Molluscan Fauna Research Articles

ПРОСТОРОВА ДИФЕРЕНЦІАЦІЯ НАЗЕМНИХ МАЛАКОКОМПЛЕКСІВ НА РІВНИННИХ І ПЕРЕДГІРНИХ ТЕРИТОРІЯХ ЗАХОДУ УКРАЇНИ

The peculiarities of the distribution of the land molluscs in the plain and foothill territories of Western Ukraine have been analysed on the basis of the personal long-term collections (1994–2017), the critical study of other collections and the literature data. The species lists were precised for 9 physical-geographical regions: Volhynian (Western) Polesia, Volhynian Upland, Male Polesia, Roztochia and Opillia, Western Podolia, Central (Northern) Podolia, Prut-Dniester Upland, Ciscarpathia, Transcarpathian Lowland. With due regard for the literature data, the records of 138 species of land molluscs (76 genera, 30 families) from the plain and foothill territories of Western Ukraine can be considered as reliable ones. The maximum species richness has been marked in Roztochia and Opillia (106 species), slightly less – in Western Podolia (95 species) and Ciscarpathia (94 species), the minimum – in Volhynian Upland (32 species). According to the taxonomic composition and ecological spectra of the land mollusc complexes, in the plain territories of Western Ukraine two faunistic complexes can be distinguished, the boundary between which passes along the northern edge of the Podolian Upland. The land mollusc fauna of Male Polesia and Volhynian Upland shows a greater similarity with the mollusc fauna of Western Polesia than with other parts of the deciduous forests zone, and is characterized by reduced taxonomic diversity, the lesser number of Carpathian species, the lesser part of the forest and, especially, stenobiontic forest species and an increased proportion of the hygrophilous species. In studied area a number of the land molluscs can be marked, which have penetrated to Western Ukraine exclusively due to the anthropochory (not less than 16 species). The most common of these at present are L imax maximus , Cepaea hortensis , Boettgerilla pallens , Krynickillus melanocephalus , Monacha cartusiana . A rapid spreading of the slugs from the complex Arion lusitanicus s.l. has been observed recently in Western Ukraine. The influence of anthropochory on shaping of present species composition of land mollusc complexes becomes the most apparent in Roztochia and Opillia, where the part of molluscs-anthropochores is not less than 11.3 %, and in the Transcarpathian Lowland (at least 12.2 %).

Land Mollusks of the California Channel Islands: An Overview of Diversity, Populations, and Conservation Status

The land snails and slugs have the highest level of endemism among all major animal groups on the California Channel Islands, with nearly 75% of the native terrestrial species confined to one or more of the 8 islands. In spite of this endemism, and in spite of the rarity of some species, the snails and slugs are one of the most poorly known groups. We present the first comprehensive overview of the land mollusk fauna of the Channel Islands, along with the results of recent intensive inventory studies. Surveys on San Clemente Island have increased the number of land mollusk species known from that island by 50%, and a single survey trip to Santa Rosa Island more than doubled the number of species known on that island. More additions to the land snail and slug fauna are certain for the poorly surveyed northern Channel Islands. This new information has provided insight into trends in species diversity and biogeographic patterns, with marked differences in species composition between the northern and southern islands. Our surveys to date suggest a strong link between the recovery of native vegetation on the islands and the population status of land snails and slugs, with substantially larger numbers of native mollusks on those islands that have been free of nonnative mammals the longest. Survey work is continuing, but it is clear that some very rare endemic snails and slugs on the islands merit specific management attention.

The influence of urbanisation on aquatic mollusc fauna: the Krzna River (east Poland)

The influence of urbanisation on aquatic mollusc fauna: the Krzna River (east Poland)

A glacial refugium and zoogeographic boundary in the Slovak eastern Carpathians

AbstractAlthough the Carpathians in Europe have often been considered a glacial refugium for temperate plants, vertebrates, and molluscs, the fossil records, the only indisputable evidence surviving glacial periods, are as yet scarce. Moreover, the distribution of fossil records is uneven, and some areas have remained unstudied. We present here three molluscan successions from such an area—the border between the western and eastern Carpathians. This area is not only a geographic border but also a border between the oceanic and continental climate in Europe, and the molluscan fauna reflects this. We found a fluctuation of this zoogeographical border during the late glacial period and the Holocene for several snail species with their easternmost or westernmost distribution situated at this border. Such a fluctuation could reflect a small-scale shifting of climate character during the Holocene. For the first time, we recorded the fossil shells of three local endemics, Carpathica calophana, Petasina bielzi, and Perforatella dibothrion. We also found a fully developed woodland snail fauna radiocarbon dated to the Bølling period. This early occurrence of canopy forest snails indicates a possible eastern Carpathian glacial refugium for them, including local endemics, and may reflect a more moderate glacial impact on local biota than expected.

Analysis of a Cretaceous (late Aptian) high-stress ecosystem: The Romualdo Formation of the Araripe Basin, northeastern Brazil

The Cretaceous (upper Aptian) Romualdo Formation of the Araripe Basin, northeastern Brazil, is a marine-influenced, predominantly fine-grained siliciclastic unit. In the eastern part of the basin, it corresponds to a depositional sequence composed of two transgressive-regressive cycles. Low-diversity benthic macrofaunas document high-stress conditions. Their palaeoecological and taphonomic analysis allows for the detailed reconstruction of the palaeoenvironments and of the temporal changes in the palaeoecosystem. The transgressive part of the lower cycle is a black shale with calcareous concretions that contain excellently preserved fishes and other vertebrates (the famous “Santana fossils”), but apart from abundant ostracods and rare decapod crustaceans, benthic faunal elements are very rare due to anoxic to dysoxic conditions. A low-diversity parautochthonous molluscan fauna of small bivalves and gastropods records fluctuating dysoxic conditions during early regression. Towards the top of the measured sections (late regression), thin gastropod shell beds become conspicuous. At the top of the sections decimetre-thick shell concentrations show signs of reworking and a greater marine influence (transgressive part of the upper cycle). The distribution pattern of three benthic associations and two assemblages is almost equally shaped by three environmental parameters: The low overall species diversity, small size of the fauna, and the lack of stenohaline elements suggest lowered and fluctuating salinity conditions. Fluctuating redox conditions with anoxia to dysoxia, identified especially in the lower parts of the succession, and substrate were the other two factors shaping the faunal distribution. The late Aptian sedimentary and faunal history of the eastern part of the basin indicates restricted marine influence, coupled with increasing freshwater input during phases of sea-level lowstand, and low-energy conditions offshore, which led to widespread anoxia, especially in the lower part of the formation. Thus, palaeoecological analyses are an excellent tool to disentangle the various environmental parameters that shaped the palaeoenvironments of the basin, to understand more closely its Fossil-Lagerstätten, and to corroborate and fine-tune the sequence stratigraphic framework.

A new genus and two new species of freshwater Gastropoda from the Ceyhan River Basin in the eastern Mediterranean (Mollusca: Gastropoda: Truncatelloidea)

In a survey of the mollusc fauna of the Ceyhan River Basin, including rivers, natural lakes, dam lakes and springs between June 2008 and September 2014, a total of 20 species of Gastropoda and 8 species of Bivalvia were identified. Two of these species are new to science, and for one of them a new genus is erected: the hydrobiid Hemite ceyhanensis gen. n., sp. n., and the bithyniid Pseudobithynia cocussusica sp. n.http://www.zoobank.org/urn:lsid:zoobank.org:pub:DE5FFC19-13CD-4B81-B74E-80059E781518

Fossil glochidia (Bivalvia: Unionida: Hyriidae) from the middle Miocene of western Amazonia (Peru)

Unionid bivalves are a common and widely distributed group of freshwater mussels, presumably known since the Triassic. One peculiar trait is their life cycle, with brooding of eggs in portions of the gills and release of usually fish-parasitizing larvae. The morphology of these larvae (glochidia or lasidia) is an important character for unionid classification and hence for phylogenetic reconstructions. Dispersal capacity and success of unionids through geological times is assumed to be largely affected by the evolution of temporary parasitism. Nevertheless, pre-Quaternary fossil proof of unionid larvae has been lacking until now, which renders some palaeobiological, phylogenetic and palaeobiogeographical scenarios arguable. Here we document late middle Miocene glochidia from the Pebas Formation (Porvenir, north-eastern Peru). Based on morphological comparisons with Recent glochidia and the accompanying fossil record, these larvae are related to the Hyriidae genus Diplodon Spix, 1827. Due to the lack of ‘hooks’ (inward-directed projections on the ventral edge of the glochidium) the larvae probably did not parasitize (fish) hosts, which restricted their dispersal ability. In this case, ‘unhooked’ is presumably a derived feature related to direct larval development. The strata containing these glochidia have been interpreted as marginal marine deposits with high-frequency salinity fluctuations. The associated mollusc and ostracod fauna is strongly dominated by euryhaline, endemic species. Only subordinately ‘freshwater’ and ‘marginal marine’ taxa co-occur, as well as euryhaline foraminifers. Stable isotope analyses (δ18O, δ13C) performed on ostracods and foraminifers furnished very light ratios, indicative of freshwater conditions. It remains unresolved if some marine-derived ostracods and also foraminifers were able to adapt to freshwater settings or if marine incursions affected western Amazonia in late middle Miocene times. Possibly the combination of, for example, fluctuating oxygenation and/or salinity and the complex reproductive strategy diminished the competitiveness of unionids within the Pebas wetlands.

First report of a Pliocene pike (Esocidae: Esox) in Transylvania, Romania

Pliocene fish species based on skeleton remains and associated teeth ever reported from the inner Carpathian area in Romania in the Brasov Basin (Baraolt sub-basin), which refers to a pike ( Esox sp.). The fish fossils illustrating a large-sized specimen originate from the South Racos coal open pit (Racosu de Sus, Covasna County), in the so-called “Formation with Limnocardium” (Dacian, Lower Pliocene). Comparisons with osteological material of recent pikes originating from various localities in Romania are presented. The associated mollusc fauna known from the formation that yielded the pike remains suggests the presence of a lake with a stratified water column in the Baraolt sub-basin.

Mammalian Fauna of the Middle Eocene Kishenehn Formation, Middle Fork of the Flathead River, Montana

The Kishenehn Formation is a unit of sedimentary rocks exposed largely in the cutbanks of the Flathead River and its tributaries in and around Glacier National Park in northwestern Montana and adjacent British Columbia. From these rocks along the Flathead's Middle Fork, which range from very fine-grained oil shales to and including pebble-cobble conglomerates, vertebrate and molluscan faunas of middle Eocene age have been collected over nearly 40 years by a combination of prospecting, with access by raft, to screen washing sediment from the most fossiliferous exposures. The mammalian fauna from the formation includes at least twenty-six taxa, ranging in size from tiny rodents and insectivores to a very large brontothere. A radiometic date of ca. 46.2 Ma was obtained from below the fossiliferous deposits. The age of the fauna, presumably within one or two million years younger than the radiometric date, is reinforced by the presence of the Uintan index taxon Amynodon Marsh, 1877, as well as the co-occurrence of an eomyid rodent referred to Metanoiamys Chiment and Korth, 1996, and the sciuravid rodent Pauromys Troxell, 1923. The fauna has a scarcity of Carnivora, which may reflect the real faunal composition. It is striking for its total absence of selenodont artiodactyls. Whether the latter should be attributed to geologic age, which is presumably early after these animals developed in North America or Asia, or is environmentally significant, must remain conjectural. Somewhat widely distributed in the North American west, earlier Uintan and/or Shoshonean mammalian faunas remain difficult to correlate, due at least in part to distinctive endemism or environmental uniqueness. The fauna also has indications of interchange between North American and Asian components at that time.Of the twenty-six mammalian taxa recognized in the fauna, one is established as new, the rodent Microparamys solis, new species.

First record of the semi-slug Omalonyx unguis (d’Orbigny, 1837) (Gastropoda, Succineidae) in the Misiones Province, Argentina

Omalonyx unguis (d’Orbigny, 1837) is a semi-slug inhabiting the Paraná river basin. This species belongs to Succineidae, a family comprising a few representatives in South America. In this work, we provide the first record for the species from Misiones Province, Argentina. Previous records available for Omalonyx in Misiones were identified to the genus level. We examined morphological characteristics of the reproductive system and used DNA sequences from cytochrome oxidase subunit I (COI) gene for species-specific identification. These new distributional data contribute to consolidate the knowledge of the molluscan fauna in northeastern Argentina.

Little lasting impact of the Paleocene-Eocene Thermal Maximum on shallow marine molluscan faunas.

Global warming, acidification, and oxygen stress at the Paleocene-Eocene Thermal Maximum (PETM) are associated with severe extinction in the deep sea and major biogeographic and ecologic changes in planktonic and terrestrial ecosystems, yet impacts on shallow marine macrofaunas are obscured by the incompleteness of shelf sections. We analyze mollusk assemblages bracketing (but not including) the PETM and find few notable lasting impacts on diversity, turnover, functional ecology, body size, or life history of important clades. Infaunal and chemosymbiotic taxa become more common, and body size and abundance drop in one clade, consistent with hypoxia-driven selection, but within-clade changes are not generalizable across taxa. While an unrecorded transient response is still possible, the long-term evolutionary impact is minimal. Adaptation to already-warm conditions and slow release of CO2 relative to the time scale of ocean mixing likely buffered the impact of PETM climate change on shelf faunas.

Contribution to the knowledge of the marine bivalve mollusk fauna of Gangwon Province, Korea

Marine bivalve mollusks were obtained from 13 collecting sites, intertidally on beaches and from fishing nets in ports, along the coast of Gangwon Province, Korea. A total of 70 species belonging to 27 families were encountered; all species are illustrated with photographs. Among them, 17 species are recorded for the first time for Gangwon-do, and two species are new records for Korea: Gari chinensis Deshayes, 1855 (Psammobiidae) and Clinocardium likharevi (Kafanov in Scarlato, 1981) (Cardiidae). Taxonomic and distributional comments on 13 species are provided, and the biogeography of the area is discussed. Some warm-water species of bivalves [e.g. Anadara talmiensis (Kalishevich, 1976), Trapezium liratum (Reeve, 1843), and Meretrix lusoria (Röding, 1798)], found in Gangwon-do for the first time, are remnants of the Holocene warming in the Russian sector of the East Sea (Sea of Japan), thus indicating the significance of Korean waters as a transitional zone for past molluscan migrations.

Testing the robustness of a coastal biodiversity data protocol in the Mediterranean: insights from the molluskan assemblages from the sublittoral macroalgae communities

The NaGISA project (Natural Geography Ιn Shore Areas) is a global initiative within the framework of the Census of Marine Life. The Mediterranean Sea has joined with 4 stations, 2 in Italy and 2 on the island of Crete, Greece. Two different sites were sampled during two consecutive years (2007 and 2008) by means of SCUBA diving. On the basis of the evidence offered by the collected material from the hard substrates of Crete, and the literature mined datasets concerning the molluscan assemblages, two main issues are investigated: (a) is the molluscan fauna sampled in the two NaGISA sites representative of the regional Mediterranean one? and (b), is the molluscan fauna sampled from the two sites randomly assembled from the regional species pool across different spatial scales? Although a strong tendency of the local molluskan composition to be randomly sampled from the regional pools at all scales, it is not possible to demonstrate with a degree of certainty whether their observed local diversity is independent of local and regional processes or if it is determined by a combination of the two acting either in concert or antagonistically.

Molluscan fauna of the lower reaches of the Syoyakha River (Yamal Peninsula)

The molluscan fauna of the Syoyakha (Zelenaya) River remain poorly explored even though the Syoyakha is one of the biggest rivers on the Yamal Peninsula. The Syoyakha River is remarkable for its high fish stocking capacity and it plays an important role in the seasonal distribution and migration of commercial fish species. Freshwater mollusks are known to be a major component of freshwater ecosystems and they make up a part of the diet of many commercially important fish species. The species composition of the mollusks inhabiting the lower reaches of the Syoyakha River has been studied. Five bivalve species of the family Sphaeriidae were found, namelySphaeriumcorneum(Linnaeus, 1758),Pisidiumcasertanum(Poli, 1791),P.globulare(Clessin in Westerlund, 1873),P.lilljeborgi(Clessin in Esmark et Hoyer, 1886) andP.dilatatum(Westerlund, 1897). In general, the molluscan fauna of the lower reaches of the Syoyakha River are taxonomically poor, which can be considered typical of freshwater invertebrate communities living at high latitudes. Another reason for the decline in species diversity may lie in the absence of any large transit watercourse in the basin in question allowing northward dispersion of the mollusks. The average density of mollusks in the watercourse stretch under study varied from 98.9 ind./m2to 620.5 ind./m2.P.globularesettlements had the highest recorded density of 1,442.9 ind./m2. The mollusks are confined to clayey, silty and sandy substrates with remnants of vegetation. The fauna is basically formed by widespread Palearctic and Holarctic mollusk species that have adapted to the extreme conditions of the Arctic. The findings may be used for hydrobiological and fishery characterization of the watercourse given that the recorded species ofS.corneum,P.globulare,P.lilljeborgi, andP.dilatatumare a major food item for important fish species, such as cisco, vendace, char, muksun, etc.

A Griesbachian (Early Triassic) Mollusc Fauna from the Sidazhai Section, Southwest China, with Paleoecological Insights on the Proliferation of Genus Claraia (Bivalvia)

After the end-Permian mass extinction, genus Claraia (Bivalvia) was the most abundant and most noticeable fossil during the survival and recovery stage. However, the reasons for the proliferation of Claraia are still debated. This paper describes a new Griesbachian (Early Triassic) mollusc fauna from deep-water settings in South China in the aftermath of end-Permian mass extinction. This fauna yielded five bivalve species in two genera (Claraia griesbachi, C. wangi, C. stachei, C. radialis, and Promyalina putiatinensis) and two ammonoid species (Ophiceras sp. and Ussuridiscus sp.) and could be assigned to the Claraia wangi-C. griesbachi assemblage zone, indicating a Middle-Late Griesbachian Age. The bivalves were dominated by Claraia griesbachi and were featured by articulated Claraia fossils. As Claraia was epibyssate, it was an excellent autochthonous fauna. While the shallow and deep marine water became dysoxic to anoxic globally, as indicated by recent studies of the early Early Triassic, we suggest the genus Claraia could tolerate dysoxic and/or anoxic conditions and its proliferation could be attributed to its physiological features which were adapted to the stressed environment. The wide distribution of Claraia was probably related to its planktonic larval stage. Where the larva of Claraia could have been transported by ocean flow and increased its potential for long-distance dispersal. In addition, Claraia was a significant disaster and opportunistic taxon during the Early Triassic based on observations in South China.

Lac des Bois, a locality in the northern Western Interior Seaway (Canada) with Tethyan faunal connections during the Cenomanian/Turonian Thermal Maximum

Early Turonian fishes are known from only a few localities in the Northern Hemisphere, including three in the present-day European/Mediterranean region and three in northern Canada. One of the latter localities, Lac des Bois (66°52.087ʹ N), preserves a diverse marine fauna composed of trace fossils, foraminifera, molluscs and actinopterygian fishes including early acanthomorphs. The molluscan fauna, as well as a radiometric date from bentonites recovered from the site, support an age of latest Cenomanian/early Turonian for the locality. This interval spans the global Oceanic Anoxic Event 2, a time characterized globally by high temperatures and high carbon burial. Although the Cenomanian/Turonian boundary interval has been documented in North America in the Arctic Sverdrup Basin and the southern Interior Seaway, the present study provides the first account of a faunal assemblage that inhabited the northern Western Interior Seaway during this interval. Organic-rich shales and sandstones indicate limited organic decomposition and low oxygen conditions, although the presence of trace fossils (Skolithos, Planolites, Taenidium and Alcyonidopsis, as well as fugichnia) indicates that the sea floor was not completely anoxic. The presence of coiled planktic foraminifera indicates warmer water and extends the known migration limit of these Tethyan-derived forms some 6° further north. Surprisingly, the fish fauna of localities in the Bohemian Cretaceous Basin (Czech Republic) bears a close resemblance to that of Lac des Bois, although acanthomorph fish have not been recorded from the former. This suggests faunal connections between the two regions, either through the northern Polar Sea, or through the postulated Hudson Strait.

A dataset of molluscan fauna sampled in river estuaries of medium and small size river in Kyushu island, Japan.

BackgroundMany studies have evaluated the ecological integrity of large-scale estuaries of continental rivers using biotic indicators such as fish, phytoplankton and benthic communities. However, few studies have focused on the river estuaries of small and medium rivers. Molluscan fauna data in large estuaries or in the estuaries of large rivers have been collected by the The National Census on River Environments (conducted by the Ministry of Land, Infrastructure, Transport and Tourism) or National Survey on the Natural Environment (conducted by the Ministry of Environment). On the other hand, molluscan fauna of small and medium rivers are managed by local governments and have rarely been investigated.New informationThis paper provides basic information on the molluscan fauna of 70 rivers in Kyushu, Japan, collected with the aim of conserving estuaries of small and medium rivers. In total, 37 families, 82 species and 21,827 individuals were collected. The data are all accessible from the document “A dataset of shellfish fauna sampled in estuaries of medium and small rivers in Kyushu, Japan (http://ipt.pensoft.net/resource.do?r=shellfishes_in_kyushu)”. According to the Red Data Book published by the Japanese Ministry of Environment in 2018, 3 species were determined as Critically endangered and Endangered, 6 species were determined as Vulnerable and 13 species were determined as Near Threatened. The proportions of individuals classified as Critically endangered and Endangered from the total number of individuals were extremely low, but the proportions of Near Threatened individuals were high. Our results indicate that the risk of molluscan extinction in small- and medium-sized river estuaries in Kyushu is high and that immediate conservation is necessary.

A multi-disciplinary macrofossil study of late glacial to early Holocene sediments from Søndre Kobberdam, Hareskovene, Denmark

During the early part of the Allerød period, from c. 13 600 to 13 330 years BP, unstable soils with a tundra-like open, treeless vegetation with Betula nana and Dryas octopetala were found around Søndre Kobberdam in Hareskovene. Open Betula pubescens woodland was not established until the middle Allerød about 13 330 years BP. During the Younger Dryas, Betula nana and Dryas octopetala spread again, and Betula pubescens almost disappeared. From the onset of the Holocene warming an open tundra landscape characterised the area. About 11 300 years BP Betula pubescens started to recolonise the region and Populus tremula and Pinus sylvetris arrived at c. 11 000 years BP, replacing the open landscape by woodland. Along the margin of the lake Carex paniculata, Carex riparia and Cladium mariscus were growing. The lake fauna included a rich and diverse fauna of molluscs that thrived in the carbonate-rich waters. We did not find any evidence for the local presence of Pinus sylvestris during the late glacial.

Rare species of freshwater mollusks of the Bolshoy Yugan River basin (Middle Ob) in collection of 2016

Information about rare species used for decide widely spectrum of problems. In practice ‒ for estimating environmental impact from human activities. For example by studying biodiversity in fundamental science. This information very important for monitoring and prevention of species extinction. Regional and Federal Red Books serve this aim. However freshwater mollusks species of the Bolshoy Yugan river basin not presented in the Federal Red Book of Russian Federation. In addition, in the Regional Red Books of Khanty-Mansi autonomous region and Tyumen region data about mollusks are absence. This paper the first step to fill in the gap. Article contains the first data about rare species of freshwater mollusks of the Bolshoy Yugan River basin collected during the field season of 2016. In future, these species possibly will be propose to inclusion in the Red Book of Khanty-Mansi autonomous region. I followed the standard techniques of mollusks sampling, fixation and laboratory treatment. In this research I call species rare if species occurrence was 5,0% and lower. I used contemporary macrosystems of mollusks in the level above family groups of both Bivalves and Gastropods. In addition, on the level under family groups and lower I used alternative approach, which consist of combination of two different taxonomic systems: “traditional” European and Ya.I. Starobogatov’s scientific school or “Russian”. The collection of mollusks is kept in the Federal Zapovednik (Nature Reserve) “Yuganskiy”, which was the material base of my study. In the article discussed aspects of rareness and difficulty of investigates freshwater mollusks. These difficulties connected with existence of different taxonomical approaches and underexplored mollusk's fauna and ecology. Studies of rare species in the Western Siberia are briefly considered. The results of own research and annotated list of rare mollusks species of Bolshoy Yugan River basin collected during the field season of 2016 are presented. Showed that significant part of species richness in the Bolshoy Yugan River basin consist of rare species. These results do not change independent of applied taxonomical approaches “traditional” or “Russian” and discussed with facts in malacologycal literature. There are 50 species of freshwater mollusks were find in 2016, 41 of them are rare in the Bolshoy Yugan River basin. In conclusion marked need for further research of freshwater mollusks. In addition denoted some important priorities of studies, such as systematics, fauna, zoogeography and ecology of mollusks. The question about inclusion in the Red Book of Khanty-Mansi autonomous region some any species of freshwater mollusks are still opened. Because needed additional facts about distribution and abundance species from others parts of region.Partial financial support for this study was obtained from the Ministry of Education and Science of Russian Federation (project 6.1352.2017/ПЧ).

Faunistic Substantiation of Stratigraphic Occurrence of the Pleuromeia (Isoëtopsida) Plant in the Triassic of Gorny Mangyshlak, Republic of Kazakhstan

Joint burial places of mollusks and Pleuromeia plants allow specification of a period of stratigraphic occurrence of this genus in the west of the Republic of Kazakhstan within the Gorny Mangyshlak. Two places of occurrences of pleuromeias were found in marine Triassic rocks: one in the Karadzhatyk Formation of the northern slope of the Karatauchik Range close to the Dolnapa well, where the fossils of Pleuromeia sternbergii (Munster) Corda plants are associated with ammonoid shells, and the other one in the Karaduan Formation of the southern slope of Mt. Karashek, where this plant was found along with bivalves and gastropods. The mollusk fauna from both occurrences indicates that the Mangyshlak pleuromeias occurred from the late Olenekian Substage to Anisian Stage.