;
L
, occlusal length;
LPT
, length of protocone;
W
, occlusal width.
|
Type
|
L
|
LPT
|
W
|
Ht
|
|
P3/
|
| IAES 21 sin. |
c.
26.2
|
9.9 |
c.
24.4
|
32 |
| IAES 21 dex. |
c.
26.5
|
10.2 |
24.8 |
31 |
|
P4/
|
| IAES 21 sin. |
25 |
11.7 |
c.
25.3
|
| IAES 21 dex. |
24.4 |
10.7 |
25.6 |
|
M1/
|
| IAES 21 sin. |
22.4 |
10.7 |
25.5 |
28 |
| IAES 21 dex. |
c.
22.9
|
10.9 |
25.8 |
28 |
|
P2/
|
| IAES 1 sin. |
35.5 |
7.4 |
24.7 |
53 |
| IAES 2 dex. |
32 |
7 |
20.7 |
27 |
|
M3/
|
| IAES 15 sin. |
28.2 |
12.8 |
23 |
51 |
|
P3/-P4/
|
| IAES 3 sin. |
26.8 |
13.8 |
27.2 |
38 |
| IAES 4 sin. |
26.2 |
14 |
27.5 |
38 |
| IAES 5 sin. |
26.8 |
13 |
28.3 |
35 |
| IAES 6 dex. |
26.8 |
14.1 |
26.2 |
37 |
| IAES 7 dex. |
26.5 |
13.6 |
26.6 |
34 |
|
M1/-M2/
|
| IAES 8 dex. |
24.8 |
13.3 |
25.5 |
43 |
| IAES 9 dex. |
26.1 |
12 |
28.7 |
31 |
| IAES 10 dex. |
25.3 |
11.4 |
27 |
30 |
| IAES 11 dex. |
24.3 |
10.3 |
26.3 |
23 |
| IAES 12 dex. |
22.3 |
10.4 |
23.2 |
24 |
| IAES 13 sin. |
22 |
10.8 |
24.7 |
36 |
| IAES 14 sin. |
25.2 |
12.2 |
28.4 |
33 |
It shows slight size differences inside the Proskuriakova material, particularly in the length of the premolar’s protocones (
Fig. 1
[Pprot.];
Table 1
). There is also a difference between the MT1-MT4- MT11 proportions between the “large” and “small” forms but since there is only one large MT (no. 6, with a damaged distal end), this does not seem very reliable).
More important are the differences between
E.
(
S.
)
ovodovi
n. sp.
and both
E. hemionus
and
E. hydruntinus
:
– unlike
E. hemionus onager
teeth are relatively small and diaphyses are deep on the metatarsals;
– unlike
E. hydruntinus
protocones are relatively long.
The smaller form has proportions close to
E.
(
S.
)
altidens
from Süssenborn,
Germany
, a species
c.
0.6 Ma old (
Maul
et al
. 2000
).
Upper cheek teeth (
Table 2
)
The enamel is simple, the plis caballin – when present – are small; the postprotoconal grooves are shallow. Size and shape of the protocones are very variable: short, pointed, and humped (
Figs 2
;
3C
) like in some Sussemiones and
E. andium
Branco, 1883
(
Fig. 4
) or flat and long (
Fig. 3I
).
Lower cheek teeth (
Tables 3
;
4
)
Small or large, the lower cheek teeth (
Fig. 5
) differ from hemiones by deep vestibular grooves on the molars, and from
E. hydruntinus
, by assymetric double knots. Some resemble to middle Pleistocene species (
Fig. 6
) found at Süssenborn and Akhalkalaki (
Georgia
), or to some
E
. (
Amerhippus
)
santaeelenae
Spillmann, 1938
of
Tarija
,
Bolivia
.
Third metacarpals
The material is very poor (
Table 5
) but it is possible to reconstruct the approximal length (
Fig. 7
).
Size and proportions look similar (
Fig.8
)to the MC fragments found in the Mousterian ofTsopi,
Georgia
(
Gabunia & Vekua 1989
; Vekua pers. com. 1995).
Tsopi yielded also a deciduous upper series, a fragment of M3/, and several associated lower cheek teeth (
Gabunia & Vekua 1989
). One of these, a lower molar, is very interesting: it bears an ectostylid, and has a very deep vestibular groove reminding of some Sussemiones (
Fig. 9
). No other photographs are available.
Third metatarsals
MT no. 6 is more robust than the others and has a very developed keel (
Table 6
;
Fig. 10
).
The size of MT no. 6 is close to the mean of
E. hipparionoides
Vekua, 1962
MT
from Akhalkalaki (
Fig. 11
) but the latter is closer by proportions to the smaller MT from Proskuriakova: deep diaphysis like MT no. 6 and 7 (measurement 4), and probably large distal articular breadth (distal end damaged) like MT no. 9 (measurement 11).
FIG. 5. — Lower cheek teeth series of
Equus
(
S.
)
ovodovi
n. sp.
, Proskuriakova cave (Khakassia, southwestern Siberia):
A
, no. 1;
B
, no. 2;
C
, no. 3;
D
, no. 4;
E
, no. 5;
F
, no. 6. Scale bar: 3 cm.
FIG. 6. — Lower cheek teeth of
Equus
(
S.
)
ovodovi
n. sp.
, Proskuriakova cave (Khakassia,southwestern Siberia):
A
, P/4 (no. 6);
B
, P/4 (no. 4);
C
, P/2 (no.6);
D
, P/4 of
E
. (
Amerhippus
)
santaeelenae
Spillmann,1938
(V 689),Tarija,Bolivia;
E
, P S 3362 of
E.marxi
Reichenau, 1915
from Süssenborn;
F
, P/2 of
E
. cf.
sussenbornensis
from Akhalkalaki (
Vekua 1962
), no number. Scale bar: 3 cm.
TABLE 3. — Measurements (in mm) of lower cheek teeth of
Equus
(
S.
)
ovodovi
n. sp.
, Proskuriakova cave (Khakassia, southwestern Siberia). Abbreviations:
L
, occlusal length;
LPF
, length of postflexid;
W
, occlusal width.
|
P/2
|
P/3
|
P/4
|
M/1
|
M/2
|
M/3
|
|
IAES no.
|
L |
LPF |
W |
L |
LPF |
W |
L |
LPF |
W |
L |
LPF |
W |
L |
LPF |
W |
L LPF |
W |
| 1 dex |
34.1 |
16 |
16 |
28.4 |
16.1 |
17.1 |
28 |
12.9 |
17.3 |
24.1 |
11.5 |
16 |
24.7 |
10.7 |
15.2 |
31 11.1 |
13.5 |
| 2 dex |
34.5 |
16.2 |
17 |
27.2 |
16 |
18 |
26.5 |
12.7 |
18 |
24.5 |
9.2 |
17 |
24.5 |
9 |
16.2 |
28.2 7.9 |
13.9 |
| 3 dex |
31.6 |
13.8 |
16.1 |
27.7 |
12.7 |
18.4 |
26.7 |
11 |
18.4 |
24 |
8.5 |
18.3 |
24.5 |
9 |
17.5 |
30.6 8.6 |
14.4 |
| 4 dex |
28.8 |
14 |
15.7 |
24.8 |
14 |
16.8 |
24.4 |
11.9 |
17.5 |
24 |
8.6 |
16.9 |
24 |
9.5 |
16.3 |
31.7 12 |
13.9 |
| 5 sin |
26.3 |
12.8 |
17.1 |
25.5 |
11.5 |
17.9 |
23.8 |
7.9 |
16.8 |
23.8 |
8.3 |
16.9 |
30.3 8.5 |
14.5 |
| 6 sin |
29 |
8.8 |
13.6 |
24.5 |
7.2 |
16.2 |
24 |
9.6 |
16.1 |
21.4 |
6.4 |
15.3 |
24.5 |
7.3 |
14 |
29.8 7.3 |
11 |
A C
TABLE 4. — Measurements (in mm) of lower cheek series from of
E
. (
S.
)
ovodovi
n. sp.
, Proskuriakova cave (Khakassia, southwestern Siberia).
|
L P/3-P/4
|
L M/1-M/3
|
L P/2-M/3
|
| 1 dex |
88.7 |
78 |
175.8 |
| 2 dex |
87.5 |
77.3 |
169.5 |
| 3 dex |
85 |
78.5 |
168.5 |
| 4 dex |
79 |
80 |
162 |
| 5 sin |
78.5 |
| 6 sin |
77.8 |
74.8 |
154 |
TABLE 5. — Measurements (in mm) of MC of
E.
(
S.
)
ovodovi
n. sp.
, Proskuriakova cave (Khakassia,southwestern Siberia).
1
, maximal length;
3
, breadth at the middle of diaphysis;
4
, depth at the same level;
5
, proximal articular breadth;
6
, proximal depth;
7
, diameter of articular facet for Os carpale III;
8
, diameter of articular facet for Os carpale IV;
10
, distal supra-articular breadth;
11
, distal articular breadth.
|
МС no. 2
|
МС no. 3
|
МС no. 4
|
МС no. 5
|
| 1 |
c
. 230
|
| 3 |
30.5 |
c
. 29.6
|
c
. 29.1
|
30.1 |
| 4 |
23.8 |
23.3 |
| 5 |
46 |
c
. 44.8
|
| 6 |
31.2 |
28.8 |
| 7 |
38.5 |
37.5 |
| 8 |
13.7 |
14.5 |
| 10 |
42 |
| 11 |
c
. 41.5
|
FIG. 7.— Anterior view of MC of
Equus
(
S.
)
ovodovi
n. sp.
, Proskuriakova cave (Khakassia,southwestern Siberia):
A
, no.3;
B
, no. 4;
C
, no.2. Scale bar: 3 cm.
REMARKS
Note that molecular analyses were performed on samples ACAD2302 (MT no. 9), ACAD2303 (MT
no. 12), and ACAD2305 (fragment of juvenile MT no. 14) belonging to the smaller form.