Nemegt Basin Research Articles

The skull of Hapalodectes (Hapalodectidae, Mesonychia) from the Paleocene of Mongolia.

The incomplete skull of Hapalodectes (Hapalodectidae, Mesonychia) is described from the Upper Paleocene Naran Member of the Naran Bulak Formation of the Khaychin-Ula 2 locality in the Bugin Tsav Basin in the south of Mongolia. This is the first discovery of the skull of a Paleocene member of the genus. The skull corresponds in size and dental occlusion to the species H. dux Lopatin, 2001, previously known only from a lower jaw from the Upper Paleocene Zhigden Member of the Naran Bulak Formation of the Tsagan-Khushu locality in the Nemegt Basin. In the structure of the facial part of the skull, H. dux exhibits features shared with Mesonychidae, namely the significant participation of the lacrimal and jugal in the preorbital region. The upper molars of H. dux were found to have distinct conules (a first for Hapalodectidae). The evolutionary changes in the structure of the upper molars of Hapalodectes (disappearance of the conules, decrease of the metacone, and narrowing of the lingual lobe) are determined. They were correlated with the transformations of the lower molars (reduction of the metaconid, protocristid, and entoconid, transverse compression of the trigonid and talonid) and together with them were aimed at enhancing the shearing action of the longitudinal trenchant blades of the posterior part of the dentitions.

Lithofacies and paleoenvironmental analysis of the Upper Cretaceous successions: Yagaan Khovil fossil locality, central Gobi region, Mongolia

The Upper Cretaceous successions are exposed at the Yagaan Khovil fossil locality in the central Gobi region, Mongolia. The successions comprise fluvial deposits that are divided into two units based on the lithological characteristics of the floodplain deposits. The lower unit (Unit 1) is characterized by eolian-influenced environments, whereas the upper unit (Unit 2) is composed predominantly of meandering river systems with lateral accretionary channel fill deposits that show concretion at the top of the bed. The shift in depositional processes from the lower to the upper unit can be hypothesized as the result of the change in the proximity of the eolian-affected area to the study area. The successions preserving the similar paleoenvironmental transition are also present in the Nemegt Basin, where the successions shift from reddish mud beds affected by eolian processes to meandering fluvial successions. Additionally, to the similar sedimentological features, similarities in vertebrate fossils between Yagaan Khovil and the formations in the Nemegt Basin imply the close relationship between the two areas in terms of environmental conditions, ages, and stratigraphic positions. To enhance the stratigraphic framework of the Upper Cretaceous strata in Mongolia, future work should integrate the findings of this study with new radiometric dating techniques.

The first troodontid (Dinosauria: Theropoda) from the Upper Cretaceous Baruungoyot Formation of Mongolia

ABSTRACT Among non-avian dinosaurs, troodontids are relatively rare but diverse. The Nemegt Basin in the Mongolian Gobi Desert, which incorporates three of the most fossiliferous beds in the world, is one such region with high troodontid diversity and has also produced eight troodontid taxa until now. The diversity of troodontids is biased towards the two formations, Nemegt and Djadochta. Despite its rich vertebrate fossil record, no troodontids have been described from the Baruungoyot Formation. This faunal absence is perplexing as the Baruungoyot Formation has often been considered intermediate between the other two units in stratigraphy and paleoenvironment, but there are no definite troodontid materials that could fill this ‘gap.’ Here, we report a new troodontid, Harenadraco prima gen. et sp. nov., from the Baruungoyot Formation in Hermiin Tsav, Mongolia. It is represented by an incomplete skeleton that mainly consists of partially articulated left hind limb elements. Harenadraco is small and lightly built like other troodontids, but its tarsometatarsus exhibits extreme slenderness comparable only to Philovenator among cursorial non-avian maniraptorans. It also implies high cursoriality that could be an adaptation of Harenadraco to its environment where potential prey animals like mammals and predators such as eudromaeosaurs were likely to be agile. The discovery of Harenadraco confirms the presence of troodontids in all three formations in the Nemegt Basin. http://zoobank.org/urn:lsid:zoobank.org:pub:0981D708-986B-4B81-8809-E239DF9E8444

A new Early Paleogene fossil mammal locality in the central-eastern Nemegt Basin, Gobi Desert, Mongolia, and notes on mammalian biostratigraphy

AbstractWe report new, fossiliferous Paleogene Naran Bulak Formation localities from the central-eastern part of the Nemegt Basin of the Gobi Desert, Mongolia. Early Paleogene localities have been identified previously only in the western half of the Nemegt Basin. The new localities, near the town of Daus, are also noteworthy for their geographical proximity to Ukhaa Tolgod, a Late Cretaceous Djadokhta Formation locality known for its numerous dinosaur, mammal, and lizard fossils. The Daus section consists of the Zhigden, Naran, and Bumban members of the Naran Bulak Formation at three localities, and mammal and ostracode fossils were discovered in the Naran Member. Noteworthy discoveries are a dentary of the pantodont Archaeolambda cf. A. planicanina, postcrania of Pantolambdodon, a skull of the gliroid Gomphos, and a partial skull with a worn and damaged dentition provisionally identified as an arctostylopid. Biostratigraphy has been the primary means of dating Paleogene Asian faunas, however, the local fauna from the new localities does not fit easily with established patterns. The Naran Member and Archaeolambda planicanina and the arctostylopid Palaeostylops typically have been allied with the Gashatan Asian Land Mammal Age (ALMA) and attributed to the latest Paleocene. By contrast, Gomphos repeatedly has been found in the Bumban Member and assigned a Bumbanian ALMA, which has been considered as the earliest Eocene. Pantolambdodon has been reported from middle Eocene Arshatan and Irdinmanhan ALMA beds. The co-occurrence of these taxa in Naran Member beds complicates the temporal interpretation of the new localities and the reliability of broader biostratigraphic patterns.

Lithobiotopes of the Nemegt Gobi Basin1

Three distinct but overlapping dinosaur-dominated faunas characterize the Upper Cretaceous Djadokhta, Baruungoyot, and Nemegt formations of the Nemegt Basin of Mongolia. Documented faunal differences cannot be explained easily by temporal succession, but can be understood in light of the physical processes controlling the life, death, and burial of taxa. The stratigraphy of the Gobi Desert region records tectonically driven geometries, clearly documenting preservational processes that differ from those acting in most other dinosaur-dominated beds worldwide. Small, asymmetric tectonic grabens were filled with Upper Cretaceous dinosaur-bearing deposits showing asymmetric distributions of facies, here termed lithobiotopes. The water-lain fluvial and alluvial plain facies of the Nemegt lithobiotope supported and preserved a fauna dominated by gigantic dinosaurs, but had a preservational bias against smaller animals. The Nemegt passed laterally into the interdune facies of the Baruungoyot lithobiotope, which represented a hostile environment for large species, but preserved smaller animals. This in turn passed laterally into the aeolianite facies of the Djadokhta lithobiotope, which is characterized by the remains of small dinosaurs and a rich fauna of other animals. The Nemegt Gobi Basin can be visualized as an oasis with a central pond supplied with water from ephemeral channels and surrounded by a semi-arid alluvial plain and dune fields.

Redescription and affinities of Hulsanpes perlei (Dinosauria, Theropoda) from the Upper Cretaceous of Mongolia.

Hulsanpes perlei is an enigmatic theropod dinosaur from the Baruungoyot Formation (?mid- to upper Campanian, Upper Cretaceous) of Mongolia. It was discovered in 1970, during the third Polish-Mongolian paleontological expedition to the Nemegt Basin. The taxon is known based on a partial braincase and an incomplete right hindlimb. However, the braincase fragment has never been described nor illustrated. We redescribe all elements that form the holotype of Hulsanpes and discuss the affinities of this taxon. The braincase fragment is interpreted as belonging to the inner ear region, and includes the floccular recess and part of the labyrinth. Hulsanpes perlei is confirmed as a valid taxon, diagnosed by a unique combination of metatarsal characters, including two autapomorphies. Historically, it represents the oldest record of the recently-established clade Halszkaraptorinae. Our findings identify subcursorial adaptations for Hulsanpes, shared with Mahakala, and differentiating them from Halszkaraptor. As such, appendicular disparity in the potentially sympatric halszkaraptorines suggest a reduced ecological overlap among these taxa, which may explain the co-occurrence of multiple species of this clade during the latest Cretaceous in what is now the Nemegt Basin.

Stratigraphy and paleoenvironmental evolution of the dinosaur-rich Baruungoyot-Nemegt succession (Upper Cretaceous), Nemegt Basin, southern Mongolia

Portions of the dinosaur-rich Upper Cretaceous Baruungoyot-Nemegt succession are exposed in four geographic areas of the Nemegt Basin, Mongolia: Nemegt, Altan Uul, Bügiin Tsav, and Hermiin Tsav. Lithostratigraphic correlations of these areas employ marker beds and non-random stratigraphic patterns of lithology, grain-size variation, and inferred paleoenvironments. Correlations suggest a minimum thickness of 350m for the succession. Exposures at Nemegt, Altan Uul, and Bügiin Tsav form a 100km east-west transect along the northern margin of the basin, exposing 265m of section. From east to west the transect exposes higher portions of the succession, extending from the uppermost Baruungoyot Formation and encompassing an almost complete section of the Nemegt Formation, which has a minimum thickness of 235m and can be consistently divided into three informal members: lower, middle, and upper. The lower Nemegt is well exposed at Nemegt and Altan Uul and is dominated by fluvial deposits. The middle and upper Nemegt are well exposed at Altan Uul 2 and Bügiin Tsav and consist of alluvial plain, paludal, lacustrine, and fluvial deposits. As confirmed by earlier studies, the Baruungoyot and Nemegt formations exhibit an interfingering transition at Nemegt. The Hermiin Tsav section is a geographic outlier, tens of kilometers west-southwest of the northern transect. It exposes about 150m of section that overlaps with, but is mostly lower, stratigraphically, than the northern transect. The uppermost Hermiin Tsav section correlates with the lowermost Nemegt section, and also exhibits an interfingering contact between the Baruungoyot and Nemegt formations. The remaining section at Hermiin Tsav comprises sediments of the Baruungoyot Formation (135m) that were deposited in alluvial fan, fluvial, paludal, lacustrine, and eolian environments, and can be divided into two informal members designated as lower and upper. The distribution of facies through the composite section records changes in paleoenvironments during the Late Cretaceous that may provide insights into the origins of the dinosaurian biostratigraphy.

Geochemical fingerprinting as a tool for repatriating poached dinosaur fossils in Mongolia: A case study for the Nemegt Locality, Gobi Desert

Over the past two decades, illegal poaching of vertebrate fossils from the well-known Cretaceous exposures in Mongolia's Gobi Desert has reached epidemic proportions. Following recent efforts led by the Mongolian government to stem the flow of illegal fossils on the black-market, numerous important specimens have now been seized from private collectors. A tandem objective has been to identify and document poached quarries in the field, which is now allowing scientists to evaluate which areas and stratigraphic intervals are more intensively targeted and impoverished by poachers. Although illegal specimens are now being returned and becoming available for research, the question of provenance still remains of both scientific and political concern. To address this issue, we investigated the geochemistry of the fossil-rich Baruungoyot and Nemegt formations in the Nemegt Basin, including both sediments and associated fossils, using portable X-ray fluorescence (pXRF). Field data were collected using a stratigraphic criterion and are representative of several localities across the Nemegt Basin, although the most complete datasets come from the Nemegt and nearby Khulsan localities. Secondarily, pXRF data were acquired from specimens housed in Ulaanbaatar, including type, recently described, and poached specimens. The final dataset includes approximately 700 pXRF readings. We used a combination of multivariate analysis and data mining techniques to match known with unknown sample provenances, and to determine the most informative elements from the geochemical array available for doing so. Results indicate that the chemical compositions of the Baruungoyot and Nemegt formations largely overlap with calcium being the most informative element for determining provenance from either bones or sediments. However, data arranged by geographic and stratigraphic occurrence (thus reflecting different facies and palaeoecological settings) resulted in more discriminant clusters. The newly developed methodology represents the first systematic attempts to provide an innovative and rapidly-implementable tool to support legal and scientific assumptions.

Rediscovery of the type localities of the Late Cretaceous Mongolian sauropods Nemegtosaurus mongoliensis and Opisthocoelicaudia skarzynskii: Stratigraphic and taxonomic implications

In 1965, the Polish-Mongolian Palaeontological Expeditions recovered two sauropods from the Nemegt Formation of the Nemegt Basin, Mongolia (Kielan-Jaworowska and Dovchin 1968). One specimen, a nicely preserved, complete skull that in 1971 became the holotype of Nemegtosaurus mongoliensis, was found in Central Sayr at the Nemegt Locality. The other was found at Altan Uul IV and is a nearly complete postcranial skeleton lacking only the skull and neck. In 1977, this skeleton became the holotype of Opisthocoelicaudia skarzynskii. Nemegtosaurus and Opisthocoelicaudia were initially assigned to different sauropod higher taxa, Dicraeosaurinae and Camarasauridae respectively. However, since the late 1990s, both genera have been recognized as members of Titanosauria. Their coincident spatiotemporal distribution and non-overlapping skeletal parts have led to the persistent suspicion that they belong to the same species. Rediscovery of the original quarries and discovery of the postcranial remains attributable to the Nemegtosaurus holotype provides the first opportunity to directly compare these two taxa. Seven additional sites at the Nemegt locality preserve sauropod remains (including vertebrae, humeri, femora, pelvic elements, pedal phalanges, and unguals), and more than 20 sauropod footprint sites have been mapped. None of this material suggests that there is more than one sauropod taxon present in the Nemegt Formation. All localities occur within a discrete stratigraphic interval encompassing the uppermost Baruungoyot (footprints), Baruungoyot-Nemegt interfingering interval (Nemegtosaurus type), and lowermost Nemegt formations. Stratigraphic comparisons indicate the Opisthocoelicaudia locality at Altan Uul IV is within the lower beds of the Nemegt Formation. As sauropod remains are now documented for a total of 34 sites in the Nemegt Formation, a more refined stratigraphic framework may shed new light on the taxonomic inclusiveness of the sample.

High-resolution maps of Khulsan and Nemegt localities (Nemegt Basin, southern Mongolia): Stratigraphic implications

Since the discovery of fossil-rich exposures at the Khulsan and Nemegt localities (Nemegt Basin, southern Mongolia), tens of paleontological expeditions returned to these exposures, which are considered some of the richest Cretaceous units in the world. However, limited data on the local geology and cartography have been limiting our comprehension on correlations between different sites and the stratigraphic occurrence of vertebrate remains. Although informative, hand-drawn maps from the 1940s still represent the sole tool for researchers to provide a framework for locating access path, quarries and major geological sections. In 2016, we started a project for the realization of high-resolution topographic maps of key localities within the Nemegt Basin based on drone-acquired images. Several tests were performed at pivotal localities such as Altan Uul 2 and 3, Tsagaan Khushuu, and Ulaan Khushuu providing partial maps of such localities, whereas the Nemegt and Khulsan localities were fully covered. Photogrammetric elaboration of high-resolution images resulted in digital surface models used to obtain high-resolution topographic maps and orthophotos. Rock cairns used in the 1940s for triangulation were relocated and painted with vivid colors in order to represent reliable ground control points. In this study, we introduce new topographic maps for both Khulsan and Nemegt localities as well as comprehensive geological maps. In so doing, we provide additional stratigraphic and geographic data on the approximately 25m thick interfingering interval that characterize the transition from the Baruungoyot and overlying Nemegt formations. Data presented in this study provide a solid framework in which detailed geological and paleontological investigations can be referred in order to significantly improve our comprehension on the Late Cretaceous Nemegt ecosystems.

A New Specimen of the Ornithischian DinosaurHaya griva, Cross-Gobi Geologic Correlation, and the Age of The Zos Canyon Beds

ABSTRACT Although Mesozoic fossils are quite common in the Gobi Desert of Central Asia, it is often difficult to correlate among different localities because of a dearth of rocks amenable to absolute dating. Specifically, correlating between the eastern Gobi Desert and more western localities has been challenging. Here we give a Santonian-Campanian age for the enigmatic Zos Canyon beds in the Nemegt basin. This is based on the occurrence of the primitive ornithopod dinosaur Haya griva at both eastern Gobi exposures of the Javkhlant Formation and the Zos Canyon locality.

A new giant salamander (Urodela, Pancryptobrancha) from the Miocene of Eastern Europe (Grytsiv, Ukraine)

ABSTRACT We present new and well-preserved giant salamander material from the Miocene of the Grytsiv locality, Ukraine. Disarticulated skull and postcranial bones from two individuals are described as a new taxon, Ukrainurus hypsognathus, gen. et sp. nov. U. hypsognathus is characterized by poorly ossified bone tissues, relatively inflexible mandibles, a high dentary, a crista on the lingual surface of the dentary, a pars dentalis of the dentary that is composed of a dental lamina and a subdental surface, presence of an eminentia dorsalis on the squamosal, a broad pericondylar facet on the occipital, extremely elongated prezygapophyses, and hemal processes with an elongate, oval base. Moreover, U. hypsognathus shows evidence of strong mandibular levator muscles that indicate great biting force. A phylogenetic analysis of all well-understood Tertiary and Recent giant salamanders recovers a monophyletic group of Asian and North American cryptobranchids, but places U. hypsognathus outside crown group Cryptobranchidae. This result suggests that Cryptobranchidae originated in Asia and dispersed to North America. The oldest representative of crown Cryptobranchidae is Aviturus exsecratus from the terminal Paleocene of the Nemegt Basin, Mongolia. SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP

New Specimens of Nemegtomaia from the Baruungoyot and Nemegt Formations (Late Cretaceous) of Mongolia

Two new specimens of the oviraptorid theropod Nemegtomaia barsboldi from the Nemegt Basin of southern Mongolia are described. Specimen MPC-D 107/15 was collected from the upper beds of the Baruungoyot Formation (Campanian-Maastrichtian), and is a nest of eggs with the skeleton of the assumed parent of Nemegtomaia on top in brooding position. Much of the skeleton was damaged by colonies of dermestid coleopterans prior to its complete burial. However, diagnostic characters are recovered from the parts preserved, including the skull, partial forelimbs (including the left hand), legs, and distal portions of both feet. Nemegtomaia represents the fourth known genus of oviraptorid for which individuals have been found on nests of eggs. The second new specimen, MPC-D 107/16, was collected a few kilometers to the east in basal deposits of the Nemegt Formation, and includes both hands and femora of a smaller Nemegtomaia individual. The two formations and their diverse fossil assemblages have been considered to represent sequential time periods and different environments, but data presented here indicate partial overlap across the Baruungoyot-Nemegt transition. All other known oviraptorids from Mongolia and China are known exclusively from xeric or semi-arid environments. However, this study documents that Nemegtomaia is found in both arid/aeolian (Baruungoyot Formation) and more humid/fluvial (Nemegt Formation) facies.

A New Platynotan Lizard (Diapsida: Squamata) from the Late Cretaceous Gobi Desert (Ömnögov), Mongolia

Here we describe a new diminutive varanoid from the Late Cretaceous Djadoktha Formation of Omnogov, Mongolia. The new taxon, Ovoo gurval, was found in the Nemegt Basin at the locality of Little Ukhaa, a locality adjacent to the rich fossil beds of Ukhaa Tolgod. The new varanoid is similar to Aiolosaurus oriens, another small varanoid from the Ukhaa Tolgod locality and several diagnostic characters of Ovoo gurval are shared with Aiolosaurus oriens. Ovoo gurval also has a pair of unusual neomorphic ossifications on the skull roof overlying the frontonasal contact. Positionally, these are unlike any neomorphic ossifications in other squamates, and certainly can be distinguished from osteoderms found in some varanoids.

Redescription of the mongolian sauropod nemegtosaurus mongoliensis nowinski (dinosauria: Saurischia) and comments on late cretaceous sauropod diversity

Synopsis The isolated skulls of Nemegtosaurus mongoliensis and Quaesitosaurus orientalis from the Nemegt Basin of Mongolia are among the most complete sauropod cranial remains known from the Late Cretaceous, yet their evolutionary relationships to other neosauropods have remained uncertain. Redescription of the skull of Nemegtosaurus identifies key features that link it and its closely related counterpart Quaesitosaurus to titanosaur sauropods. These include a posterolaterally orientated quadrate fossa, ‘rocker'‐like palatobasal contact, pterygoid with reduced quadrate flange and a novel basisphenoid‐quadrate contact. Other features are exclusive to Nemegtosaurus and Quaesitosaurus, such as the presence of a symphyseal eminence on the external aspect of the premaxillae, a highly vascularised tooth bearing portion of the maxilla, an enclosed ‘maxillary canal’, orbital ornamentation on the postorbital, prefrontal and frontal, exclusion of the squamosal from the supratemporal fenestra and dentary teeth smaller in diameter than premaxillary and maxillary teeth. Re‐examination of Late Cretaceous sauropod distributions in the light of this well‐supported phylogenetic hypothesis has important implications for their diversity at the end of the Mesozoic in Asia and elsewhere. Cretaceous Asian sauropod faunas consist solely of titanosauriforms, which probably migrated there from other landmasses during the Late Jurassic, during which time neosauropods were absent from Asia. Globally, narrow‐crowned titanosaurs and rebbachisaurids radiated during the Cretaceous, but only titanosaurs survived into the latest Cretaceous. These late‐surviving sauropods flourished on most continental landmasses until the end of the Maastrichtian.

Postcranial skeleton of Ukhaatherium nessovi (Eutheria, Mammalia) from the Late Cretaceous of Mongolia

ABSTRACT The postcranial skeleton of Ukhaatherium nessovi, a eutherian mammal from the Upper Cretaceous of the Gobi Desert, Mongolia, is described. Nearly the entire skeleton is represented by three skeletal assemblages associated with each other, found at Ukhaa Tolgod, a locality in the Nemegt Basin. Morphological comparisons of Ukhaatherium are made with several other mammals, including placentals, marsupials, and Asioryctes, another Cretaceous eutherian from Mongolia. As has been previously pointed out, Ukhaatherium and Asioryctes possess a number of characters that suggest they occupy a basal position in the eutherian evolutionary tree. Ukhaatherium has epipubic bones, an unexcavated astragalar trochlea, and a depressed calcaneum, among other primitive characters. Derived characters that link it with eutherians include an upper ankle joint which is more restricted to the parasagittal plane than in basal marsupials and other outgroups, and an astragalar neck that is superimposed on the sustentacular facet, as opposed to the condition found in metatherians and other outgroups, in which the sustentacular facet is either medial to the astragalus, or it is ventral to the astragalar neck but the latter overhangs the sustentacular facet medially. Ukhaatherium offers some intermediate conditions between placentals and its outgroups which facilitate a better understanding of character evolution at the root of Placentalia.

Osteology and Relationships of Byronosaurus jaffei (Theropoda: Troodontidae)

The troodontid Byronosaurus jaffei is known from two specimens from adjacent localities in the Nemegt basin, Omnogov Aimag, Mongolia. These specimens are composed of well- preserved cranial material and fragmentary postcrania. All of these elements are described here. Byronosaurus jaffei is included in a comprehensive phylogenetic analysis of Coeluro- sauria to ascertain its relationships. Several interesting characters of Byronosaurus jaffei have implications both for theropod relationships and for understanding patterns of variation within coelurosaurian theropods. These include the position of a foramen that marks the exit of the supra-alveolar canal (which we suggest is homologous with the subnarial foramen), the flat- tened internarial bar, the unusual interfenestral bar, and the unserrated teeth. Additionally, the well-preserved braincase allows detailed comparison with other troodontid taxa.

Life and death in a Late Cretaceous dune field, Nemegt basin, Mongolia

For more than 70 years, red sandstones of the Gobi Desert have yielded abundant articulated skeletons of Late Cretaceous dinosaurs, lizards, and mammals. At Ukhaa Tolgod, structureless sandstones are the only fossiliferous facies, and we present new evidence for deposition on dune-sand–sourced alluvial fans that were built at the margins of stabilized eolian bedforms during mesic climatic episodes. In laterally and vertically adjacent large-scale eolian cross-strata in which skeletons are absent, we have found abundant tracks of dinosaurs that walked on sparsely vegetated dunes that were active under xeric conditions. Our study of calcareous concretions in vaguely bedded eolian sandstones suggests that bedding was nearly destroyed by burrowing invertebrates and trampling dinosaurs. The accumulation of illuvial clays and pedogenic calcite in these sediments reduced infiltration of rainwater and, with attendant climatic change and heavy rainfall events, led to fan development.

Isoetalean megasporophylls with megaspores from the Upper Cretaceous of Mongolia

Detached megasporophylls bearing relatively large sporangia with megaspores are described from the lower Maastrichtian dinosaur beds of the Nemegt Basin, eastern Gobi, Mongolia. The megasporophylls are fertile along their entire length except a short tip. The megaspore tetrads are aligned in a single file. On the base of these distinctions the Mongolian fossils are assigned to a new genus Monilitheca of the Isoetalean affinities. The megaspore casts show replicas of both the external and internal reticulate structures. The megaspores are comparable with dispersed spore genera Horstisporites and Erlansonisporites thus suggesting their isoetalean affinities.

Charophyta from the deccan intertrappean beds near Rangapur, Andhra Pradesh, India

Two charophytes-Platychara perlala (Peck & Reker) Grambast and Nemegtichara grambosti sp. nov- are described and illustrated from the Deccan Intertrappean beds near Rangapur, district Rangareddi, Andhra Pradesh. The genus Nemegtichara Karczewska & Ziembinska-Tworzydlo, first described from the Palaeogene "White Beds" of the Nemegt Basin in Mongolia and also known from the Cretaceous- Middle Eocene of China is being recorded for the first time from India. The age and palaeobiogeographic implications of the assemblage are also discussed.