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Harris et al., eds., 2006, The - Terrestrial Transition. New Mexico Museum of Natural History and Science Bulletin 37. 77 FAUNAL TURNOVER DURING THE TRIASSIC-JURASSIC TRANSITION: AN INDIAN SCENARIO

SASWATI BANDYOPADHYAY AND DHURJATI PRASAD SENGUPTA

Geological Studies Unit, Indian Statistical Institute, 203 Barrackpore Trunk Road, Kolkata 700108, , E-mail: [email protected] and [email protected]

Abstract—The basins of India yield unique Permo- . Among these, the Pranhita- Godavari (P-G) basin has an almost continuous faunal succession spanning the Late to , and possibly into the . In the P-G basin, nine successive vertebrate-bearing horizons have been identified – these include five Triassic and three Jurassic biotic zones. The faunal assemblages of the (Early to Late ) and Early Jurassic ( to ) zones of the P-G basin clearly exhibit evidence of faunal turnover from the Late Triassic to Early Jurassic. The elements of the Late Norian Lower Dharmaram fauna, which includes , , and small prosauropods, is replaced by large prosauropods and a sphenosuchian in the Hettangian Upper Dharmaram Formation, which is, in turn, succeeded by the overlying Sinemurian to Lower that includes sauropods, triconodonts, and “symmetrodonts.” The Upper Dharmaram fauna does not contain aetosaurs or phytosaurs, and the Triassic-Jurassic boundary lies at the base of the upper part of the Dharmaram.

INTRODUCTION Triassic and Jurassic continental deposits of India are found mainly in the Gondwana successions that are preserved in a number of discreet basins of peninsular India. These intracratonic basins are nucleated along preexisting zones of weakness in the (Chakraborty et al., 2003). Until recently, these were well known for their rich coal reserves and plant rather than their faunal remains. Recovery of many new vertebrates, significant both in numbers of genera and as well as complete skeletons, during the last five decades have made them more useful in the understanding of the evolutionary history of vertebrates on the continent. The major Gondwanan basins of India (Fig. 1), the Pranhita-Godavari (P-G), Satpura, Son-Mahanadi (S-M) and Damodar basins (Fig. 2) are now known for their vertebrate assem- blages that occur mostly in fluvial . Among these four, the P-G basin provides the most complete succession of vertebrate faunas rang- ing from Permian to Jurassic. The Satpura basin has a succession from Permian to . In the S-M basin, a succession from Per- mian to Late Triassic has been identified so far, whereas a succession from Permian to is seen in the Damodar basin. A global terrestrial faunal turnover during the Late Triassic and Early Jurassic epochs has been noted by several workers (Colbert, 1949, 1958; Olsen et al., 1987, 1990). Though initially this was not generally accepted, a scrutiny of the faunal assemblage during this time showed that some major groups, namely phytosaurs, procolophonids, and prolacertiforms, were replaced by crocodylomorphs and/or sphenodontians. Later detailed, end-Triassic faunal analyses in different parts of the world indicated that various -like , , and “thecodontians” also disappeared at the end of Trias- sic and were replaced by early , crocodylomorphs, etc. – in short, there was a faunal shift at the beginning of the Jurassic (Olsen and Galton, 1977; Benton, 1986a). This Late Triassic-Early Jurassic faunal turnover led to a downward shift in the boundary of the Early Jurassic (Olsen and Galton, 1977; Padian, 1986), which prompted Bandyopadhyay and Roy Chowdhury (1996) to examine the Triassic and Jurassic verte- brate faunal assemblage of the P-G basin. Earlier, the Kota Formation had been considered to represent the continental Jurassic in Indian Gondwana. The faunal component of the Kota Formation, however, FIGURE 1. Stratigraphic successions of the major Gondwana basins of India. showed that the upper part of the Dharmaram Formation, which had been previously considered Upper Triassic (Norian), actually contains mainly demarcated the beginning of the Jurassic in India. In the other vertebrates that mark the beginning of the Jurassic in India. Their study Gondwanan basins, a continuous succession from Triassic to Jurassic is 78 faunal succession on the whole, evolving chronologically within a sedi- mentary package that is continuous in nature. The Upper Permian Kundaram Formation is characterized by red mudstone, , sandstone-mudstone alternations, and ferruginous . The sand bodies are laterally persistent, trough cross-stratified exhibiting unimodal palaeocurrent direction, and were formed by the lateral migration and avulsion of channels (Ray, 1997). The Kundaram Fauna An assemblage of Permian reptiles, characterized by abundant , has been recovered from the mudstone unit of the Kundaram Formation. The dicynodonts are dominated by followed by Cistecephalus, Pristerodon, Emydops, Oudenodon and Kingoria (Ray and Bandyopadhyay, 2003). The vertebrate assemblage also contains a gorgonopsian and a captorhinid. Paleontologically, this horizon is im- portant because it is the only horizon in India that produces Permian reptiles. On the basis of similarities of the Kundaram fauna with those of the Tropidostoma Assemblage zone and Cistecephalus Assemblage zone of the of , Ray (1999, 2001) dated the Kundaram fauna as late Late Permian (Tatarian). Recently, Ward et al. (2005, supplementary information fig. S4) showed that, except Endothiodon, the other Kundaram fauna ranges either up to the middle or to the end of Zone, of which Emydops is again restricted only in the Dicynodon Zone. Besides, only Pristerodon ranges from the Zone to the middle of the Dicynodon Zone. The abun- dance of Endothiodon in the Kundaram Formation, and the stratigraphical ranges of other Kundaram dicynodonts, further strengthen a late Late FIGURE 2. Major Gondwana basins of India. Permian (Tatarian) age for this horizon. The lithology of the overlying Kamthi Formation includes silt- not recorded (Fig. 1); hence, they will not be treated further here. stone and ferruginous sandstone that is pebbly in places. A medium- The present paper describes briefly the geological history of the grained, poorly-sorted, argillaceous quartzose sandstone (quartz wackes P-G basin, along with the faunal associations of important vertebrate containing up to 45% clay matrix) and thin sheets of sandy siltstone horizons. This is followed by a discussion of faunal distribution and characterize the lower part, while the upper part has coarse, poorly- faunal turnover across the Triassic-Jurassic boundary, substantiating the sorted argillaceous yellowish brown sandstone with siltstone clasts and pattern of , origination and diversification of terrestrial verte- quartz and quartzite pebbles (Sengupta, 1970). From the siltstone, brates. It may be mentioned that the details of the Gondwanan verte- two as-yet undescribed specimens of sp. have been found brates of India, current through 1999, are given in Bandyopadhyay (1999). (S. Ray, personal commun.), while Brachyops laticeps has been collected Below, only the references of subsequent publications on Indian from the upper part of Kamthi Formation (Mangli ‘beds’) (Owen, 1855). Gondwanan vertebrates are mentioned. The formations successively overlying the Kamthi Formation, the Yerrapalli, Bhimaram, Maleri, and Dharmaram, are mostly mud- BRIEF GEOLOGICAL HISTORY OF THE dominated, red bed units rich in vertebrate fossils. The red mudstones PRANHITA-GODAVARI BASIN are considered to have been deposited from suspension in interchannel The Gondwana succession in the Pranhita-Godavari basin occurs floodplain areas (Sengupta, 1970) and indicate good drainage and well- as a narrow, rectilinear outcrop trending NNW-SSE and is bordered on aerated floodplain deposits under a warm, moist climate with seasonally both sides by Proterozoic and/or Archean rocks. The overall dip of the distributed rainfall (Robinson, 1970; Behrensmeyer and Hook, 1992, succession is 5º to 12º N and NW, with a general northward paleocurrent Sheldon, 2005). direction (Sengupta, 1970; Veevers and Tewari, 1995). Glacial, Red to violet mudstone with scattered, thin sheets of quartzose fluvioglacial, fluvial, and lacustrine sediments were deposited in this sandstone and relatively smaller lenticular sand bodies made up of cali- basin during the Permo-Mesozoic period (Robinson, 1970; Read and che-derived calcarenite/calcirudite are characteristic features of the Watson, 1975; Veevers and Tewari, 1995). (Dasgupta, 1993). Small, lenticular sand bodies Glacial sediments of the Talchir Formation were the first Phanero- enclosing the mudstones (Fig. 3) represent fillings of small ephemeral zoic deposits in this basin. Boulder-pebble conglomerate, pebbly sand- channels that wandered over an extensive floodplain. Parallel laminated, stone, and khaki-green shale of Early Permian age characterize this unit. sheet-like often displaying parting lineation were deposited The overlying Barakar Formation contains medium to coarse, white to by waning currents of sheet flows associated with episodic overbank yellow sandstone with major coal seams and carbonaceous shale. These flooding of ephemeral streams (Maulik and Chaudhuri, 1983). units do not contain any vertebrate fossils. The succession above the The Yerrapalli Fauna Barakar Formation starts with the Late Permian Kundaram Formation followed by a number of Triassic, Jurassic, and formations. The Yerrapalli vertebrate community comprises a dipnoan (Fig. 1). (), an actinopterygian, (), a capitosaurid It is important to note that the Permian to Jurassic succession of (Stanocephalosaurus) (Schoch and Milner, 2000), and some and the P-G basin apparently shows no inter- or intraformational reptiles. Two large dicynodonts, Wadiasaurus and Rechnisaurus . Hence, the ages of all the faunal assemblages starting from (Roy Chowdhury, 1970), and some undescribed the Kundaram Formation, where the first occurrence of Permian verte- (trirachodontid) teeth (Chatterjee et al., 1969) represent the Synapsida, brate fossils have been noted, are important to build up the picture of the while include a (Mesodapedon) (Chatterjee, 1980), 79

FIGURE 3. Lithologic successions of the Triassic-Jurassic horizons of the Pranhita-Godavari basin along with its vertebrate fauna. Additional lithologs of the Yerrapalli and Maleri formations are provided on the left side to indicate variations of thickness (after Dasgupta, 1993; Bandyopadhyay et al., 2002). a prolacertid () (Sen, 2003), a rauisuchian (Yarasuchus) (Sen, Namibia, the age of the Yerrapalli Formation had been assigned to the 2005), and an undescribed erythrosuchid (cf. ) (Fig. 3). early Middle Triassic () (Bandyopadhyay, 1988; Cox, 1991; Jain et al. (1964) considered the age of Yerrapalli Formation as late Lower Anderson and Anderson, 1993; Bandyopadhyay and Sengupta, 1999). Triassic or possibly early Middle Triassic. Later, with the recovery of Sen (2005) opined that the presence of Pamelaria and Yarasuchus fur- new material, their assessment and correlation with coeval formations, ther strengthen this correlation between Middle Triassic. namely the of Tanzania, N’tawere Formation of Zam- The overlying Bhimaram Formation is dominated by coarse, peb- bia, the Donguz Series of Russia, and the Omingonde Formation of bly, yellowish brown, feldspathic sandstone intercalated with abundant 80 red mudstone; fragmentary remains of temnospondyl and dicynodonts have been found from this unit (Kutty et al., 1987). The Maleri Formation, above the Bhimaram Formation, is an- other mud-dominated, richly fossiliferous horizon. It begins with a thick, red mudstone and passes upward into a succession of sandstone-mud- stone alternations. Thick, sheet-like sandstones alternate with relatively thicker mudstones intervals. The mudstones are dominantly red to brown- ish red and occasionally green, structureless, and poorly lithified. The sandstones are quartzose, medium- to coarse-grained, and are cross bed- ded with overlapping channel fills forming multistoried packages with individual channel fills having bottom rich in clay galls and trans- ported bone fragments. Lenticular bodies of caliche-derived peloidal calcirudite/calcarenite are common (Sarkar, 1988). These appear either at the bottom of channel sand bodies or as solitary bodies enclosed in the mudstones. The Maleri Fauna The Maleri Formation has been biochronologically divided into a lower part with a fauna, and an upper part with an Early Norian fauna (Fig. 4). The characteristic Lower Maleri fauna includes a metoposaurid (Buettneria) (Sengupta, 2002), a rhynchosaur (), a (), a prolacertid (Malerisaurus), a basal saurischian (Alwalkeria) (Langer, 2004), and a cynodont () (Figs. 3, 4). In addition, there are a dipnoan (Ceratodus), an undescribed xenacanthid, an unnamed resem- bling (Kutty et al., 1987), and a prosauropod (cf. FIGURE 4. The main biotic horizons of the of the Pranhita-Godavari basin. ) (Kutty et al., 1987). The Upper Maleri fauna consists of two chigutisaurs (Compsocerops and Kuttycephalus), and two The Kota Fauna phytosaurs ( and ) (Hungerbühler et al., 2002). A The Lower Kota has produced several reptiles and (Fig. and an aetosaur are also found in this horizon. 3, 4). Among the reptiles, there are two sauropod dinosaurs ( A thick, basal sandstone followed by an alternating series of sand- and ) (Yadagiri, 2001), two sphenodontians (Rebbanasaurus stone and mudstone occurs in the overlying Dharmaram Formation. The and Godavarisaurus) (Evans et al., 2001), and two other lepidosaurs sand bodies are comparatively thicker and the sand-mud ratio is higher (Bharatagama and Paikasisaurus) (Yadagiri, 1986; Evans et al., 2002). than the Maleri Formation (Fig. 3). On the basis of isolated teeth, nine mammals have been identified. Among The Dharmaram Fauna the non-therians, there are two triconodonts (Paikasigudodon and Dyskritodon) (Prasad and Manhas, 2002), two docodonts (Gondtherium Two successive vertebrate faunal zones have also been identified and Godavariodon) (Prasad and Manhas, 2001; Prasad, 2003), a in the Dharmaram Formation (Fig. 4). The Lower Dharmaram fauna kuehneotheriid (Kotatherium); the other two non-therians are contains a dipnoan (Ceratodus), a xenacanthid (Xenacanthus), a large Indozostrodon and Indotherium (Datta and Das, 2001). In addition, phytosaur and three different types of aetosaurs. One of the aetosaurs there are a therian (Trishulotherium) and a holotherian incertae sedis has been mentioned as a “-like form” by Kutty and (Nakunodon) (Averianov, 2002). Sengupta (1989), a characteristic member of the lower Dharmaram fauna. The Upper Kota contains three semionontids (, On the basis of the faunal components, Kutty and Sengupta (1989) have Paradapedium and Tetragonolepis), a pholidophorid (), suggested a Late Norian age for this zone. The Upper Dharmaram fauna and a (Indocoelacanthus). The reptiles of the Upper Kota includes a large plateosaurid and a sphenosuchian. The age of the Upper include a (Campylognathoides), a mesosuchian Dharmaram was previously considered Late Triassic (Kutty and crocodylomorph, and a cryptodiran (Indochelys) (Datta et al., Sengupta, 1989). On the basis of faunal analyses, Bandyopadhyay and 2000). An Early Jurassic age has been considered for the Kota Formation Roy Chowdhury (1996) suggested that the beginning of the terrestrial since the nineteenth century. Close scrutiny of the taxa of both the lower Jurassic started in the Upper Dharmaram. Though the details of the and the upper units of the Kota Formation led Bandyopadhyay and Roy fauna are not yet available, stratigraphic disposition, absence of typical Chowdhury (1996) to suggest that the Kota Formation has an age rang- Triassic fauna and preliminary comparison of the upper Dharmaram ing from Hettangian to , and it may even extend into the Middle fauna with other Early Jurassic faunas indicates an early Early Jurassic Jurassic. It may be mentioned that among the Kota , Lepidotes age (Hettangian) for this horizon. This will be discussed in detail later. deccanensis is closest to L. elvensis, which is found from the Toarcian of The overlying Kota Formation is also divisible into two parts, (Jain, 1983). The other Kota fishes, Paradapedium and each with its own distinct (Fig. 4). The lower part of Kota Tetragonolepis, also show strong similarities with the Toarcian forms of includes a thick, hard, compact and coarse sandstone that is pebbly in western Europe (Schaeffer and Patterson, 1984). Presence of such forms places and grades both laterally and vertically into finer siltstone and in the lacustrine Kota was believed to be due to influence of mudstone. On top of siltstone-mudstone beds, the Kota Formation con- extensive Toarcian transgression that according to Patterson and Owen tains marl and limestone, and then mudstone and ferruginous shale (1991), might have been instrumental for the invasion of the European interbedded with sandstone. Rudra and Maulik (1994) opined that a Liassic fishes in the Indian sub-continent as well as other circum-Tethyan meandering river deposited the lower part of this horizon, while continents. Bandyopadhyay and Roy Chowdhury (1996) thus suggested a braided river system formed the upper part; the limestone facies was a Toarcian age for these Kota fishes. Hence, the age of the Lower Kota interpreted as a lacustrine deposit. with its sauropods and therian and non-therians, overlying the Hettangian 81 Upper Dharmaram, ranges from Sinemurian to Pliensbachian, while the A scheme of land vertebrate faunachrons (LVF) of the Triassic, overlying Upper Kota, with its Toarcian fishes, crocodylomorph, and with the first appearance datum (FAD) of Lystrosaurus followed by the , has a Toarcian to probably ? age. FADs of , Shansiodon, , , The Kota Formation is unconformably overlain by the Gangapur Rutiodon, Pseudopalatus, , and , respectively, Formation (Kutty, 1969) characterized by coarse ferruginous sandstones has been proposed by Lucas (1998). The LVFs were, however, based on with pebble bands succeeded by a succession of alternations of sand- the FAD with its beginning and an end, whereas a considerable gap stone, mudstones, and siltstones. The mudstone often contains ferrugi- occurs “between the last occurrence of the type assemblage of a LVF and nous concretions. The mudstone of Gangapur yields a floral assemblage the FAD of the fossil taxon that marks its end” (Langer, 2005, p. 220). of age, but no vertebrate fossils have yet been identi- Lucas (1998) did not define the LVF on the basis of any type assemblage, fied. but rather named the LVF on the basis of the geographical location from where the type fauna was recovered. Rayfield et al. (2005) commented DISCUSSION that index fossils like , Paleorhinus, and Rutiodon and few From the above, it can be seen that the P-G basin has a vertebrate of the aetosaur taxa, which are important in the context of P-G basin, record with nine – one Permian, five Triassic, and three Jurassic show taxonomic instability and are not easily correlatable. Lehman and (Fig. 4). It starts with the (1) upper Upper Permian (Tatarian) Kundaram Chatterjee (2005) stated that the Otischalkian and Apachean faunachrons Formation, followed by (2) the Lower Triassic Kamthi. The following of Lucas’ LVF scheme do not support their vertebrate findings from the Middle Triassic (Anisian) Yerrapalli Formation (3) occurs below the Dockum . Bhimaram Formation, which can also be tentatively identified as a sepa- In an Indian context, the undescribed phytosaurs, aetosaurs, rate biozone of Anisian to age. The Maleri Formation has been sphenodontian, and prosauropods of the P-G basin create some uncer- biochronologically divided into a Carnian Lower Maleri (4) and an early tainty for definite correlation. However, Anderson and Anderson (1993) Norian Upper Maleri (5). The overlying Dharmaram is again had noted that the Yerrapalli and Maleri faunas are important Triassic biochronologically subdivided into late Norian Lower Dharmaram (6) faunas in global aspect. Recently, Langer (2005) equated the Lower and an early Early Jurassic (Hettangian) Upper Dharmaram (7). The Maleri with the lower fauna-bearing zone of the Ischigualasto Forma- Jurassic Kota Formation has an Early Jurassic (Sinemurian to tion, lower part of the Cacheuta and the upper part of lower Makay, Pliensbachian) age Lower Kota (8) and a late Early Jurassic to early Pebbly Arkose, and Molteno formations. The Upper Maleri faunal zone Middle Jurassic (Toarcian to ?Aalenian) age Upper Kota (9). has been correlated with the Lower Elliot, lower part of the upper Makay, It is evident from the above faunal analyses and stratigraphy of and lower parts of the Rio Blanco and Los Colorados. Langer (2005) also the P-G basin that the fauna of the Kota Formation is the youngest fauna indicated a gap between the lower and upper fauna of the Maleri and he present in this basin. The Upper Kota fauna includes semionontids marked the base of the Ischigualasto as 227.8 Ma from the radiometric (Lepidotes, Paradapedium and Tetragonolepis), a pholidophorid, a co- dating of bentonites (Rogers et al., 1993). All these push up the age of elacanth, a pterosaur, a mesosuchian crocodylomorph, and a cryptodiran the Upper Maleri fauna (post Ischigualasto sensu Langer, 2005) beyond turtle. The Lower Kota has sauropods, sphenodontians, a lepidosaur, a what was envisaged by Lucas (1998), who kept the Upper Maleri and , therians and non-therian mammals. The faunal analyses of both the among some other “principal correlatives” the Upper and Lower Kota have established an Early Jurassic to early of the Adamanian LVF of Upper Carnian age. On the other hand, Lehman Middle Jurassic age for the entire formation. Hence, the Triassic Jurassic and Chatterjee (2005) noted that Redondasaurus and Typothorax (= boundary in the P-G basin has to be placed below the Kota Formation. ), the two major taxa of the Apachean LVF of Lucas Immediately underlying the Kota Formation is the Dharmaram Forma- (1998), are also present in the Cooper Canyon Formation, whose detrital tion that has two faunal zones. The lower faunal zone contains phytosaurs biotites have been dated as 210 Ma (Long and Lehman, 1993). Hence, and aetosaurs and hence, its age is definitely Triassic. The Upper the large phytosaur and “Paratypothorax”-like aetosaur of the Lower Dharmaram contains a plateosaurid and a sphenosuchian, which are not Dharmaram fauna are more likely to indicate a Late Norian age. definite markers of Jurassic. However, the phytosaurs and aetosaurs of Thus, the faunachronology of the P-G basin also suggests a depar- the Lower Dharmaram are completely absent there. Other Triassic ture from the LVF scheme of Lucas (1998). The ages of the Maleri and sphenosuchians of the world are always associated with Triassic faunal Dharmaram faunas, according to the present analysis, should be younger elements. from the is intimately than was envisaged by Lucas (1998), and the Triassic-Jurassic boundary associated with a rauisuchian close to (Sues et al., (TJB) should be at the base of the Upper Dharmaram fauna 2003). from the Chinle (Clark et al., 2001) and (Bandyopadhyay and Roy Chowdhury, 1996). The Upper Dharmaram Saltoposuchus from the Middle Stubensandstein (Schoch and Wild, 1999) fauna, which occurs between the phytosaur and aetosaur-bearing Lower are all associated with Triassic faunal elements. The Los Colorados For- Dharmaram and mammal- and sauropod-bearing Lower Kota faunas, is mation that is now considered as uppermost Triassic and has a “mixture” the “transitional fauna” between the Triassic and Jurassic in India. of Triassic and Jurassic faunas, also has aetosaurs with advanced theropod As stated above, lithostratigraphically, the Triassic-Jurassic for- dinosaurs (Arcucci et al., 2004). Exploration in the Upper Dharmaram mations of the P-G basin form a continuous, conformable succession zone during the last three decades has not yielded a single piece of any (Figs. 3, 4). Though the P-G basin does not have a complete faunal phytosaur and aetosaur skeletal remains, which are quite abundant in the assemblage of Permian or Early Triassic age, a continuity in the faunal Lower Dharmaram zone. There is incompleteness in the faunal scenario succession from Triassic to early Middle Jurassic can be envisaged. The of the P-G, basin as the phytosaurs, aetosaurs, plateosaurids and presence of Lystrosaurus, Brachyops, and the estheriid ostracode Cyzicus sphenosuchian of the Upper and the Lower Dharmaram are yet to be (Euestheria) mangliensis Jones 1862 (Tasch et al., 1973; Ghosh et al., described. However, the Upper Dharmaram fauna, sandwiched between 1987) indicate an Early Triassic age for the Kamthi Formation. the Late Triassic Lower Dharmaram and the Jurassic Kota fauna, has no Dicynodonts and labyrinthodonts continue through the Yerrapalli and faunal element that goes against the Jurassic age. Besides, no faunal Bhimaram formations and into the Upper Triassic Maleri Formation. element of the Lower Dharmaram or the Lower Kota has been found in The Yerrapalli faunal association also has a rauisuchian, a prolacertid, this zone. Moreover, the Dharmaram Formation is conformable with the and an erythrosuchid. The Upper Maleri and the Lower Dharmaram Kota Formation. Hence, the base of the Upper Dharmaram faunal zone faunas have phytosaurs and aetosaurs, but these abruptly disappear at is a place likely to indicate the Triassic-Jurassic boundary in the P-G the mudstone horizon at the base of the uppermost sandstone unit of the basin, and the scanty Upper Dharmaram fauna is all that is present of an Dharmaram Formation. From this point upward, a new faunal assem- early Early Jurassic terrestrial fauna in India. blage, containing a large plateosaurid and a sphenosuchian, occurs in the 82

FIGURE 5. The Triassic-Jurassic boundary plotted on the geological map of the northern part of the Pranhita-Godavari basin around the villages of Maleri and Dharmaram. The white and black bands in the Maleri indicate sandstone and calcirudites, respectively, within the mudstone. The dark grey bands in the Dharmaram indicate sandstones within mudstone. The amount of dip varies from 10º to 18º. Upper Dharmaram. Lucas (1998) defined the Apachean, a land Thecodontosauridae. However, Lucas (1994) argued that, out of this vertebrate faunachron characterized by the metoposaurid Apachesaurus list, only the Phytosauridae and have well-established gregorii, a sphenodontian, a procolophonid, the phytosaur Late Triassic records, whereas the other families became extinct prior to Redondasaurus bermani, the aetosaur Redondasuchus reseri, theropods, the Norian. But, in the P-G basin, the phytosaurs and aetosaurs are and a possible cynodont. None of these elements are noted in the Upper present up to the Late Norian in the Lower Dharmaram but are absent in Dharmaram fauna, whereas the metoposaurid-phytosaur-aetosaur com- the Hettangian Upper Dharmaram or Sinemurian to Pliensbachian Lower bination is typical of the horizons occurring below the Upper Dharmaram. Kota Formation. Benton (1986a, b, 1994) further suggested two differ- Metoposaurids, in fact, disappeared after the Lower Maleri, which is ent episodes of extinction during the Triassic – one at the end of quite early in comparison to the North American genera (Sengupta, 2003). the Carnian and the other at the end-Triassic. In the P-G basin, So, an abrupt faunal change actually occurs between biozone 6 (i.e., the metoposaurids, rhynchosaurs, prolacertids, and non-mammalian Lower Dharmaram) and biozone 7 (i.e., the Upper Dharmaram); farther became extinct after the end-Carnian Lower Maleri. The Early upward, a new faunal association, dominated by sauropods, Norian Upper Maleri is marked by the appearance of chigutisaurids, sphenodontians, lepidosaurs, crocodylomorphs, turtles and mammals, advanced phytosaurs (Rutiodon, Leptosuchus) and aetosaurs. Thus, the appears (Fig. 4). So, the Triassic-Jurassic transition in the Indian sce- P-G basin faunal succession shows two faunal turnovers during the nario appears to commence at the base of the upper part of the Dharmaram Triassic. Stratigraphic positions of these two major faunal turnovers in Formation, close to the uppermost sandstone band of the Dharmaram the P-G basin are indicated in the lithologic map and succession (Figs. 3, Formation (Fig. 5). 5). Benton (1993) listed several terrestrial families that be- The biotic turnover in the Triassic-Jurassic faunal community, came extinct at the end-Triassic; these are the Proganochelyidae, both in the marine and terrestrial realms, is considered to be due to an Kuehneosauridae, Pachystropheidae, , Phytosauridae, end-Triassic extinction (Colbert 1949, 1958; Padian, 1986; Olsen et al., Stagonolepididae, , , Saltoposuchidae and 1987, 1990). A major end-Triassic extinction was first proposed by 83 Newell (1963) on the basis of the extinction of ammonoid families and “long-term ecological degradation” (Tanner et al., 2004; p. 115). replacement of many groups of amphibians and reptiles by dinosaurs. Several workers have argued, and are still arguing, about the “hazy” However, Lucas and Tanner (2004) considered the “Triassic-Jurassic” record of terrestrial tetrapod extinction during the end-Triassic (Lucas, as a series of smaller, step-wise during which 1994; Fraser and Sues, 1994; Tanner et al., 2004). However, it can be about 76% of species became extinct (Raup, 1992). A gradualistic faunal said that a significant faunal turnover did occur in India between the Late replacement due to sea-level change, oceanic anoxia, climatic change, and Norian Lower Dharmaram and the Hettangian Upper Dharmaram. It is widespread aridity during the Late Triassic was proposed by several hoped that more details of Upper Dharmaram fauna will shed new light authors (Newell, 1963; Tucker and Benton, 1982; Hallam, 1990). A on the exact timing and nature of this change. contrasting suggestion, however, involved a sudden change induced by a ACKNOWLEDGMENTS catastrophic bolide impact at the end of the Triassic that caused an increase in atmospheric opacity, outgassing of CO2 and SO2 due to severe The authors take the opportunity to thank Prof. Tapan K. volcanism, and sudden release of methane hydrates from the seafloor, Roy Chowdhury, formerly of Indian Statistical Institute, for fruitful which affected the total milieu of the (Raup and Sepkoski, 1984; discussion on this topic. The authors are extremely thankful to Dr. J.D. Raup, 1986; Olsen et al., 1987, 2002a, b; Retallack, 2001). Tanner et al. Harris for his comments and careful scrutiny that helped to improve the (2004), however, concluded that the Late Triassic-Early Jurassic biotic quality of the manuscript. Comments from other reviewers, Dr. S.G. turnover involved multiple forcing mechanisms, e.g., sea-level or climate Lucas and Dr. M.C. Langer, were also very helpful. The infrastructrual change along with a bolide impact or volcanism, that resulted in the facilities wre provided by ISI.

REFERENCES

Anderson, J.M. and Anderson, H.M., 1993, Terrestrial flora and fauna of the discovery of Triassic cynodont reptiles from India: Science and the Gondwana Triassic. Part I - occurrences: New Mexico Museum of Culture, v. 35, p. 411. Natural History and Science, Bulletin 3, p. 3-12. Clark, J.M., Sues, H.-D. and Berman, D.S., 2001, A new specimen of Arcucci, A.B, Marsicano, C.A. and Caselli, A.T. 2004, Tetrapod association Hesperosuchus agilis from the Upper Triassic of New Mexico and the and palaeoenvironment of the (): a interrelationships of basal crocodylomorph : Journal of Ver- significant sample from western Gondwana at the end of Triassic: Geobios, tebrate , v. 20, p. 683-704. v. 37, p. 557-568. Colbert, E.H., 1949, Progressive adaptations as seen in the fossil record, in Averianov, A. O., 2002, Early Cretaceous “symmetrodont” mammal Jepsen, G.L., Mayr, E. and Simpson, G.G., eds., Genetics, paleontology Gobitheriodon from Mongolia and the classification of and evolution: Princeton, Princeton University Press, p. 390-402. “”: Acta Palaeontologica Polonica, v. 47, p. 705-716. Colbert, E.H., 1958, Tetrapod extinctions at the end of Triassic period: Bandyopadhyay, S., 1988, Vertebrate fossils from the Pranhita-Godavari Proceedings of the National Academy of Science, v. 44, p. 973-977. valley of India with special reference to the Yerrapalli Formation: Mod- Cox, C.B., 1991, The Pangean dicynodont Rechnisaurus and the compara- ern Geology, v. 13, p. 107-117. tive biostratigraphy of Triassic dicynodont faunas: Palaeontology, v. Bandyopadhyay, S., 1999, Gondwana vertebrate faunas of India: Proceed- 34, p. 767-784. ings of the Indian National Science Academy, v. A65, p. 285-313. Dasgupta, K., 1993, Some contributions to the stratigraphy of the Yerrapalli Bandyopadhyay, S. and Roy Chowdhury, T., 1996, Beginning of the conti- Formation, Pranhita-Godavari Valley, Deccan, India: Journal of the Geo- nental Jurassic in India – a palaeontological approach: Museum of North- logical Society of India, v. 42, p. 223-230. ern Arizona, Bulletin 60, p. 371-378. Datta, P.M., Manna, P., Ghosh, S.C. and Das, D.P., 2000, The first Jurassic Bandyopadhyay, S. and Sengupta, D.P., 1999, Middle Triassic vertebrates of turtle from India: Palaeontology, v. 43, p. 99-109. India: Journal of African Earth Sciences, v. 29, p. 233-241. Datta, P.M. and Das, D.P., 2001, Indozostrodon simpsoni, gen. et. sp. nov., Bandyopadhyay, S., RoyChowdhury, T.K. and Sengupta, D.P., 2002, an Early Jurassic megazostrodontid mammal from India: Journal of Taphonomy of some Gondwana vertebrate assemblages of India: Sedi- , v. 21, p. 528-534. mentary Geology, v. 147, p. 219-245. Evans, S.E., Prasad, G.V.R. and Manhas, B.K., 2001, Rhynchocephalians Behrensmeyer, A.K. and Hook, R.W., 1992, Paleoenvironmental context (Diapsida: ) from the Jurassic Kota Formation: Zoological and taphonomic modes, in Behrensmeyer, A.K., Damuth, J.D., Journal of the Linnean Society, v. 133, p. 309-334. DiMichele, W.A., Potts, R., Sues, H.-D. and Wing, S.L., eds., Terrestrial Evans, S.E., Prasad, G.V.R. and Manhas, B.K., 2002, Fossil from the ecosystems through time: Chicago, University Chicago Press, p. 15- Jurassic Kota Formation of India: Journal of Vertebrate Paleontology, v. 136. 22, p. 299-312. Benton, M.J., 1986a, More than one event in the Late Triassic extinction: Fraser, N.C. and Sues, H.-D., 1994, Comments on Benton’s “Late Triassic Nature, v. 321, p. 857-861. to Middle Jurassic extinctions among continental : testing the Benton, M.J., 1986b, The Late Triassic tetrapod extinction events, in pattern”, in Fraser, N.C. and Sues, H.-D., eds., In the shadow of the Padian, K., ed., The beginning of the Age of Dinosaurs: Cambridge, dinosaurs: Cambridge, Cambridge University Press, p. 398-400. Cambridge University Press, p. 303-320. Ghosh, S.C., Dutta, A., Nandi, A. and Mukhopadhyay, S., 1987, Estheriid Benton, M.J., 1993, Reptilia, in Benton, M.J. ed., The fossil record 2: zonation in the Gondwana: The Palaeobotanist, v. 36, p. 143-153. London, Chapman and Hall, p. 681-715. Hallam, A., 1990, The end-Triassic mass extinction event, in Sharpton, Benton, M.J., 1994, Late Triassic to Middle Jurassic extinctions among V.L. and Ward, P.D., eds., Global catastrophes in Earth history: an continental tetrapods: testing the pattern, in Fraser, N. C. and Sues, H.- interdisciplinary conference on impacts, volcanism, and mass mortal- D., eds., In the shadow of the dinosaurs: Cambridge, Cambridge Univer- ity: Geological Society of America Special Paper, v. 247, p. 577-583. sity Press, p. 366-397. Hungerbühler, A., Kutty, T.S. and Chatterjee, S., 2002, New phytosaurs Chakraborty, C., Mandal, N. and Ghosh, S.K., 2003, Kinematics of the from the Upper Triassic of India: Journal of Vertebrate Paleontology, v. Gondwana basins of peninsular India: Tectonophysics, v. 377, p. 299- 22, p. 68A. 324. Jain, S.L., 1983, A review of the Lepidotes (: Chatterjee, S., 1980, The evolution of rhynchosaurs, in Taquet, P., ed., ) with special reference to the species from Kota For- Ecosystèmes continentaux du Mésozoique: Memoires de la Société mation (Lower Jurassic), India: Journal of the Palaeontological Society Géologique de France, N.S., v. 139, p. 57-65. of India, v. 28, p. 7-42. Chatterjee, S., Jain, S.L., Kutty, T.S. and Roy Chowdhury, T.K., 1969, On Jain, S.L., Robinson, P.L. and Roy Chowdhury, T.K., 1964, A new vertebrate 84 fauna from the Triassic of Deccan, India: Journal of the Geological Cambridge University Press, 378 p. Society of London, v. 120, p. 115-124. Patterson, C., and Owen, H.G., 1991, Indian isolation or contact? A re- Jones, T.R., 1862, A monograph on fossil Estheriae: London, sponse to Briggs: Systematic Zoology, v. 40, p. 96-100. Palaeontological Society of London, 134 p. Prasad, G.V.R., 2003, Stratigraphic distribution and diversity of Mesozoic Kutty, T.S., 1969, Some contributions to the stratigraphy of the Upper mammals of India, in XIX Indian colloquium on micropalaeontology Gondwana formations of the Pranhita-Godavari Valley, central India: and stratigraphy & symposium on recent developments in Indian Journal of the Geological Society of India, v. 10, p. 33-48. palaeontology and palaeoclimate: Varanasi, Benaras Hindu University, Kutty, T.S., Jain, S.L. and Roy Chowdhury, T., 1987, Gondwana sequence of p. 124. the northern Pranhita-Godavari Valley: its stratigraphy and vertebrate Prasad, G.V.R. and Manhas, B.K., 2001, First docodont mammals of Laurasian faunas: The Palaeobotanist, v. 36, p. 214-219. affinity from India: Current Science, v. 81, p. 1235-1238. Kutty, T.S. and Sengupta, D.P., 1989, Late Triassic formations of the Prasad, G.V.R. and Manhas, B.K., 2002, Triconodont mammals from the Pranhita-Godavari valley and their vertebrate faunal sequence-a reap- Jurassic Kota Formation of India: Geodiversitas, v. 25, p. 445-464. praisal: Indian Journal of Earth Science, v. 16, p. 189-206. Raup, D.M., 1986, Biological extinction in Earth history: Science, v. 231, Langer, M.C., 2004, Basal , in Weishampel, D. B., Dodson, P. and p. 1528-1533. Osmólska, H., eds., The Dinosauria, second edition: Berkeley, Univer- Raup, D.M., 1992, Large-body impact and extinction in the : sity of California Press, p. 25-46. Paleobiology, v. 18, p. 80-88. Langer, M.C., 2005, Studies on continental Late Triassic tetrapod Raup, D.M. and Sepkoski, J.J., Jr., 1984, Periodicity of extinctions in the biochronology. II. The Ischigualastian and a Carnian global correlation: geologic past: Proceedings of the National Academy of Sciences, v. 81, Journal of South American Earth Sciences, v. 19: p. 291-239. p. 801-805. Lehman, T. and Chatterjee, S., 2005, Depositional setting and vertebrate Ray, S., 1997, Some contributions to the Lower Gondwana stratigraphy of biostratigraphy of the Triassic of : Journal of the Pranhita-Godavari valley, Deccan, India: Journal of the Geological Earth System Science, v. 114: p. 325-351. Society of India, v. 50, p. 633-640. Long, L.E. and Lehman, T.M., 1993, Rb-Sr ages of detrital mica in sand- Ray, S., 1999, Permian reptilian fauna from the Kundaram Formation, stones of the Triassic Dockum Group, Texas panhandle: Geological Pranhita-Godavari valley, India: Journal of African Earth Sciences, v. Society of America, Abstracts with Program, v. 25, p. A66. 29, p. 211-218. Lucas, S.G., 1994, Triassic tetrapod extinctions and the compiled correla- Ray, S., 2001, Small dicynodonts from the Permian of India: Paleontologi- tion effect: Canadian Society of Petroleum and Geological Memoir, v. cal Research, v. 5, p. 177-191. 17, p. 869-875. Ray, S. and Bandyopadhyay, S., 2003, Late Permian vertebrate community Lucas, S.G., 1998, Global Triassic tetrapod biostratigraphy and of the Pranhita-Godavari valley, India: Journal of Asian Earth Sciences, biochronology: Palaeogeography, Palaeoclimatology, Palaeoecology, v. v. 21, p. 643-654. 143, p. 347-384. Rayfield, E.J., Barrett, P.M., McDonnell, R.A. and Willis, K.J., 2005, A Lucas, S.G. and Tanner, L.H., 2004, Late Triassic extinction events: geographical information system (GIS) study of Triassic vertebrate Albertiana, v. 31, p. 31-40. biochronology: Geological Magazine, v. 142, p. 327-354. Maulik, P.K. and Chaudhuri, A.K., 1983, Trace fossils from continental Read, H.H. and Watson, J., 1975, Introduction to geology, vol. 2: New Triassic red beds of the Gondwana sequence, Pranhita-Godavari Valley, York, Macmillan Press Ltd., 353 p. south India: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 41, Retallack, G.J., 2001, A 300-million- record of atmospheric carbon p. 17-34. dioxide from fossil plant cuticles: Nature, v. 411, p. 287-290. Newell, N.D., 1963, Crises in the history of life: Scientific American, v. Robinson, P.L., 1970, The Indian Gondwana formations – a review: First 208, p. 76-92. International Symposium of Gondwana Stratigraphy, I.U.G.S., South Olsen, P.E. and Galton, P. M., 1977, Triassic-Jurassic tetrapod extinctions: America, p. 201-268. are they real?: Science, v. 197, p. 983-985. Rogers, R.R., Swisher, C.C., III, Sereno, P.C., Monetta, A.M., Forster, C.A., Olsen, P.E. and Sues, H.-D., 1986, Correlation of continental Late Triassic and Martinez, R.N., 1993, The Ischigualasto tetrapod assemblage, Late and Early Jurassic sediments, and patterns of the Triassic-Jurassic tetra- Triassic, Argentina, and 40Ar/39Ar dating of origins: Science, v. pod extinction, in Padian, K., ed., The beginning of the Age of Dino- 260, p. 794-797. saurs: Cambridge, Cambridge University Press, p. 321-351. Roy Chowdhury, T., 1970, Two new dicynodonts from the Triassic Yerrapalli Olsen, P.E., Shubin, N.H. and Anders, M.H., 1987, New Early Jurassic tetra- Formation of central India: Palaeontology, v. 13, p. 132-144. pod assemblages constrain Triassic-Jurassic tetrapod extinction: Sci- Rudra, D.K. and Maulik, P.K., 1994, Lower Jurassic Kota Limestone of ence, v. 237, p. 1025-1029. India, in Gierlowski-Kordesch, E. and Kelts, K., eds., Global geological Olsen, P.E., Koeber, C., Huber, H., Montaniri, A., Powell, S.J., Et-Touhani, record of lake basins vol. 1: Cambridge, Cambridge University Press, v. M. and Kent, D.V., 2002b, The continental Triassic-Jurassic boundary 1, p. 185-191. in central Pangea: recent progress and preliminary report of an Ir anomaly, Sarkar, S.N., 1988, Petrology of caliche derived calcirudite/calcarenite in in Koeber, C., and MacLeod, K., eds., Catastrophic events and mass the Late Triassic Maleri Formation of the Pranhita-Godavari valley, extinctions: impacts and beyond: Geological Society of America Special south India: Sedimentary Geology, v. 55, p. 263-282. Paper, v. 356, p. 505-522. Schaeffer, B. and Patterson, C, 1984, Jurassic fishes from western United Olsen, P.E., Kent, D.V., Sues, H.-D., Koeber, C., Huber, H., Montanari, A., States, with comments on Jurassic distribution: American Museum Rainforth, E.C., Fowell, S.J., Szajna, M.J. and Hartline, B.W., 2002a, Novitates, v. 2796, p. 1-86. Ascent of dinosaurs linked to iridium anomaly at the Triassic-Jurassic Schoch, R.R. and Wild, R., 1999, Die Wirbeltier Fauna im von boundary: Science, v. 296, p. 1305-1307. Süddeutschland, in Hauschke, N. and Wilde, V., eds., Trias-Eine ganz Olsen, P.E., Powell, S.J. and Cornet, B., 1990, The Triassic/Jurassic bound- andere Welt: Munich, Verlag Dr. Friedrich Pfeil, p. 395-408. ary in continental rocks of eastern ; a progress report, in Schoch, R.R. and Milner, A.R., 2000, Encyclopedia of herpetology: Sharpton, V.L. and Ward, P.D., eds., Global catastrophes in Earth his- , part 3: Munich: Verlag Dr. Friedrich Pfeil, 203 p. tory: an interdisciplinary conference on impacts, volcanism, and mass Sen, K., 2003, Pamelaria dolichotrachela, a new prolacertid reptile from mortality: Geological Society of America Special Paper, v. 247, p. 585- the Middle Triassic of India: Journal of Asian Earth Sciences, v. 21, p. 593. 663-681. Owen, R., 1855, Description of the cranium of a labyrinthodont reptile, Sen, K., 2005, A new rauisuchian archosaur from the Middle Triassic of Brachyops laticeps, from Mangali, central India: Quarterly Journal of India: Palaeontology, v. 48, p. 185-196. the Geological Society of London, v. 11, p. 37-39. Sengupta, D.P., 2002, Indian metoposaurid amphibians revised: Paleonto- Padian, K., ed., 1986, The beginning of the Age of Dinosaurs: Cambridge, logical Research, v. 6, p. 41-65. 85 Sengupta D.P., 2003, Triassic temnospondyls of the Pranhita-Godavari versity Press, p. 443-452. basin: Journal of Asian Earth Sciences, v. 21, p. 655-662. Tucker, M.E. and Benton, M.J., 1982, Triassic environments, climates, and Sengupta, S., 1970, Gondwana sedimentation around Bheemaram reptile evolution: Palaeogeography, Palaeoclimatology, Palaeoecology, (Bhimaram), Pranhita-Godavari Valley, India: Journal of Sedimentary v. 40, p. 361-379. Petrology, v. 40, p. 140-170. Veevers, J.J. and Tewari, R.C., 1995, Gondwana Master Basin of peninsular Sheldon, N.D., 2005, Do red beds indicate paleoclimatic conditions? A India between Tethys and the interior of the Gondwanaland Province of Permian case study: Palaeogeography, Palaeoclimatology, Palaeoecology, Pangea: Geological Society of America, Memoir 187, p. 1-72. v. 228, p. 305-319. Ward, P.D., Botha, J., Buick, R., De Kock, M.O., Erwin, D.H., Garrison, Sues, H.-D., Olsen, P.E., Carter, J.G. and Scott, D.M., 2003, A new G.H., Kirsch, J.L. and Smith, R., 2005, Abrupt and gradual extinction crocodylomorph archosaur from the Upper Triassic of North Carolina: among Late Permian land vertebrates in the Basin, South Africa: Journal of Vertebrate Paleontology, v. 23, p. 329-343. Science, v. 307, p. 709-713. Tanner, L.H., Lucas, S.G. and Chapman, M.G., 2004, Assessing the record Yadagiri, P. 1986, Lower Jurassic lower vertebrates from Kota Formation, and causes of Late Triassic extinctions: Earth Science Reviews, v. 65, p. Pranhita-Godavari valley, India: Journal of the Palaeontological Society 103-139. of India, v. 31, p. 89-96. Tasch, P., Sastry, M.V.A., Shah, S.C., Rao, B.R.J., Rao, C.N. and Ghosh, S.C., Yadagiri, P., 2001, The osteology of Kotasaurus yamanpalliensis, a sauro- 1973, Estheriids of Indian : significance for continental fit, pod dinosaur from the Early Jurassic Kota Formation: Journal of Verte- in Campbell, K.S.W., ed., Gondwana geology: Canberra, Australian Uni- brate Paleontology, v. 21, p. 242-252.