Ostracod Species Research Articles

A diversified Ostracoda (Crustacea) assemblage from the Upper Cretaceous intertrappean beds of Gujri, Dhar District, Madhya Pradesh, India

Two new non-marine ostracod species, named Gomphocythere testudo sp. nov. and Candona phaseolus sp. nov. are described from the intertrappean beds exposed near Gujri village in District Dhar, Madhya Pradesh, Central India along with common Deccan intertrappean ostracod species Cyclocypris sahnii, Cypria cyrtonidion, Paracypretta jonesi, Periosocypris megistus and Stenocypris cylindrica. Presence of five other ostracod taxa, viz., Frambocythere tumiensis anjarensis, Gomphocythere strangulata, G. paucisulcatus, Zonocypris gujaratensis and Eucypris intervolcanus documented earlier from this locality are also present in our sample. Barring the two new taxa, the other ten species are also known to occur in coeval intertrappean and infratrappean beds of eastern, central, southern and western parts of the Deccan volcanic province. A Maastrichtian age is inferred for the fossiliferous horizon based on the ostracod fauna. Biostratinomical assessment of ostracod assemblages was carried out followed by palaeoecological and palaeoenvironmental analyses. The presence of non-marine ostracods in association with terrestrial vertebrate remains, gastropods, and charophytes favours a freshwater depositional environment for the Gujri intertrappean beds and do not provide any evidence for the prevalence of supposed marine conditions along the Narmada lineament in the latest Cretaceous.

Recent brackish water Foraminifera and Ostracoda from two estuaries in Ghana, and their potential as (palaeo)environmental indicators

To improve the indicator value of marginal marine Foraminifera and Ostracoda of Ghana, we analysed 22 surface sediment samples for microfauna. They were obtained from the Keta Lagoon and Densu Estuary covering a salinity range from marine waters to 17.5 and one sample within the hyperhaline range (70). Except one, all samples contain Ostracoda and Foraminifera. There are 34 ostracod species belonging to 24 genera. Dominating is Cyprideis remanei Klie, 1940, other abundant species are Pseudoconcha sp., Pseudoconcha hartmanni Omatsola, 1970, Loxoconcha lacunensis Omatsola, 1970 and Chrysocythere foveostriata Brady, 1870. We found 28 Foraminifera species belonging to 22 genera with the dominant taxa Ammonia sp. and Quinqueloculina spp. There are five associations, which are mainly driven by the hydrological regime and organic pollution. In contrast to a usual diversity trend reflecting high levels of pollution by lower diversity, our results show higher diversity associated with sites of higher pollution levels. The most tolerant (salinity and pollution) ostracod taxon is Cyprideis remanei, which is occurring over the whole salinity range documented as well as in contaminated areas with very high LOI and heavy metal concentrations. In the investigated samples we found many deformed Foraminifera with anomalies like multiple tests, changes in coiling and aberrant shapes of the chambers.Ongoing investigations in estuaries of Ghana are expanding our data set and will provide a better understanding of species-specific reactions of Ostracoda and Foraminifera to anthropogenic pressure.

Endemic Silurian ostracod faunas of the Southern Tien Shan, Central Asia

The overall occurrence, composition, stratigraphic distribution and palaeobiogeographic and biostratigraphic significance of ostracod faunas in the Silurian of the Southern Tien Shan in Uzbekistan and Tajikistan, central Asia is, for the first time, documented herein. The faunas are diverse in each of the four Silurian series, with podocopes, palaeocopes and mydocopes present and podocopes dominant throughout. The faunas are species rich, with some 300 ostracod species recorded, predominantly from shallow water mostly shelf and shelf slope carbonates of various kinds. The ostracod faunas are dominantly (95%) endemic to the area, and the endemicity is apparent throughout the Silurian. The occurrence of benthic podocope and palaeocope ostracods endorses the palaeogeographic model of a close assembly of several microcontinental blocks (e.g., Karakum-Tadjik, Uratyube-Osh, Kyzyl-Kum/Alai) associated with a putative (Turkistan) Ocean during the Silurian. There is also evidence, from the co-occurrence of some ostracod species, that supports tectonic models indicating proximity of the Urals (‘Urals Ocean’) to central Asia (areas bordering the ‘Turkistan Ocean’) during the Silurian. Ostracods provide markers for dating and correlation at various stratigraphic levels of the Silurian within and between localities across central Asia. Ostracods are also valuable in intercontinental biostratigraphy and correlation in the Ludlow Series, using cosmopolitan myodocope species that occur in deeper slope facies in Uzbekistan.

First annotated draft genomes of nonmarine ostracods (Ostracoda, Crustacea) with different reproductive modes.

Ostracods are one of the oldest crustacean groups with an excellent fossil record and high importance for phylogenetic analyses but genome resources for this class are still lacking. We have successfully assembled and annotated the first reference genomes for three species of nonmarine ostracods; two with obligate sexual reproduction (Cyprideis torosa and Notodromas monacha) and the putative ancient asexual Darwinula stevensoni. This kind of genomic research has so far been impeded by the small size of most ostracods and the absence of genetic resources such as linkage maps or BAC libraries that were available for other crustaceans. For genome assembly, we used an Illumina-based sequencing technology, resulting in assemblies of similar sizes for the three species (335–382 Mb) and with scaffold numbers and their N50 (19–56 kb) in the same orders of magnitude. Gene annotations were guided by transcriptome data from each species. The three assemblies are relatively complete with BUSCO scores of 92–96. The number of predicted genes (13,771–17,776) is in the same range as Branchiopoda genomes but lower than in most malacostracan genomes. These three reference genomes from nonmarine ostracods provide the urgently needed basis to further develop ostracods as models for evolutionary and ecological research.

Ostracods as pollution indicators in Lap An Lagoon, central Vietnam.

Southeast Asia is particularly susceptible to the negative impacts of increasing coastal pollution as coastal populations and cities grow at unprecedented rates. Although water chemistry can be monitored, there are greater advantages in using bioindicators as reflectors of the combined effect of multiple pollution types on coastal ecosystem health and for early detection of the negative impacts of pollutants on biotic systems. This study explores the utility and application of ostracods as pollution bioindicators and examines the response of ostracod assemblages to variable pollution in Lap An Lagoon, central Vietnam. From 14 sites within the lagoon, 79 species of 46 genera were identified and sediment grain size, total organic carbon, organic matter and heavy metal concentration were measured. Cluster analysis, detrended correspondence analysis and canonical correspondence analysis identified four distinct ostracod biofacies that were highly correlated to the physical environmental variables (salinity, depth, sediment type, heavy metal concentrations, total organic carbon and organic matter) and are shown to be the main factors controlling ostracod biofacies. Low ostracod diversities were found in silty sediments with heavy metal concentrations likely toxic. Sinocytheridea impressa was indicative of a marginally polluted environment within the lagoon. This study provides evidence for the potential for Southeast Asian ostracods to be used in water quality assessments and the data collected can be used as a baseline for future pollution monitoring.

Seed Shrimp, Mussel Shrimp (Freshwater Ostracods) scientific name: (Crustacea: Ostracoda: Podocopa)

Ostracods are a class of small crustaceans that inhabit both saltwater and freshwater environments. There are approximately 8,000 living species of ostracods. Non-marine ostracods belong to the Order Podocopida, which is comprised of the superfamilies Cypridoidea, Darwinuloidea, and Cytheroidea (Thorp 2015). They are commonly known as seed shrimp due to their small size, typically smaller than a poppy seed or up to 1 mm. Their carapace, the upper shell of crustaceans, is bivalved, giving it the common name mussel shrimp.

Subterranean Waters of Yucatán Peninsula, Mexico Reveal Epigean Species Dominance and Intraspecific Variability in Freshwater Ostracodes (Crustacea: Ostracoda)

The Yucatán Peninsula is a karstic region, rich in subterranean environments with a diverse crustacean stygobiont fauna. In order to gain insights into the biological evolution of the subterranean environments of this region, we evaluated the ostracode species composition of caves and cenotes in five independent sampling campaigns (2008, 2013, 2017–2019). Using morphometric analyses, we evaluated inter-population morphological variability; using molecular analysis based on mitochondrial COI and nuclear 18S rDNA, we evaluated genetic differentiation in selected species. The observed fauna is composed of 20 (epigean) species, presenting a lack of strict stygobionts. Morphometric analyses discriminated up to three morphotypes in each of the three most abundant species: Cytheridella ilosvayi, Alicenula sp. and Cypridopsis vidua. High intraspecific morphological variability was found either in shape or size. Phylogenetic analysis based on COI demonstrated the existence of three lineages on C. ilosvayi, with high support (>0.9). The 18S rDNA sequences were identical among individuals of different populations. A lack of congruence between the genetic markers precluded us from postulating speciation in subterranean environments. It is likely that Late Pleistocene—Early Holocene climate variation related to sea level and precipitation was forcing agent for epigean ostracode dominance in subterranean environments of the Peninsula.

Foraminifera and Ostracoda from the Lower Cretaceous (Aptian–lower Albian) romualdo formation, Araripe basin, northeast Brazil: Paleoenvironmental inferences

The goal of this study is to investigate the Aptian–lower Albian microfossil association present in the Romualdo Formation, Araripe Basin, Pernambuco State, northeastern Brazil. Fifty-six samples of calcarenites and claystones were collected from the level where marine invertebrates are concentrated and in the coquinoid limestones, which compose the transgressive strata of the Romualdo Formation. The samples were from five outcrops (Cedro, Santo Antônio, Arrojado, Canastra and Torre Grande) located in the south-central region of the Araripe Basin. Nine species of foraminifera and five species of ostracods were found. The foraminifera species were: Agathammina cf. pusilla, Agathammina sp., Spiroloculina sp. 1. Spiroloculina sp. 2, Quinqueloculina sp. Astacolus sp., Gaudrynopsis sp., Conorboides minutissima and Lingulogavelinela sp. The recorded foraminifera associations are representative of different environments, from shallow marine settings to hypersaline lagoons. The five species of ostracods were: Pattersoncypris salitrensis, Pattersoncypris symetrica, Pattersoncypris sinuata, Pattersoncypris cf. micropapillosa and Damonella grandiensis. The ostracods inhabited a myxohyaline environment and tolerated the variation of salinity occurred during the deposition of the Romualdo Formation. Three assemblages were identified and their stratigraphic position was determined for each outcrop, suggesting that the south-central portion of the Araripe Basin presents clearer evidence of marine influence than the southwestern portion. Although a precise reconstruction of the route of marine ingression would require additional studies, the presence of the foraminifera genus Agathammina indicates an affinity with the Tethyan fauna. Therefore, we can conclude that the marine ingression during the Aptian–Albian followed a north-northeast direction, reaching initially the south-central part of the basin.

Seasonal Variation of Zooplankton Density and Physicochemical Parameters of A Perennial Freshwater Body, Samudrabundh of Joypur, Bankura, West Bengal, India

Water is the most essential and vital component required for the survival of all organisms in this earth. The physico-chemical and biological characteristics of a water body determine its efficacy for the production of plankton especially the zooplankton. Zooplankton are the most important primary consumer of aquatic food chain which in turn influence the productivity of finfishes in an aquatic body .The present study is primarily based on assessment of seasonal density and diversity as well as the physico-chemical condition of Samudrabundh, of Joypur block of Bankura district, West Bengal. Such type of assessment on this water body has not been done before this.. The study was carried during March.2019 to February, 2020. The water quality parameters which were used for study were temperature, PH, Dissolved Oxygen (DO), Free carbon dioxide (CO2),Chloride, salinity, alkalinity and total hardness. A total of 26 taxa of zooplankton were recorded. Out of which 8 sp ecies comprises of Rotifera, 05 species of Copepoda, 10 species of Cladocera and 03 species of Ostracoda. The total zooplankton density ranges from 756 (Ind/L) to 957 (Ind/L) which is quiet lower than the desired value required for good fish culture. The study concludes that the water body is of soft water type and medium productive in nature.

Ostracods from the late Albian–early Cenomanian of the Sergipe–Alagoas Basin, Brazil: New taxonomic and biostratigraphic inferences

This paper presents new taxonomic reports and biostratigraphic inferences based on ostracods in the basal section of the cored well UFRJ-2-LRJ-01-SE, perforated in the Votorantim quarry, Sergipe-Alagoas Basin, Brazil. The studied material comprised 44 samples in the range 438.65 to 315.30 m, identifying 52 species of ostracods distributed in 31 genera and 16 families. Five new species are proposed: Aracajuia separatta sp. nov.; Cytheropteron laranjeirensis sp. nov.; Microxestoleberis riachuelensis sp. nov.; Parahemingwayela fauthi sp. nov. and Quasihermanites? punctata sp. nov. The age of the studied interval was established by the occurrence of Aracajuia antiqua (MSA–1) between 434.00 and 347.25 m indicating the upper Albian. The first occurrence of Bythoceratina tamarae marks the upper Albian–lower Cenomanian boundary at 315.30 m. The biozones proposed with ostracodes coincides with the biozones of calcareous nannofossils made found at cored well.

Ostracods from the non-marine Lower Cretaceous interval at Liying section of Luanping basin, North China: A stratigraphic correlation

Non-marine strata of Lower Cretaceous age in western Liaoning and northern Hebei, North China, are famous for its Jehol Biota, including abundant ostracods. However, there are still some controversies about the stratigraphic correlation in these regions, for instance, it is still debated whether the interval from the Liying section of Luanping Basin belongs to the Dadianzi Formation or the member 1 of the Xiguayuan Formation. Ostracods act as an important tool for the correlation of the stratigraphy within or between basins. Here we report and illustrate the ostracods from the Liying section in detail for the first time, and aim to determine the section's stratigraphic correlation. Results show that, the Liying section has a thickness of 157.65 m and can be divided into 33 layers. Ostracods from this section are mainly distributed in the lower and middle part, and 7 genera and 13 species have been preliminarily recognized. These ostracod species can be summarized as the Cypridea-Limnocypridea-Lycopterocypris Assemblage Zone temporarily. Based on the identified ostracods, occurrence of other abundant representative fossils of the Jehol Biota, and isotope dating results, the major interval of the Liying section should be assigned to member 1 of the Xiguayuan Formation, and can be correlated with the Yixian Formation from western Liaoning.

Recent Ostracoda from the shelf sediments of Southwestern part of Bay of Bengal: Implication on Microenvironments

A detailed study on Recent Ostracoda was carried out in twenty-six surface sediment samples collected from shelf region of the Southwestern part of Bay of Bengal. A total of 21 species of Ostracoda belonging to 18 genera have been identified, of which, seven species are abundant (>5%). The Q-mode and R-mode cluster analyses of the abundant species resulted in two assemblage defining different microenvironments. The shallowest assemblage (I) from 10 to 80 m water depth is characterised by Hemikrithe Orientalis, Pterygocythereis chennaiensis and Lankacythere multifora which are associated with sand to slightly muddy sand. The second assemblage (II) from 80 to 200 m water depth is associated by Keijella reticulata, Bairdoppilata paraalcyonicola, Actinocythereis scutigera and Stigmatocythere indica and the nature of sediments varies from slightly muddy sand to slightly sandy mud. The sediments from 50-100 m water depth are foundto contain higher concentration of organic matter (TOC and TN) suggesting the high productivity zone. The C/N ratio value ranges from 4 to 8 in 52% of sediment samples indicating both marine and terrestrial source. The shallower part of the seafloor up to 30 m depth is dominated by sandysediments, reflecting the occurence of high-energy conditions. The higher mud content in the deeper part is due to the prevalance of low energy condition. The carapace-valve ratio (1:9) indicates that the study area experiencing a slower rate of sedimentation. Our study results revealed that the distribution of Ostracoda in the Southwestern part of Bay of Bengal is controlled by the type of sediment, depth and physicochemical parameters of the bottom water.

Oxfordian Benthic Foraminifera and Ostracods from the Hanifa Formation (Hawtah Member), Central Saudi Arabia

The Hanifa Formation in Saudi Arabia consists of mostly carbonate units of Late Jurassic age and is well exposed along the Tuwaiq Mountain escarpment. Micropaleontological analyses of samples from three outcrops have revealed the presence of benthic foraminifera and ostracods. The study of fossil faunas from the Hawtah Member, has led to the identification of six foraminiferal species: Alveosepta (Redmondellina) powersi, Oolina globosa, Nautiloculina oolithica, Kurnubia palastiniensis, Pseudomarssonella cf. maxima, Lenticulina sp. and two ostracod species: Hutsonia asiatica and Cytherella cf. umbilica. The survey of species covered in this research suggests that they indicate a predominantly euryhaline to polyhaline marine setting, possibly with a slightly brackish influence and deposited in a supratidal environment, suggesting a progressively shallowing environment on the inner shelf with intermittent shoal complexes.

Transfer of type specimens of Caribbean Foraminifera and Ostracoda to the European Micropalaeontological Reference Centre

While working on Trinidad and Tobago and the western tropical Atlantic Ocean, the author published four papers (Wilson 2006a, 2006b, 2006c;Wilson et al. 2011) that included descriptions of ten new species of foraminifera and ostracoda from the Neogene of the SE Caribbean Sea. These holotypes and associated paratypes have now been transferred to the European Micropalaeontological Reference Centre, AGH, University of Science and Technology, Krakow, Poland, for safekeeping. Among the foraminifera, these are: Amphistegina martybuzasi Wilson, Ramkissoon and McLean 2011; Bolivina jiattongi Wilson 2006; Textularia carrbrowni Wilson 2006; Textularia framptoni Wilson 2006; and Textularia sawhi Wilson 2006. Regarding ostracodes, they are: Bythoceratina coimbrai Wilson 2006; Cytheropteron bremani Wilson 2006; Polycope swietinia Wilson 2006; Polycope trinitatensis Wilson 2066; and Pterygocythereis fithiani Wilson 2006. The specimen slides have been curated in Cabinet 7, Drawer 27.

Eumeiobenthic crustaceans on the plastic litter in the nearshore water area of the Cape Malyi Fontan (Odesa Gulf, Black Sea)

In the article there are research results of the eumeiobenthic crustaceans on the plastic litter surface in the nearshore Cape Malyi Fontan water area in Odesa Gulf (north-western Black Sea). Species diversity, density and biomass of eumeiobenthic crustaceans were determined on the plastic litter collected in July and October 2018 in the nearshore cape aquatic zone. Eumeiobenthic organisms made up grate percentage in meiobenthos and were represented by order Harpacticoida (Copepoda) and class Ostracoda. The eumeiobenthos percentage of the total meiobenthos density in July made up 36.05% and in October – 58,08%. The indexes of the eumeiobenthos biomass almost didn’t distinct in the different months of the sampling. The percentage of the harpacticoids copepods was more 80%, and ostracods – up to 15%. On the plastic litter 14 meiobenthos taxa were registered. Were identified 9 ostracodes species, associated with plastic marine litter, that are from 5 families. Most widespread species of ostracodes on the fouling of the plastic litter were Hemicytherura bulgarica (Klie, 1937), Paradoxostoma variabile (Baird, 1835) and Xestoleberis decipiens Mueller, 1894. Fauna of harpacticoid copepods on the plastic litter from coastal cape waters consists of 16 species belongs to 10 families. Among them Ameira parvula parvula (Claus, 1866), Canuella perplexa (Scott T. et A., 1893), Dactylopusia tisboides (Claus, 1863), Ectinosoma melaniceps (Boeck, 1845) та Harpacticus littoralis (Sars G. O., 1910) were most common. Meiobenthos assemblages on the plastic litter fouling are similar to the diversity, formed on the artificial and natural substrates of the Odesa Gulf, but distinct from the last much lower density and biomass values. Eumeiobenthic crustaceans represented by widespread species, inhabiting in the nearshore water zone of the Ukrainian part of the north-western Black Sea.

Environmental factors shaping assemblages of ostracods (Crustacea: Ostracoda) in springs situated in the River Krąpiel valley (NW Poland)

We investigated the ostracod assemblage structure in springs of a small lowland River Krąpiel valley. Environmental factors and the potential of ostracods as indicators of spring type were analysed. The analysis involved the type of spring, substrate, physicochemical parameters, and the river valley's hydrological status as environmental factors. A total of thirty ostracod species were recorded. The average count of ostracod individuals in a sample amounted to 100. The assemblages were dominated by juvenile Candona sp., juvenile Psychrodromus sp., Cypria ophtalmica, and Cypridopsis vidua. The spring species accounted for less than 1% of the individual counts, except for juvenile Psychrodromus sp. with 21% and Eucypris pigra with 4%. The average number of taxa per spring was 5. The ostracod assemblages were significantly influenced by limnocrene springs, spring flooding by the river overflow, the presence of coarse leaf litter, the presence of fine organic matter, a high content of NH4 as well as by BOD5, conductivity, pH, Fe, the river habitat modification index (RHM), the habitat modification score (HMS), and the river habitat quality (RHQ). The habitat conditions for the spring species appeared to be enhanced by the domination of mineral substrate over fine particulate organic matter, an elevated pH, the presence of leaf-derived organic matter, and the absence of flooding by the river. The spring species showed no association with the Krąpiel valley hydrological factors.

Description of two new Proceroecia species (Ostracoda: Halocyprididae) from neritic waters off South Korea with an insight into the morphological and molecular diversity of the genus.

Two new planktonic ostracods of the genus Proceroecia Kock, 1992, P. hwanghaensis sp. nov. and P. joseondonghaensis sp. nov., collected from neritic waters off the south coast of South Korea are described. Morphologically, they are similar to P. microprocera (Angel, 1971), the type species of the genus, but show several clear morphological differences, most prominent being the shape of the male endopodite on the second antenna and the presence of a sensilla on the coxale of the fifth limb. The two new species have subtle differences, such as the length of the frontal organ, number of spines on the comb-like e-seta on the first antenna in males, number of spinules on the b-seta on the second antenna in females, etc. Sequences derived from partial mitochondrial cytochrome oxidase c subunit 1 (mtCOI) for these novel species have been compared with sequences available for other Proceroecia species on GenBank, including P. microprocera. These comparisons suggest that both new species are distinct taxa. They also indicate that one set of sequences on GeneBank previously attributed to P. microprocera and derived from material collected from Chinese waters, belong to P. hwanghaensis, and that another set of sequences of an unidentified Proceroecia species from the South China Sea can be attributable to P. joseondonghaensis. Hence, these new species occur widely in the neritic waters of East Asia. The present study increases the number of the known Proceroecia species to nine, and the numbers of halocyprid ostracod species recorded from Korean waters to six.

Some Ostracoda Species of the Genera Cytherelloidea, Baidria, Loxoconcha, Buntonia, From Khurmala Formation (Late Paleocene-Early Eocene) in Bekhme Dam Village, Peart Anticline, Kurdistan Region, Northeastern Iraq

Some Ostracoda Species of the Genera Cytherelloidea, Baidria, Loxoconcha, Buntonia, From Khurmala Formation (Late Paleocene-Early Eocene) in Bekhme Dam Village, Peart Anticline, Kurdistan Region, Northeastern Iraq

Late Messinian ostracods from Eastern Tunisia

Two stratigraphic sections referable to the late Messinian have been identified and studied in eastern Tunisia; the first, south of Cape Bon (Salakta-SAL section), the second in the Sahel region (Wadi el Kebir–OK section). The analysis of the ostracod fauna content (assemblages) has revealed that in some stratigraphic levels some taxa are certainly attributable to the Lago-Mare fauna, while other taxa, observed in subsequent or previous stratigraphic levels, are referable to true shallow-water marine environments. From these latter shallow water marine levels, several ostracods species were recognized; some of which, due to their morphological particularities, have been described as new species.Consequently, in this article, 24 species belonging to the genera Cytherella, Paijenborchellina, Cimbaurila, Pokornyella, Dorukella, Graptocythere, Capsacythere, Chrysocythere, Okadaleberis, Ruggieria, Cytheretta, and Neomonoceratina are described and illustrated as new.

Discovery of charophyte flora across the Cretaceous–Paleocene transition in the Jiaolai Basin

Charophyte assemblages from the Cretaceous/Paleogene (K/Pg) boundary transition in the JZK-2 borehole of the Jiaolai Basin (eastern China) were studied. The charophyte flora includes Tolypella grambastii, Peckichara praecursoria, Microchara cristata, Microchara prolixa, Chara changzhouensis, Lamprothamnium ellipticum, Nodosochara (Turbochara) specialis, Lychnothamnus aff. vectensis, and Lychnothamnus lanpingensis n. comb. The discovery of the ostracod species Porpocypris sphaeroidalis Guan in the upper section of the JZK-2 borehole strongly indicates the arrival of the Paleocene. Three floras of the latest Cretaceous to the early Paleocene were compared among the Jiaolai, Pingyi, and Songliao basins. The Pingyi Basin is special because it is the only carbonate palaeolake that occurred throughout the K/Pg transition in China. It is characterized by the appearance of the Cretaceous brackish water element, Feistiella anluensis (Wang), and is dominated by the Paleocene species, Peckichara varians Grambast. The Songliao and Jiaolai floras grow in clastic lakes; the Jiaolai Basin is thought to correspond to an altitude lake, which was formed in the coastal mountains with high palaeoelevation (≥ 2.0 km), while the Songliao Basin is presumed to have been formed in a low elevation site according to previous studies. This difference in altitude explains why the Songliao Basin is more species-rich than the Jiaolai Basin.