Search

Investigation of large populations of peteinoid acritarchs recovered from Middle Ordovician strata of the Hälludden and Horns Udde quarry sections (Öland, Sweden) allows for statistical analyses based on morphometric measurements. The results indicate the presence of assemblages with a continuous variability of morphotypes, thus a distinction of different peteinoid acritarch taxa in the sections proved to be impossible. This challenges the currently accepted classification based on a differentiation into the three genera Peteinosphaeridium, Cycloposphaeridium and Liliosphaeridium, and a multitude of different species; individual taxa are essentially arbitrary as morphotypes intergrade. Investigations on modern dinoflagellates show that these can develop variable cyst morphologies depending on environmental factors. By analogy, it can be hypothesised that the different morphologies observed among the peteinoid acritarchs from Öland are cysts produced by only very few phytoplanktic organisms (or even a single species) with high morphological variability. [ABSTRACT FROM AUTHOR]

Various authors have described and illustrated exceptionally large acritarchs from the Furongian (upper Cambrian) from different parts of the world. The different morphotypes clearly belong to the ‘diacromorph’ acritarchs, but have until now usually been attributed, tentatively or erroneously, to the genusVeryhachium. Based on new material from the Holy Cross Mountains (central Poland) and the literature, the new genusGigadiacrodiumis erected to include these stratigraphically diagnostic and easily distinguishable morphotypes. The new genus includes the following species:Gigadiacrodium martinae(Pittau 1985) comb. nov., emend. nov. (type species) andGigadiacrodium vidaliisp. nov. In addition, a new combination is proposed: ?Solisphaeridium mutabileDi Milia et al. 1989, comb. nov. [ABSTRACT FROM PUBLISHER]

The triangular-shaped acritarch genusFrankea, which displays characteristically branched appendices, has considerable stratigraphical and palaeobiogeographical significance in the Ordovician. High intraspecific variability of terminal processes (appendices) numbers and process lengths withinFrankeasuggest that the genus could be suitable for use in studying the relationship between morphological characters and environmental conditions. Quantitative multivariate exploratory analyses onFrankeaindicate that the length of the appendices varies according to different localities and is most probably ecologically dependent and not age diagnostic as previously suggested. Principal components analyses and discriminant analyses are used to assess the original specific classification ofFrankea. The morphometric analyses suggest that usage of quantitative characters, such as the process length, should be taken into consideration during the separation of species. A comprehensive discussion of qualitative and quantitative characters is carried out and suggests there are only three species ofFrankea: F. hamata, F. hamulata and F. sartbernardensis. [ABSTRACT FROM PUBLISHER]

Dactylofusa veliferaCocchio 1982 is an easily recognisable, fusiform Ordovician acritarch species with a characteristic membrane. The taxonomy of this taxon is revised based on a literature review and on the investigation of new fossil assemblages from sections in South China. Morphological and biometric studies show that a subdivision into three varieties is justified. The taxonomical rank ofDactylofusa veliferavar.brevisAlbani 1989 is changed and its diagnosis is emended;Dactylofusa veliferavar.veliferais the automatically created autonym. An additional new subspecific taxon is erected:Dactylofusa veliferavar.sinensisvar. nov. The stratigraphical and palaeogeographical occurrences ofDactylofusa veliferaare reviewed, indicating that the species was widely distributed around the peri-Gondwanan margin during the Early Ordovician and early Middle Ordovician.Dactylofusa veliferais of biostratigraphical importance because its First Appearance Datum (FAD) can be used to indicate the late Tremadocian. Palaeobiogeographically, its distribution generally corresponds to that of the Early Ordovician ‘messaoudensis-trifidum’ acritarch assemblage in the peri-Gondwanan region. [ABSTRACT FROM PUBLISHER]

Rhopaliophora Tappan and Loeblich, 1971 emend. Playford and Martin, 1984 is one of the most commonly recorded Ordovician acritarch genera. Originally described in the early 1970s from Laurentia, it had subsequently been found on most other palaeocontinents with 8 species attributed to the genus. This paper is a revision of the genus based on the analyses of published literature and on observations of large populations of new material from the South Chinese Ordovician. Our review indicates that the following species belong to the genus: Rhopaliophora brevituberculatum (Kjellström, 1971) Martin, 1983, Rhopaliophora florida Yin et al., 1998, Rhopaliophora foliatilis Tappan and Loeblich, 1971 (type species), Rhopaliophora impexa Tappan and Loeblich, 1971, Rhopaliophora mamilliformis Lu, 1987 emend. Tongiorgi et al., 1995, Rhopaliophora membrana Li, 1987, Rhopaliophora palmata (Combaz and Péniguel, 1972) emend. Playford and Martin, 1984, Rhopaliophora pilata (Combaz and Péniguel, 1972) emend. Playford and Martin, 1984. However, we consider that Rhopaliophora granulata Yin, 1995 is a junior synonym of R. pilata, whereas Rhopaliophora reticulata Uutela and Tynni, 1991 is considered as a junior synonym of R. foliatilis. Intraspecific variability is great and the boundaries between individual species are sometimes not clear. At the genus level, Rhopaliophora shows some transitional forms with Peteinosphaeridium Staplin et al., 1965 emend. Playford et al., 1995 and with some species of Pachysphaeridium Burmann, 1970 emend. Ribecai and Tongiorgi, 1999, whereas its relation to the morphologically similar genera Asketopalla Loeblich and Tappan, 1969 emend. Loeblich and Tappan, 1971, Loeblichia Playford and Wicander, 1988, Tenuirica Playford and Wicander, 1988 and Papilliferum Yin, 1994 needs to be clarified. Rhopaliophora first appears, together with Peteinosphaeridium, in the middle Tremadocian (first stage of the Lower Ordovician). After its original description from Laurentia and later from Australia, in low latitude warmer water environments, it has subsequently been found in intermediate latitudes in Baltica and South China, and few findings are also reported from high latitude areas of Gondwana, indicating a pandemic distribution in warm and temperate water masses. In terms of palaeoecology, the genus is rarely found in nearshore palaeoenvironments, but it is a typical indicator of offshore marine habitats, being abundantly present on carbonate shelf platforms. [ABSTRACT FROM AUTHOR]

Abstract: After the initial description of Ampullula Righi 1991 and Stelomorpha Yin 1994, several researchers discussed these two acritarch genera and their relationship. A literature revision and investigation of new material from South China indicate that the genus Stelomorpha is a synonym of the genus Ampullula, but Ampullula is not the synonym of the genus Tranvikium Tynni 1982 emend. Uutela and Sarjeant 2000. The generic diagnosis of Ampullula is emended. Six species belong to the genus: Ampullula calix (Quintavalle and Playford, 2008) comb. nov., Ampullula composta (Yin et al., 1998) comb. nov., Ampullula crassula (Vavrdová, 1990) comb. et emend. nov., Ampullula erchunensis (Fang, 1986) Brocke 1997 emend. nov., Ampullula princeps Brocke 1997, and Ampullula suetica Righi 1991. Ampullula was widely distributed throughout peri-Gondwana and Baltica suggesting a global distribution during the late Early–Middle Ordovician. Biostratigraphically, Ampullula is an important genus indicating upper Lower to Middle Ordovician intervals. Ampullula was first present in the eobifidus graptolite Biozone in South China, where it possibly originated, and subsequently was also present on Baltica and other parts of the margin of Gondwana. Thus, Ampullula was an important Early–Middle Ordovician acritarch with a global distribution, which probably was both eurythermic and eurytopic. [ABSTRACT FROM AUTHOR]

The acritarch Ninadiacrodium gen. nov. is erected to include forms with a basically triangular outline,but with a clearly bipolar arrangement of processes. It belongs to the 'diacrodian' dade; these are morphotypes with ornament and/or processes at the two opposite poles of the central body. They were extremely abundant and highly diverse during the Late Cambrian and Early Ordovician. The new genus includes the two widely-cited species Ninadiacrodium caudatum (Vanguestaine 1973) comb. nov. and Ninadiacrodium dumontii (Vanguestaine 1973) comb. nov. Both taxa are emended here. Ninadiacrodium is easily recognizable due to its elongate triangular shape, but is clearly differentiated from Veryhachium Deunff 1954, which appears in the Ordovician. Ninadiacrodium is apparently confined to the Late Cambrian, and has a global distribution. It is therefore an index fossil for the Late Cambrian. [ABSTRACT FROM AUTHOR]

The investigation of large populations of galeate acritarchs recovered from the Late Cambrian to Early Ordovician of the Algerian Sahara allows the definition of 11 morphological criteria which may be useful for the differentiation of individual morphotypes. These parameters have been used for statistical analyses to understand better the classification of this important acritarch plexus. Following a critical evaluation of all parameters, five of them can be retained for multivariate and cluster analyses. The current taxonomic model, with a differentiation into the four genera Caldariola, Cymatiogalea, Priscogalea and Stelliferidium, cannot be maintained. The most important variables appear to be the process length and the presence/absence of ramifications of the distal end of the processes. A provisional four cluster model is proposed to classify the galeate acritarchs from the Algerian assemblages. This study is a first step in the process of investigating the potential use of multivariate statistics in galeate acritarch classification and may serve as a model for future studies to understand acritarch taxonomy. [Copyright &y& Elsevier]

After its first description in Cambrian–Ordovician boundary strata from Gondwana, the acritarch genus Vulcanisphaera Deunff, 1961 has been found subsequently on most other paleocontinents, with a total of 32 species assigned to this genus. A comprehensive revision of the published literature indicates that the genus contains only three species that are easily differentiable: (1) V. africana Deunff, 1961; (2) V. mougnoana Martin, 1973; and (3) V. simplex Jardiné et al., 1974. The other species are either synonymous with these three or must be excluded from the genus. The generic and specific diagnoses of Vulcanisphaera are emended herein. The new classification scheme is tested and validated by using quantitative multivariate analyses based on morphometric studies on abundant material from England, Algeria and Iran. The species show large morphological variability, and transitional forms between V. africana and V. mougnoana are observed. The stratigraphic ranges of the species have been determined. V. mougnoana occurs from the Miaolingian to the Early Ordovician, V. africana is found with certainty from the Furongian to the Floian and V. simplex is recorded in the latest Furongian and throughout the Tremadocian. The genus Vulcanisphaera shows a cosmopolitan paleogeographic distribution with most occurrences recorded in higher paleolatitudes. Unlabelled Image • Only 3 of 32 described species of Vulcanisphaera Deunff, 1961 can be maintained. • Vulcanisphaera is recorded from the Miaolingian to the Lower Ordovician. • Vulcanisphaera is paleogeographically widespread in rather higher latitudes. [ABSTRACT FROM AUTHOR]

The acritarch genus Orthosphaeridium Eisenack 1968 is one of the most frequently recorded acritarch taxa in the Ordovician. The taxonomy of this easily recognizable genus is revised herein based on a detailed literature review and on new investigations of palynological material from northeastern Iran and South China. The review confirms that Baltisphaera Burmann 1970 is a junior synonym of Orthosphaeridium of which the diagnosis is here emended. Over 20 species have been described in the literature, but many of them are apparently synonyms. The review indicates that the following four species can be easily differentiated: Orthosphaeridium bispinosum Turner 1984, Orthosphaeridium ternatum (Burmann 1970) Eisenack et al. 1976, Orthosphaeridium rectangulare (Eisenack 1963) Eisenack 1968 (type species) and Orthosphaeridium octospinosum Eisenack 1968. The taxonomical ranks of Orthosphaeridium rectangulare var. quadricornis Burmann 1970 and Orthosphaeridium octospinosum var. insculptum Loeblich 1970 are changed from the species to the varietas level. The review indicates that Orthosphaeridium first appeared in South China in the Expansograptus hirundo graptolite Biozone, i.e. in the early Dapingian (stage slice Dp1 and time slice 3a of the Middle Ordovician) and that it reached a global distribution during the Middle and Late Ordovician. The genus disappeared at the end of the Ordovician and has never been recorded from the Silurian. The genus is thus a stratigraphical index fossil for the Middle and Late Ordovician. Orthosphaeridium has been recorded from the margins of all paleocontinents and paleoecologically seems to be an eurythermic taxon. • The complete literature of Orthosphaeridium is revised. • New material from Iran and China allows for emendation of the genus. • Orthosphaeridium is an excellent index tool for the Middle-Upper Ordovician biostratigraphy. • Orthosphaeridium apparently represents an eurythermic organism. [ABSTRACT FROM AUTHOR]