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A new oospecies, Megaloolithus matleyi, from the Lameta Formation (Upper Cretaceous) of Chandrapur district, Maharashtra, India, and general remarks on the palaeoenvironment and nesting behaviour of dinosaurs
Cretaceous Research (1996) 17, 183 – 196
A new oospecies, Megaloolithus matleyi , from the Lameta Formation (Upper Cretaceous) of Chandrapur district, Maharashtra, India, and general remarks on the palaeoenvironment and nesting behaviour of dinosaurs D. M. Mohabey Palaeontology Division , Geological Survey of India , Seminary Hills , Nagpur-440 006 , India Revised manuscript accepted 27 October 1995
New occurrences of fossilised eggs of different structural types have been documented from the Upper Cretaceous Lameta Formation of the Chandrapur district of Maharashtra, central India. For the eggshells of tubospherulitic morphotype a new oospecies, Megaloolithus matleyi sp. nov., has been established. For the shells of prolatospherulitic and testudoid morphotypes, a general description is given. The eggshells occur in calcretized sandstones that reflect deposition in alluvial– limnic environments under semi-arid conditions. There is evidence for colonial nesting, selection of nesting sites on river-banks, and burial of nests by sauropods. ÷ 1996 Academic Press Limited KEY WORDS: Dinosaur eggs; nests; shell microstructure; palaeoenvironment.
1. Introduction Although dinosaurian skeletal remains in the Upper Cretaceous Lameta Formation in Maharashtra have been known for a long time, until recently in situ occurrences of dinosaurian eggs remained unknown except for reports of fragmentary shells from the Pisdura, Dongargaon and Nand areas (Jain & Sahni, 1985; Vianey-Liaud et al ., 1987; Mohabey & Udhoji, 1990). During the past decade, a number of nesting sites with well preserved dinosaur eggs of diverse morphotypes have been found in Lameta Formation of Gujarat (Mohabey, 1984, 1987; Srivastava et al ., 1987; Mohabey & Mathur, 1989) and Madhya Pradesh (Vianey-Liaud et al ., 1987; Mohabey, 1990b; Sahni & Tripathi, 1990). The majority of the eggshells are assignable to Megaloolithidae, with variation at oogeneric and oospecific levels (variants of tubospherulitic morphotype), and it is assumed that they are related to titanosaurid sauropods. A recent search resulted in locating a nesting site in the calcretised sandstones of the Lameta Formation north of Pavna village (Figure 1) in Chandrapur district, and a single isolated nest near Kholdoda in the Nagpur district of Maharashtra (Mohabey, 1990a). Dinosaurian skeletal remains from the Lameta Formation have been reported earlier by a number of workers from the Umrer, Pisdura, Dongargaon and adjoining areas in parts of the Chandrapur and Nagpur districts of Maharashtra (Matley, 1921; Von Huene & Matley, 1933; Verma, 1967). These skeletal remains have been assigned mainly to titanosaurid sauropods. In addition, several other fossil vertebrates such as chelonia, pelobatids and fishes have been described from the Dongargaon – Pisdura area by Woodward (1908) and Jain (1986). A diverse biota has been reported recently (Mohabey et al ., 1993) from 0195 – 6671 / 96 / 020183 1 14 $18.00 / 0
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Figure 1. Geological map of the Dongargaon – Pavna area, Chandrapur district, Maharashtra, showing dinosaur nesting area.
the Lameta Formation in the area including fishes (Lepidotes sp; Eoserranus hislopi , Lepisosteus indicus , Pycnodus lametae , Enchodus , dasyatids and clupeids); chelonia (pelomedusids—Shweboemys pisdurensis ); pelobatids; gastropods (Melania , Lymneae , Paludina , Valvata , Physa ); bivalves (Unio deccanensis ), ostracods (Candoniella , Cypridopsis , Darwinula , Metacypris , Bisulcocypris , Paracypretta ); charophytes (Microchara sp., Platychara perlata , P. compressa , Peckichara ); conifers (Araucarites , Brachyphyllum sp.) and leaf impressions of palms and dicotyledonous angiosperms. Both palaeontologcal and lithological studies indicate alluvial – limnic environments of deposition for the sediments in a semi-arid but seasonal climate (Mohabey et al ., 1993). 2. Geological setting In the study area, the Lameta Formation rests unconformably on Precambrian or Gondwana rocks and is overlain by the Deccan Trap volcanic suite. Its maximum thickness is about 20 m. The succession comprises basal red and green silty clays with lateral accretional and channel sandstones that represent overbank deposits. The overbank clays are overlapped by cream and yellow, very finely laminated
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lacustrine clays interbedded with calcareous mudstone and limestone. The yellow clays pass upwards into greenish clays in the Dongargaon section (Figure 1) where they are very much enriched in carbonaceous matter. The green clays in turn are replaced by red- and green-mottled to brick red clays. A palaeosol horizon has been identified between the lower green and upper red clays on the basis of the presence of rhizoliths, pedotubules, concretions and bioturbation (Mohabey et al ., 1993). In the Pavna section, a 3-m-thick sandstone rests on the lacustrine clays (Figure 2). It is calcretized in the upper part. Calcretization is indicated by the presence of nodular and mottled micrite, laminated micrite, micrite envelopes, rhinds and meniscus cement (Mohabey, 1990b). The intimately associated chert within the calcrete in the upper part has been interpreted as silcrete. The dinosaur nests are found entombed in the calcrete. 3. Palaeoenvironment The biota of the Lameta Formation is represented by terrestrial, aquatic and semi-aquatic communities. The sediments represent the channel, overbank, lacustrine and back-swamp facies of alluvial – limnic environments (Mohabey et al ., 1993). Increases in alkalinity and salinity are indicated by the presence of repeated thin partings of limestone, and marls within the lacustrine clay sequence, commonly occurring authigenic gypsum crystals in the clays, and indirect evidence such as the common presence of charophytes and ostracods (Forster, 1983). The sediments are interpreted to have been deposited under semi-arid conditions on the basis of the presence of calcrete and carbonates, hence supporting the palaeontological evidence noted above. 4. Field setting of dinosaur eggs In the Pavna nesting site, the dinosaurian eggs are found embedded in calcretized sandstone which overlies grey laminated clays that are crowded with bivalves, mainly Unio deccanensis . The eggs occur in nests at two stratigraphic levels (Figures 2, 3). The eggs were laid in a single layer in nests that cover less than
Figure 2. Birds-eye view of the Pavna area showing nesting sites A and B at two stratigraphic levels.
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Figure 3. Distribution of nests and eggs at nesting sites A & B in the Pavna area. Broken lines represent indistinct to fragmented eggshell outlines. The exposed diameter of the eggs varies as they are cut along the different erosional planes inside the nest.
1 m2 in area. The edges of the nests have almost homogenized with the host rock to the extent that no appreciable difference in lithology is observable in them. The number of eggs in the nests varies (Figure 3). At nesting site A, which occurs at a lower level than nesting site B, only two nests have been located. These contain 6 and 2 eggs respectively, together with eggshell fragments (Figure 3, 4D). They are separated by a distance of nearly 2 m. Mostly incomplete and lower halves of the eggs are preserved and the spherical outlines of such eggs are exposed at the surface. The diameters of the exposed eggs vary between 16 and 18 cm. They have a nodose ornamentation. The shell thickness ranges from 1.5 to 1.8 mm. The eggs are of the same morphotype (tubospherulitic) as the numerous other eggshells found at the upper level. At nesting site B in the upper level (Figure 2), at least 10 nests of eggs have been located within an area of less than 60 m2 (Figure 3). The eggs in the nests occur in single layers laid in saucer or shallow bowl-shaped pits. Such pits have a depth limited to 50 cm and an area limited to a one m2. A few of these nests have up to 18 eggs, which are generally in contact with each other (Figure 4A, B). The nests contain almost completely preserved eggs (?unhatched), collapsed and broken eggs or lower halves of the eggs with scattered eggshell fragments (?hatched eggs). A partially preserved nest of three small oval-shaped eggs having a polar and equatorial diameter of nearly 5 and 2.5 cm respectively, has been also unearthed from this nesting site. Based on their structure, these eggshells are of testudoid affinity (Hirsch & Packard, 1987; Hirsch, 1994; Mikhailov, 1991).
Figure 4. A, Part of dinosaur nest showing eggs (arrow) Megaloolithus matleyi from site B (nest 5 of Figure 3). Note that the eggs are in contact with each other. B, Part of a nest of two eggs (arrow) of M. matleyi from site B (nest 6 of Figure 3). Note that the eggshells are collapsed and fragmented. C, A nearly complete spherical egg of M. matleyi from site A (nest 3 of Figure 3). Note cracked and fragmented eggs and cracked shell showing compactituberculate ornamentation. D, Nest showing four eggs (arrow) of M. matleyi from site A (nest 1 of Figure 3). The eggs are almost homogenized with the host-rock (calcretized sandstone).
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5. Eggshell systematics The material described in this section (Registration nos 123-127 / CR / P / 89 and 140 / CR / P / 89) is housed in the Palaeontology Division of Geological Survey of India, Central Region, Nagpur. Oofamily Megaloolithidae Zhao 1979 Oogenus Megaloolithus Vianey - Liaud et al . 1994 Diagnosis. Dinosauriod-spherulitic basic type; tubospherulitic morphotype; tubocanaliculate pore system; compactituberculate ornamentation (Mikhailov, 1991). Spherical to subspherical eggs; eggshell thickness 1.5 – 3 mm. Megaloolithus matleyi sp. nov. Figures 4 – 7 Holotype. A nest of one full and three partially preserved eggs (reg. no. 123-125 / CR / P / 89). Etymology. After C.A. Matley, for his pioneering work on the dinosaur skeletal remains of the Lameta Formation in the area. Type locality. Pavna, Chandrapur district, Maharashtra. Calcretised sandstone bed, Lameta Formation, Upper Cretaceous. Diagnosis. Spherical eggs; diameter 16 – 18 cm; eggshell thickness 1.5 – 2 mm and may be more; compactituberculate ornamentation; tubocanaliculate pore system; discreet fan-like shell units having a height (h) to width (w) ratio of nearly 3:1. Description. Spherical eggs having a diameter that ranges from 16 – 18 cm. Ornamentation compactituberculate. Circular to subcircular pores in the internodal areas, which are uniformly distributed all over the surface. The vertical shell units have a length and width that varies between 1.0 – 1.8 mm and 0.4 – 0.7 mm respectively. The shell units are moderately long and have a general tendency to maintain the h / w ratio to the order of 2.8:1. The shell units are discreet with well defined margins and end on the outer shell surface in a node. The growth-lines are arched and distinctly terminate against the lateral shell unit boundaries. The shell units tend to have straight rather than fan or cone-shaped outlines. The shell units are single layered and have a spherulitic structure. Radiating crystallites of calcite originate from the organic core and extend up to the top of the shell units. As observable under the scanning electron microscope (SEM), the radiating calcite crystallites have horizontal growth-layers and correspond to the zone of tabular aggregate (ZTA) of Mikhailov (1991, 1992). A sweeping fan extinction is observable along such radiating calcite crystallites (Hirsch & Quinn, 1990). The pore system is tubocanaliculate. Remarks. Megaloolithus matleyi differs from the other tubospherulitic morphotypes described from the Kheda, Jabalpur and Jhabua districts (Mohabey & Mathur, 1987; Sahni et al ., 1994) in that the shell units have a distinct shape, with a tendency to be straight rather than conical or fan-shaped, and are moderately long (h / w ratio more often .2.5:1). Pores are more commonly developed and are uniformly distributed over the eggshell surface.
Figure 5. Schematic drawings of radial sections of eggshells of different types. A, Megaloolithus matleyi . Note canaliculae, C-C, of tubocanaliculate pore system. B, Prolatospherulitic (?) morphotype eggshells. Note canaliculae, C-C, of prolatocanaliculate pore system. C, Chelonian (testudoid morphotype) eggshells. Note radiating structure of orginal aragonitic crystallites emerging from the organic core O-C. D, Same as C, diagenetically altered. Horizontal secondary micrite layers prominent.
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Figure 6. Photomicrographs of Megaloolithus matleyi taken under polarized light. Bar 500 m m. A, Radial thin section showing shell units of single and multinode type. C-C, canaliculae of tubocanaliculate pore system. B, Radial thin section depicting broad shell units with traces of fan extinction. C, Same as A, magnified view of shell unit (S). Note fan extinction and canaliculae, C-C. D, Same as A and C in enlarged view of mammillary zone showing arched accretional and vertically radiating lines. O-C, organic core. E, Tangential thin section towards upper part of the shell units showing circular nodes (n) and pores (p).
Eggshells of prolatospherulitic and testudoid morphotype Oofamily ? Spheroolithidae ? Prolatospherulitic morphotype ? Spheroolithus (? ornithopoda) Figures 5B, 8D-F Material. Fragmentary eggshells (reg. no. 140 / CR / P / 89). Locality and horizon. Large number of eggshell fragments recovered by wetscreening of the red clays and sandstones of the Lameta Formation of the
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Figure 7. SEM photomicrographs of Megaloolithus matleyi . A, Outer surface showing compactituberculate ornamentation. B, Radial section showing individual shell units (top upwards). Note narrow canaliculae, C-C, and traces of radiating structure of the shell units. C, Radial section (top upwards). Note arched accretional lines A-A and traces of radiating structure. D, Radial section showing horizontal growth layers G-L. E, Same as D, enlarged.
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Nagpur and Chandrapur districts of Maharashtra. The localities that yielded the eggshell material include Dongargaon, Pisdura, Polgaon and Tidkepar. The eggshell fragments are up to 1 cm2 in size. Description. The eggshell thickness varies between 1 and 1.5 mm. The ornamentation is of sagenotuberculate type. However, a few fragments have a tendency to have both sagenotuberculate and dispersituberculate ornamentation. This indicates the non-spherical shape of the eggs wherein the ornamentation varies in different places on the shell. The vertical units of the eggshell are broad and comprise a narrow mammillary zone (up to 0.5 mm thick) in the lower part and moderately long upper zone (up to 1 mm thick). The shell units have generally well defined margins and moderately arched growth lines. They are fan-shaped and end in a broad domal shape at the outer surface, and they are separated in the lower third and fused in the upper parts. The radiating lines that emerge from the organic core are distinct. As observed under the SEM, a fish-bone structure is produced by the intersection of growth laminae and wedges. Rounded pores are present in the valley regions between the ridges and nodes. The mammillae are coalesced and form prominent ridges on the mammillary surface. The pore system is prolatocanaliculate. Remarks. Recently, a clutch of dinosaur eggs has been unearthed from the Lameta sediments in the adjoining area near Kholdoda (Udhoji & Mohabey, 1993), which resembles this morphotype. Chelonia eggshell Testudoid (basic) type (Mikhailov, 1991) Testudoid morphotype (? Pelomedusids) Figure 8A – D Material. A partial nest of oval eggs (reg. no. 127 / CR / P / 89). Locality and horizon. As for Megaloolithus matleyi . Description. Smooth oval eggs having a polar and equatorial diameter of 5 and 2.5 cm respectively. The shells are 0.8 mm thick and micritized; as a result the microstructure is considerably altered. The lower parts of the shell units are discrete and broad conule-shaped. The radiating structure of the original aragonite is still preserved despite the micritisation. The middle and upper parts of the vertical shell units show horizontal stratification of the micrite. However, a sweeping fan extinction along the remnant radiating structure is observable in the middle and upper parts of the shell units. This shows that the radiating, originally aragonitic, structure originates from the organic core in the base of the shell unit and extends to the uppermost part of the shell units (Hirsch & Packard, 1987).
Figure 8. A-C, Chelonia; E-G, Spheroolithidae. A, Partial nest of chelonia eggshells. Note two oblong eggs (arrow) embedded in the sandy calcretized matrix. B, Tangential section (SEM) and view of outer eggshell surface; no distinct structure; surface appears smooth. Circular pores (P) visible. C, Radial thin section under polarized light. Eggshell embedded in sandy, calcretized matrix C-M. Outer surface of the eggshell is upwards. High diagenetic alteration is apparent. D, Outer surface of the eggshell showing sagenotuberculate ornamentation; P, pores. E, Radial thin section of prolatospherulitic (? Spheroolithidae) eggshell under polarized light. Note continuous arched accretional lines, fused shell units, and radiating structure lines of the mammillae wedges. F, Radial section, showing columns and growth-layers G-L. G, Same as F at higher magnification.
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Discussion. Fossil chelonia eggshells remained almost unknown in India until some were recently recovered from Middle Pleistocene sediments of the Narmada valley (Mohabey et al ., in preparation). The skeletal remains of chelonia from the Lameta sediments in the area are exclusively assigned to the pelomedusids and the chelonia eggs discussed here, may be related to them. 6. The nesting behaviour of dinosaurs The dinosaur fauna of the Late Cretaceous in India were generally dominated by sauropod titanosaurs, less commonly by theropod megalosaurs. The majority of the eggshells found are of tubospherulitic morphotype (Megaloolithidae) related to titanosaurs. Recently, eggshells of ratite morphotype (Elongatoolithidae) of the basic Ornithoid type (Mikhailov,1991), probably related to the theropod megalosaur, have been also reported from the Lameta Formation of Gujarat (Mohabey, 1994). Dinosaur nests are found only in the riverine sandstone of the Lameta Formation, which suggests that the parent dinosaurs preferred to nest in the soft sand of river banks. Irrespective of the diversity of the eggs, they all occur in a single layer in the nest, and are disposed in a saucer-shaped pattern. As noted above, the margins of the nests are often homogenized with the host rock so that no appreciable lithological difference between them is observable. These observations suggest that the dinosaurs buried their eggs for incubation. No embryonic or juvenile skeletal remains have been found in the nests apart from a single juvenile sauropod (?titanosaurid) in the Dhoridungri nesting site in Gujarat (Mohabey, 1987). It is difficult to say if this is indicative of a low-mortality rate amongst the hatchlings. The nests comprise (i) well preserved lower halves of the eggs and eggshell fragments (? hatched eggs) and / or (ii) fully preserved (unhatched) eggs which are rarely cracked. The intact lower halves of the eggs (if hatched) show that they were not trampled by the activities of the hatchlings in the nests. The eggs, Megaloolithus matleyi , are found at two stratigraphic levels (Figure 2) in the Pavna nesting site, reflecting site fidelity amongst the titanosaurs. Evidence of site fidelity has been noted previously from the Kheda area in Gujrat (Srivastava et al ., 1986; Mohabey, 1991). Oxygen-isotope analysis of the eggshells has suggested that the parent dinosaurs drank water from a variety of freshwater sources such as rivers and pools from which evaporation was extensive (Sarkar et al ., 1991). Carbon-isotope values of the shells indicate that the dinosaurs were sustained on the plants that utilized C3 photosynthetic pathways. It may be that they nested seasonally during the dry season (Mohabey, 1991), when the river-water level was too low to pose any threat of flooding of the nests. 7. Conclusion Until recently, dinosaur nesting sites were known only from the Lameta Formation of Gujarat and Madhya Pradesh states of India. Dinosaur nesting areas are now reported from Pavna in Maharashtra wherein they are found at two stratigraphic levels. A new oospecies, Megaloolithus matleyi , is established for the eggshells. Floats of prolatospherulitic (?Spheroolithus ) eggshell fragments and a partial nest of a testudoid morphotype have been found associated at the nesting site.
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Reports of dinosaur eggshells in India are restricted to the Upper Cretaceous (Maestrichtian) Lameta Formation (Infratrappeans) and Intertrappean formations. Of these, the former has yielded many nesting sites with well preserved eggs, whereas the latter, has produced only fragmentary eggshells. A wide diversity is present in the eggshells. The majority of those from the Lameta Formation are variants of the tubospherulitic morphotype (Megaloolithidae). Less common are eggshells of ratite morphotype (Elongatoolithidae), and prolatospherulithic (?Spheroolithus ) morphotypes are rare. No final conclusion can be reached, at present, on the parataxonomy of the eggshells from the Intertrappean beds, as they are fragmentary, and data on the size, shape and variation in ornament on the surface of the shells are lacking.
Acknowledgement I thank Dr. P. K. Raha and S. G. Udhoji for helpful discussions and B. C. Poddar for his keen interest in the find and fruitful discussions. Thanks are due to the Director General, Geological Survey of India, for permission to publish the find. I am grateful to K. Muthuraman, Mohd. Iqbal and Sanjay Mulkar for assistance in the computer processing of the manuscript. Naveed Sheikh helped with the drawing. Thanks are extended to K. F. Hirsch and an anonymous reviewer, who offered many a useful suggestions for improving the manuscript.
References Forster, R. M. 1983. Relationship of two lacustrine ostracode species to solute composition and salinity: implications for palaeohydrochemistry. Geology 11, 435 – 438. Hirsch, K. F. & Packard, M. J. 1987. Review of fossil eggs and their shell structure. Scanning Microscopy 1, 383 – 400. Hirsch, K. F. & Quinn, B. 1990. Eggs and eggshell fragments from Upper Cretaceous Two Medicine Formation of Montana. Journal of Vertebrate Palaeontology 10, 491 – 511. Hirsch, K. F. 1994. Upper Jurassic eggshells from the Western Interior of North America. In Dinosaur eggs and babies (eds Carpenter, K., Hirsch, K. F. & Horner, J. R.), pp. 137 – 150 (Cambridge University Press, Cambridge). Jain, S. L. 1986. New pelomedusid turtle (Pleurodira: Chelonia) remains from Lameta Formation at Dongargaon, central India and a review of pelomedusids from India. Journal of the Palaeontological Society of India 31, 63 – 75. Jain, S. L. & Sahni, A. 1985. Dinosaurian egg shell fragments from the Lameta Formation at Pisdura, Chandrapur district, Maharashtra. Geoscience Journal (India) 6, 211 – 220. Matley, C. A. 1921. On the stratigraphy, fossils and geological relationships of the Lameta beds of Jubbalpore. Records of the Geological Survey of India 53, 142 – 164. Mikhailov, K. E. 1991. Classification of fossil eggshells of amniotic vertebrates. Acta Palaeontologica Polonica 36, 193 – 238. Mikhailov, K. E. 1992. The microstructure of avian and dinosaurian eggshell: phylogenetic implications. In Papers in avian paleontology honoring Pierce Brodkorb , contributions in science (ed. Campbell, K.), pp. 361 – 373 (Natural History Museum of Los Angeles County, Los Angeles). Mikhailov, K. E., Sabath, K. & Kurzanov, S. 1994. Eggs and nests from the Cretaceous of Mongolia. In Dinosaur nests and babies (eds Carpenter K., Hirsch K. F. & Horner J. R.), pp. 88 – 114 (Cambridge University Press, Cambridge). Mohabey, D. M. 1984. Study of dinosaurian eggs from Infra – trappean Limestone in Kheda district, Gujarat. Journal of the Geological Society of India 25, 329 – 337. Mohabey, D. M. 1987. Juvenile sauropod dinosaur from Upper Cretaceous Lameta Formation of Panchmahals district, Gujarat, India. Journal of the Geological Society of India 30, 210 – 216. Mohabey, D. M. & Mathur, U. B. 1989. Upper Cretaceous dinosaur eggs from new localities of Gujarat. Journal of the Geological Society of India 33, 32 – 37. Mohabey, D. M. 1990a. Discovery of dinosaur nesting site in Maharashtra. Gondwana Geological Magazine 3, 32 – 24.
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Mohabey, D. M. 1990b. Dinosaur eggs from Lameta Formation of western and central India; their occurrence and nesting behaviour. Abstracts , Cretaceous event stratigraphy and correlation of the Indian non-marine stratigraphy. International Geological Correlation Programme 216 and 245 , Symposium cum Workshop , Chandigarh, pp. 18 – 21. Mohabey, D. M. 1991. Palaeontological studies of the Lameta Formation with special reference to the dinosaurian eggs from Kheda and Panchmahal districts of Gujarat , India . Unpublished Ph.D. thesis, Nagpur University, 124 pp. Mohabey, D. M. & Udhoji, S. G. 1990. Fossil occurrences and sedimentation of Lameta Formation of Nand area, Maharashtra: palaeoenvironemntal, palaeoecological and taphonomical implications. Abstracts , Cretaceous event stratigraphy and the correlation of Indian nonmarine stratigraphy; International Geological Correlation Programme 216 and 245 , Symposium cum Workshop , Chandigarh, pp. 75 – 77. Mohabey, D. M., Udhoji, S. G. & Verma, K. K. 1993. Palaeontological and sedimentological observations on non-marine Lameta Formation (Upper Cretaceous) of Maharashtra, India: their palaeoecological and palaeoenvironmental significance. Palaeogeography , Palaeoclimatology , Palaeoecology 105, 83 – 94. Mohabey, D. M. 1994. Nests of ellipsoidal eggs of theropod dinosaurs. Geological Survey of India , News 12, 12. Sahni, A. & Tripathi, A. 1990. Age implications of the Jabalpur Lameta Formation and Inter-trappean biotas. Abstracts , Cretaceous event stratigraphy and the correlation of Indian non-marine stratigraphy; International Geological Correlation Programme 216 and 245 , Symposium cum Workshop , Chandigarh, pp. 35 – 37. Sahni, A., Tandon, S. K., Jolly, A., Bajpai, S., Sood, A. & Srinivasan, A. 1994. Upper Cretaceous dinosaur eggs and nesting sites from the Deccan volcano-sedimentary province of peninsular India. In Dinosaur eggs and babies (eds Carpenter, K., Hirsch, K. F. & Horner, J. R.), pp. 204 – 225 (Cambridge University Press, Cambridge). Sarkar, A., Bhattacharya, S. K. & Mohabey, D. M. 1991. Stable isotope analysis of dinosaur eggshells: paleoenvironmental implications. Geology 19, 1068 – 1071. Srivastava, S., Mohabey, D. M., Sahni, A. & Pant, S. C. 1986. Upper Cretaceous dinosaur egg clutches from Kheda district, Gujarat, India; their distribution, shell ultrastructure and palaeoecology. Palaeontographica , A 193, 219 – 233. Udhoji, S. G. & Mohabey, D. M. 1993. Cretaceous-Eocene biohistory of sedimentary formations associated with Deccan trap volcanic episode. Records of the Geological Survey of India 126, 219 – 221. Verma, K. K. 1967. Occurrences of dinosaurian remains from the Lameta beds at Umrer, Nagpur district, Maharashtra. Current Science 37, 547 – 548. Vianey-Liaud, M., Jain, S. L. & Sahni, A. 1987. Dinosaur eggshells (Saurischia) from the Late Cretaceous Inter-trappean and Lameta Formations (Deccan India). Journal of Vertebrate Palaeontology 7, 408 – 424. Vianey-Liaud, M., Mallan, P., Bascail, O. & Montgerald, C. 1994. Review of French dinosaur eggshells; eggshell morphology, structure, mineral and organic composition. In Dinosaur eggs and babies (eds Carpenter, K., Hirsh, K. F. & Horner, J. R.), pp. 151 – 183 (Cambridge University Press, Cambridge). Von Huene, F. B. & Matley, C. A. 1933. The Cretaceous Saurischia and Ornithischia of the Central Provinces of India. Palaeontologia Indica , New Series 21, 1 – 70. Woodward, A. S. 1908. On some fish remains from the Lameta beds at Dongargaon, Central Provinces. Palaeontologica Indica , New Series 3, 1 – 6. Zhao, Z. K. 1979. Discovery of dinosaur eggs and foot-prints from Neixing County, Henan Province. Vertebrata Palasiatica 17, 304 – 309.
A new oospecies, Megaloolithus matleyi , from the Lameta Formation (Upper Cretaceous) of Chandrapur district, Maharashtra, India, and general remarks on the palaeoenvironment and nesting behaviour of dinosaurs D. M. Mohabey Palaeontology Division , Geological Survey of India , Seminary Hills , Nagpur-440 006 , India Revised manuscript accepted 27 October 1995
New occurrences of fossilised eggs of different structural types have been documented from the Upper Cretaceous Lameta Formation of the Chandrapur district of Maharashtra, central India. For the eggshells of tubospherulitic morphotype a new oospecies, Megaloolithus matleyi sp. nov., has been established. For the shells of prolatospherulitic and testudoid morphotypes, a general description is given. The eggshells occur in calcretized sandstones that reflect deposition in alluvial– limnic environments under semi-arid conditions. There is evidence for colonial nesting, selection of nesting sites on river-banks, and burial of nests by sauropods. ÷ 1996 Academic Press Limited KEY WORDS: Dinosaur eggs; nests; shell microstructure; palaeoenvironment.
1. Introduction Although dinosaurian skeletal remains in the Upper Cretaceous Lameta Formation in Maharashtra have been known for a long time, until recently in situ occurrences of dinosaurian eggs remained unknown except for reports of fragmentary shells from the Pisdura, Dongargaon and Nand areas (Jain & Sahni, 1985; Vianey-Liaud et al ., 1987; Mohabey & Udhoji, 1990). During the past decade, a number of nesting sites with well preserved dinosaur eggs of diverse morphotypes have been found in Lameta Formation of Gujarat (Mohabey, 1984, 1987; Srivastava et al ., 1987; Mohabey & Mathur, 1989) and Madhya Pradesh (Vianey-Liaud et al ., 1987; Mohabey, 1990b; Sahni & Tripathi, 1990). The majority of the eggshells are assignable to Megaloolithidae, with variation at oogeneric and oospecific levels (variants of tubospherulitic morphotype), and it is assumed that they are related to titanosaurid sauropods. A recent search resulted in locating a nesting site in the calcretised sandstones of the Lameta Formation north of Pavna village (Figure 1) in Chandrapur district, and a single isolated nest near Kholdoda in the Nagpur district of Maharashtra (Mohabey, 1990a). Dinosaurian skeletal remains from the Lameta Formation have been reported earlier by a number of workers from the Umrer, Pisdura, Dongargaon and adjoining areas in parts of the Chandrapur and Nagpur districts of Maharashtra (Matley, 1921; Von Huene & Matley, 1933; Verma, 1967). These skeletal remains have been assigned mainly to titanosaurid sauropods. In addition, several other fossil vertebrates such as chelonia, pelobatids and fishes have been described from the Dongargaon – Pisdura area by Woodward (1908) and Jain (1986). A diverse biota has been reported recently (Mohabey et al ., 1993) from 0195 – 6671 / 96 / 020183 1 14 $18.00 / 0
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Figure 1. Geological map of the Dongargaon – Pavna area, Chandrapur district, Maharashtra, showing dinosaur nesting area.
the Lameta Formation in the area including fishes (Lepidotes sp; Eoserranus hislopi , Lepisosteus indicus , Pycnodus lametae , Enchodus , dasyatids and clupeids); chelonia (pelomedusids—Shweboemys pisdurensis ); pelobatids; gastropods (Melania , Lymneae , Paludina , Valvata , Physa ); bivalves (Unio deccanensis ), ostracods (Candoniella , Cypridopsis , Darwinula , Metacypris , Bisulcocypris , Paracypretta ); charophytes (Microchara sp., Platychara perlata , P. compressa , Peckichara ); conifers (Araucarites , Brachyphyllum sp.) and leaf impressions of palms and dicotyledonous angiosperms. Both palaeontologcal and lithological studies indicate alluvial – limnic environments of deposition for the sediments in a semi-arid but seasonal climate (Mohabey et al ., 1993). 2. Geological setting In the study area, the Lameta Formation rests unconformably on Precambrian or Gondwana rocks and is overlain by the Deccan Trap volcanic suite. Its maximum thickness is about 20 m. The succession comprises basal red and green silty clays with lateral accretional and channel sandstones that represent overbank deposits. The overbank clays are overlapped by cream and yellow, very finely laminated
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lacustrine clays interbedded with calcareous mudstone and limestone. The yellow clays pass upwards into greenish clays in the Dongargaon section (Figure 1) where they are very much enriched in carbonaceous matter. The green clays in turn are replaced by red- and green-mottled to brick red clays. A palaeosol horizon has been identified between the lower green and upper red clays on the basis of the presence of rhizoliths, pedotubules, concretions and bioturbation (Mohabey et al ., 1993). In the Pavna section, a 3-m-thick sandstone rests on the lacustrine clays (Figure 2). It is calcretized in the upper part. Calcretization is indicated by the presence of nodular and mottled micrite, laminated micrite, micrite envelopes, rhinds and meniscus cement (Mohabey, 1990b). The intimately associated chert within the calcrete in the upper part has been interpreted as silcrete. The dinosaur nests are found entombed in the calcrete. 3. Palaeoenvironment The biota of the Lameta Formation is represented by terrestrial, aquatic and semi-aquatic communities. The sediments represent the channel, overbank, lacustrine and back-swamp facies of alluvial – limnic environments (Mohabey et al ., 1993). Increases in alkalinity and salinity are indicated by the presence of repeated thin partings of limestone, and marls within the lacustrine clay sequence, commonly occurring authigenic gypsum crystals in the clays, and indirect evidence such as the common presence of charophytes and ostracods (Forster, 1983). The sediments are interpreted to have been deposited under semi-arid conditions on the basis of the presence of calcrete and carbonates, hence supporting the palaeontological evidence noted above. 4. Field setting of dinosaur eggs In the Pavna nesting site, the dinosaurian eggs are found embedded in calcretized sandstone which overlies grey laminated clays that are crowded with bivalves, mainly Unio deccanensis . The eggs occur in nests at two stratigraphic levels (Figures 2, 3). The eggs were laid in a single layer in nests that cover less than
Figure 2. Birds-eye view of the Pavna area showing nesting sites A and B at two stratigraphic levels.
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Figure 3. Distribution of nests and eggs at nesting sites A & B in the Pavna area. Broken lines represent indistinct to fragmented eggshell outlines. The exposed diameter of the eggs varies as they are cut along the different erosional planes inside the nest.
1 m2 in area. The edges of the nests have almost homogenized with the host rock to the extent that no appreciable difference in lithology is observable in them. The number of eggs in the nests varies (Figure 3). At nesting site A, which occurs at a lower level than nesting site B, only two nests have been located. These contain 6 and 2 eggs respectively, together with eggshell fragments (Figure 3, 4D). They are separated by a distance of nearly 2 m. Mostly incomplete and lower halves of the eggs are preserved and the spherical outlines of such eggs are exposed at the surface. The diameters of the exposed eggs vary between 16 and 18 cm. They have a nodose ornamentation. The shell thickness ranges from 1.5 to 1.8 mm. The eggs are of the same morphotype (tubospherulitic) as the numerous other eggshells found at the upper level. At nesting site B in the upper level (Figure 2), at least 10 nests of eggs have been located within an area of less than 60 m2 (Figure 3). The eggs in the nests occur in single layers laid in saucer or shallow bowl-shaped pits. Such pits have a depth limited to 50 cm and an area limited to a one m2. A few of these nests have up to 18 eggs, which are generally in contact with each other (Figure 4A, B). The nests contain almost completely preserved eggs (?unhatched), collapsed and broken eggs or lower halves of the eggs with scattered eggshell fragments (?hatched eggs). A partially preserved nest of three small oval-shaped eggs having a polar and equatorial diameter of nearly 5 and 2.5 cm respectively, has been also unearthed from this nesting site. Based on their structure, these eggshells are of testudoid affinity (Hirsch & Packard, 1987; Hirsch, 1994; Mikhailov, 1991).
Figure 4. A, Part of dinosaur nest showing eggs (arrow) Megaloolithus matleyi from site B (nest 5 of Figure 3). Note that the eggs are in contact with each other. B, Part of a nest of two eggs (arrow) of M. matleyi from site B (nest 6 of Figure 3). Note that the eggshells are collapsed and fragmented. C, A nearly complete spherical egg of M. matleyi from site A (nest 3 of Figure 3). Note cracked and fragmented eggs and cracked shell showing compactituberculate ornamentation. D, Nest showing four eggs (arrow) of M. matleyi from site A (nest 1 of Figure 3). The eggs are almost homogenized with the host-rock (calcretized sandstone).
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5. Eggshell systematics The material described in this section (Registration nos 123-127 / CR / P / 89 and 140 / CR / P / 89) is housed in the Palaeontology Division of Geological Survey of India, Central Region, Nagpur. Oofamily Megaloolithidae Zhao 1979 Oogenus Megaloolithus Vianey - Liaud et al . 1994 Diagnosis. Dinosauriod-spherulitic basic type; tubospherulitic morphotype; tubocanaliculate pore system; compactituberculate ornamentation (Mikhailov, 1991). Spherical to subspherical eggs; eggshell thickness 1.5 – 3 mm. Megaloolithus matleyi sp. nov. Figures 4 – 7 Holotype. A nest of one full and three partially preserved eggs (reg. no. 123-125 / CR / P / 89). Etymology. After C.A. Matley, for his pioneering work on the dinosaur skeletal remains of the Lameta Formation in the area. Type locality. Pavna, Chandrapur district, Maharashtra. Calcretised sandstone bed, Lameta Formation, Upper Cretaceous. Diagnosis. Spherical eggs; diameter 16 – 18 cm; eggshell thickness 1.5 – 2 mm and may be more; compactituberculate ornamentation; tubocanaliculate pore system; discreet fan-like shell units having a height (h) to width (w) ratio of nearly 3:1. Description. Spherical eggs having a diameter that ranges from 16 – 18 cm. Ornamentation compactituberculate. Circular to subcircular pores in the internodal areas, which are uniformly distributed all over the surface. The vertical shell units have a length and width that varies between 1.0 – 1.8 mm and 0.4 – 0.7 mm respectively. The shell units are moderately long and have a general tendency to maintain the h / w ratio to the order of 2.8:1. The shell units are discreet with well defined margins and end on the outer shell surface in a node. The growth-lines are arched and distinctly terminate against the lateral shell unit boundaries. The shell units tend to have straight rather than fan or cone-shaped outlines. The shell units are single layered and have a spherulitic structure. Radiating crystallites of calcite originate from the organic core and extend up to the top of the shell units. As observable under the scanning electron microscope (SEM), the radiating calcite crystallites have horizontal growth-layers and correspond to the zone of tabular aggregate (ZTA) of Mikhailov (1991, 1992). A sweeping fan extinction is observable along such radiating calcite crystallites (Hirsch & Quinn, 1990). The pore system is tubocanaliculate. Remarks. Megaloolithus matleyi differs from the other tubospherulitic morphotypes described from the Kheda, Jabalpur and Jhabua districts (Mohabey & Mathur, 1987; Sahni et al ., 1994) in that the shell units have a distinct shape, with a tendency to be straight rather than conical or fan-shaped, and are moderately long (h / w ratio more often .2.5:1). Pores are more commonly developed and are uniformly distributed over the eggshell surface.
Figure 5. Schematic drawings of radial sections of eggshells of different types. A, Megaloolithus matleyi . Note canaliculae, C-C, of tubocanaliculate pore system. B, Prolatospherulitic (?) morphotype eggshells. Note canaliculae, C-C, of prolatocanaliculate pore system. C, Chelonian (testudoid morphotype) eggshells. Note radiating structure of orginal aragonitic crystallites emerging from the organic core O-C. D, Same as C, diagenetically altered. Horizontal secondary micrite layers prominent.
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Figure 6. Photomicrographs of Megaloolithus matleyi taken under polarized light. Bar 500 m m. A, Radial thin section showing shell units of single and multinode type. C-C, canaliculae of tubocanaliculate pore system. B, Radial thin section depicting broad shell units with traces of fan extinction. C, Same as A, magnified view of shell unit (S). Note fan extinction and canaliculae, C-C. D, Same as A and C in enlarged view of mammillary zone showing arched accretional and vertically radiating lines. O-C, organic core. E, Tangential thin section towards upper part of the shell units showing circular nodes (n) and pores (p).
Eggshells of prolatospherulitic and testudoid morphotype Oofamily ? Spheroolithidae ? Prolatospherulitic morphotype ? Spheroolithus (? ornithopoda) Figures 5B, 8D-F Material. Fragmentary eggshells (reg. no. 140 / CR / P / 89). Locality and horizon. Large number of eggshell fragments recovered by wetscreening of the red clays and sandstones of the Lameta Formation of the
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Figure 7. SEM photomicrographs of Megaloolithus matleyi . A, Outer surface showing compactituberculate ornamentation. B, Radial section showing individual shell units (top upwards). Note narrow canaliculae, C-C, and traces of radiating structure of the shell units. C, Radial section (top upwards). Note arched accretional lines A-A and traces of radiating structure. D, Radial section showing horizontal growth layers G-L. E, Same as D, enlarged.
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Nagpur and Chandrapur districts of Maharashtra. The localities that yielded the eggshell material include Dongargaon, Pisdura, Polgaon and Tidkepar. The eggshell fragments are up to 1 cm2 in size. Description. The eggshell thickness varies between 1 and 1.5 mm. The ornamentation is of sagenotuberculate type. However, a few fragments have a tendency to have both sagenotuberculate and dispersituberculate ornamentation. This indicates the non-spherical shape of the eggs wherein the ornamentation varies in different places on the shell. The vertical units of the eggshell are broad and comprise a narrow mammillary zone (up to 0.5 mm thick) in the lower part and moderately long upper zone (up to 1 mm thick). The shell units have generally well defined margins and moderately arched growth lines. They are fan-shaped and end in a broad domal shape at the outer surface, and they are separated in the lower third and fused in the upper parts. The radiating lines that emerge from the organic core are distinct. As observed under the SEM, a fish-bone structure is produced by the intersection of growth laminae and wedges. Rounded pores are present in the valley regions between the ridges and nodes. The mammillae are coalesced and form prominent ridges on the mammillary surface. The pore system is prolatocanaliculate. Remarks. Recently, a clutch of dinosaur eggs has been unearthed from the Lameta sediments in the adjoining area near Kholdoda (Udhoji & Mohabey, 1993), which resembles this morphotype. Chelonia eggshell Testudoid (basic) type (Mikhailov, 1991) Testudoid morphotype (? Pelomedusids) Figure 8A – D Material. A partial nest of oval eggs (reg. no. 127 / CR / P / 89). Locality and horizon. As for Megaloolithus matleyi . Description. Smooth oval eggs having a polar and equatorial diameter of 5 and 2.5 cm respectively. The shells are 0.8 mm thick and micritized; as a result the microstructure is considerably altered. The lower parts of the shell units are discrete and broad conule-shaped. The radiating structure of the original aragonite is still preserved despite the micritisation. The middle and upper parts of the vertical shell units show horizontal stratification of the micrite. However, a sweeping fan extinction along the remnant radiating structure is observable in the middle and upper parts of the shell units. This shows that the radiating, originally aragonitic, structure originates from the organic core in the base of the shell unit and extends to the uppermost part of the shell units (Hirsch & Packard, 1987).
Figure 8. A-C, Chelonia; E-G, Spheroolithidae. A, Partial nest of chelonia eggshells. Note two oblong eggs (arrow) embedded in the sandy calcretized matrix. B, Tangential section (SEM) and view of outer eggshell surface; no distinct structure; surface appears smooth. Circular pores (P) visible. C, Radial thin section under polarized light. Eggshell embedded in sandy, calcretized matrix C-M. Outer surface of the eggshell is upwards. High diagenetic alteration is apparent. D, Outer surface of the eggshell showing sagenotuberculate ornamentation; P, pores. E, Radial thin section of prolatospherulitic (? Spheroolithidae) eggshell under polarized light. Note continuous arched accretional lines, fused shell units, and radiating structure lines of the mammillae wedges. F, Radial section, showing columns and growth-layers G-L. G, Same as F at higher magnification.
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Discussion. Fossil chelonia eggshells remained almost unknown in India until some were recently recovered from Middle Pleistocene sediments of the Narmada valley (Mohabey et al ., in preparation). The skeletal remains of chelonia from the Lameta sediments in the area are exclusively assigned to the pelomedusids and the chelonia eggs discussed here, may be related to them. 6. The nesting behaviour of dinosaurs The dinosaur fauna of the Late Cretaceous in India were generally dominated by sauropod titanosaurs, less commonly by theropod megalosaurs. The majority of the eggshells found are of tubospherulitic morphotype (Megaloolithidae) related to titanosaurs. Recently, eggshells of ratite morphotype (Elongatoolithidae) of the basic Ornithoid type (Mikhailov,1991), probably related to the theropod megalosaur, have been also reported from the Lameta Formation of Gujarat (Mohabey, 1994). Dinosaur nests are found only in the riverine sandstone of the Lameta Formation, which suggests that the parent dinosaurs preferred to nest in the soft sand of river banks. Irrespective of the diversity of the eggs, they all occur in a single layer in the nest, and are disposed in a saucer-shaped pattern. As noted above, the margins of the nests are often homogenized with the host rock so that no appreciable lithological difference between them is observable. These observations suggest that the dinosaurs buried their eggs for incubation. No embryonic or juvenile skeletal remains have been found in the nests apart from a single juvenile sauropod (?titanosaurid) in the Dhoridungri nesting site in Gujarat (Mohabey, 1987). It is difficult to say if this is indicative of a low-mortality rate amongst the hatchlings. The nests comprise (i) well preserved lower halves of the eggs and eggshell fragments (? hatched eggs) and / or (ii) fully preserved (unhatched) eggs which are rarely cracked. The intact lower halves of the eggs (if hatched) show that they were not trampled by the activities of the hatchlings in the nests. The eggs, Megaloolithus matleyi , are found at two stratigraphic levels (Figure 2) in the Pavna nesting site, reflecting site fidelity amongst the titanosaurs. Evidence of site fidelity has been noted previously from the Kheda area in Gujrat (Srivastava et al ., 1986; Mohabey, 1991). Oxygen-isotope analysis of the eggshells has suggested that the parent dinosaurs drank water from a variety of freshwater sources such as rivers and pools from which evaporation was extensive (Sarkar et al ., 1991). Carbon-isotope values of the shells indicate that the dinosaurs were sustained on the plants that utilized C3 photosynthetic pathways. It may be that they nested seasonally during the dry season (Mohabey, 1991), when the river-water level was too low to pose any threat of flooding of the nests. 7. Conclusion Until recently, dinosaur nesting sites were known only from the Lameta Formation of Gujarat and Madhya Pradesh states of India. Dinosaur nesting areas are now reported from Pavna in Maharashtra wherein they are found at two stratigraphic levels. A new oospecies, Megaloolithus matleyi , is established for the eggshells. Floats of prolatospherulitic (?Spheroolithus ) eggshell fragments and a partial nest of a testudoid morphotype have been found associated at the nesting site.
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Reports of dinosaur eggshells in India are restricted to the Upper Cretaceous (Maestrichtian) Lameta Formation (Infratrappeans) and Intertrappean formations. Of these, the former has yielded many nesting sites with well preserved eggs, whereas the latter, has produced only fragmentary eggshells. A wide diversity is present in the eggshells. The majority of those from the Lameta Formation are variants of the tubospherulitic morphotype (Megaloolithidae). Less common are eggshells of ratite morphotype (Elongatoolithidae), and prolatospherulithic (?Spheroolithus ) morphotypes are rare. No final conclusion can be reached, at present, on the parataxonomy of the eggshells from the Intertrappean beds, as they are fragmentary, and data on the size, shape and variation in ornament on the surface of the shells are lacking.
Acknowledgement I thank Dr. P. K. Raha and S. G. Udhoji for helpful discussions and B. C. Poddar for his keen interest in the find and fruitful discussions. Thanks are due to the Director General, Geological Survey of India, for permission to publish the find. I am grateful to K. Muthuraman, Mohd. Iqbal and Sanjay Mulkar for assistance in the computer processing of the manuscript. Naveed Sheikh helped with the drawing. Thanks are extended to K. F. Hirsch and an anonymous reviewer, who offered many a useful suggestions for improving the manuscript.
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