Morphologic, sinumetric and enamel investigations of the pliocene arvicolids (Rodentia) from the Karewas of Kashmir, India

MORPHOLOGIC, SINUMETRIC AND ENAMEL INVESTIGATIONS OF THE PLIOCENE ARVICOLIDS (RODENTIA) FROM THE KAREWAS OF KASHMIR, INDIA BAHADURSINGH KOTLIA & PAWNASHWARDAYAL MATHUR DGpartmentof ~ k ~ , Kuraaun University,Nainital, 263002,India

ABSTRACt The Karewa arvicolids, 2.4 Ma in age, are analysed quantitatively and qualitatively. By using various techniques such as the characteristics of all molars and the record of morphology of the chewing surface in connection with the ontogenetic chewing stages in their variability, Kilarcola, Kotlia (1985) is documented with a new sub-species. Kilarcola indicus sahnii nov. ssp. has slightly more derived characters than those in K~ indicus KOTLIA & KOENIGSWALD (1992). The interpretation of the sinuous line (sinumetry) has resulted in understanding the increase of hypsodonty from/£ indicus to/~ indicus sahnii nov. ssp. Additional material of/~ indicus is also described. I~¢HBRCHES SUR LA MORPHOLOGIB, LA SlNUMI~TRIB BT, L'ULTRASTRUCTURBDB L'I~[AIL DRS ARVlCOLIDES PL1OCf~NBS DB LA FORMATION DES KARKWAS,¢ACHEMIRB.

RI~SUMI~ Les Arvicolid6s de la formation des Karewas, dat6s de 2,4 Ma, sont ici 6tudi6s d'une mani6re quantitative et qualitative. Les ch~-gements de la morphologie occlusale en fonction des stades d'usure sont 6tudi6s chez toutes les dents et non pas seulement chez M1 et M 3. Une nouvelle forme du genre IOlarcola KOTLIA, 1985 est d6crite ; cette derni6re-pr6sente des caract6res plus 6volu6s que ceux observ6s chez_E indicus KOTLIA & KOENIGSWALD, 1992. KEY WORDS : MORPHOLOGIC VARIATION, SINUOUS LINE, SCHMELZMUSTER, ARVICOLIDS, PLIOCENE, KASHMIR INTERMONTANE BASIN. MOTS-CLI~ : ARIVICOLIDAE, MORPHOLOGIE OCCLUSALE, LINEA SINUOSA, ULTRASTRUCFURE DE L'I~MAIL, PLIOCI~.NE, KASHMIR.

INTRODUCTION

AND FOSSIL LOCAIJTY

The arvicolid rodents (voles and lemmln~) belon~ng to the family Arvicolidae are rapidly evolving mammals. They are very useful in dating rocks, reconstructing environments and determining past climatic changes (Chaline 1972, 1987 ; van der Meulen 1973 ; Repennlng 1983, 1985 ; Repenning eta/. 1990). Arvicolid biochronology is best studied in North America and Europe where it allows the identification of arvicolid dispersal events each of which restorted faunal similarity between these two continents. In these regions, the arvicolid history is well dated and the fauna now can be dated within 200 Ka during Plio-Pleistocene (Repenning et al.

199o). Manuscrit d~.posd le 18.11.1991 Manuserit accept6 d6finitivement le 01.04.1992

Recently, the arvicolids have been discovered in India from the lacustrine and glacio-fluvial sedlments of the Kashmir Valley (Kotlia 1985 ; Sahni & Kotlia 1985 ; Kotlia & Koenigswald 1992). The IndiaJa arvicolids are si~ificant for the reasons that this is one of the most southern limits of arvicolid occurrence in the Northern Hemisphere, the fossil localities are very near to what is considered as the centre of arvicolid origin and their having phylogenetic link with theEuropean arvicolids. The Karewa sequence, above 1 km in thickness has earlier been dated by palaeomagnetism and fission-track methods (Kusumgar 1980 ; Burbank & Johnson 1982, 1983 ; Kusumgar et. al. 1986 ; Agrawal eL al. 1989). Since the basement of the Karewas is dated to ca 4.0 Ma by these workers, it is possible to provide the arvicolid ~eobios, 1992~ n ° 25, fasc. 6 [ p. 781-796 1)

782

(m)

75"1£

120

~

....

+ ""'I 7:-.L-~ -.:.:-:.: .' o°o,, 80

---_-_-

~ ~

. ,..

~Qo~

eee

,.c,

/

~

Butapathri

c~

"~

~

Bodgom *

k


SRINAGAR

~,~ JI+-N~ ~// U \L~i. S o m t

t,

t¢ J~\

...~Hirpur

%Oo i ,n"

ra
,. 10km

]" (

._,5.~"~'",. .

~;'~"N

Khaigam profile

0L__.~al0Okm "~,~ INDEX MAP

..." A"D~.

J NDE

"~..1~'~~ "~:

~.~ J A M M U

f

l( A

+',. .

$HMIR

+Srinog+r

"_.2.2-_'.= . , ~

0

co .%" r"

.-

r .s

i....~ :""~i

~J

Mudstone

~ ~

Lignite

Claystone

~

Vertebrate horizon

Siltstone

~

Wave ripples

Conglomerate ~

The Khaigam sub-section representing the basal-most part of the Romushi reference section (Agrawal et a/. 1989) is about 125 m thick and is composed of mudstone occasionally interlayered with em scale lignite layers, s.andstone and conglomerate. Five volcanic ash layers, each about 5-1.2 can in thickness are present in the subsection. One of the ash layers is fission-track dated to 2.4 + 0.3 Ma (Burbank & Johnson 1982) and the other to 2.3 _ 0.3 Ma (Kusumgar e t aL 1986). The placement of Matuyama/Gauss boundary (2.48 Ma) just below Khaigam subsection (Kusumgar et aL 1986) confirms this age to these sediments. The arvicolid horizon, coarse grained to gritty bluish sandstone, is exposed stratigraphically about 33 m above the base of the subsection and is above the second volcanic ash layer (Hg. 1). The rodent horizon has also yielded a rich sorieid fauna (Kotlia 1991) and murid rodents (Kotlia 1992). MATERIAL AND METHODS The material was collected by the senior author in 1987-88. It is housed in the Geology Department,

volcanic

ash

layers,

fission-track dated to 2A -4- 0.3 Ma (Burbank & Johnson 1982) and to 2.3 --.+ 0.3 Ma (Kusumgar et aL 1986) are shown. Carte de lu vail& du Kashmir momram la l~alttd f ~ g l ~ e do Khaigam ot la seaion litboloR~ do Kbaigam. Los deux nivoaux do ¢muiros vokaniquas datds r~t~t#voment de 2.4 +_ 0.3 Ma (Burbank ~ Johnson 1982) at

do 2.3 +-- 0.3 Ma (Ku.~agar et. aL 198o') par la mdlhedo

dos trac~ do fro'ton .aSurent sur la section.

X

Sandstone

horizons the absolute age. So far, three arvicolid yielding horizons, 2.4, 1.6 and ca 0.2 Ma in age, have been discovered (Kotlia 1985 ; Kotlia & Koenigswald 1992). This paper describes the fauna of the lowermost horizon which is exposed along the River Romushi at locality Khaigam near village Pakharpura, 59 km south of Srinagar (Fig. 1).

Figure 1 - Map of the Kashmir Valley indicating the fossil locality, Khaigain, and lithoiogy of the Khaigam sub-section. The

Volcanic ash

Graded bedding

Kumaun University, Nainital. The reference material is kept at the Pal~iontologisches Institut, Bonn, Germany. The morphological units of cheek teeth are counted from posterior to anterior in the lower molars and in the reversed direction in the upper molars (Fig. 2a). In this way, we observe that the homologous parts within the molar series always bear the same serial number. The drawings of the occlusal surface are made by M-5 (Wild) stereomicroscope. The lower and upper molars are drawn as right and left respectively. For Sehmehmuster study, the samples were etched with 5% HC1 for 5-10 seconds and rest of the procedure was followed as in Koenigswald (1980, 1982). The measurements of molars are given in tables 1-12. The length is taken as the maximum anteroposterior diameter on the occlusal surface and the width is the maximum width of the posterior loop of the molars. To document the characteristics of the Pliocene arvicolids of India and to differentiate between /C indicus and K. indicus sahnii nov. ssp., the following methods are used. Firstly, the dental elements and morphological change within the population which involves the an zJysis of the series of specimens illustrating the successive stages of wear be~nnlng with the unworn (juvenile) individuals and ending with the completely worn (senile) specimens as has been done by Koenigswald (1977). Using the measurement of crown height (on the posterior and anterior loops of the lower and upper molars respectively), the molars from juvenile to senile stage can be arranged and the morphological

783 llngual LA2

LA3

/

',7,

/

M

BAt mesiol

BA2

BA3 Anterior

<

PA

,=

Index =~(Prs)2.(As) 2

I PE

AJ~'BA 2

BAI

Hsd HsId

M1

LA/-, /

LA3

LA2

M2

LA1

labial

( ~ BuCCol pclrl of sinuous lin~. ;-~..~ L i n g u o l port of sinuous line

a

HH In dex=J(Hsd)2(Hsld)2 AS A n t e r o s i n u s Prs Proloslnus

Hsd Hyposinuid Hsld Hyposinulld

b

Figure 2 - a : Terminology of chewing surface of Kilarcola (Kotlia & Koenigswald 1992) : AC. anteroconid complex, L A = lingual anticline, LS = lingual syncline, B A = buccal (labial) anticline, BS = buccal syncline, T = triangle, A L --- anterior loop, P L = posterior loop, EI = enamel islet, IF = islet fold, M K = M/momys-kante, PF = prism fold, P E = prism edge. b : Terminology of sinuous line (linea sinuosa) taken from Carls & Rabeder (1988). a : terminologte de la su~aca ocduaak de gtlarcola (Kotlia & Koentgswald 1991). b : terminologie da la linaa stnuosa.

changes studied. The second method used is simtmetric analysis which is related to the height of the dentine tracts (Fig. 2b) of the molars to understand the hypsodonty (Rabeder 1981 ; Carls & Rabeder 1988). One of the latest techniques, called as Sclmaelzmuster (enamel structure studies) is also used to workout the distribution of enamel types in the enamel band of the molars as has been done by Koenigswald (1980, 1982) and Koenigswald & Martin (1984).

KILARCOLA

SYSTEMATICS AND DESCRIPTION

Hoiotype - Right M1 (Specimen n ° KH/102), housed in Department of Geology, Kumaun University, Nainital, India (Kotlla & Koenigswald 1992, fig. 9).

The material consists of molars, incomplete jaws, numerous bone fragments and vertebrae, and is very well preserved. Only the complete molars are described here. A considerable part of the material is figured. Family ARVICOLIDAE Genus Kilarcola KOTLIA, 1985

INDICUS KOTLIA & KOENIGSWALD, 1992 : Figs. 3-61, 118-120 ; Tables 1-6.

Type locality - Khaigam, 59 km south of Srin/tgar. Horizon and age - Unconsolidated coarse gained to gritty sandstone (2.4 Ma in age). Material- 24 M: (9 {eft) ; 21 M2 (9 [eft) ; 13 M3 (7 left); 23 M t (8 left) ; 21 M 2 (8 left) ; 23 M ~ (13 left).

Diagnosis - As in Kotlia & Koenigswald (1992). The main characters are : medium sized arvicolid with rooted molars ; syaclines without crown cementum ; uniform thickness of enamel band on occlusal surface; linea sinuosa primitive compared to similar aged Mimo-

784

Specimen n* 103 142 133 102 it2 t04 147 140 lI1

LL0 109 144 116 107 156 127 t 18 153 113 115 151 114 L55 L48

Tooth type

Length

Width

Crown height

R L R R R R L L R

2.44 2.64 2.60 2.56 2.88 2.72 2.84 2.72 2.80 2,72 2,72 2.44 2.68 2.68 2.64 2.60 2.52 2.48 2.44 2.40 2.40 2.40 2.40 3,00

1.08 120 1.16 1,12 1.20 t.12 ...... 1.20 1.16 1.16 1,12 1.12 1.12 1.16 1,16 l. 12 1.08 1.04 L.L2 L.00 1.04 1.12 L.20 1.20

3.84 2.80 2.56 2.44 2.16 1.60 1.52 1.40 1.32 1.04 1.24 2.44 1.52 2.24 3.60 3.60 2.72 2.00 ZOO 0.76 ---2.76 1.92 2.12

R R L R R L R R L R R L R L L

Mean2.62 (N = 24) - Mean L.13(N = 23) Table 1 - Measurements (in ram) of MI of Kilarcola tndtmts KOTLIA & KOENIGb"WALD,1992.

Specimen n* 165 186 160 187 175 166 196 198 199 169 174 201 173 170 197 167 185

Tooth type

Length

Width

Crown height

R L R L R R L L L R R L R R L R L

1.52 1.64 1.60 1.40 1,28 1.40 1.40 1.56 1.40 1.32 1.52 t.60 1.56 1.64 1.40 1.36 1.48

0.88 1,04 1.00 0.88 0,76 0.84 0.76 1.04 0.76 0,76 0.84 0.96 1.04 1.12 0,72 O.80 0.88

3.16 2.00 2.60 2.28 2.04 1.92 1.64 1.48 1.28 0.84 0.80 O.48 2.52 2.28 ..... 1.12 2.92

180

R

1.48

1.00

2.28

162 188

R L

1.52 1.52

0.96 0.96

2.60 3.00

161

R

1.52

0.92

2.24

Mean 1.47 (N = 21) - Mean 0.90 (N =

21)

Table 2 - Measurements (in mm) of M2 of Kllarcola tndtcus KOTLIA & KOENIGSWALD, 1992.

my3s ; M1 with Mimornys-kante; enamel islet on M1 and M present in adults ; M 1 with three roots and all other molars having two roots ; Schmelzmuster primitive having only discrete lamellar enamel in the anticlines ; more primitive than the Eurasian Mimomys and most other arvicofids of similar age ; morphologically .~imilar to Cseria, e.g., lack of cementum in the synelines and uniform thickness of enamel band on the occlusal surface but somewhat more derived in having less confluent triangles, more evolved sinuous line and two roots in M 2 compared to three roots in Csefia (Kotlia & Koenigswald 1992). D e s c r i p t i o n o f material - The basic characters and the morphological variation from unworn to completely worn specimens o f / £ indicus are discussed by Kotlia & Koenigswald (1992). The additional characters are as

follows. Lower dentition - In M1, the anterior loop is smaller and generally skewed lingually often forming 5th lln£ual anticline in the juveniles. Very deep islet fold in juveniles is responsible for forming the enamel islet in the adults and the fold finally becomes shallower in the seniles. The prominent Mimomys-kante is present throughout. The appearance of enamel islet at a crown height of 2.56 mm (Fig. 5) and disappearance at a crown height of 2.16 mm (Fig. 7) indicates its short existence on M1. The enamel band is interrupted firstly on the posterolabial side, followed by at the cap of anterior loop at a crown height of 1.60 mm (Fig. 8) and finally on the posterolingual area at a crown height of 1.32 mm (Fig. 11). The important morphological variations are : prominent islet fold in form of 3rd labial (buccal) syneline in juveniles to its extreme shallowing in the seniles, prism edge occupying higher place compared to Mimomys-kante in the juveniles to Mirnornys-kante and prism edge occupying almost the same plane in the seniles, and the absence of enamel islet in the juveniles to its presence in the adults and loss in the seniles. The length/width measurements are given in table 1. In M2, the labial triangles are confluent with respective lingual triangles. The enamel opens on the anterior loop at a crown height of 0.84 mm (Fig. 22) and on the posterolabial side at the crown height of 0.80 mm (Fig. 23 ). The narrower and deeper synclines in the juveniles become wider and shallower in the older individuals. See table 2 for length/width measurements. M3 is similar to M2 in morphology but is narrower. The enamel opens only in the older individuals at anterior loop and postero-labial side before the crown height of molars reaches to about 0.80 mm (Fig. 29). The loss of confluency between the respective triangles and simpler anterior loop characterise the senile individuals. The measurements are given in table 3.

785

KH/103

KH/I~2

KH/~33

3

4

KHh02

KH/.2

5

6

7

Figure 3-12 Morphologie variation within the M1 of g tnd/oas. The crown height is measured on the posterior loop. Specimens, KH/140, 142 and 147 are left molars. Var/at/onsmorp/mlogiques des M1 de I(. tndtclt,. La hautaur de la couronna #st masurd# t~ la boucla poadrieura. Las spdciraens Ktt/140, 142 at 147 seat des mdaires gauches inversdas.

K./lo~

KH/I~7

KH/I~0

8

KH/1,

KH/110

10

9

11

12

I

K H//165

KH//186

13

KH/160

14

KH/187

15

2ram

I

KH/175

16

Figure 1 3 - 2 3 Morphoiogic variation within the M2 of K tnd/cus. Specimens, KH/186-187, 196 and 198-199 are left molars.

17

Variations morphologiques de la M2 do g tmitcu.~ Zes sI~'~mens KIt~ 186,187,196198 at 199 sent des molaires gauches inversdes.

t

2ram

I

KH/166

18

KH//196

19

KH/198

20

KH//199

KH/169

21

22

As described by Kotlia& Koenigswald (1992), all lower molars are two rooted, the anterior being larger. The molars are without crown cementum and the enamel band is uniformally distributed on the chewing surface.

I

K H/174

23

U p p e r d e n t i t i o n - In M 1' the tendency of confluency between the triangles is observed. The enamel band gets interrupted on the anterior loop at a crown height of 2.12 mm (Fig. 37). The completely Worn molars have

786

KH/212

KH/241

KH/243 n°

24

25

26

I

KH/215

2 mm

KH/237

259

282 290 265 163 264 280 286 251 254 252 298

I

KH/242

261 270 289 267

28

27

29

268 250 291 269 294

Tooth type

Length

Width

Crown height

R L •R L R R R L L R R R L R R R L R R R L R L

2.24 2.24 2.40 2.36 2.32 2.24 2.20 2.32 2.32 2.40 2.12 2.08 2.36 2.0O 2.20 2.12 2.12 2.16 2.16 2.16 2.28 2.32 2.12

1.00 1.04 1.16 1.12 1.20 1..04 1..04 1.04 1.08 1.12 1..00 1.12 1.24 0.92 0.96 1..00 1.00 1.16 1.00 1.04 1.04 1.16 1.08

4.12 3.60 3.24 3.20 2.80 2.48 2.44 2.12 1.72 1.68 1.32 0.80 1..56 3.34 ...... 1.48 3.68 2.40 0.92 1.92 2.16 --2.60

Mean 2.22 (N = 23) - Mean 1.06 (N = 23). Table 4 - Measurements (in ram) of M 1 of K tnd/aus KOTL1A& KOENIGSWALD,1992. Figure 24-29 - Morphologic variation within the M3 of K tnd/eus. Specimens, KH/237 and 241-243 are left molars. Variations morphologiques d#s M3 da If. t n d ~ Las spdcimens Kti/237, et 241-243 sent das molatrasgauches inversdes.

Specimen n° 215 214 218 237 243 213 232 234 242 220 212 245 141

Tooth type

Length

R R R L L R L L L R R L L

t.24 1.24 1.24 1.28 1.28 1.32 1.32 1.32 1.32 t.32 1.20 1.60 1.36

Width 0.64 0.72 0.72 0.80 0.76 0.72 0.72 0.72 0.76 0.80 ..... 1.00 0.72

Crown height I .48 2.04 2.48 1.40 1.80 2.32 1.92 2.00 0.80 1.16 2.16 1.52 2.12

M~an 1.31 (N = 13) - Mean 0.75 (N = 12) Table 3 - Measurements (in ram) of M3 of g tndtaus KOTLIA& KOENIGSWALD, 1992. enamel interruption at the apex of L A 2 at a crown height of 1.32 mm (Fig. 40). The eonfluency between the

respective triangles is reduced from unworn to worn specimens mainly because of the deepening of LS2 and BS2 together with bending of LS2 (Fig. 40). The posterior loop in the y o - n g e r individuals is forwardly directed and is almost flat in the seniles. For measurements, see table 4. M 2 is characterised by the wider lingual syncline (LS2) and deeper labial synclines (BS1 and BS2). The confluency is lost in the worn specimens. The enamel opens together at the anterolabial side and at posterior edge at a crown height between 2.76 and 1.'64 mm (Fig. 47-48). It finally opens on the anterofingual area, at the tip of B A 2 and almost throughout the posterior loop at a crown height of 0.56 m m (Fig. 50). The forward inclination of LS2 and the well separation of the triangles are the major morphological changes occuring from unworn to worn specimens. Measurements are given in table 5. The additional characters on M 3 have some modifications over the characters observed by Kotlia & Koenigswald (1992). The maximum crown height is 3.16 ram, The anterior and posterior islets are formed roughly at the same time at a crown height of 2.44 mm (Fig. 53). The anterior islet disappears at crown height of 1.72 m m (Fig. 55) followed by the disappearance of posterior islet at a crown height between 1.04 and 0.96

787 Figure 30-41 - Morl~hologic variation within the M of £ tndtcu,~. The crown height is measured on the anterior loop, Specimens, K I ~ 1 - 2 5 2 , 254, 259-260 and 263-265 are right molars.Varfat~ma morpho/og/~ des M1 de £ i n d ~ La hautaur de la couronne a$t me,'urde ~ la bouda antdrkum. Les s ~ c t m ~ KII-251, 252, 254, 259, 260, 263-265 sont des molatres droitas inver$$e$.

KH/282

KH/259

30

KH/260

31

32

33 2mm

KH/264

KH/280

K./265

KH/290

KH/280

KH/263

34

35

)

KH/251

KH/254

KH/252

¢.1

Specimen n° 333 348 325 323 322 351 332 343c 342 352 320 310 345 312 316 356 362 330 363 353 324

Tooth type

Length

Width

Crown height

R L R R R L R R R L R R L R R L L R L L R

1.76 1.60 1.64 1.76 1.76 1.64 1.76 1.56 1.60 1.48 1.56 2.00 1.84 1.64 1.68 1.68 1.52 1.72 1.72 1.76 1.80

1.04 1.00 1.04 0.96 1.08 1.08 1.08 1.00 1.00 1.04 0.92 t.I6 1.24 1.12 1.08 1.00 0.98 I. 12 1.12 1.12 1.08

3.84 3.64 3.48 3.08 3.04 2.76 1.64 0.92 0.56 2.64 2.96 1.64 0.96 3.40 3.68 2.44 3.16 2.16 1.52 2.52 2.04

Specimen n°

380 400 398 395 407 409 384 377 388 411 410 408 396 375 390 391 402 406 376 383 397 399 381

Tooth type

Length

width

Crown height

R L L L

t.44 1.60 1.72 1.72

0.88 .... 0.88 0.96

3.16 2.44 1.92 1.60

L

1,68

0.92

1.04

L R R R L L L L R R R L L R R L L R

t.52 1.68 1.60 t .52 1.72 1.40 1.36 1.36 1.44 /.60 t.56 t.60 1.60 1.64 1.64 1.56 1.56 1.64

0.84 0.96 0.88 1.00 0.96 0.80 0.84 0.92 0.80 0.80 0.80 0.84 0.92 t.00 1.00 0.96 0.96 0.92

0.96 0.68 0.52 2.84 1.72 0.40 2.32 2.32 ..... .... ...... 1.20 1.92 2.40 1.48 1.84 2.60 2.80

Mean 1.69 (N = 21) - Mean 1.06 (N = 21). Mean t.57 (N = 23) - Mean 0.90 (N = 22). Table 5 - Measurements (in ram) of M 2 of g tndtcus KOTLIA & KOENIGSWALD,1992.

Table 6 - Measurements (in ram) of M 3 o f / ~ tnd/cu, KOTLIA & KOENIGSWALD,1992.

788

II KH/333

mm (Figs. 57-58). The hook shaped posterior loop in the juveniles gets elongated in the senile individuals in which the metacon-talon complex becomes the prominent feature of the molars. The length/width measurements are shown in table 6. With the excep.tion of M 1 which has three roots, all upper molars are two rooted (Koflia & Koenigswald KH/3 l.,8

1992). KH/325

KH/323

KH//322 KILARCOLA INDICUS SAHNII NOV. SSP. : Figs.

62-119, 121 ; Tables 7-12. 42

43

44

45

46

Type locality - Khaigam, 59 km south of Srinagar. Horizon and age - Unconsolidated coarse grained to gritty sandstone (2.4 Ma in age). Holotypes - RM1 (KH/131, Fig. 62). Paratypes

KH/351

KH//332

KH/343 e

-

LM1 (KH/143, Fig. 66) ; RM1 (KH/158, Fig.

68).

KH/342

Material - _ 15 Mt (7 left) ; _16 M2 (9 left) ;_ 13 M3 (9

47

48

49

left); 20 M ] (12 left) ; 27 M z (6 left) ; 4 M 3 (7 left) ; Many incomplete molars.

50

Figure 42-50 - Morphologic variation within the M z of £ tndtrus. Specimens, KH/322-323, 325, 332-333, 342 and 343e are right molars. Variations morphologtquas des M2 de K. tndtcus. Les spdaimens Kti/322, 323, 325, 332, 333, 342, 343e sent das molaires droites inversd, s.

KH/380

KH/388

KH/400

51

52

Differential diagnosis - Bigger in size (M1 mean length 2.76 mm, see table 7) than K. indicus (M1 mean length 2.62 mm, see table 1) ; M~ having broad anteroconid

KH/398

53

KH/411

54

I

KH/395

KH/409

KH/40?

56

57

KH/384

58

55

2ram

KH/377

59

KH/410

60

61

Figure 51-61 - Mor~ohologic variation within the M of /g tnd/rus. Specimens, KH/377, 380, 384 and 388 are right molars. Variaaons morphologiques des M3 de K. tndtcus. Las spdcimens KII/377, 380, 384 et 388 sont des molairas droites tnversdes.

789

Specimen n° 131 105 106 101 143 128 158 I29 132 141 159 149 108 145 152

Tooth type

Length

Width

Crown height

R R R R L R L R R L L L R L L

2.60 2.76 2.92 2.92 2.60 2.80 2.88 2.88 3.00 2.76 2.76 2.72 2.64 2.68 2.60

t.08 l. 12 t. 12 1.24 1.16 1.16 1.28 1.16 1.20 1.20 1.20 t.20 1.20 1.12 1.28

3.52 2.48 2.32 2.00 1.88 1.76 1.32 0.76 1.64 1.20 1.36 3.28 2.40, 2.32 2.00

F,H/128

-

F,H/158

KH/129

Mean 2.76 (N = t5) -Mean 1.18 (N = 15). Table 7 - Measurements (in mm) of M1 of 16 tndlcus salmtt nov. ssp. Specimen n°

Tooth type

Length

Width

Crown height

163 19[

R L

1.64 1.60

1.00 0.96

3.04 2.68

t7t 190 202 178 189 179 177 t8t 201 195 193 194 172 192

R

t.72

t.[2

2.52

L

1.64

1.00

2.52

L R L R R R L L L L R L

1.64 1.60 1.68 1.80 1.72 t.68 t.60 1.64 1.60 t.60 1.56 1.56

1.04 t.04 1.04 1.04 1.08 0.96 0.96 1.08 0.92 1.08 0.96 1.00

2.28 1.40 1.40 0.96 0.68 0.60 O.48 0.56 2.40 2.40 2.56 2.20

Mean 1.64 (N = 16) - Mean 1.0I (N = 16). Table 8 - Measurements (in mm) of M2 of 16 iud~us sanbt nov. ssp.

complex with anterior cap skewed lingually in unworn specimens, and formation of enamel islet much earlier at a crown height of 3.52 mm than i n / d indicus (at a crown height of 2.56 ram) ; enamel interruption in M1 firstly on posterolabial side at a crown height of 2.00 m m compared to on anterior loop and posterolabial side in K. indicus (at crown height of 1.60 ram). M2 bigger (mean length 1.64 mm compared to 1.47 mm ill /~ indicus, tables 8 and 2) ; M 1 having narrower communication between T2 and T3, and enamel interruption earlier than in K indicus ; M 2 with wide anterior l o o p ,• M 3 having both the enamel islets formed

Figure 62-69 - Morphologic variation within the M1 of £ lnd/r-us salmtt nov. ssp. Specimens, KH/143 and 158 are left molars. Variations morpholog~lues des lltl de 16 tmltcus salratt nov. ssp. Las spdcimens KH/143 et 158 sont des molaires gauches inversdes.

much earlier than i n / d indicus, with elongated posterior loop and better development of LS3 ; slightly more derived than/£ indicus. Etymology - Named in honour of Prof. Dr. Ashok Sahni for his excellent work on the Indian micromammals.

Description of material Lower dentition - M1 : The broader chewing surface is composed of three closed and alternating triangles between the anteroconid complex and the posterior loop. The anteroconid complex has a linmaally directed anterior cap, deep to shallow islet fold and posterior to it the prominent Mimornys-kante, the prism fold somewhat lower to prism edge and an islet formed by the islet fold. The labial syncfines are smaller than the lingual synclines and none is filled with crown cementum. The occlusal surface has uniform distribution of enamel band both on the leading and trailing edges. The enamel islet is formed at a crown height of 3.52 mm (Fig. 62) and disappears before the crown height reaches to 2.00 m m (Fig. 65). The linea sinuosa rises firstly on the posterolabial side at a crown height of 2.00 m m (Fig. 65), followed by on the anterior loop and on the posterolingual side at crown heights of 1.88 and 1.32 mm respectively (Figs. 66, 68). The measurements are given in table 7. The morphological variation in the chewing surface depends upon the wear stage (Koenigswald 1977). The unworn individuals are characterised by a broad antero-

790 KH/163

KH/191

KH../190

KH/171

KHI/178

KH/Z202

Specimen n° 70

KH//189

71

72

KH/179

76

73

77

78

KH/201

79

Length

Width

Crown height

233 240 236

L L L

1.36 1.36 1.40

0.72 0.80 0.84

1.48 1.20 1.76

244 219 239 238

L R L L

1.40 1.40 t.40 1.40

0.84 0,80 0.80 0.72

!.92 t20 1.00 1.92

211

R

1.44

1.00

1.60

235

L

1.44

0.84

i.64

231

L

1.48

0.72

1.68

217 210 230

R R L

1.56 1.28 1.32

0.84 t.00 0.72

1.08 2.00 0.96

75

7z,

KH/181

KH/177

Tooth type

80

Mean 1.40 (N = 13) - Mean 0.8t (N = 13). Table 9 - Measurements (in mm) of M3 of K indicus sanhtt nov. ssp.

Figure 70-80 - Morphologic variation within the Mz of K i ~ / a u s sabnll nov. ssp. Specimens, KH/189-191 and 201-202 are left molars. Variations morpholog~ues des 2152 de K indicus sahnii nov.saff. LOS specimens KH/189-191 et 201.202 sont dos molairos gauches inversdes.

KH/210

K./24~

K./236

82

81

KH/231

83

8/-,

,

KH/211

HH/233

86

87

KH/219

88

K./235

2ram

KH/219

89

enamel islet and shallowing of islet fold with synclines more strongly bend anteriorly are the characters observed in the adults (Figs. 65-67). In the worn molars, forward bending of LS3 and BS2 and extreme shallowing of BS3 give way to T4 and T5 broadly opennlng into the anterior loop. The Mimomys-kante and the prism edge, occupying the different planes in the juveniles, lie almost in the same plane in the seniles.

85

i

HH/230

90

Figure 81-90 - Morphologic variation within the M3 of K tndicus sahnii nov. ssp. Specimens, KH/230-231, 233, 235-236 and 244 are left molars. Variations morpbolog~uos des M3 de 1£ tndieus saimti nov. ssp. Los spdamans KI1/230, 231, 233, 235, 236 et 244 sont des molairos gauchos inversdos.

conid complex with slight confluency between T4 and T5 and with somewhat deep islet fold, incipient LS4 and BA4, deeper LS3 and an enamel islet. The loss of

M2 " The M2 has a posterior loop and two small and shallow labial triangles and two deeper and larger lingual triangles. The noticeable confluency between TI and T2, and T3 and T4 throughout the wear is the characteristic feature of M2. The enamel gets interrupted firstly on the posterolabial area at a crown height of 1.40 mm (Fig. 76) and then on the anterior loop and postero-lingual side at a crown height of 0.96 mm (Fig. 77). For measurements, see table 8. The unworn specimens are characterised by : simple synclines without bending anteriorly, posterolinguaUy directed posterior loop, weakly developed LS3, elongated anterior cap and the confluent triangles. In slightly worn molars, the synclines bend anteriorly interrupting the confluency between the triangles. The loss of anterior elongation and of LS3 characterise the adults. The LA1 and BA1 form almost straight vertical line on the posterior loop and show complete 10ss of anteriorly elongated tip of the anterior loop in the worn individuals. M3 : It possesses two synclines on each side, shallow labial and deep lingual, and the lingually directed posterior loop having a wide communication with the confluent triangles, T1 and T2. An incipient LS3 is present. The linea sinuosa is as in M2. It rises up at the anterior loop and posterolabial edge at crown heights of

791

KH/262

KH/281

KH/258

92

91

KH~326

KN/257

93

K./3~3,

KH/255

KH/300

Figure 91-98 - Morphologic variation within the M 1 of g tndk'us salmti nov. ssp. Specimens, KH/255, 257-258 and 262 are right molars.Variations morphologtquos des M1 do K. lndlcus sahnti nov.ssp. Les sp~amens Ktt/255, 257, 258 et 262 sont des molairos droitos tnversdes.

262 258 281 257 284 255 300 301 288 287 266 256 305 285 303 253 299 283 293 272

KH/339

KH/327

Tooth type

Length

Width

Crown height

R R L R L R L L L L R R L L L R L L L R

2.40 2.28 2.20 2.56 2.32 2.12 2.32 2.28 2.44 2.44 2.36 2.36 2.36 2.20 2.20 2.24 2.28 2.32 2.32 2.32

1.04 1.08 1.04 lAX 1.04 1.04 1.00 1.08 1.12 1.16 1.04 1.08 1.12 1.00 1.04 1.04 1.04 1.12 1.20 t.08

3.52 2.96 2.96 2.60 2.12 1.36 1.00 0.68 2.76 2.12 2.00 3.08 1.12 3.28 2.80 2.80 1.40 2.44 2.24 1.64

Mean 2.31 (N = 20 - Mean 1.07 (N = 20). Table 10 - Measurements (in ram) of M 1 of K, lndtcus sahnlt nov. ssp.

104

KH//318

®

KH/301 3

Specimen n°

KHhso

94

KH/3'11

KH//284

K./3~9

105

106

107

Figure 99-107 - Morphologic variation within the M 2 of K /nd/cus sahntt ssp. nov. Specimens, KH/311, 318, 326-327, 338-339 and 343c a r e right molars.Variations morpholog~uas des M2 de K. tndicus sahnii nov.ssp. Los spdcimans KH/311, 318, 326, 327, 338, 339 et 343v sont des molairos drottes inversdos.

1.48 and 1.08 mm respectively (Figs. 87, 89). The maximum crown height measured in the analysed molars is 2.00 mm~ Measurements are given in table 9. The broad confluency between T1 and T2 in the juvenile M3s is narrowed in the adults mainly because of the anteriorly bending synclines. The anterior edge, somewhat pointed in unworn molars becomes almost fiat in the seniles. All the lower molars are two rooted with the anterior root bigger, and in M 1 somewhat elongated in the anteroposterior direction. d e n t i t i o n - M 1 : The M 1 possesses an anterior loop and four alternating triangles which are well separated due to curved re-entrant valleys. The deep labial synclines are more strongly bend posteriorly than the shallow lingual synclines and none o f the synclines are filled with the crown cementum. The enamel is uniformly distributed on the chewing surface. The weakly developed LS3 allows the posterior tip somewhat pointed. The enamel opens together on both sides of the anterior loop, the posterior edge and the tip of LA2 at crown height of 2. 12 mm (Fig. 95). For measurements, see table 10. The wider communication between AL and T1, and T2 and T3 in the young specimens is interrupted in the seniles due to the strong bending of the Upper

792 Specimen n°

Tooth type

Length

Width

Crown height

g R L L R R R R R R R R L L L R R R R R R R R R R R L

1.84 1.92 1.88 1.88 1.88 2.00 1.92 1.80 1.68 1.92 1.88 1.88 1.88 t.88 1.76 1.76 1.76 1.80 1.80 1.80 1.80 1.80 1.80 1.80 1.80 1.84 1.88

1.04 1.16 1. I2 l. 16 t. 16 t.28 1.20 I. 16 0.92 1.20 1.t6 1.16 1.16 1.16 1.24 1.12 1.12 1.00 1.00 1.08 1.08 1.12 1.12 t.20 1..20 1..1.2 1.04

3.72 3.68 3.08 2.68 1.76 1.52 1.48 0.96 0.52 1.76 0.80 1.20 1.72 3.08 0.76 1.92 1.44 3.52 3.40 2.20 3.20 3.52 ..... 2.76 3.28 1..72 1.80

326 343c 349 350 338 311 339 327 318 340 319 335 346 347 355 337 343d 321 343b 328 329 314 341 315 331. 343a 364

synclines. The incipient development of LS3 remains persistent but the pointed tip of the posterior edge in the juveniles becomes slightly rounded in the adults and almost fiat in the seniles. M 2 : It has a lingually wider anterior loop and three alternating triangles, T2 and T3 somewhat confluent. The labial synclines are deeper than the prominent lingual syncline (LS2) and the LS3 is weakly developed. The posterior edge i~ rounded to flat. The linea sinuosa rises together on the anterolabial area and the posterior edge whenever the crown height exceeds 1.52 mm (Fig. 104). The enamel is further interrupted at the tips of LA2 and LA3 at the crown heights of 1.48 and 0.96 mm respectively (Figs. 105-106) and at BA2 and almost throughout the posterior loop at a crown height of 0.52 mm (Fig. 107). The length/width measurements are shown in table 11. The wide re-entrant folds in the unworn M 2 become strongly curved in the worn specimens interrupting the confluency between T2 and T3. The loss of the incipient LS3 is observed only in the completely worn individuals. M 3 : It has a variable anterior loop, two prominent synclines on each side and an elongated posterior loop. The labial synclines (BS1 and BS2) are shallower than the LS2 but more prominent than LS3. Incipient BS3 is present throughout the wear. The anterior and posterior islets are formed by BS1 and LS3 respectively, the posterior being formed earlier than the anterior at a

Mean 1.83 (N = 27) - Mean 1.13 (N = 27). Table 11 - Measurements (in ram) of M 2 of g tnd~us salmtt nov.

KH/387

KH//401

KH/379

108

KH/412

109

KH/413

KH/385

110

KH//382

KH/386

111

112

KH/378

I

KHf405

2ram

Figure 108-117 - Mo~hologic variation within the M of K imlteus saln~i nov. ssp. Specimens KH/378-379, 382 and 385 -387 are right molars. Variations morphologiques des M3 de K tndicus sahntt nov. asp. Lea spdcimens KH/378, 379, 382 et 385-387 sent des molatras droitas invers~es.

I

793

Specimen n° 405 379 401

387 385 386 412 413 382 378 389 414 4t5

404

Tooth type

Length

Width

Crown height

L R L R R R L L R R R

1.88 1.48 1.60 1.64 1.56 1.44 1.76 L.60 1.68 t.76 1.52

1.08 0.92 0.92 1.00 0.96 0.96 0.96 0.84 0.96 1.08 t.00

L

1,68

0.84

1.00

L L

1.68 1.76

0.84 1.04

2.00 2.56

0.60 3.12 2.80 2.32 2.12 2.04 1.76 1.72 0.96 0.80 0.56

Mean 1.64 (N = 14)- Mean0.95 (N = 14). Table

12 - Measurements (in mm) of M 3 g indlcus saftbli nov. ssp.

crown height of 3.12 mr, (Fig. 108). The anterior islet is formed at crown height of 2. 80 mm (Fig. 109) and is disappeared at the crown height of 2.04 mm (Fig. 112). The posterior islet remains for little longer duration and disappears at a crown height of 1.72 ,,,,- (Fig. 114). The enamel gets interrupted firstly at the anterolabial area and then on the posterior loop at the crown heights of 0.96 and 0.80 ram respectively (Figs. 115-116). It is finally interrupted on the anterolin,~mml area at a crown height of 0.60 ram (Fig. 117). S e e table 12 for measurements. It has a few striking morphological changes from the juvenile to senile molars. In young specimens before the formation of the enamel islets, BS1 is deeper allowing the narrow communication between the anterior loop and T2. Although none of the collected juvenile molars are without posterior islet, it is expected that before the formation of the posterior islet, deeper LS3 leaves very narrow communication between T3 and the posterior loop. Once the islets are formed, BS1 and LS3 start shallowing and this character of the adults together with deepenir~g of LS2 and BS2 separates the anterior and posterior parts of molars. This junction has been termed as metacon-talon complex by Rabeder (1981). The metacon-talon complex becomes somewhat wider in the senile teeth to allow better communication between T2 and T3. Very strangely, the LS3 becomes somewhat prominent to allow the posterior loop become elongated. The BS3 always remains incipient. Among the upper molars, the M 1 is three rooted and all others are two rooted. The molars axe without the crown cementum in the synclines and nor do they show enamel differentiation on the occlusal surface.

ASPECTS

OF MOLAR

EVOLUTION

Various characters as well as the evolutionary line of Family Arvicolidae have been described at length by many workers suggesting the "primitive (generalised)" and "advanced (derived)" characters. In order to give a better appreciation, of the facts about Kilarcola, the mosaic of the primitive and derived characters to be seen in the arvicolids is briefly summarised. Chewing surface - The smaller chewing surface of the molars (Carls & Rabeder 1988), confluency of the dentinal spaces (H_inton 1926 ; Kotlia & Koenigswald 1992), absence of the crown cementum in the synclines (Hinton 1926 ; Fejfar 1964 ; Fejfar & Heinrich 1983, 1990 ; Repennlng & Fejfar 1977 ; Martin 1989 ; Chaline 1987 ; Chaline & Laurin 1986), shallow LS3 in M1 (Carts & Rabeder 1988), and the uniform thickness of enamel band on the chewing surface (H.inton 1926 ; Fejfar 1964 ; Fejfar & Heimich 1983, 1990 ; Repenniug & Fejfar 1977 ; Kotlia & Koenigswald 1992) are the characters considered as more primitive. Size - The longer and broader molars are more advanced (Martin 1979 ; Chaline 1987 ; Koflia & Koenigswald

1992).

i s l e t - The primitive M i m o m y s in M1 and M 3 has the enamel islet which disappears very late in the worn specimens (van de Weerd 1979 ; Zheng & Li 1986). The presence of enamel islet only in the juveniles and slightly worn molars and their total disappearance from the occlusal surface during the evolutionary process are considered as advanced characters (Janossy & van der Meulen 1975 ; Repenning & Fejfar 1977 ; Fejfar & Heinrich 1983 ; Challne 1987). Enamel

Sinuous line - The higher dentine tracts or the higher values of H H and PA indices in linea sinuosa represent the increase in hypsodonty and are observed in more advanced arvicolids (Chaline 1987 ; Rabeder 1981 ; Caris & Rabeder 1988 ; Fe]far & Heinrich 19~.0 ; Kotlia & Koenigswald 1992). Sehmelzmuster - The radial enamel is the least derived enamel (Koenigswald 1980). The presence of lamellar enamel in the anticlines as well as in the leading edges is an advanced character (Koenigswald 1982 ; Kotlia & Koenigswald 1992). - Reduction in roots is an advanced character (Repenning & Fejfar 1977 ; Challne 1987 ; Fejfar & Heinrich 1990). Root

It is now evident that the progressive morphological changes, commonly called as phyletic gradualism occur very often in the avricolids. Based on the general characters on the oeclusal surface, European M i m o m y s

794 K. I n d i c u s 3"0-

K. i n d l c u s

3"2

sahnii

K. indicus

ssp, nov.

indicus

K.

SQhn; i

SSp. nov.

3.0 E

M1

E

E

o E

2-5 M1

o 2"5

~ 2.o

o

M2 M2

.E

~2.0

.E

2 -J

1.5

M3

M2 1.0

.

.

.

.

,

0"5 M3 . . . .

, . . . . 0"5

i . . . . 1'0

, . . . . 1'5

.

.

.

.

,

1'0

.

.

.

.

,

.

.

.

1-5 PA Index

, . . . . 2"0

, • 2"5

.

.

•

, 3'0

.

,

2"0

.

.

.

.

.

.

2'5

.

.

.

,

.

.

3'0

(rn rn)

•

HH Index(ram)

Figure 118 - Sinugrams (lower molars) of/l: tnd/vus and g: tndlcus sa/mtt nov. ssp. Note the identical HH index values in M2 of both forms. Dispersion des rnolatr~ infdriaures de K. tndlcu$ et de K. tndtcus sahnit nov.~p. ~ fonction de la longueur at de l'indice HtL. On remarquera que les daux formas prdsentant las m~rae$ valeurs do l'imltce HIt pour la M2.

Figure 119 - Sinugrams (upper molars) of £ tmllcus and K2 tnd/aus saimtt nov. ssp. Note the identical PA index values in M of both forms. Dispersion des molaires ~ r e s de 16 t u d ~ et da K. t m l ~ salmii nov.ss# en fonaion do la longueur at de l'indtce PA. On remarquera qua les daux fonnes prdsantant los m~nas valeurs de l'indica PApour la M2.

is very well documented from M. occitanus to Arvicola sapidus showing the major stages of progressive development of evolutionary trends (Chaline 1987 ; Chaline & Laurin 1986 ; Fejfar & Heinrich 1990). The progressive evolutionary characters are confirmed by studying the development of sinuous line (Rabeder 1981; Cads & Rabeder 1988 ; Kotlia & Koenigswald 1992) as well as the Schmelzmuster (Koenigswald 1980, 1982 ; Koflia & Koenigswald 1992).

The Sclmaelzmuster pattern of /~ indicus (Kotlia & Koenigswald 1992 ; Fig. 120 of this text) has a very close similarity with that of/~ indicus sahnii nov. ssp. (Fig. 121). In both the forms, the leading edge of the triangles is composed mainly of radial enamel and the trailing edge consists of the radial and tangential enamel. The discrete lamellar enamel is present on the apices of the anticlines extending for a little into the leading edge within the radial enamel (Figs. 120-121). This type of simply constructed enamel pattern has been termed as isoknem enamel type (Carls & Rabeder 1988) and we consider it the primitive Schmelzmuster particularly when compared to the similar aged Mimomys (for example M. polonicus) which has highly advanced Schmelzmuster with well developed lamellar enamel throughout the leading edge as shown by Koenigswald (1980, 1982), Koenigswald & Martin (1984) and Kotlia & Koenigswald (1992).

RESULTS AND DISCUSSION The detailed comparison of dental and sinumetric characters of lOlarcola with similar aged European, S~erian and North American arvicolids has been made by Kotlia & Koenlgswald (1992) who conclude that the Indian I¢2larcola is much more primitive than the Mirnornys and its most sub-genera at about 2.5 Ma ago. Similarly, the Chinese arvicolids (for example Mimomys peii) of this age (Zheng & Li 1986, 1990) should be considered as more advanced than K. indicus. K. indicus and K. indicus sahnii nov. ssp. share nearly all characters on the occlusal surface excepting two comparatively evolved characters in the latter ; bigger size and the enamel islet disappearing earlier. The increase in hypsodonty is observed from/~ indicus to K~ indicus sahnii nm;. ssp. The higher dentine tracts result in the higher values of HI-/index in the lower molars (Fig. 118) and of PA index in the upper molars (Fig. 119). The increase in hypsodonty is normally reflected in the first and last molars. On the contrary, the similar values of the indices in the second molars in both the forms may explain the lesser use of second molars in the evolutionary process of the chewing system.

Cswia, originally described by Kretzoi (1959) and Kowalski (1960) of the Late Pliocene age with many primitive characters is undoubtedly derived from Mimornys (M. davakosi) of the Lower Pliocene age (van de Weerd 1979) and seems to be as primitive as M. occitanus of the Ruscinian age. M. occitanus zone is considered as the first arvicolid radiation in Europe and the sudden appearance of many arvicolids at this time is probably due to the climatic changes which might have been responsible for arvicolid migration into Europe (Fejfar & Heinrich 1990). Following Kotlia & Koenigswald (1992), we are of the opinion that European Cseria migrated to southwest Asia prior to 2.4 Ma in form of IQlarcola which retained the primitive characters. /d indicus underwent endemic evolution in the Ka~hmlr

795 Figure 120 Schmelzmnster pattern in /~ ind/ct~ (R. radial enamel, T = tangential enamel, L = lamellar enamel, D = dentine). Disposition des prlsmes d'draail (Schradzrauster) an tma ocdusat, da IC ~ndtcux (R = n a i l radial, T = Iraaa tang~nt, l~ L = lameUatre, D = danttna).

Figure 121 Schmelzmnster pattern in K. inducus sabnti nov. ssp. Abbreviations as in fig. 120. Disposition das prtmnes d'~mail (Sdrmd~uster) en rue ~dusale (m~mes abbreviations que pour la fig. 120).

Himalayas a n d gave rise to K~ k a s h m i r i e n s i s at about 1.6 M a ago with comparatively m o r e a d v a n c e d characters (Kotlia & Koenigswald 1992). Acknowledgements - A part of this work was carried out in the Institute 9 f Paleontology, University of Bonn, Germany by BSK who received the financial support from the Alexander yon Humboldt stiftung as Post-Doctoral Fellow. We are highly thankful to the Department of Science and Technology and University Grants Commission, New Delhi, and the Department of Geology, Kumaun University, Nainital for the financial assistance during the later part-of the work. This paper was presented during the XIII INQUA Congress (1991) at Beijing, China by BSK who had with Prof. E.H. Lindsay, Arizona (U.S.A.), Prof. W.v. Koenigswald, Bonn (Germany), Prof. J. Chaline, Dijon (France) and Prof. M.A. Erbajeva, Ulan-Ude (U.S.S.R.) a lengthy and profitable discussion which helped improving the text of this paper. We also thank Prof. A. Sahni, (=AS in Geology, Chandigarh for reviewing the manuscript.

REFERENCES AGRAWAL D.P., DODIA R., KOTHA B.S., RAZDAN H. & SAHNI A. 1989 - T h e Plio-Pleistocene geologic a n d climatic r e c o r d of the K a s h m i r valley, I n d i a : A review a n d new data. P a l a e o g e o g r . P a l a e o c l i m a t o l . P a l a e o e c o L , 73 : 267-286. BURBANK D . W . & JOHNSON G.D. 1982 - I n t e r m o n t a n e basin d e v e l o p m e n t in the past 4Myr in the northwest Himalaya. N a t u r e , 298 : 432-436. BURBANK D . W . & JOHNSON G.D. 1983 - T h e L a t e Cenozoic chronologic a n d stratigraphic d e v e l o p m e n t of the Kashmir i n t e r m o n t a n e basin, northwestern Himalaya. P a l a e o g e o g r . P a l a e o c l i m a t o l . P a l a e o e c o L , 43 : 205-235. CARLS N. & RABEDER G. 1988 - Arvicolids (Rodentia, M a m m a l i a ) from the Earliest Pleistocene of

796 Schernfeld (Bavaria). Beitr. Palaont. Osterr., 14 : 123-237. CI-IALINE J. 1972 - Les rongeurs du P16istoc~ne moyen et sup6rieur de France. Cahiers Pal~ont. CNRS. :

1-410. CHAI_INE J. 1987 - Arvicolid data (Arvicolidae, Rodentia) and evolutionary concepts. Evolutionary Biology, 21 : 237-310. CHAL/NE J. & LAURIN B. 1986 - Phyletic gradualism in a European Plio-Pleistocene Mimomys lineage (Arvieolidae, Rodentia). Palaeobiol., 12, 2 : 203-216. FEJFAR O. 1964 - The Lower Villafrancbian vertebrates from Hajnacka near Filakovo in southern Slovakia. Rozpr. Ustr. Ust. Geol., 30 : 1-115. FEJFAR O. & HEINRICH W.O. 1983 - Arvicoliden Sukzession und Biostratigraphic des OberplioT~n.q und Quartfirs in Europa. Schriflenr. Geol. Wiss., 19/20 : 61-109. FFAFAR O. & HEINRICH W.D. 1990 - Muroid rodent bioehronology of the Neogene and Quaternary in Europe. In LINDSAY E.H., FAHLBUSCH V. & MEIN P. (eds.) : European Mammal Chronology. NATO ASI series A, 180 : 91-117. HINTON M.A.C. 1926 - Monograph of the voles and lemmings (Microtinae) : Living and Extinct. British Museum (Natural History), 1 : 1-488. JANOSSY D. & van der MEULEN A.I. 1975 - On Mimomys (Rodentia) from Ostramos-3, North Hungary. Kon. Ned. Akad. Westensch. Proc. B, 78, 5 : 381-391. KOENIGSWALD W.v. 1977 - Mimomys cf. reidi ans der villafranchischen Spaltenfullung schambaeh bei Treuchtlingn. M/it. Bayer. StaatssammL Palaont. Hist. GeoL, 17 : 197-212. KOENIGSWAI_J) W.v. 1980 - Schmelzstruktur und Morphologie in den Molaren der Arvicolidae (Rodentia). Abh. senckenberg. Natur forsch. Ges., 539 : 1-129. KOENIGSWALD W.v. 1982 - Enamel structure in molars of Arvieofidae (Rodentia) : a key to functional morphology and phylogeny. In KURTEN B. (ed.) : Teeth, Function and Evolution. Columbia Univ. Press : 109122. KOENIGSWALD W.v. & MARTIN L.D. 1984 - The status of the genus Mimomys (Arvieolidae, Rodentia, Maremafia) in North America. N. .lb. Geol. PaRiont. Abh., 168 : 108-124. K ~ B.S. 1985 - Quaternary rodent fauna of the Kashmir Valley ; Systematic, biochronology and palaeoecology, loum. Palaeont. Soc. India, 30 : 81-91. K o ' I I ~ B.S. 1991 - Pliocene soricidae (Insectivora, Mammafia) from Kashmir intermontane basin, northwestern Himalaya. Journ. Geol. Soc. ,'ndia, 39 : 453476. KOTLIA B.S. 1992 Pliocene murids (Rodentia, Mammalia) from Kashmir basin, Northwestern India. N. Jb. Geol. Paliiont. Abh., 184, 3 : 339-357. KOTLIA B.S. & KOENIGSWALD W.v. 1991 - Plio-Pleistocene arvicolids (Rodentia, Mamrnalia) from Kashmir Intermontane basin, Northwestern India. Palaeontographica, Abt A., 223 : 103-135.

KOWALSKI K. 1960 Cricetidae and Microtidae (Rodentia) from the Pliocene of Weze (Poland). Acta. Zool. Cracov, 5, 11 : 447-505. KREFZOI M. 1959 - Insectivoren, Nagetiere und Lagomorphen der Jungstpfiozanen Fauna von Csarnota im villanyer Gebirge (Sudungarn). Vertebr. Hungarica, 1, 2 : 237-246. KUSUMGAR S. 1980 - Geochronology and palaeoefimatic events on the Late Cenozoic periods in the Kashmir Valley. (Unpub.) P h . D . Thesis, Bombay Univ. : 1-191. KUSUMGAR S., KOTLtA B.S., AGRAWAL D.P. & SAHNI A. 1986 - Biochronologie des fossiles de vert6br6s des formations des Karewas du Cachemire, Inde. L~'lnthropologie, 90, 2 : 151-164. MARTIN L.D. 1979 - The biostratigraphy of Arvicoline rodents in North America. Trans. Nebraska Acad. Sci. Lincoln, 7 : 91-100. MARTIN L.D. 1987 - t/rio-Pleistocene rodents in North America. In BLACK C.C. & DAWSON M.R. (eds.), 33: 47-58. Van Der MEULEN A.J. 1973 - Middle Pleistocene smaller mammals from the Monte Peglia (Orvieto, Italy) with special reference to the phylogeny of Microms (Arvieolidae, Rodentia). Quatemaria, 17 : 1-144. RABEDER G. 1981 - Die Arvicoliden (Rodentia, Maremafia) aus dem Pliozan und dem alteren Pleistozan yon Niederosterreich. Beitr. palaont. Osterr., 8 : 1-373. REPENNING C.A. 1983 - Quaternary rodent biochronology and its correlation with climatic and magnetic stratigraphies. In MAHANEY W.C. (ed.) ; Correlation of Quaternary Chronologies. Geo Books, Norwich : 105-118. REPENNING C.A. 1985 - Pleistocene mammalian faunas; Climate and Evolution. Acta zool. Fennica, 170 : 173-176. REPENNING C.A. & FFAFARO. 1977 - Holarctic correlations of microtid rodents. In SIBRAVA V. (ed.) : Quaternary Glaciations in the Northern Hemisphere. IUGS Internat. Geol. Corr. Progr. Project 73/1/24, Rep. 4, Ustr. Ust. Geol. : 234-250. REPENNINO C.A., FEJFAR O. & HEINRICH W.D. 1990 Arvicolid rodent biochronology of the Northern Hemisphere. Int. Symp. Evol. Phil. Biostr. Arvicolids Praha, Pfeil-Verlag : 385-418. SAHNI A. & KOTL~ B.S. 1985 - Karewa mierovertebrates : biostratigraphical and palaeoecological implications. Current Trend. Geol., 6 : 27-42. WEERD A. van de 1979 - Early Ruscinian rodents and lagomorphs (Mammafia) from the lignites near Ptolemais (Macedonia,Greece). Kon. Ned. Akad. Wetensch. Proc. Ser. ,B, 82, 2 : 155-162. ZHENG S. & LI C. 1986 - Review of Chinese Mimomys (Arvicolidae,Rodentia). Vertebrata Palasiatica, 24, 2 : 81-109. ZHENO S. & LI C. 1990 - Comments on fossil arvicolids of China. Int. Syrup. Evol. Phil. Biostr. Arvicolids, Praha, Pfeil-Verlag : 431-442.