Charophyte Assemblages Research Articles

First occurrence of family Clavatoraceae (fossil Charophyta) in the Middle Jurassic (Bathonian) of France

AbstractA rich and diverse charophyte flora is described from the Bathonian marginal marine beds of southern France. It includes nine species that belong to the families Porocharaceae, Characeae and Clavatoraceae: Porochara gr. fusca, P. gr. kimmeridgensis subgr. kimmeridgensis, P. gr. kimmeridgensis subgr. westerbeckensis, P. gr. kimmeridgensis subgr. douzensis, P. gr. kimmeridgensis subgr. obovata, Auerbachichara saidakovskyi, A. tataouinensis, Aclistochara mädleri and Echinochara cf. peckii. This is the most diverse Middle Jurassic flora reported from France and Laurasia to date, elucidating a turnover in the evolution of charophytes during this time interval. The occurrence of the clavatoracean Echinochara cf. peckii in these Bathonian deposits represents the oldest record of the genus and of the whole family, c. 10 myr older than previous records. This species is considered to be the most basal species in the phylogeny of Clavatoraceae and during its evolutionary history reached a wide biogeographical range in Laurasia. The new Bathonian charophyte assemblage from southern France provides supplementary evidence that the Middle Jurassic was a reactivation pulse in the Mesozoic evolution of charophytes, rather than a stasis as previously thought. Moreover, it provides further support to the hypothesis that during the Late Jurassic and Early Cretaceous the islands of the Cretaceous Tethyan Archipelago represented one of the most active spots of charophyte diversity.

The Lower Cretaceous charophyte flora from the Cuchía section (Cantabrian Basin, North Spain): Biostratigraphy and palaeobiogeography

The Lower Cretaceous charophyte flora from the Wealden of the Cuchía section (Barremian, North Cantabrian Basin, northern Spain) was investigated. This locality represents the northernmost charophyte flora on the Iberian microplate. Twenty-one charophyte taxa were identified and two distinct charophyte assemblages, belonging to two different biozones, were recognized. The lower part (beds 1–6) of the studied section yielded the first charophyte assemblage composed of the species Echinochara lazarii, Atopochara trivolvis var. triquetra, Globator mallardii var. trochiliscoides, Clavator grovesii var. combei, Clavator harrisii var. dongjingensis, C. harrisii var. harrisii, C. calcitrapus var. jiangluoensis, Ascidiella stellata var. lata, A. triquetra, Hemiclavator neimongolensis var. neimongolensis, H. neimongolensis var. posticecaptus, aff. Mesochara harrisii, Porochara gr. kimmeridgensis subgr. kimmeridgensis, Clavatoraxis sp., and Favargerella aquavivae. This charophyte assemblage belongs to the Eurasian “Hemiclavator neimongolensis var. neimongolensis” biozone, assigned to the upper lower Barremian–lower upper Barremian.The upper part (beds 7–12) of the studied section yielded the second charophyte assemblage composed of the species E. lazarii, A. trivolvis var. triquetra, A. trivolvis var. trivolvis, G. mallardii var. biutricularis, C. grovesii var. jiuquanensis, C. harrisii var. dongjingensis, C. harrisii var. harrisii, C. harrisii var. reyi, C. calcitrapus var. calcitrapus, H. neimongolensis var. neimongolensis, H. neimongolensis var. posticecaptus, aff. Mesochara harrisii, Munieria grambastii, Clavatoraxis sp., and Favargerella aquavivae. This charophyte assemblage is correlated to the Eurasian “Clavator grovesii var. jiuquanensis” biozone, assigned to the upper Barremian–lower Aptian.Considering that the Wealden at Cuchía section is capped by the lower Aptian calcarenites (Umbrera Formation), this series is chronostratigraphically constrained to the upper lower Barremian–upper Barremian, instead of Hauterivian–Barremian as previously thought.The Cuchía charophyte flora has some of the highest species diversity from Wealden-type facies worldwide. The charophyte hotspot of Cuchía displays a strong similarity with the previously reported contemporaneous flora diversity hotspot in the Maestrat Basin (eastern Spain), which to date shows the most diverse Barremian charophyte assemblage worldwide (33 taxa). Our results further support the significant role of the Iberian Peninsula in the evolution of Lower Cretaceous charophytes within the Central Tethyan Archipelago bioprovince.

Middle to late Eocene charophytes from the Gaize Basin in central Tibet

Charophytes from the middle to late Eocene Kangtuo Formation in the Gaize Basin, central Tibet, are studied from the perspectives of taxonomy, palaeoecology, and biogeography. In the upper member of the Kangtuo Formation of the Mengdangle (MDL) section, southern Gaize Basin, two charophyte species were studied, including Hornichara jianglingensis comb. nov. and Chara cf. wujinensis comb.nov. The flora lives in the temporary pond's depositional environment, based on sedimentological analysis and fossil species occurrence. A palaeobiogeographic analysis of the charophyte assemblage suggests that H. jianglingensis was widely distributed in China basins during the middle to late Eocene, and later as a regional species in the coastal area in the Oligocene. H. jianglingensis and C. cf. wujinensis disappeared during the Oligocene in the interior of the Tibetan Plateau, and it was likely attributed to the rapid uplift of the Central Tibetan Valley.

Charophytes from the Pozo D-129 Formation (lower Aptian, Lower Cretaceous), source rock in the Golfo San Jorge Basin, Patagonia, Argentina

The charophytes studied here are from the uppermost part of the Pozo D-129 Formation in Sierra Silva, which belongs to the Golfo San Jorge Basin. Fructifications from three charophyte species belonging to the families Characeae and Clavatoraceae are described and illustrated. Two charophyte assemblages obtained from the lower part of the section were characterized: Assemblage 1, formed exclusively of characeans, Mesochara stipitata and Lamprothamnium? barcinensis, and Assemblage 2, composed of L.? barcinensis and the clavatoraceans Clavator harrisii var. harrisii and Clavator harrisii var. zavialensis. These differences in the composition of the charophyte floras are related to different paleoecological conditions that changed from the temporary, unstable water bodies represented in the lower assemblage studied to more stable and permanent lake conditions. The charophyte assemblages together with the previously recorded palynological data suggest a late early Aptian age for the succession of the Pozo D-129 Formation studied. Likewise, the charophytes contribute to the paleobiogeographic history of two conspicuous taxa, M. stipitata and C. harrisii var. zavialensis, which are reported here for the first time in the Lower Cretaceous deposits of the basin.

Upper Barremian−lower Aptian charophyte biostratigraphy from Arrifes section (Algarve Basin, Southern Portugal): correlation with dinoflagellate cyst biostratigraphy

The Arrifes section (Algarve Basin, Southern Portugal) has been studied from the viewpoint of charophyte biostratigraphy. The previous sedimentological studies in this section showed that it is built of the interbedding of continental and marine facies that contain both marine and continental palynomorphs (pollen, spores, and dinoflagellates), providing an excellent sedimentary context to perform direct correlations between marine and continental domains. In the present work, the identified charophyte biozones have been correlated with dinoflagellate biozones previously recognized in the Arrifes section, being the first time that these two biochronologies can be directly correlated. From the charophyte biostratigraphy viewpoint, two assemblages are distinguished. The older one is found between 65 and 135 m of the stratigraphic section, and it is composed of the species Echinochara lazarii, Atopochara trivolvis var. triquetra, A. trivolvis var. trivolvis, Clavator grovesii var. jiuquanensis, Clavator harrisii var. harrisii, C. harrisii var. reyi, and C. harrisii var. zavialensis. This assemblage belongs to the upper Barremian–lower Aptian Clavator grovesii var. jiuquanensis Eurasian biozone and also to the Ascidiellacruciata-Pseudoglobatorpaucibracteatus European biozone and it is described in beds with the dinoflagellate cyst Subtilisphaera scabrata (lower to lowermost upper Barremian) and Odontochitina operculata (from upper Barremian upwards). The younger charophyte assemblage is found between 135 and 155 m of the stratigraphic section, and it is composed of the species A. trivolvis var. trivolvis, Clavator grovesii var. corrugatus, Clavator harrisii var. harrisii, C. harrisii var. reyi, and C. harrisii var. zavialensis. This assemblage belongs to Clavator grovesii var. corrugatus biozone, previously assigned to upper Aptian (Clavator grovesii var. lusitanicus biozone). However, in the Arrifes section, this assemblage is found in beds assigned to the dinoflagellate cyst Odontochitina operculata (from upper Barremian–lower Aptian). The direct correlation of the base of the C. grovesii var. corrugatus biozone with the dinoflagellate cyst O. operculata, indicates that the base of the Clavator grovesii var. corrugatus biozone is in the upper lower Aptian, which is slightly older than was previously suggested, and it is extended until the middle Albian.

Charophyte flora from the Oligocene fossil site of Suceag (Transylvanian Basin, Romania)

A charophyte assemblage composed of six species has been recovered from lower Oligocene deposits of the Dâncu Formation at the fossil site of Suceag (Transylvanian Basin, Romania). The assemblage is dominated by the two varieties of the species Lychnothamnus pinguis (L. pinguis forma pinguis and L. pinguis forma major). Accessory species include Lychnothamnus prealangeri, Nitellopsis (Tectochara) merianii, and few Sphaerochara sp. and Harrisichara sp. gyrogonites. L. pinguis is the index species of the homonymous Rupelian European biozone which was previously correlated in Western Europe with the Mammal Paleogene Reference Levels of MP21–MP23, and calibrated with the Geomagnetic Polarity Time Scale (GPTS), chrones C13N and C12R. From a paleobiogeographic viewpoint, this study confirms the presence of L. pinguis forma pinguis and L. praelangeri in Romania and in the whole Eastern Europe. Moreover, the charophyte assemblage from Suceag belongs to the Priabonian–Rupelian European charophyte bioprovince. While the vertebrate fossils reported in the same fossil locality indicate that the Dâncu Formation at Suceag sedimented in an estuarine environment, the charophyte assemblage suggests a more complex pattern, with presence of freshwater lakes too.

Palaeoecology of Middle Miocene charophytes from the Vallès‒Penedès and Vilanova basins (Catalonia, Spain)

ABSTRACT A diverse charophyte assemblage from the Middle Miocene of the Vallès‒Penedès and Vilanova basins (Catalonia, NE Spain) is here described and illustrated for the first time. This flora has been recovered from three localities: els Casots (Subirats), Vilobí del Penedès, and Mas de l´Alonso‒el Pi Gros (Vilanova i La Geltrú). The charophyte assemblages comprise ten different species distributed among three distinctive aquatic environments, and are approximately simultaneous to major fossil vertebrate sites of these basins. Sphaerochara ulmensis, Chara cf. vulgaris, Chara molassica var. notata, Lychnothamnus barbatus var. antiquus, Lychnothamnus sp., Nitellopsis (Tectochara) merianii, and Nitellopsis sp. occur associated to abraded benthic foraminifera in organic-rich claystones related to palustrine and shallow freshwater coastal lakes. Lamprothamnium papulosum forms monospecific assemblages in gypsum-claystone alternations attributed to a coastal brackish water salina. Chara cf. hispida and Chara sp. are found to be associated with ostracods in marls and limestones related to a permanent oligohaline and alkaline lake. The discovery of this aquatic flora sheds new light on the palaeoenvironmental conditions that prevailed in the Vallès‒Penedès Basin during the Langhian in the context of the Mid-Miocene Climatic Optimum and in the Vilanova Basin during the Serravallian.

Early Pleistocene charophyte flora from Dursunlu (Ilgın Basin, Turkey): palaeoecological implications

Here, a charophyte assemblage from lower Pleistocene deposits at the coal mine locality of Dursunlu (Ilgın Basin, Turkey) is described and illustrated for the first time. The assemblage is composed of 11 species recovered from 50 samples taken from an 18 m-thick sedimentary sequence. The base of the sequence is dominated by lignites and organic-rich claystones/siltstones with root marks attributed to palustrine facies. The charophyte assemblage in this palustrine interval is dominated by Chara vulgaris and C. globularis. The upper part of the section is constituted by light grey-yellowish marls, siltstones and a limestone bed related to shallow lacustrine deposits. Two charophyte species dominate this lacustrine interval, Chara hispida and Nitellopsis obtusa, which occurred in intervals in association with Chara pappii, Chara molassica var. notata, Chara sp.1, Chara sp.2, Sphaerochara prolifera, Sphaerochara intricata and Lychnothamnus barbatus var. antiquus. The palaeoenvironmental characteristics and evolution of the Ilgın palaeolake during the Early Pleistocene (Günz glaciation) are inferred from a facies analysis and the ecological requirements of the charophyte assemblages. The results suggest that during this glacial period, the Ilgın Basin was occupied by a very shallow eutrophic lake with a dense palustrine vegetation belt, which evolved to a shallow (2–15 m deep), stable, oligotrophic, alkaline and oligohaline lake. The increase in water availability in the palaeolake can be related to climatic oscillation during the Günz glaciation. Finally, the lake depocentre migrated towards the NW due to tectonism, and these deposits were later subjected to intense pedogenic alteration.

Subrecent charophyte flora from Çeşmealti (Izmir Gulf, Western Turkey): Palaeoecological implications

A charophyte assemblage from lower Holocene sediments in Çeşmealtı (Izmir Gulf, Turkey) is described and illustrated for the first time here. This assemblage is composed of well-preserved gyrogonites and oospores of Lamprothamnium papulosum, which occur in association with seeds of Ruppia cf. maritima and up to eight ostracod species and 22 benthic foraminiferal taxa. The fossil assemblage was extracted from five clay intervals of the SK-2 borehole. The presence of monospecific assemblages of L. papulosum indicates that very shallow (up to 1 m deep), brackish, alkaline, and oligotrophic waters prevailed in the gulf under strong seasonality (marked cyclical changes in humidity and/or temperature). The dominance of germinated gyrogonites suggests that the water salinity of the lagoon decreased during the humid season, reaching at least 10‰. The associated ostracod fauna supports the palaeoenvironmental conditions inferred from the flora. Despite the gulf receiving considerable freshwater input, it remained semiconnected to the sea, as indicated by the diverse foraminifera assemblage. The availability of freshwater in the Izmir Gulf during the early Holocene Climatic Optimum, between ∼9000 and 5000 years BP, might have played an important role for the first human settlements in the area dating back 5500 years BP.

Eocene to Miocene Charophytes from the Qaidam Basin on the northern Tibetan Plateau and its calibration to the Geomagnetic Polarity Time Scale

Charophyte assemblages from the Qaidam Basin on the northern edge of the Tibetan Plateau were studied. The taxonomy of charophytes is based on a study of intraspecific gyrogonite polymorphism and biometric data. A total of 6 species belonging to 5 genera were identified, including Sphaerochara inconspicua Feist-Castel, 1977, Psilochara sp., Chara media Grambast, 1958, Lychnothamnus barbatus var. antiquus Soulié-Märsche, 1989, Lychnothamnus pinguis forma major (Grambast and Paul, 1965) Soulié-Märsche, 1989, Nitellopsis (Tectochara) merianii (Braun ex Unger, 1852) Grambast and Soulié-Märsche, 1972. Lamprothamnium ganchaigouensis (Tang and Di, 1991) Li et al., 2020 and Lychnothamnus vectensis (Groves et al., 1926) Soulié-Märsche, 1989 have already been reported from the Xiaganchaigou Formation by Li et al. (2020). These Eurasian species allow direct correlation between Chinese and European basins. The distribution of these species in the Qaidam Basin is correlated to the high-resolution magnetostratigraphy of the Paleogene–Neogene sequence, ranging from >52 Ma to ∼7 Ma at Dahonggou in the northern Qaidam Basin. N. (T.) merianii, with living representatives Nitellopsis obtusa, was reported to be expanded eastwards to Asia during the late Oligocene and Miocene. On the contrary, L. barbatus var. antiquus was found in the Oligocene (Chattian) of the Tibetan Plateau, representing the oldest record of this still living species. This may indicate that L. barbatus originated in Asia and expanded to other parts of Eurasia during the Miocene.

First report on late Miocene (Tortonian: ~ 11–10 Ma) charophyte gyrogonites from Tapar, Kachchh District, Gujarat State, western India

This paper describes the first record of charophyte gyrogonites from the late Miocene (Tortonian; ~ 11–10 Ma) Tapar locality of Kachchh, Gujarat State, western India. The recovered charophyte assemblage is constituted by Chara globularis var. aspera, C. globularis var. globularis, Lychnothamnus cf. sahnii, Lychnothamnus sp. and Nitellopsis sp. In addition, the present article discusses the palaeoenvironment based on the recorded charophyte gyrogonites (this study) and previously known faunal data (mainly vertebrates) from the Tapar locality, Kutch Basin, western India. Further, considering the significant extension of the biostratigraphic range [especially the First Appearance Datum (FAD)] of fauna from the Kutch Basin (in particular from the Tapar locality), we herein make an attempt to compare biostratigraphically the faunal assemblages from Kutch with those from the Siwalik Group, north India.

Charophytes from the Cretaceous–Palaeogene transition in the Jhilmili intertrappean beds of Central India

The Jhilmili intertrappean beds (Chhindwara District, Madhya Pradesh) of Central India are studied from a palaeoenvironmental, palaeoecological, and palaeobiogeographical perspective using fossil charophytes. These beds have yielded a diverse charophyte assemblage, consisting of Platychara perlata, Platychara raoi, Platychara sahnii, Peckichara cf. varians, Nemegtichara cf. grambasti, and Chara sp. 1. These charophytes were recovered from a 60 cm thick clayey and nodular limestone unit that is underlain by claystone and overlain by laminated claystones deposited on fluvial floodplains. This charophyte assemblage suggests a Late Cretaceous–Early Danian age, which agrees with the previous dating carried out using freshwater to brackish water ostracods and planktic foraminifera found in the same beds, together with dasycladalean and halimedacean chlorophytes. The Jhilmili intertrappean charophyte assemblage resembles those found in other infra‐and intertrappean sections of western, central, and southern India. The charophyte assemblage indicates that during the Cretaceous–Palaeogene timespan the Indian subcontinent mainly experienced interchange with Laurasia (China, Europe, and North America) but also with Gondwana (North Africa and South America). In the opposite sense, Laurasian species might have dispersed to India by means of a sweepstakes route across the Kohistan–Dras volcanic arcs.

Early Cretaceous Mesochara-rich assemblages from central Patagonia, Argentina, predate the origin of homogenous Charoidean floras by about 30 million years

During the Early Cretaceous charophyte assemblages were dominated by the family Clavatoraceae, especially in low latitudinal lakes from the Peri-Tethyan basins. In higher latitudes, however, charophyte assemblages were mainly formed by early characeans associated to a reduced diversity of clavatoraceans. The charophyte studied assemblages from the Los Adobes Formation in the Cañadón Asfalto Basin (central Patagonia) are unique as they are exclusively composed of several species belonging to the early characean genus Mesochara, which is considered the ancestor of modern species of the subfamily Charoideae. These assemblages show well-preserved gyrogonites and unusual species richness for this genus, including Mesochara maruchoensis, aff. Mesochara harrisii, Mesochara stipitata and Mesochara adobensis sp. nov. Two of these species display a worldwide distribution (M.harrisii and M. stipitata), while two (M. maruchoensis and M. adobensis sp. nov.) were only recorded in Patagonia, Argentina, being considered endemic to this region. The charophyte assemblages of the Los Adobes Formation represent autochthonous floras of alkaline ponds or small lakes in distal fluvial floodplains, developed under dry climatic conditions, as indicated by sedimentary facies analysis of the studied beds, and taphonomic and palaeoecological analyses of charophytes and associated fossil groups, such as palynomorphs and ostracods.This type of charophyte assemblage predates by about 30 million years the first floras composed exclusively of members of the subfamily Charoideae, which radiated worldwide in the Late Cretaceous and continued to dominate the charophyte floras during the Cenozoic until the present.

Microfossils (ostracods and charophytes) from the non-marine Lower Cretaceous of Lebanon: Palaeoecology, biostratigraphy and palaeobiogeography

A rich microfossil assemblage composed of six charophyte species and fifteen ostracod taxa has been recovered from eight stratigraphic sections raised in Lower Cretaceous rocks of the Abeih Formation/upper part of the Grès de base unit in Mount Lebanon (Central-South Lebanon). Four depositional environments have been distinguished within this unit based on sedimentological and microfacies analyses: fluvial, coastal freshwater lakes, estuary (intertidal and subtidal) and shallow marine. The charophyte assemblage is composed of Sphaerochara asema, aff. Mesochara harrisii, Atopochara trivolvis var. trivolvis, Ascidiella reticulata, Clavator ampullaceus, and Munieria martinclosasi extracted from costal freshwater lakes facies. The associated ostracod fauna is mainly represented by Cypridea libanensis, C. heliopolisensis, C. aaleyensis recovered along with accessory carapaces of C. baidarensis, C. quadrangulata, Cypridea sp. 1, Cypridea sp. 2, and Timiriasevia cardiformis. Part of this freshwater microfossil assemblage (A. trivolvis var. trivolvis, A. reticulata, C. ampullaceus, Cypridea libanensis, C. heliopolisensis, and C. aaleyensis) has been found in facies related to brackish water characterized by marine ostracods such as Fastigatocythere aff. naftaliensis, Fastigatocythere sp., Metacytheropteron parnesi, Majungaella (Progonocythere?) sp. Pontocyprella sp., Asciocythere sp., and Damonella sp. Shallow marine elements are also abundant including dasycladalean thalli, foraminifera and echinoid remains. This study indicates that the Abeih Formation/upper part of the Grès de base unit is late Barremian/early Aptian in age. The microfossil assemblage is dominated by endemic to subcosmopolitan taxa characteristic of the Levantine Island at the southeastern margin of the Tethys during the Early Cretaceous.

Early Cretaceous charophytes from south Dobrogea (Romania). Biostratigraphy and palaeobiogeography

Eleven boreholes and one outcrop of the Lower Cretaceous in South Dobrogea (south-eastern Romania) were sampled for charophytes. Twenty species are described and illustrated in two non-marine rock units, the Zăvoaia Member and the Gherghina Formation. The Zăvoaia Member contains a charophyte assemblage dominated by Feistiella bijuescensis, aff. Mesochara harrisii, Nodosoclavator bradleyi, Clavator bilateralis, and Clavator grovesii var. grovesii, indicating a Berriasian age. Other less abundant species include Feistiella sp., Latochara sp., Mesochara dobrogeica sp. nov., Globator maillardii var. nurrensis, Atopochara trivolvis var. micrandra, Clavator grovesii var. discordis, Hemiclavator adnatus, and Hemiclavator neimongolensis var. posticecaptus. The occurrence of G. maillardii var. nurrensis in this assemblage suggests late Berriasian age. The Gherghina Formation is dominated by the species Atopochara trivolvis var. triquetra and Clavator grovesii var. jiuquanensis. Other less abundant species include Sphaerochara andersonii, aff. Mesochara harrisii, Globator maillardii var. trochiliscoides, Globator maillardii var. biutricularis, Clavator harrisii var. reyi, and Clavator ampullaceus var. latibracteatus var. nov. This assemblage indicates a late Barremian–early Aptian age. This study sheds new light on the palaeobiogeographical distribution of Lower Cretaceous charophytes in the Tethyan realm. Well-known western European charophyte species such as F. bijuescensis, S. andersonii, G. maillardii var. trochiliscoides, H. adnatus, and H. neimongolensis var. posticecaptus are herein described for the first time in eastern Europe. Very significantly, this is the first report in Europe of the hitherto North American taxon C. bilateralis, while the species C. ampullaceus has previously been reported only from the Middle East and eastern Africa.

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.

New Record of Charophytes (Characeae, Charophyta) from Socotra Island, Indian Ocean, Yemen

The charophyte flora from Socotra Island, Indian Ocean, studied for the first time from streams waterbodies that distributed at the northern part of the Island. The recognized charophyte taxa were taxonomically investigated, and four dominant species belonging to family Characeae are identified as Chara braunii, C. globularis, C. hispida and Lamprothamnium papulosum. These taxa are reported as a new record for algal flora of Socotra Island. A brief account of the environment where the charophytes were found is provided, as a first evaluation of the ecological requirements of Indian charophytes. A taxonomically diverse of charophyte assemblage and ecological variables explain abiotic features of biotope as shallow (max 1.3 m), alkaline fresh (pH 7.5–8.4), slightly saline, and moderate eutrophic.

New charophyte flora from the Pine Hollow and Claron formations (southwestern Utah). Taxonomic, biostratigraphic, and paleobiogeographic implications

Paleogene non-marine deposits of the Pine Hollow and Claron formations (southwestern Utah, USA) provided a rich microfossil assemblage composed of charophytes, freshwater gastropods and ostracods. Charophytes were extracted from a ca. 450-m-thick section, especially from floodplain deposits belonging to the Claron and the Pine Hollow formations. The samples from the Pine Hollow Formation includes small and recrystallized populations of Psilochara sp., Peckichara sp. and Harrisichara sp. The occurrence of these genera suggests that this unit is Paleogene in age. The richer charophyte assemblage was recovered from the Claron Formation and is dominated by Microchara cristata, Microchara cf. punctata and Peckichara torulosa (here synonymized with the well-known Eurasian species Peckichara varians), along with Lychnothamnus sp. and Dughiella sp. Based solely upon charophyte Euroasiatic biostratigraphic ranges of M. cristata, M. punctata and P. torulosa, the basal/middle part of the Claron Formation is probably Danian in age. However, recent biostratigraphic studies based on mammals indicate that the middle part of the Claron Formation (unit 7) is early Eocene in age. The correlation of charophytes with mammals and the lack of significant unconformities in this formation suggest that these species could live longer in North America than Eurasia. The lack of North American charophyte studies, along with the long biostratigraphic ranges of the dominant taxa, M. cristata and P. torulosa, makes precise relative dating, solely on the basis of charophytes, difficult. This study also provides valuable data about Eurasian charophyte species and genera discovered for the first time in North America.

New charophyte assemblage from middle Miocene lacustrine deposits of Moneva (Ebro Basin, Spain)

Two new fossil charophyte species from middle Miocene lacustrine deposits of Moneva (Ebro Basin, NE Spain) are described and illustrated. Sphaerochara miocenica nov. sp. is represented by medium sized gyrogonites with a characteristic spheroidal shape and ornamented with numerous small and regularly spaced tubercles arranged along the spiral cells. Several specimens show an unusual carbonate encrusted layer that covers completely or partially the gyrogonite. Psilochara monevaensis nov. sp. is characterized by large gyrogonites, with typical prolate shape and protruding apical poles. A second population of S. miocenica nov. sp. from a distant early upper Miocene lacustrine basin located in the Middle East (Bekaa Valley, Lebanon), identified in a previous study as Sphaerochara sp., is described and illustrated here, allowing the comparison of these distant populations. Ecologically, the associated fauna and facies from both localities suggest that these taxa grew in very shallow athalassic lakes. Interestingly, S. miocenica nov. sp. having a wide geographic distribution in peri-Mediterranean lakes with variable salinity, may become a fossil guide for the Miocene, providing at the same time important palaeoecological information.

Middle Jurassic charophytes from southern Tunisia: Implications on evolution and paleobiogeography

The Middle Jurassic section from the Kef El Anéba in southern Tunisia, near the Beni Kheddache area, provided exceptionally species-rich charophyte assemblages that are studied here for the first time. The Krachoua Formation yielded a Bajocian assemblage composed of Porochara fusca, P. schudackii nov sp., P. kimmeridgensis, P. westerbeckensis, Auerbachichara saidakovskyi, Stenochara sp., Stellatochara aff. subsphaerica, Aclistochara longiformis and Aclistochara africana. A second assemblage from the Krechem El Miit Member (Foum Tataouine Formation), of Late Callovian age, includes Auerbachichara tataouinensis nov. sp., Porochara kimmeridgensis, P. westerbeckensis, P. douzensis, P. obovata var. gondwanensis nov. var. and Mesochara voluta. Taphonomic and paleoenvironmental data suggest autochthony of these two assemblages in a brackish lagoon and a temporary freshwater pond from a littoral environment, respectively. In addition, these floras suggest that Middle Jurassic charophyte biodiversity formed an evolutionary bridge between Upper Triassic charophyte floras dominated by genera Stellatochara, Stenochara and Auerbachichara and Upper Jurassic floras dominated by Porochara, Aclistochara and Mesochara. Furthermore, the biogeography of Middle Jurassic charophytes from southern Tunisia provides further arguments to support the hypothesis of significant biological exchanges between Laurasian and Gondwanan islands, indicating that Peri-tethyan biogeography remained relatively uniform during the Middle Jurassic.