This paper records the occurrence of 12 non-marine ostracod species belonging to nine genera from a new intertrappean section located at Khar in Madhya Pradesh, Central India. These are: Frambocythere tumiensis anjarensis, Gomphocythere akalypton, G. paucisulcatus, G. strangulata, Paracypretta jonesi, Stenocypris cylindrica, Zonocypris gujaratensis, Cypridopsis hyperectyphos, Eucypris intervolcanus, E. pelasgicos, Cyclocypris amphibolos and Cypria cyrtonidion. All these are assigned to previously known species from the Upper Cretaceous Lameta Group and Deccan intertrappean beds of central and western Peninsular India. The present ostracod assemblage favours a Late Cretaceous (Maastrichtian) age for the intertrappean beds of Khar and also indicates the existence of a permanent freshwater, lacustrine body during the deposition of these intertrappean beds. The lack of marine fossils in the intertrappean beds of the Narmada rift valley does not attest to any marine incursion along the Narmada rift valley, at least in the latest Cretaceous.
Introduction
The Deccan Traps, covering an area of about 500,000 km2 in Peninsular India, are considered as one of the largest continental flood basalts on the earth's surface. At many places, the Deccan basaltic flows are found occurring in association with fossiliferous sedimentary sequences, either below the volcanic flows or intercalated with them. The sedimentary sequences that occur sandwiched between the volcanic flows are also known as the intertrappean beds. Since the middle of 19th century, the intertrappean beds are known to yield non-marine microfossil assemblages especially ostracods and molluscs (Hislop, 1860; Whatley, 2012 and references therein) and vertebrate microfossils (Woodward, 1908; Hora, 1938; Prasad, 2012 and references therein). Until now, there are only two known reports of marine intertrappean sedimentary sequences; one on the east coast of Andhra Pradesh near Rajalimundry yielding abundant foraminifers and marine ostracods (Bhalla, 1965, 1967; Govindan, 1981; Bhandari, 1995; Khosla, 1999; Khosla and Nagori, 2002; Keller et al., 2008 and Malarkodi et al., 2010) and the second one at Jhilmili, in Chhindwara district, Madhya Pradesh yielding early Danian planktic foraminifers in association with brackish and non-marine ostracod assemblage (Keller et al., 2009a, b; Sharma and Khosla, 2009; Khosla et al., 2009a, 2011a). The remaining intertrappean beds of the Deccan volcanic province yielded essentially fluvio-lacustrine biota.
Previous work
Until now, no micropalaeontological studies have been carried out on the intertrappean beds of the lower Narmada rift valley. The earliest work on the ostracod fauna of the Deccan intertrappean beds is by Sowerby (in Malcolmson, 1840), who for the first time described two new species of lacustrine ostracods from the Sichel Hills, Andhra Pradesh. Subsequently, Carter (1852) and Jones (1860) reported three and five species of ostracods from the intertrappean beds of Bombay and Nagpur, respectively. Despite these early initiatives, lacustrine ostracods of the intertrappean beds remained neglected for over 125 years until Bhatia and co-workers (Bhatia and Rana, 1984; Bhatia et al., 1990a, b, 1996) described Upper Cretaceous (Maastrichtian) intertrappean ostracods from a number of localities. These authors suggested that the intertrappean ostracod fauna exhibits Laurasian affinities. Thereafter, Mathur and Verma (1988) described six species of ostracods from the intertrappean beds of Rajasthan. Singh and Sahni (1996) discussed the age and faunal affinities of the Bombay intertrappean beds based on a variety of fossil groups with special emphasis on Ostracoda. Bhandari and Colin (1999) described 11 species of Ostracoda, including a new species and a subspecies, from the intertrappean beds near Anjar, Kachchh District, Gujarat. Whatley and his co-workers published a series of papers on ostracods from the lacustrine intertrappean beds of different localities in central and western India. A rich ostracod fauna has been reported by these authors from Lakshmipur, Anjar and Kora intertrappean beds of Kachchh district, Gujarat (Whatley and Bajpai, 2000a, b; Bajpai and Whatley, 2001). Further, Whatley et al. (2002a–c, 2003a–c) described a large number of ostracod species from the intertrappean beds of Chandarki and Yanagundi, Gulbarga district (Karnataka), Mohgaonkalan, Chhindwara district (Madhya Pradesh), Mamoni, Kota district (Rajasthan), and from the intertrappean type collections housed in the Natural History Museum, London. Whatley and Bajpai (2005, 2006) discussed at length the palaeoecological implications of the intertrappean ostracods and felt that the Indian Late Cretaceous ostracod fauna is endemic at species level and does not exhibit any taxonomic affinity to contemporary lacustrine ostracod faunas of Mongolia and China as visualized earlier by Bhatia et al. (1990a, b, 1996). Later, Khosla and Nagori (2005,2007a, b) reported the occurrence of many ostracod species from the intertrappean beds of Anjar, Mohgaon-haveli and Takli. A single report of 14 species of ostracods from the northernmost intertrappean outcrop at Papro near Lalitpur, Uttar Pradesh, was made by Sharma et al. (2008). More recently, Khosla et al. (2011a) described 20 lacustrine-brackish water ostracod species from the early Danian planktic foraminiferal zone of the Jhilmili intertrappean beds, Chhindwara district, Madhya Pradesh.
Besides from the intertrappean beds, a freshwater ostracod fauna has also been documented from the Upper Cretaceous Lameta Group of Jabalpur, Madhya Pradesh (Sahni and Khosla, 1994; Khosla and Sahni, 2000; Khosla et al., 2011b) and Nand-Dongargaon basin (Udhoji and Mohabey, 1996; Khosla et al., 2005, 2010), Chandrapur district, Maharashtra.
Geological setting and the sample location
The geological succession of the study area comprises Precambrian basement rocks (Bijawar and Mahakoshal groups) covered by marine Cretaceous rocks of the Bagh Group (Bose, 1884; Tripathi, 2006). The Bagh Group comprises three formations namely, Nimar Sandstone, Nodular Limestone and Coralline Limestone in ascending order. The Nimar Sandstone, Nodular Limestone and Coralline Limestone yield marine fossils abundantly and are regarded as Cenomanian, Turonian and Coniacian in age, respectively (Jaitly and Ajane, 2013). These beds are exposed along a narrow stretch of land as detached outcrops along the lower Narmada valley. The Bagh Group in turn are unconformably overlain by the Upper Cretaceous (Maastrichtian) Lameta Group. Some poorly preserved bones, nests and eggshells of sauropod dinosaurs have been documented from the Lameta Group of this region (Khosla and Sahni, 1995; Fernandez and Khosla, 2015). Following the deposition of the Lameta sediments, the eruption of Deccan lava flows, which conceal the underlying sedimentary units to a large extent, took place. At some places, these lava flows are found intercalated with thin sedimentary beds (intertrappean beds).
Several intertrappean localities have been investigated along the Narmada rift valley (Figure 1A) for vertebrate fossils (G. V. R. Prasad, personal study). The ostracod fauna reported and described in this paper is from an intertrappean section exposed near Khar Village (22° 18′N. 75°32′E), Khargaon (Khargone) District, Madhya Pradesh (Figure 1B). At this locality, the intertrappean section measures 0.75 m in thickness and extends laterally for about 100 m. It occurs sandwiched between two weathered basaltic flows. The base of the lower basaltic flow is not exposed, whereas the upper flow is 3.65 m thick. This intertrappean section comprises olive-green, pebbly mudstone (0.45 m) at the base followed upwards by pale yellow shaly marl (0.30 m) (Figure 2) and the same lithological units continue over the exposed lateral extent of the section. Ostracods have been recovered from both the intertrappean sedimentary units along with gastropods, charophytes, a few fish teeth and scales and carbonaceous plant remains. The molluscan assemblage includes Physa, Paladina, Lymnaea and Valvata. This assemblage has been identified based on the study of Deccan intertrappean molluscs by Hartman et al. (2008). As far as ostracods are concerned, 12 species have been recovered from this section. All these ostracod species have been previously described from the other intertrappean localities of central and western Peninsular India. However, the new finds are important as no such fauna is known from the intertrappean beds of the lower Narmada rift valley.
Age and affinity of the ostracod fauna
The non-marine intertrappean beds have been extensively studied for their biota during the last three decades. These beds have been assigned ages ranging from Late Cretaceous to early Paleocene or even Eocene (Bhatia and Mannikeri, 1976; Bande et al., 1981; Bande and Prakash, 1982; Bhatia and Rana, 1984; Ghevariya, 1988; Sahni and Bajpai, 1988; Mehrotra, 1989; Srinivasan et al., 1994; Srinivasan, 1996; Kar and Srinivasan, 1998; Bajpai and Prasad, 2000; Singh and Kar, 2002; Keller et al., 2009a, b; S amant and Mohabey, 2009).
Figure 1.
Map showing different intertrappean sections around Narmada rift valley (A) and the location of Khar intertrappean section (B), Khargaon district, Madhya Pradesh, India.
The ostracod fauna from the intertrappean beds of Khar shows close affinity with that of the intertrappean beds of Anjar (Bhandari and Colin, 1999; Khosla and Nagori, 2005), Lakshmipur (Whatley and Bajpai, 2000a) and Kora (Bajpai and Whatley, 2001) in Kachchh District (Gujarat), Takli in Nagpur District (Maharashtra) (Bhatia and Rana, 1984; Bhatia et al., 1996; Khosla and Nagori, 2007b), Chandarki and Yanagundi in Gulbarga District (Karnataka) (Whatley et al., 2002a), Mamoni in Kota District (Rajasthan) (Whatley et al., 2003a), Phulsagar in Mandla District (Madhya Pradesh) (Bajpai et al., 2004), Mohagaonkalan (Whatley et al., 2002b), Mohgaon-Haveli (Khosla and Nagori, 2007a) and Jhilmili (Khosla et al., 2009a, 2011a; Sharma and Khosla, 2009) in Chhindwara District (Madhya Pradesh), Papro in Lalitpur District (Uttar Pradesh) (Sharma et al., 2008), and the Lameta Group of Jabalpur Cantonment (Madhya Pradesh) (Khosla and Sahni, 2000; Khosla et al., 2011b), Pisdura (Khosla et al., 2010) and Nand-Dongargaon Basin (Udhoji and Mohabey, 1996; Khosla et al., 2005) in Chandrapur District (Maharashtra).
All the ostracod species recorded in the present paper have been previously described from the other intertrap-pean localities (Table 1). A Late Cretaceous (Maastrichtian) age is assigned to the intertrappean beds of Khar in view of the close resemblance of its ostracod fauna to that of Upper Cretaceous intertrappean sections dated as Late Cretaceous in age based on radiometric ages of the underlying or overlying basaltic flows and associated fish fauna and palynofossils.
Table 1.
Distribution of ostracod species in the Lameta Group and intertrappean beds of Peninsular India.
Palaeoecology of the ostracod fauna
The constituents of the ostracod fauna of the Khar intertrappean beds occur in the following order of predominance—Paracypretta (55%), Gomphocythere (9.8%), Frambocythere (9.2%), Stenocypris (8.4%), Eucypris (8.0%), Cypridopsis (3.4%), Cyclocypris (3.0%), Cypria (2.3%) and Zonocypris (0.8%). Whatley and Bajpai (2005) discussed at length the palaeoecological implications of the non-marine Ostracoda from the Upper Cretaceous intertrappean beds and the Lameta Group of Peninsular India and the same criteria are utilized here in our interpretations. Accordingly, the above-reported ostracod genera can be divided into two groups: (i) non-swimmers, endobenthonic or epibenthonic walkers/crawlers (Frambocythere and Gomphocythere) and (ii) swimmers, varying from moderate to very active (Paracypretta, Stenocypris, Zonocypris, Cypridopsis, Eucypris, Cyclocypris and Cypria).
Among the first group, ostracod genera Frambocythere and Gomphocythere belonging to the family Limnocytheridae are clearly epibenthonic walkers/crawlers and live in permanent water bodies, mainly in ponds and lakes. In the second group, the genus Paracypretta is well known as a good swimmer at present. The genus Stenocypris is characteristic of shallow, warm, freshwater environments. The genus Zonocypris with its heavy ornament is probably a rather sluggish swimmer. Cypridopsis is mainly found in permanent lakes and ponds, and rarely in rivers and streams. The genus Eucypris mostly lives in temporary water bodies that dry out in summer months. Whatley and Bajpai (2005) suggested that it is probable that Eucypris and other taxa that prefer temporary waters lived around the margins of lakes and ponds that dried out in the dry season, while those preferring permanent waters would then retreat to the deeper parts of the water body. Modem species of Cyclocypris are very active swimmers. Although some of them occur in temporary ponds and others in only shallow permanent waters, many live in water bodies ranging from small ponds to large lakes. Recent species of Cypria are probably even better swimmers and Cypria ophthalmica (Jurine), which is an almost universally distributed freshwater and oligohaline species in the Northern Hemisphere, is an excellent example of the genus requiring permanent waters. It is clear from the above discussion that except for the genus Eucypris, which is indicative of a temporary pool environment, all the other genera suggest the existence of permanent waters (pond/lake) during the deposition of the mudstone and shaly marl of the intertrappean beds of Khar.
Palaeobiogeographic implications
The recent discovery of planktic foraminifera in association with a lacustrine to brackish-marine ostracod assemblage from the intertrappean beds of Jhilmili, Central India (Keller et al., 2009a, b) was interpreted in terms of a marine incursion taking place from the western margin of India along the east-west trending Narmada rift valley close to the Cretaceous-Palaeogene boundary. Khosla et al. (2011a), on the other hand, based on the occurrence of brackish-water ostracod Neocyprideis raoi in great profusion from the intertrappean beds of Jhilmili in Central India and Rajahmundry along the southeastern coast of India, suggested that the planktic foraminifers and brackish-water ostracods might have been brought to Central India by a marine incursion from the east coast along the northwest-southeast trending Godavari graben. These palaeogeographic models can be tested only with the discovery of marine fossils from the latest Cretaceous/early Palaeocene rocks exposed along the Narmada and Godavari rift valleys. The Upper Cretaceous (Maastrichtian) Lameta Group of Pisdura (Jain and Sahni, 1983) and Marepalli (Prasad and Singh, 1991) and the Upper Cretaceous (Maastrichtian) intertrappean beds of Asifabad (Prasad and Sahni, 1987; Prasad and Cappetta, 1993), Nagpur (Rana, 1984), and Piplanarayanwar (Lourembam et al., 2017) located along the Godavari rift valley yielded an admixture of freshwater, brackishwater, and marine faunal elements favoring the existence of a marine seaway along the Godavari rift valley, at least in the latest Cretaceous (Sahni, 1983; Prasad and Singh, 1991).
Besides Khar, five other intertrappean localities, viz. Banjari, Bhagwaniya, Gandhwani, Kakarda and Gujri Gate in and around the Narmada valley have been studied in detail (ongoing work in our lab) for their fossil content and all of them have revealed the presence of predominantly freshwater ostracods, molluscs, charophytes and vertebrates. The molluscan fauna from the present study area is represented by Physa, Paladina, Lymnaea and Valvata which are typical freshwater forms. The associated freshwater fishes Lepisosteus indicus and Osteoglossidae gen. et sp. indet, further support a freshwater depositional environment for the Khar intertrappean beds. Despite intensive search, none of these six studied intertrappean sections yielded brackish water or marine taxa.
Marine to brackish water batoid fishes characteristic of the vertebrate fauna of the Lameta Group and the intertrappean beds exposed along the Godavari rift valley are absent in the intertrappean fauna of the Narmada rift valley. Therefore, the existing fossil data from the latest Cretaceous deposits of Godavari and Narmada rift valleys favor a possible marine incursion along the Godavari rift valley, at least at the end of the Cretaceous. This needs to be definitively confirmed by further extensive studies on the intertrappean sections all along the Nannada valley. However, it does not rule out an early Palaeocene (Danian) marine transgression from the western margin of India as proposed by Keller et al. (2009a, b) as no early Palaeocene intertrappean beds are known from the Narmada valley.
Systematic palaeontology
In this paper, the authors have adopted the classification of ostracods as given by Moore and Pitrat (1961) or have followed the works of Whatley and Bajpai (2000a, b); Bajpai and Whatley (2001) and Whatley et al. (2002a, b, c, 2003a, b, c). All the illustrated ostracod specimens in this paper are deposited in the Department of Geology, University of Delhi, India and are catalogued as DUGF (Delhi University Geology Fossils) numbers.
Subclass Ostracoda Latreille, 1806
Order Podocopida Muller, 1894
Suborder Podocopina Sars 1866
Superfamily Cypridoidea Baird, 1845
Family Cyprididae Baird, 1845
Genus Paracypretta Sars, 1924
Paracypretta jonesi Bhatia and Rana, 1984
Figures 3.1–3.3
Paracypretta jonesi Bhatia and Rana, 1984, p. 30, pl. 2, figs. 1–3.
Material.—426 carapaces.
Remarks.—This species was reported for the first time from the intertrappean beds of Gitti Khadan, Nagpur by Bhatia and Rana (1984). It was subsequently recorded from the intertrappean beds of Kora, Kachchh district (Bajpai and Whatley, 2001); Chandarki, Gulbarga district (Whatley et al., 2002a); Mohgaon-Haveli and Jhilmili, Chhindwara district (Khosla and Nagori, 2007a; Khosla et al., 2009a, 2011a; Sharma and Khosla, 2009); Takli, Nagpur (Khosla and Nagori, 2007b). Besides, the species has also been recorded from the Lameta Group of Dongargaon (Khosla et al., 2005, 2011b), Pisdura hill section (Khosla et al., 2010, 2011b), Nand-Dongargaon basin; and Chui hill and Bara Simla hill sections, Jabalpur (Khosla et al., 2011b).
The species has the following characters: subtriangular in lateral outline and very arcuate to subumbonate dorsally, anterior 1/6 of length conspicuously compressed and lip-like; greatest height and width nearly equal; left valve larger than right valve; dorsal margin symmetrically convex, subangulate in the middle; ventral margin straight; surface of each valve ornamented with minute, very dense puncta, arranged in longitudinal striations parallel to the ventral margin in lower half.
Genus Stenocypris Sars, 1889
Stenocypris cylindrica (Sowerby, in Malcolmson, 1840)
Figures 3.4–3.6
Cypris cylindrica Sowerby, in Malcolmson, 1840, pl. 67, fig. 2.
Mongolianella cylindrica (Sowerby). Whatley and Bajpai, 2000a, p.403, pl. 6, figs. 1–8.
Stenocypris cylindrica (Sowerby). Khosla et al., 2009b, p. 580, pl. 1, figs. 1–7, text-fig. 3A
Material.—65 carapaces.
Remarks.—The species was initially described as Cypris cylindrica by Sowerby (in Malcolmson, 1840) from the intertrappean beds of the Sichel Hills, Andhra Pradesh. Whatley and Bajpai (2000a) recorded the species from the intertrappean beds of Lakshmipur, Kachchh district, and on the basis of a thorough study of the collections and registers of the Natural History Museum (NHM), London stated that the Kachchh specimens are identical with the types of Cypris cylindrica housed there. They recorded the species as Mongolianella cylindrica and erected a lectotype and a number of paralectotypes out of Sowerby's syntypes in the NHM. Apart from Lakshmipur, the species has also been recorded from the intertrappean beds of Kora (Bajpai and Whatley, 2001) and Anjar (Khosla and Nagori, 2005), Kachchh district; Chandarki and Yanagundi, Gulbarga district (Whatley et al., 2002a); Mamoni, Kota district (Whatley et al., 2003a); Takli, Nagpur (Khosla and Nagori, 2007b); Phulsagar, Mandla district (Bajpai et al., 2004); Papro, Lalitpur (Sharma et al., 2008); Jhilmili, Chhindwara district (Khosla et al., 2009a, 2011a; Sharma and Khosla, 2009); from the Lameta Group of Pisdura hill section, Nand-Dongargaon basin (Khosla et al., 2010, 2011b); and Chui hill and Bara Simla hill sections (Khosla et al., 2011b), Jabalpur basin.
Recently Khosla et al. (2009b) restudied the species from the intertrappean beds of Lakshmipur, Kachchh district and based on the outline shape of the carapace and some internal characters transferred the species to Stenocypris Sars, 1889.
The species is elongate, subcylindrical in lateral outline and fusiform in dorsal outline; left valve larger than the right, overlapping it prominently along the posterior and ventral margins; dorsal margin arched, ventral margin slightly concave; anterior margin rounded, posterior somewhat pointed; valve surface smooth.
Genus Zonocypris Müller, 1898
Zonocypris gujaratensis Bhandari and Colin, 1999
Figures 3.7, 3.8
Zonocypris gujaratensis Bhandari and Colin, 1999, p. 17, pl. 2, figs. 1–4.
Material.—Six carapaces.
Remarks.—This species has been so far described from the intertrappean beds of Anjar, Kachchh district (Bhandari and Colin, 1999; Khosla and Nagori, 2005); Mohgaon-Haveli, Chhindwara district (Khosla and Nagori, 2007a); Takli, Nagpur (Khosla and Nagori, 2007b); and the Lameta Group of Bara Simla hill section (Khosla et al., 2011b), Jabalpur basin.
The species is characterized by its small carapace, subovate to subtriangular lateral outline globular, regularly rounded in dorsal view; valve surface ornamented by spiral ribs extending over a number of whorls and at times bifurcating giving rise to secondary ribs.
Figure 3.
SEM photomicrographs of ostracods recovered from the Khar intertrappean section. 1–3, Paracypretta jonesi Bhatia and Rana, 1984; 1, carapace (DUGF/301), right valve view; 2, carapace (DUGF/302), dorsal view; 3, carapace (DUGF/303), left valve view; 4–6, Stenocypris cylindrica (Sowerby in Malcolmson, 1840); 4, carapace (DUGF/304), right valve view; 5, carapace (DUGF/305), dorsal view; 6, carapace (DUGF/306), left valve view; 7, 8, Zonocypris gujaratensis Bhandari and Colin, 1999; 7, carapace (DUGF/307), left valve view; 8, carapace (DUGF/308), dorsal view; 9–11, Cypridopsis hyperectyphos Whatley and Bajpai, 2000a; 9, carapace (DUGF/309), right valve view; 10, carapace (DUGF/310), dorsal view; 11, carapace (DUGF/311), left valve view; 12–14, Eucypris intervolcanus Whatley and Bajpai, 2000a; 12, carapace (DUGF/312), right valve view; 13, carapace (DUGF/313), dorsal view; 14, carapace (DUGF/314), left valve view; 15–17, Eucypris pelasgicos Whatley and Bajpai, 2000a; 15, carapace (DUGF/315), right valve view; 16, carapace (DUGF/316), dorsal view; 17, carapace (DUGF/317), left valve view; scale bar for 1–6 and 12–17 = 200 µm, for 7–11 = 100 µm.
Subfamily Cypridopsinae Kaufmann, 1900
Genus Cypriclopsis Brady, 1868
Cypriclopsis hyperectyphos Whatley and Bajpai, 2000a
Figures 3.9–3.11
Cypridopsis hyperectyphos Whatley and Bajpai, 2000a, p. 397, pl. 4, figs. 4–10.
Material.—26 carapaces.
Remarks.—The species has been widely recorded from the intertrappean beds of Lakshmipur (Whatley and Bajpai, 2000a), Kora (Bajpai and Whatley, 2001) and Anjar (Khosla and Nagori, 2005), Kachchh district; Yanagundi, Gulbarga district (Whatley et al., 2002a); Mamoni, Kota district (Whatley et al., 2003a); Takli, Nagpur (Khosla and Nagori, 2007b); Papro, Lalitpur (Sharma et al., 2008); Jhilmili, Chhindwara district (Khosla et al., 2009a, 2011a; Sharma and Khosla, 2009); and the Lameta Group of Dongargaon (Khosla et al., 2005, 2011b), Pisdura hill section (Khosla et al., 2010, 2011b), Nand-Dongargaon basin; and Chui hill section (Khosla et al., 2011b), Jabalpur basin.
The species is triangularly subovate in lateral outline and very strongly inflated, almost circular in dorsal outline; length sometimes equal to width; left valve slightly overlapping the right valve along the dorsal and posterior margins; dorsal margin strongly convex, ventral margin with slight concavity; valve surface punctated.
Subfamily Eucypridinae Bronshtein, 1947
Genus Eucypris Vávra, 1891
Eucypris intervolcanus Whatley and Bajpai, 2000a
Figures 3.12–3.14
Eucypris intervolcanus Whatley and Bajpai, 2000a, p. 402, pl. 5, figs. 16–19.
Material.—23 carapaces.
Remarks.—The species has been previously described from the intertrappean beds of Lakshmipur (Whatley and Bajpai, 2000a), Kora (Bajpai and Whatley, 2001) and Anjar (Khosla and Nagori, 2005), Kachchh district; Mohgaonkala (Mohgaon-Kalan), Chhindwara district (Whatley et al., 2002b); and Yanagundi, Gulbarga district (Whatley et al., 2002a). This species is similar to Eucypris pelasgicos Whatley and Bajpai, 2000a, in overall shape but the latter differs in being larger in size and having pronounced anteroventral angulation.
The species has a large subovate carapace in lateral outline and a fusiform shape in dorsal view; left valve overlapping right valve all along the free margin; dorsal margin posteriorly inclined and ventral margin slightly concave; anterior margin narrowly rounded, apex below mid-height; posterior margin broadly rounded, apex at mid-height; greatest length, height and width medianly; valve surface smooth.
Eucypris pelasgicos Whatley and Bajpai, 2000a
Figures 3.15–3.17
Eucypris pelasgicos Whatley and Bajpai, 2000a, p. 400, pl. 5, figs. 7–15.
Material.—39 carapaces.
Remarks.—This species has been recorded earlier from the intertrappean beds of Lakshmipur (Whatley and Bajpai, 2000a), Kora (Bajpai and Whatley, 2001) and Anjar (Khosla and Nagori, 2005), Kachchh district; Mohgaonkala (Mohgaon-Kalan) (Whatley et al., 2002b) and Jhilmili (Khosla et al., 2009a, 2011a), Chhindwara district; Takli, Nagpur (Khosla and Nagori, 2007b); and Lameta Group of Dongargaon (Khosla et al., 2005, 2011b), Pisdura hill section (Khosla et al., 2010, 2011b), Nand-Dongargaon basin; and Chui hill and Bara Simla hill sections (Khosla et al., 2011b), Jabalpur basin.
Carapace large, elongate to subovate in lateral outline and fusiform in dorsal view, anterior half slightly more compressed than posterior half; dorsal margin distinctly umbonate at mid-length, ventral margin nearly straight; anteroventral angulation in the left valve where it pronouncedly overreaches the right valve; valve surface very smooth.
Family Cyclocyprididae Kaufmann, 1900
Genus Cyclocypris Brady and Norman, 1889
Cyclocypris amphibolos Whatley, Bajpai and Srinivasan, 2002a
Figures 4.1–4.3
Cyclocypris amphibolos Whatley et al., 2002a, p. 182, pl. 6, figs. 6–18.
Material.—23 specimens.
Remarks.—The species was first reported from the intertrappean beds of Yanagundi, Gulbarga district (Whatley et al., 2002a); Kora, Kachchh district (Whatley et al., 2002c); Mamoni, Kota district (Whatley et al., 2003a); Mohgaon-Haveli (Khosla and Nagori, 2007a) and Jhilmili (Khosla et al., 2009a, 2011a), Chhindwara district; Takli, Nagpur (Khosla and Nagori, 2007b); and from the Lameta Group of Dongargaon (Khosla et al., 2005, 2011b); Pisdura (Khosla et al., 2010, 2011b), Nand-Dongargaon basin; and Jabalpur (Khosla et al., 2011b), Jabalpur basin.
The species is irregularly subovate in lateral outline and regularly fusiform in dorsal outline; left valve larger than the right valve, overlapping the latter all along the entire margin except posteriorly where right valve overreaches the left; dorsal margin convex anterodorsally but straight, sloping posteriorly; ventral margin overhung by valve tumidity and with shallow oral concavity; surface ornamented with numerous minute papillae.
Figure 4.
SEM photomicrographs of ostracods recovered from the Khar intertrappean section. 1–3, Cyclocypris amphibolos Whatley et al., 2002a; 1, carapace (DUGF/318), right valve view; 2, carapace (DUGF/319), dorsal view; 3, carapace (DUGF/320), left valve view; 4–6, Cypria cyrtonidion Whatley and Bajpai, 2000a; 4, carapace (DUGF/321), right valve view; 5, carapace (DUGF/322), dorsal view; 6, carapace (DUGF/323), left valve view; 7–10, Frambocythere tumiensis anjarensis Bhandari and Colin, 1999; 7, female carapace (DUGF/324), right valve view; 8, female carapace (DUGF/325), ventral view; 9, male carapace (DUGF/326), dorsal view; 10, female carapace (DUGF/327), left valve view; 11, 12, Gomphocythere akalypton Whatley et al., 2002a; 11, carapace (DUGF/328), right valve view; 12, carapace (DUGF/329), ventral view; 13–15, Gomphocythere paucisulcatus Whatley et al., 2002b; 13, carapace (DUGF/330), right valve view; 14, carapace (DUGF/331), dorsal view; 15, carapace (DUGF/332), left valve view; 16–20, Gomphocythere strangulata (Jones, 1860); 16, male carapace (DUGF/333), dorsal view; 17, female carapace (DUGF/334), left valve view; 18, male carapace (DUGF/335), right valve view; 19, female carapace (DUGF/336), dorsal view; 20, female carapace (DUGF/337), left valve view; scale bar for 1–6, 11, 12, 15, 16 = 200 µm, for 7–10, 13, 14 and 17–20 = 100 µm.
Genus Cypria Zenker, 1854
Cypria cyrtonidion Whatley and Bajpai, 2000a
Figures 4.4–4.6
Cypria cyrtonidion Whatley and Bajpai, 2000a, p. 404, pl. 6, figs. 9–14.
Material.—18 carapaces.
Remarks.—This species has been widely recorded from the intertrappean beds of Lakshmipur (Whatley and Bajpai, 2000a), Kora (Bajpai and Whatley, 2001) and Anjar (Khosla and Nagori, 2005), all in Kachchh district; Yanagundi and Chandarki, Gulbarga district (Whatley et al., 2002a); Mohgaonkala (Whatley et al., 2002b), Mohgaon-Haveli (Khosla and Nagori, 2007a) and Jhilmili (Sharma and Khosla, 2009; Khosla et al., 2009a, 2011a), all in Chhindwara district; Papro, Lalitpur district (Sharma et al., 2008); and the Lameta Group of Dongargaon (Khosla et al., 2005, 2011b) and Pisdura hill section (Khosla et al., 2010, 2011b), Nand-Dongargaon basin. Also, Whatley et al. (2002a, b) assigned Cyprois sp. recorded from the Intertrappean beds of Nagpur by Bhatia and Rana (1984) and Kota by Mathur and Verma (1988) to this species.
The species is subquadrate to subcircular in lateral outline and fusiform in dorsal outline, left valve larger than right valve, overlapping it all around the periphery except dorsally where right valve overreaches left valve; surface smooth.
Superfamily Cytheroidea Baird, 1850
Family Limnocytheridae Klie, 1938
Subfamily Timiriaseviinae Mandelshtam, 1960
Genus Frambocythere Colin in Colin and Danielopol,
1980
Frambocythere tumiensis anjarensis Bhandari and
Colin, 1999
Figures 4.7–4.10
Frambocythere tumiensis anjarensis Bhandari and Colin, 1999, p. 12, 13. pl. 1. figs. 1–10.
Material.—71 carapaces.
Remarks.—The subspecies was initially described from the intertrappean beds of Anjar, Kachchh district by Bhandari and Colin (1999). Apart from this, it has been also recorded from the intertrappean beds of Chandarki and Yanagundi, Gulbarga district (Whatley et al., 2002a); Mamoni, Kota district (Whatley et al., 2003a); Mohgaon-Haveli, Chhindwara district (Khosla and Nagori, 2007a); Takli, Nagpur (Khosla and Nagori, 2007b); Jhilmili, Chhindwara district (Khosla et al., 2009a, 2011a); and the Lameta Group of Dongargaon (Khosla et al., 2005, 2011b) and Pisdura hill section (Khosla et al., 2010, 2011b), Nand-Dongargaon basin. A strongly dimorphic subspecies of Frambocythere tumiensis with normal overlap, i.e., left valve larger than right valve; females strongly inflated posteriorly whereas males much narrower, with maximum width near middle; surface ornamented by dense concentrically disposed papillate tubercles, tubercles somewhat coarser in anterodorsal region.
Genus Gomphocythere Sars, 1924
Gomphocythere akalypton Whatley, Bajpai and Srinivasan, 2002a
Figures 4.11, 4.12
Gomphocythere akalypton Whatley et al., 2002a, p. 170, pl. 1, figs. 12–23. pl. 2. figs. 1–5.
Material—12 carapaces.
Remarks.—The species was originally described from the intertrappean beds of Chandarki, Gulbarga district, Karnataka (Whatley et al., 2002a). It was subsequently recorded from the intertrappean beds of Phulsagar, Mandla district, Madhya Pradesh (Bajpai et al., 2004); and Papro, Lalitpur district, Uttar Pradesh (Sharma et al., 2008).
This species is subrectangular in lateral outline and subhastate in dorsal outline; dorsal margin nearly straight with anterior cardinal angle; ventral margin obscured by surface ornamentation; valve surface marked by a short anterodorsal sulcus and a prominent median sulcus; a row of 8-10 spinose tubercles ventro-laterally overhanging the margin and other tubercles posteriorly, rest of the area smooth or punctate.
Gomphocythere paucisulcatus Whatley, Bajpai and Srinivasan, 2002b
Figures 4.13–4.15
Gomphocythere paucisulcatus Whatley et al., 2002b, p. 107, pl. 1, figs. 1–6.
Material—21 carapaces.
Remarks.—This species has been described from the intertrappean beds of Mohgaonkalan, Chhindwara district (Whatley et al., 2002b); Anjar, Kachchh district (Bhandari and Colin, 1999; Khosla and Nagori, 2005); Takli, Nagpur (Khosla and Nagpur, 2007b); Papro, Lalitpur (Sharma et al., 2008); Jhilmili, Chhindwara district (Khosla et al., 2009a, 2011a); and the Lameta Group of Dongargaon (Khosla et al., 2005, 2011b) and Pisdura hill section (Khosla et al., 2010), Nand-Dongargaon basin.
It is a medium-sized species of Gomphocythere having a subovate to subrectangular outline in lateral view, subfusiform in dorsal view; almost equally acuminate at both ends and with a very slight median sulcus; valve surface comprises large reticulae having one to four secondary puncta within fossae. Sexual dimorphism indistinct.
Gomphocythere strangulata (Jones, 1860)
Figures 4.16–4.20
Cypris strangulata Jones, 1860, p. 187, pl. X, fig. 73a–d.
Gomphocythere strangulata (Jones). Whatley et al., 2002a, p. 169, pl. 1. figs. 10. 11.
Material.—43 carapaces.
Remarks.—This species has been widely described from the intertrappean beds of Nagpur and Asifabad (Bhatia and Rana, 1984; Bhatia et al., 1990a, 1996; Khosla and Nagori, 2007b); Mamoni, Kota district (Bhatia et al., 1990b); Yanagundi, Gulbarga district (Whatley et al., 2002a); Lakshmipur and Anjar, Kachchh district (Whatley and Bajpai, 2000a; Khosla and Nagori, 2005); Jhilmili, Chhindwara district (Khosla et al., 2009a, 2011a); and the Lameta Group of Dongargaon, Nand-Dongargaon Basin (Udhoji and Mohabey, 1996; Khosla et al., 2005, 2011b).
A strongly dimorphic form, females being much inflated posteriorly, males lensoid in dorsal outline with maximum width near middle; valve surface marked by a deep median sulcus, a smaller anterior sulcus, ornamentation comprises polygonal and hexagonal reticulations, each of the reticulae containing 4–5 puncta, and a narrow ventrolateral rib. In some specimens, the external layer of the outer lamella is well preserved and comprises dense papillate tubercles on the surface whereas it is absent in those specimens where the outer layer is not preserved.
Acknowledgements
The authors are thankful to the Head Department of Geology, University of Delhi for providing the laboratory facilities required for this study. The Department of Entomology, Indian Agricultural Research Institute, Delhi is acknowledged for SEM photography of ostracod specimens described in this work. ASR is thankful to the University Grants Commission for a grant of financial assistance in the form of a D. S. Kothari postdoctoral fellowship. GVRP acknowledges financial support from a J. C. Bose National Fellowship (No. SR/S2/JCB-14/2010) of the Department of Science and Technology.
