Indian Dinosaurs

Ashok Sahni. Encyclopedia of Dinosaurs. Editor: Philip J Currie & Kevin Padian. Amsterdam: Academic Press, 1997.

Fragmentary bones, later to be identified as dinosaurs, were first described by Captain (later Major- General) Sleeman in 1828 from the now classic sections of Jabalpur Cantonment (Matley, l921) in India. The first systematic description of Indian dinosaurs was carried out by Lydekker (1877), who erected the new sauropod taxon Titanosaurus indicus on the basis of two caudal vertebrae and an imperfectly preserved femur. Later, Matley laid the foundations of the study of Indian dinosaurs with the collection and description of several taxa from central India (Matley, 1921) and south India (Matley, 1929), culminating in a monographic description of all known material at the time (von Huene and Matley, 1933). The next major phase of investigations started in the early 1960s when scientists from the Geological Studies Unit, Indian Statistical Institute, Calcutta, began to explore the Pranhita-Godavari Basin (Jain et al., 1979). In the past decade, the contributions of the Geological Survey of India and Panjab and Delhi Universities have been largely instrumental in reviving interest in Indian dinosaurs (Sahni et al., 1994).

The occurrence of Indian dinosaurs is currently confined to central and southern India, and the record extends to all three Mesozoic periods. The Triassic and Jurassic dinosaurs are known from the Pranhita- Godavari Gondwana Rift Basin, where a complete sedimentary sequence is found ranging from the Upper Permian to the Lower Cretaceous (Dasgupta, 1993). Cretaceous dinosaur localities are much more widespread and occur in two contrasting geologic Spatial and temporal distribution of Indian dinosaurs based on skeletal material, traces, and tracks. settings: one in the basal Deccan volcano-sedimentary sequences (Sahni et al., 1994) and the other in a regressive phase (Ariyalur Formation) toward the top of a paralic sequence yielding abundant shallow marine benthic invertebrates (Yadagiri and Ayyasami, 1979). Indian Cretaceous dinosaurs are represented by a diversity of fossils comprising cranial and postcranial material, braincases, nests and eggshell fragments, coprolites, and footprints.

The Triassic record includes the small coelurosaur Walkeria maleriensis, which represents one of the oldest dinosaurs known from Asia. It was reported by Chatterjee (1987) from the Late Triassic Maleri Formation at Nennal, Andhra Pradesh. Walkeria appears to be a lightly built, predaceous, bipedal form with a functionally tridactyl bird-like foot. The age of the Maleri Formation, which contains at least four generically similar taxa to the Dockum fauna of Texas, has been established on the basis of associated vertebrates, including metoposaurid and chigutisaurid temnospondyls, rhynchosaurid and phytosaurid reptiles, and traversodontid cynodonts (Dasgupta, 1993).

Dinosaurs have also been discovered in the overlying Dharmaram Formation (Kutty, 1969; Jain and Roychowdhury, 1987). The Dharmaram dinosaurs housed in the Museum of the Indian Statistical Institute are still to be systematically described. The limited information on these Rhaetian-Norian forms (Jain and Roychowdhury, 1987) suggests the presence of at least two prosauropods, one representing a large plateosaurid and the other a small anchisaurid.

The best known Jurassic dinosaur from India is Barapasaurus tagorei (Jain et al., 1975, 1979) from the Kota Formation (Early Jurassic) of the Pranhita- Godavari Basin. Barapasaurus, on display at the Museum of the Indian Statistical Institute, is a large sauropod with rather slender limbs (Fig. 2). Its spoon- shaped teeth bear coarse denticles on their sides. The cervical and anterior dorsal centra are opisthocoelous, whereas all others are nearly platycoelous (Jain et al., 1975). The sacrum has four co-ossified vertebrae with “waisted” amphiplatyan centra. The girdles are typically saurischian in nature. Some interesting aspects of Barapasaurus have been highlighted by Jain et al. (1979). These include early attempts at gigantism, bone reduction and economy in the vertebrae, and peculiar modifications in the region of the neural canal with the development of interlamellar hollows between the infradiapophysial laminae.

The presence of a possible ornithischian in the Kota Formation has been postulated on the basis of personal observation by E. H. Colbert in 1977 based on material collected by the Geological Survey of India (Jain, 1980). An Early Jurassic age for the Kota Formation has been established on the basis of an associated and fairly diverse vertebrate assemblage that includes pholidophorid teleosteans, coelacanthid crossopterygians, the cetiosaurid, a campylognathoid pterosaur, a teleosaurid crocodylian, and kuhneotheriid and amphidontid symmetrodonts (Dasgupta, 1993).

The Cretaceous dinosaurs of India are the most diverse and best known. The fauna is dominated by saurischians (sauropods and theropods) and a few doubtful ornithischians. The sauropods are characterized by at least two well-defined genera, Titanosaurus and Antarctosaurus. Another sauropod, cf. Laplatasaurus madagascarensis (von Huene and Matley, 1933), from the Pisdura locality, needs confirmation as to its affinities with the corresponding taxa from South America and Madagascar. The theropods are more diverse and can be grouped into about five taxa. The large carnivores are represented by Indosuchus raptorius (Abelisauridae) and Indosaurus matleyi (Abelisauridae), whereas the smaller-sized predaceous carnivores are exemplified by Compsosuchus, Jubbulporia, Laevisuchus, Dryptosauroides, Coeluroides, and Ornithomimoides.

At least three Cretaceous ornithischian genera have been named: Lametasaurus and Brachypodosaurus (Matley, 1923; Chakravarti, 1935) and Dravidosaurus (Yadagiri and Ayyasami, 1979). The taxonomic status of all three taxa is controversial (Chakravarti, 1935; Buffetaut, 1987) and until diagnostic material is forthcoming, the occurrence of stegosaurids and large ornithischians should be considered doubtful.

The age of the Lameta dinosaurs has been the subject of considerable recent work. Based on their microfossil assemblages and bio- and magnetostratigraphy (Sahni and Bajpai, 1988; Buffetaut, 1987; Courtillot et al., 1986), the Lameta Formation is considered to be largely Maastrichtian in age and coeval with the beds at Dongargaon and Pisdura (Jain and Sahni, 1983; Mohabey et al., 1993).

In recent years, spectacular finds of dinosaur (sauropod) nesting sites have been documented from the Lameta Formation occurring extensively across central peninsular India. To date, hundreds of nesting grounds and hatcheries have been reported (Mohabey, 1990). The eggs are large and spherical (Fig. 3) and range in size from 14 to more than 20 cm. These have tentatively been assigned to the Titanosauridae. On the basis of microstructural characteristics, the eggs have been grouped into four or five morpho- structural types (Sahni et al., 1994). Of general interest is the fact that one of the thick-shelled morphotypes from the Indian localities is similar to eggs attributed to the titanosaurid Hypselosaurus from Aix-en- Provence, France (Vianey-Liaud et al., 1987). Thin ornithischian eggshell fragments assignable either to small dinosaurs or to birds have also been described from the intertrappeans of Kutch (Bajpai et al., 1993).

Oxygen isotope analysis of the sauropod eggshells from the Lameta Formation from widespread localities (Sarkar et al., 1991) suggests that the dinosaurs imbibed water from small rivers and ponds. On the other hand, the carbon isotope values indicate that they were eating plants that follow the C3 photosynthetic pathway, such as small palms and conifers.

Large coprolites have been attributed to dinosaurs because of their size, morphology, and association with dinosaurian skeletal material from the Jurassic Kota Formation and from the Lameta Formation of the Pisdura area (Jain, 1983; Matley, 1939). During the collection of dinosaur fossil bones from the Kota Formation, Jain (1983) mentions the occurrence of a large number of coprolites—rounded, oval, or elliptical in shape and marked by dessication cracks. Matley (1939) reported the occurrence from Pisdura of numerous coprolites, up to 170 mm in length, that he regarded as belonging to the titanosaurid sauropods.

Currently, two braincases of sauropod dinosaurs have been recorded from India. The first of these constitutes part of the type material of the sauropod taxon Antarctosaurus septentrionalis (von Huene and Matley, 1933), whereas the second comprises a specimen from the Dongargaon locality described by Berman and Jain (1982) from the Lameta Formation.

The Triassic and Jurassic dinosaur localities are situated in the intracratonic rift basin of the Pranhita- Godavari Rift Basin. Walkeria maleriensis occurs in the Late Triassic Maleri Formation, which consists of red clays, fine to medium sandstones, and peloidal calcarenites and calcirudites (Dasgupta, 1993). This early dinosaur is found in association with the lungfish Ceratodus, labyrinthodont amphibians, rhynchosaurs, the eosuchian Malerisaurus, and therapsids. The landscape appears to be seasonally well watered with a preponderance of water bodies in which unionids and a variety of fishes and semiaquatic tetrapods lived (Jain, 1980).

The Kota Formation consists of fluvial sediments with a prominent highly fossiliferous limestone band representing a playa-type condition (Maulik and Rudra, 1986). The limestone shows desiccation cracks and was probably laid down in a moderately hot climate under mainly sediment-depauperate conditions. Jain (1980) has suggested thatBarapasaurus was terrestrial in habit but probably fed on nearby aquatic vegetation.

The environments of the Indian Lameta dinosaurs indicate the existence of a semiarid alluvial plain undergoing active pedogenesis. Massive and nodular calcretes form the dominant lithology for the nesting sites and occur as “limestone” outcropping in discontinuous patches across central peninsular India. The sandy carbonate horizons show desiccation cracks, honeycomb calcretes, brecciation, and pebbles derived from sheetwash events (Tandon et al., 1990; Sahni et al., 1994). The dinosaurian skeletal material is either found in coarse conglomerates as in the Kheda District of Gujarat or found as lag deposits or, more commonly, as reworked, fragmented, and weathered bones (Mohabey et al., 1993).

The relationships of Indian dinosaurs along with those of associated freshwater biotas have been used to assess the contiguity or isolation of the Indian Plate in the context of other Gondwana landmasses (Sahni and Bajpai, 1988). In general terms, the Indian dinosaurs have cosmopolitan affinities. According to Chatterjee (1987) and Jain (1990), the Late Triassic Walkeria is similar to Procompsognathus of Germany, Coelophysis of North America, and Syntarsus from Zimbabwe and North America. In the absence of coeval, comparable material from the Lower Jurassic from other parts of the world, it is more difficult to evaluate the relationships of the Kota Barapasaurus. It was probably a specialized offshoot of the central sauropod evolutionary line.

In one of the latest assessments of the affinities of Indian Cretaceous dinosaurs, Buffetaut (1987) has commented on the inadequacies in our knowledge of Gondwana dinosaurs. Based on the meager evidence at hand, the Indian sauropods are close to those known from Argentina. To the extent that titanosaurids are also known from southern France and Cretaceous sauropod eggshell types from both regions are similar, affinities of the Indian forms to those of southern Europe cannot be ruled out. However, relationships to the Madagascan taxon, Laplatasaurus madagascarensis, must await the discovery of better comparative material (Buffetaut, 1987).

Despite a long history of study, much still has to be learned about Indian dinosaurs. Many of the previously described forms, in particular the sauropod taxa, are based on inadequate material and are in need of systematic revision. Fairly complete dinosaurian skeletal material, barring a few notable exceptions, is generally lacking. The presence and nature of Indian ornithischians needs to be better documented because reliance cannot be placed on earlier descriptions. Until the taxonomic status of Indian dinosaurs is better known, it is difficult to comment on their affinities and paleobiogeographic relationships. Finally, the Lameta dinosaur hatcheries provide an exciting area for studying nesting behavior and preferences.