Late Pliocene-Early Pleistocene Microvertebrates ... - ProQuest Search

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Earth Science India, eISSN: 0974 – 8350 Vol. 4(III), July, 2011, pp. 143-158 http://www.earthscienceindia.info/

? Late Pliocene-Early Pleistocene Microvertebrates from the Upper Siwalik Subgroup of Jammu, Jammu and Kashmir, India Som Nath Kundal1 and G.V.R. Prasad2 1

Department of Geology, CAS, Banaras Hindu University, Varanasi-221005 2 Department of Geology, University of Delhi, Delhi-110007 E.mail: [email protected]

Abstract Microvertebrate remains comprising isolated fish teeth and spines, lacertilian dentaries, unidentified mammalian claws and phalanges and a couple of astragali referable to Rattus (Rodentia) are being described for the first time from the mudstone horizon immediately underlying the geochronologically dated (2.48 m.y., Late Pliocene-Early Pleistocene) bentonitized tuff band of the Nagrota Formation (=Pinjore Formation, Upper Siwalik Subgroup) at Barakhetar, Khanpur, Anandpur and Uttarbehani localities, Jammu province, India. The age and palaeoecology of the recoverd fauna has also been discussed in the present paper. Key words: Late Pliocene-Early Pleistocene, Microvertebrates, Nagrota Formation, Upper Siwalik Subgroup, Jammu, India

Introduction Geological succession in the southernmost part of the Himalaya were deposited in the Himalayan Foreland basin. These foreland successions comprise the Subathu Group (Late Paleocene to Middle Eocene), the Murree Group (?Late Oligocene to Early Miocene) and the Siwalik Group (Miocene to Late Pleistocene), in ascending order. The ~7km thick Siwalik rocks are exposed all along the Sub-Himalaya. The Siwalik succession is known in the world mainly for the mega vertebrates and is also called as storehouse of vertebrate fossils. Much work has been carried out on Siwalik megavertebrates in the past as compared to microvertebrates in different parts of India, Nepal and Pakistan. Some of the most significant works carried out on the Siwalik microvertebrates are by Black, 1972; Dutta, 1975; Chopra and Jacobs, 1978; Vasishat, 1979; Flynn, 1982; Flynn et al., 1985, 1986; Gaur, 1986; Flynn et al., 1990; Barry and Flynn, 1990; Patnaik, 1990, 1995; Kotlia, 1996; Patnaik and Sahni, 1996; Patnaik et al., 1996; Patnaik, 1997; Patnaik, 1997; Patnaik and Schleich, 1997, 1998; Patnaik, 2001, 2002; Mathur and Kotlia, 2002; Cheema et al., 2003; Kotlia and Samwal, 2004; Kotlia, 2008; Sehgal and Patnaik, 2011). The microvertebrates known so far from the Upper Siwalik deposits of Jammu area were reported by Suneja and Kumar (1979), Suneja et al., (1980), Rage et al. (2001), Gupta and Prasad (2001) and Prasad et al., (2005). Suneja and Kumar (1979) discovered microfossil

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yielding horizons within the Upper Siwalik sequence of Jammu. The faunal remains reported by them mainly comprised reptiles and fishes. The repitlian fauna was represented by over a dozen conical spike-like teeth of Crocodilia. The fish remains consisted of teeth, numerous vertebrae, pectorl spines, and supra-occipital parts. Suneja et al. (1980) reported fish remains with other microfossils from a site near village Khanpur in Jammu district, but did not describe these findings. Rage et al. (2001) described the first amphibians and some colubroid snakes from the Siwaliks beds of Jammu. Amphibians were represented by anurans, a possible ranid, and some non-ranid frogs, squamates by the lone lizard, Varanus sp. and snakes by three taxa: Acrochordus dehmi (Acrochordidade), an indeterminate colubridae, and another colubrid or an elapid. Varanus sp. and A. dehmi were recovered from the Upper Miocene Ramnagar Member, whereas the anurans and colubroid snakes came from the Upper Pliocene Labli Member. Recently, Gupta and Prasad (2001) described micromammals from two levels in the Labli Member (Uttarbehani Formation of Gupta and Verma, 1998) lying 910 m and 760 m below a geochronologically dated bentonitized tuff band. The micromammal fauna from the Labli Member is represented by cf. Mus flynni, cf. Parapelomys robertsi, Golunda kelleri, Golunda sp., Dilatomys pilgrim, Millardia sp. indet., Abudhabia cf. A. kabulense, Rhizomyides sivalensis and an insectivore Soricidae gen. et. sp. indet. More recently, Prasad et al., (2005) recovered a left mandibular fragment bearing M1-M3 of Golunda from the mudstones underlying a bentonitized tuff band exposed 0.375 km NW of Barakhetar village, Jammu. Following this, Bhandari and Kundal (2008) recovered sixteen species of ostracods from the same mudstone horizon exposed at Barakhetar. A detailed study on Stable Carbon Isotope analysis of pedogenic carbonates of two sections i.e. Purmandal-Uttarbehani and Jammu-Nandni has been carried out by Singh et al., (2011) and provides an important link to the extensive palaeovegetational studies done in the Pakistan and Nepal Siwaliks. The present collection of microvertebrates was recovered from a mudstone horizon lying just below the geochronologically dated (2.48 my) bentonitized tuff band exposed at Barakhetar, Khanpur, Anandpur and Uttarbehani localities (Fig. 1). Stratigraphy A number of workers contributed to the general stratigraphy of the Siwalik Group both in India and Pakistan. These include Falconer (1868), Lydekkar (1883), Pilgrim (1910, 1913, 1934), Colbert (1935), Lewis (1937), Opdyke et al. (1979), Azzaroli and Napoleone (1982) and Johnson et al. (1982, 1985), among others (Table-1). The local stratigraphy of the Siwalik succession of Jammu region has been worked out by Ranga Rao et al. (1988), Gupta and Verma (1988), Agarwal (1993) and Gupta (1997, 2000). Ranga Rao et al. (1979) gave a stratigraphic classification for the Jammu Siwaliks on the basis of heavy minerals, lithology and palaeontology. They divided the Siwalik Group into the Lower Siwalik (argillaceous unit, arneaous unit), Middle Siwalik (sandstone dominant unit, alteration of sandstone and clay unit and pebbly sandstone unit) and the Upper Siwalik (Purmandal Sandstone, Nagrota Formation and Boulder Conglomerate). Ranga Rao et al. (1988, 1993) studied three sections of the Upper Siwalik Subgroup of Jammu region i.e., Purmandal – Uttarbehani, Jammu-Nagrota, Balli, and some sections of the Upper and Middle Siwalik 144



Subgroups exposed in Samba – Mansar area in detail. Ranga Rao et al. (1988) redesignated Tawi Conglomerate as Boulder Conglomerate retaining the other two formational names of Ranga Rao et al. (1979). They marked the Gauss–Matuyama boundary at 2.48 m.y. on the basis of correlation with the magnetic polarity time scale. They suggested that the Upper Siwalik Subgroup ranges in age from 4.92 to 0.42 m.y. in Purmandal–Uttarbehani section with the Purmandal Sandstone from 4.92 to 3.90 m.y. and and the Nagrota Formation from 3.90 to 0.6 m.y. The formational boundaries (between Purmandal and Nagrota) of Samba–Mansar, Jabarkhad near Nurpur and Patialio Rao areas were considered diachronous based on magnetic polarity (Ranga Rao, 1993). Agarwal (1993) classified the Nagrota Formation of Ranga Rao et al. (1988) into three members viz., NA, NB, and NC on the basis of lithological characters and remote sensing spectral analysis. Gupta and Verma (1988) suggested a new lithostratigraphic classification for the Siwalik succession of Jammu region and provided a checklist of fauna recovered from these lithounits. According to this classification, the Siwalik sequence of Jammu is divisible into the following formations in ascending order: Mansar Formation (Lower Siwalik); Dewal Formation (Middle Siwalik); Mohargarh Formation (Middle Siwalik); Uttarbehani Formation, and Dughor Formation (Upper Siwalik). Gupta (1997) further classified the Mansar Formation into the lower Dodenal Member consisting of an arenaceous dominant facies and an upper Ramnagar Member representing claystone, siltstone and sandstone alternations, and the Uttarbehani Formation into Labli Member and Marikhui Member. The present collection is from the NB Member of the formation.

Fig.1: A. Range of Siwalik hills (Pakistan, India and Nepal); B.Stratigraphic sub-divisions of Jammu Siwalik showing microvertebrate yielding sites. 145



Table-1: Classification and correlation of Siwalik in Indian Sub-continent.

Methods and Material Samples were collected from a mudstone horizon of the Nagrota Formation (NB Member) immediately underlying the geochronologically dated bentonitized tuff band (2.48 m.y.) exposed around Barakhetar (100Kg), Uttarbehani (100kg), Khanpur (75kg) and Anandpur (100kg) areas of Jammu region for microvertebrate recovery. The soft samples were screenwashed with different sets of sieves after immersing in water for an hour or so. Most of the microvertebrates were collected using 60 mesh (ASTM) sieves. Harder mudstone samples were screen-washed using kerosene-water method. In this method, the samples are dried in sunlight or in an oven to remove the moisture and then soaked in kerosene for 3 to 4 hours. The kerosene is then decanted and the samples are kept immeresed in water for an hour. Because of the differences in the specific gravity of water and oil, water forces its way into the samples by expelling kerosene out resulting in the breakdown of samples into slurry which is then screenwashed in running water. The screen-washed residue so obtained then dried and sorted under the microscope for microfossils. Employing these techniques more than fifty specimens of fish teeth and spines, two of lacertilian, one Incerate sedis, two mammalian claw and several mammalian phalanges along with a good assemblage of ostracodes and charophytes was recovered. The microfossils so obtained were cleaned for photomicrography. The specimens described in this paper are deposited in the Vertebrate Palaeontological Laboratory (VPL), Department of 146



Geology, Centre of Advanced Study, Banaras Hindu Universty, Varanasi under catalogue numbers BHU/GEOL/VPL/MV/ Systematic Palaeontology Class Osteichthyes Infraclass Teleostei Subclass Actinopterygii Superorder Ostariophysi Sagemehl, 1885 Order Cypriniformes Bleeker, 1859/60 Family Cyprinidae Bonaparte, 1840 Gen. et sp. indet. (Plate 1, Fig.s 1a-c, 5; 2a-c, 4a-b; 3a-c,) Referred Material: BHU/GEOL/VPL/MV/100-103, 113; 23 isolated Cyprinid teeth, BHU/GEOL/VPL/MV/104-106, 110-111; 12 isolated Cyprinid teeth, BHU/GEOL/VPL/MV/107-109; 18 isolated Cyprinid teeth, Morphptype III

Morphotype I Morphotype II

Locality: One km northwest of Khanpur villages, 0.4km North of Barakhetar village, 0.5 km north of Uttarbehani across the River Devak, Jammu District, Jammu and Kashmir. Stratigraphic Horizon: Mudstone immediately underlying the Upper Siwalik bentonitized tuff band of the Nagrota Formation, Upper Siwalik Subgroup. Descrption: About fifty isolated pharyngeal teeth are described here as three morphotypes differentiated on the basis of morphology. Morphotype I: Teeth have swollen base and a subglobular outline. The crown terminates distally in a short, conical hook. The masticatory area below the terminal hook is slightly depressed and corrugated. Morphotype II: These teeth have less elongated and laterally flattened crowns, which terminate distally in relatively less developed hook. Below the terminal cusp, occurs a depressed masticatory area bounded on either side by small worn cusplets. Morphotype III: These teeth are broader than teeth of morphotype I and II. The crowns are anteroposteriorly compressed and terminate distally in a short and blunt hook. In worn teeth, this terminal hook is nearly flattened. The masticatory area is neither depressed nor corrugated. In these teeth, the crown is bounded on either side by elongated crests enclosing a central shallow depression.

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Morphotype I teeth may be from the anterior part of the principal series, morphotype II from the median or lateral series, and morphotype III from the posterior part of the principal series. Remarks: Isolated cyprinid teeth have been reported from many Miocene and Pliocene deposits of Europe and Asia. Scardinius, Tinca, Rutilus, Palaeoleuciscus, Tarsichthys, Palaeocarassius and Barbus are some of the reported fossil taxa (Nakajima, 1985; Gaudant, 1989, 1994, 1997, 2000; Nakajima et al., 2001; Gaudant et al., 2002). The present teeth differ from the pharyngeal teeth of Scardinius and Palaeoleuciscus in masticatory area, which is long and narrow and bounded anteriorly by a crest with 5 to 6 coarse tubercles in the latter forms. In Tinca, on the other hand, the masticatory area is triangular in shape compared to present teeth. Rutilus has massive, stocky teeth with reduced terminal hook and without a distint masticatory area. In overall crown morphology, the Upper Siwalik cyprinid teeth are closely camparable to teeth described as Cyprinidae gen. et sp. indet. from the Ladakh Molasse (Singh, 2004), and to those of Tarsichthys, Palaeocarassius and Barbus. However, in specific development of masticatory area below the terminal hook and the masticatory groove, the Upper Siwalik teeth differ from the latter three taxa. The present teeth differ from those known from the Ladakh Molasse in the absence of a central crest between the two marginal crests of the masticatory area is probable that the Siwalik cyprinid teeth may represent a new taxon, but the absence of complete dentition does not permit designation of a new taxon at this stage. Class Reptilia Order Squamata Suborder Lacertilia Own, 1842 Lacertilia indet. (Plate 1, Fig. 13a-b) Referred Material: BHU/GEOL/VPL/MV/121-122, fragmentary dentaries. Locality: 0.6 km northwest of Anandpur village, Jammu District, Jammu and Kashmir. Stratigraphic Position: Mudstone horizon immediately underlying the bentonitized tuff band of the Nagrota Formation. Description: The dentary is 1.36 mm long fragile and poorly preserved with broken ventral. The labial side is smooth, slightly convex, and bears no mental foramen. The lingual surface bears five closely spaced teeth and three sockets of pleurodont nature. The teeth are cylindrical or tubular in outline with open spherical crown apices. There are no cusps on the crowns. The teeth project 1/3rd of their length beyond the parapet of dentary, which is in a straight line. The dental ridge is broken so the dental gutter is indistinct. Remarks: Fragmentary nature of the dentary does not allow its identification beyond the subordinal level.

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Reptilia Incertae sedis (Plate 1, Fig. 15) Referred Material: BHU/GEOL/VPL/MV/124, a poorly preserved maxillary fragment. Locality: 0.6 km northwest of Anandpur village, Jammu District, Jammu and Kashmir state, India. Stratigraphic postion: Mudstone horizon immediately underlying the bentonitized tuff band of the Nagrota Formation. Description: The maxillary fragment has a swollen tooth-bearing surface with three acrodont teeth and two sockets. The bases of teeth are implanted in a rim at the top of the jaw projecting slightly above it. The labial side of the maxilla is concave, whereas the lingual surface is convex. Lingually, the base of the maxilla is produced into a thin flange. Remarks: Due to the fragmentary nature of material no definite taxonomic assignment is possible. Class Mammalia Order Rodentia Bowdich, 1821 Family Muridae Gray, 1821 Subfamily Murinae Genus Rattus Fischer, 1803 cf. Rattus sp. (Plate 1, Fig. 18a-18b) Referred Material: BHU/GEOL/VPL/MV/129-130, right and left astragali Locality: One km northwest of Khanpur village, Jammu District, Jammu and Kashmir state, India. Stratigraphic Position: Mudstone horizon immediately underlying the bentonitized tuff band of the Nagrota Formation. Description: The astragali have short, broad, and deep tibial trochlea, and sharp and high trochlear crests. The neck is oriented obliquely to the trochlear head. The lateral trochlear crest is higher than the medial crest but both are parallel to each other. The medial face of trochlea slopes medioplantarly and is nearly vertical. The trochlear groove is sloping distomedially. The fibular facet of the astragalar body is laterodistally extended with a small distal shelf. There is no superior astragalar foramen, but a distinct astragalar canal is present in the interosseous sulcus on the plantar side. The calcaneoastragalar facet is concave, oriented obliquely to the long axis, transversely wider than long. The two lateral margins of this facet are in the form of convex ridges forming a deep groove between them. The large astragalar body is separated from the 149



astragalar head by a narrow and long neck, which is slightly medially bent in dorsal view. A “tear-shaped” sustentacular facet, located on the plantar surface of the neck, is oriented obliquely to the long axis of the neck and converges with medial facet of the astragalar body proximomedially. The sustentacular facet is separated from the lateral facet of the astragalar body by the interosseous sulcus and distally from the navicular facet of the astragalar head. It is raised relative to the surface of the neck. In the distal view, the astragalar head is oval in outline, higher laterally than medially and extends proximally half the length of the neck on the medial side. In the distal view, the head is relatively more developed on the lateral side than on the medial side. Remarks: The astragali resemble those of Rattus rattus (Szalay, 1985; fig. 9) and R. norvegicus in having a short and broad trochlear body with high lateral and low medial crests parallel to each other, long obliquely oriented neck, deep trochlear groove, obliquely oriented calcaneoastragalar facet, "tear-shaped" sustentacular facet merging proximally with the medial facet but distally separated from the astragalar head, laterally more developed astragalar head, and in lacking the superior astragalar foramen. However differ from R. norvegicus in the proximal extension of medial head and in the presence of a plantar astragalar foramen. In the absence of superior astragalar foramen and proximal extension of medial head, the present form is closer to R. rattus. Among the fossil taxa, Prodiacodon (Leptictidae: Leptictida) from the Torrejonian (Paleocene) of New Mexico (Szalay, 1966) compares very well with the present specimen. Both the taxa have deep tibial trochlea dorsally, fairly high and sharply defined lateral trochlear crest and equally sharp medial crest, the deepest point of trochlea on the medial side of the body, no superior astragalar foramen but a plantar astragalar foramen, concave, large, isosceles triangle-like calcaneoastragalar facet, “tear-shaped” sustentacular facet with a pointed proximal end, laterally broad astragalar head tapering in a medial and proximal direction. The close similarity of tarsal characters between the Paleocene leptictid and a rodent-like form is not unusual as early rodents are supposed to have been derived from a leptictid-like morphotype (Szalay, 1985). The present form is also comparable to Sciurus in having a vertical tibial facet, the lateral fibular facet slightly extending distolaterally, no superior astragalar foramen and presence of plantar astragalar foramen, astragalar body not extending on to the neck, concave and steeply inclined calcaneoastragalar facet. Sciurus differs from the present specimen in having a sustentacular facet confluent with medial tibial facet and joining the medial part of the head more than on the lateral side leaving no groove between itself and the astragalar head on the medial side, and convex and concave medial and lateral faces, respectively, in the distal view, Before arriving at a definitive conclusion on the affinity of present specimen to Rattus, comparison with the astragali of other murid rodents, such as Golunda, Millardia, Cremnomys etc. is necessary. In the absence of comparative fossil and recent material of these taxa, the present specimen is provisionally referred to Rattus. Earlier molars with affinity to Rattus have been recorded from the Pinjor Formation of Chandigarh (Gaur, 1986) and from the Early Pleistocene Siwalik sequence of Pabbi Hills, Pakistan (Jacobs, 1978). Musser (1987) transferred these molars to Hadromys. 150



Functional analysis of astragali: The high and sharp crests of astragalar trochlea sharply restrict all transverse movements at the upper ankle joint (UAJ). A short-grooved astragalar trochlea indicates that flexion (dorsiflexion) and extension (plantar flexion) were predominant movements at UAJ. Isolated sustentacular facet on the astragalus suggests that this facet on both the calcaneum and astragalus was closely bound together and little movement occurred through their articulation. Laterally enlarged head indicates that relatively more compressive force was transmitted through this side of astragalus. Therefore, some kind of eversion was possible in the foot. Extremes of plantar flexion was possible at the UAJ as evident from the absence of superior astragalar foramen coupled with increased transverse stability as suggested by the increased sharpness of the lateral border of tibial trochlea. In plantar flexion, when the tibia completely covers the astragalar foramen, the foramen becomes a restrictive factor. Mammals not requiring a complete plantar flexion bear a superior astragalar foramen. The astragalar foramen is generally traversed by blood vessels. But in mammals that require restrictive plantar flexion (where the tibia completely covers the astragalar trochlea during plantar flexion), the superior astragalar foramen may be closed off with terminal blood vessels branching from plantar astragalar foramen. On the whole, the tarsal morphology suggests mediolateral stability at the UAJ and limited eversion of the foot favouring adaptations to terrestrial uneven substrate. Palaeoecology and Age The present study was aimed primarily at delineating the microfossil-bearing horizon just above and below the bentonitized tuff band of the Nagrota Formation, which has been dated as 2.48 my. Several microfossil yielding horizons were identified during the course of the present work and a limited number of specimens have been recovered from the fossiliferous sites. A complete and clear picture of palaeoecology of the area will emerge only when a representative sample of the palaeocommunities is obtained by bulk screen-washing of samples from all microfossil yielding sites. Nevertheless, an outline of the palaeoecology of the studied Upper Siwalik sections can be provided based on the fauna recovered during the present work. Majority of the taxa recovered from the Upper Siwalik strata of the study area have living representatives or closely related forms in the living fauna. The fossil evidence for the palaeoecological inferences is also derived from ostracodes (Bhandari and Kundal, 2008) and charophytes (S.N. Kundal unpublished work), apart from fishes, lizards and rodents. Cyprinid fishes inhabit small rivulets, streams, ponds and in bodies of stagnant or sluggish muddy waters. But a few of them prefer clean water bodies with sandy substrate. Extant members of this family are known from streams and rivulets of the Himalayan region. Mathur and Kotlia (2002) reported cyprinid remains from the Surai Khola Formation of Nepal and referred them to Schizothorax, Labeo, Notropis and Oreinus. Palaeoecological reconstructions based on micromammal assemblages are quite reliable as mammals are found confined to beds of small lateral extent and deposited in a short period of time. Micromammals are very sensitive to climatic changes and usually have small home ranges, which make them very useful climatic indicators. Since most of the micromammals in the present collection resemble extant forms, the palaeoecological inferences are based on the principle of actualism. Murids (rats and mice) are considered to be among the most successful groups of living micromammals. They adapted 151



themselves to many ecological conditions and show marked species diversity. Rodents preserved usually with their skeletal remain close to the site of their intial accumulation; they have been used here for a better resolution for palaeoecological reconstruction. The living members of Rattus (R.meltada) and Golunda (G.ellioti) are known to live in crop fields, thickets and bushlands or densely vegetated plains. In fact, all terrestrial habitats, from houses and rice fields to marshy rain forest to edges of grasslands, are occupied by various species of Rattus. Presence of fish fauna, lizards and rodents indicate that both fresh water and terrestrial conditionms existed during the Pliocene-Pleistocene times. As far as age is concerned, the bentonitized tuff band exposed in the Upper Siwalik Subgroup, both in India and Pakistan, has been dated by various workers. Johnson et al. (1982) gave a detailed account of bentonite and fission track ages of the zircon phenocrysts in the Bentonite Tuff Band (BTB) and Tuffaceous Mudstone (TM) in the Siwalik Group of Jhelum, Campellpore and Chinji-Nagri areas in Pakistan. They demarcated the boundary between the Tatrot and Pinjor faunal zones at 2.48 Ma coincident with Gauss-Matuyama magnetozone (Table-1). The change from Tatrot fauna to the Pinjor fauna has been shown to occur at 2.47 Ma based on significant changes in the faunal composition characterised by the appearance of Equus and Elephas, and cervids with antlers near the top of the Gauss magnetic epoch. Azzaroli and Napoleon (1982) have also fixed Gauss magnetozone and the Tatrot-Pinjor boundary at the contact of Gauss-Matuyama magnetozone (2.48 Ma) near Pinjor in India. Yokoyama et al. (1987) and Mehta et al. (1993) suggested conflicting ages of 1.6+0.2 Ma and 1.59+0.32 Ma respectively for the BTB at Purmandal in Jammu (India). However, Ranga Rao et al. (1988) constrained the age of BTB by zircon fission track dating in Nagrota (=Khanpur) and Purmandal sections at 2.31+0.54 Ma and 2.8+56 Ma, respectively. They calibrated the fission track ages by magnetostratigraphy and correlation with global magnetic polarity time scale, and biostratigraphy and vertebrate faunal analysis in these sections. The age determined by Ranga Rao et al. (1988), and followed by Agarwal et al. (1993) supposedly marks the Gauss-Matuyama transition at 2.48 Ma and coincides with the Tatrot-Pinjor boundary. It is intersting to note that the first appearance datum of Lychnothamnus barbatus in Barakhetar and Purmandal sections below the BTB (Bhatia et al., 2001) and in the inter-montane basin of Kashmir valley (as in the Hirpur Formation, Karewa Group) is identical or synchronous viz., in the Late Pliocene, below the volcanic ash bed dated at 2.4±0.4 Ma (vide Bhatia et al., 1998). Bhat et al. (2008) gave details about the depositional origin of the Upper Siwalik bentonitized tuffaceous band of Jammu province and suggested a lacustrine setting. From the palaeoecological analysis of the recovered microvertebrate fauna and the associated ostracodes (Bhandari and Kundal, 2008) and charophytes (S.N. kundal unpublished work), it is apparent that there were two important palaeocommunities-1) aquatic and 2) terrestrial. The aquatic community is mainly represented by lacustrine / paludal fauna and flora, whereas the land community is known by wooded grassland and bushland taxa. The occurrence of microvertebrates in the mudstone horizon just below the bentonitized tuff band (Fig. 2) suggests that they are at least as old as the Upper Siwalik bentonitized tuff, i.e., 2.48m.y.

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Explanation of PLATE 1 1a. BHU/GEOL/VPL/MV/101 Cyprinid tooth, Morphotype I, lateral view 1b. BHU/GEOL/VPL/MV/102 Cyprinid tooth, Morphotype I, lateral view 1c. BHU/GEOL/VPL/MV/103 Cyprinid tooth, Morphotype I, lateral view 2a. BHU/GEOL/VPL/MV/104 Cyprinid tooth, Morphotype II, lateral view 2b. BHU/GEOL/VPL/MV/105 Cyprinid tooth, Morphotype II, lateral view 2c. BHU/GEOL/VPL/MV/106 Cyprinid tooth, Morphotype II, lateral view 3a. BHU/GEOL/VPL/MV/107 Cyprinid tooth, Morphotype III, lateral view 3b. BHU/GEOL/VPL/MV/108 Cyprinid tooth, Morphotype III, lateral view 3c. BHU/GEOL/VPL/MV/109 Cyprinid tooth, Morphotype III, lateral view 4a. BHU/GEOL/VPL/MV/110 Cyprinid tooth, Morphotype II, lateral view 4b. BHU/GEOL/VPL/MV/111 Cyprinid tooth, Morphotype II, lateral view 5. BHU/GEOL/VPL/MV/112 Cyprinid tooth, Morphotype I, lateral view 6. BHU/GEOL/VPL/MV/113 Fish tooth indet. , lateral view 7. BHU/GEOL/VPL/MV/114 Fish tooth indet. , lateral view 8. BHU/GEOL/VPL/MV/115 Fish tooth indet. , lateral view 9. BHU/GEOL/VPL/MV/116 Fish tooth indet. , lateral view 10. BHU/GEOL/VPL/MV/117 Fish tooth indet. , lateral view 11. BHU/GEOL/VPL/MV/118 Fish bone indet., lateral view 12a. BHU/GEOL/VPL/MV/119 Fragmentary fish spine of Siluriformes indet., lateral view 12b. BHU/GEOL/VPL/MV/120 Fish tooth indet. , lateral view 13a. BHU/GEOL/VPL/MV/121 Dentary of lacertilian indet., labial view 13b. BHU/GEOL/VPL/MV/122 Dentary of lacertilian indet., lingual view 14. BHU/GEOL/VPL/MV/123 Dentary of lacertilian indet., lingual view 15. BHU/GEOL/VPL/MV/124 Incertae sedis, lingual view 16a.BHU/GEOL/VPL/MV/125 Isolated mammalian claw, lateral view 16.b BHU/GEOL/VPL/MV/126 Isolated mammalian claw, lateral view 17a. BHU/GEOL/VPL/MV/127 Isolated mammalian claw, lateral view 17b. BHU/GEOL/VPL/MV/128 Isolated mammalian claw, lateral view 18a. BHU/GEOL/VPL/MV/129 Astragalus of cf. Rattus, dorsal view 18b. BHU/GEOL/VPL/MV/130 Astragalus of cf. Rattus, Plantar view 19a-h. BHU/GEOL/VPL/MV/131-138 Phlanges of Mammalia indet. Scale bar equals 1mm

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Conclusion The microvertebrates recovered from the mudstone horizon underlying the geochronologically dated (2.48 m.y.) bentonitized tuff band (BTB) belong to two palaecommunites: aquatic/lacustrine and terrestrial. The aquatic fauna is represented by fishes while the terrestrial by lacertilians and rats. The recovered microfaunal assemblage is at least as old as the bentonitized tuff band, i.e. 2.48 m.y. The fossiliferous mudstone was deposited under the aquatic/lacustrine conditions. Acknowledgements: The author is thankful to Department of Science and Technology, New Delhi for financial support under Fast Track Project (SR/FTP/ES-07/2008, P-45-10). The aurhor is also thankful to Professor G.M. Bhat of Jammu Universty for constant encouragement, helping me in preparation of manuscript in the present form and in the field as well in Laboratory. Thanks are also due to Profesor S. Kanji Lal, Banaras Hindu Universty for helping and encouragement.

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