Taxonomic significance of short forms of middle Permian Pseudoalbaillella Holdsworth and Jones, 1980 (Follicucullidae,Radiolaria)

Middle Permian Pseudoalbaillella from the Xiaodong area in South China were studied using fossil morphology. Short forms of Pseudoalbaillella fusiformis (Holdsworth and Jones), Pseudoalbaillella internata Wang, and Pseudoalbaillella monacantha (Ishiga and Imoto), characterized by a short and skirt-like pseudoabdomen, were confirmed. We conclude that the short forms were derived from their respective species by breaking off during disruptive processes. If this is true, there may be structurally weakened parts in the pseudoabdomen.     

桂东、桂东南晚泥盆世一个弗拉斯期放射虫动物群

本文系统描述了广西玉林、贺县等地晚泥盆世榴江组硅质岩中的放射虫化石4属14种,其中有1新属2新种。这个放射虫动物群的多数分子曾见于苏联南乌拉尔地区和澳大利亚的弗拉斯阶。     

Les Radiolaires d'âge jurassique supérieurà crétacé supérieur dans les Radiolarites du Pinde-Olonos (Presqu'île de Koroni; Péloponnèse méridional,Grèce)

Radiolarians of several radiolarites sections of the Pindos-Olonos zone, southern Peloponnesus, lead to propose direct datations of mesozoic sediments. The acuity of such datations allow to distinguish two periods for depositionof radiolarites s.s. in the tethyan region. The first period would be Upper Jurassic and general in tethyan realm, radiolarites depositing under various latitudes (0–35°N). This would be the result of a strong ocean surface current. The second period would be Upper Cretaceous (Vraconian—Coniacian) and be geographically much more restricted (0–15°N). This could result from a weaker current. The absence of radiolaritic sedimentation is possibly the result of the destruction or insulation of the accurate basins during the obduction of ophiolites on the apulo-african realm. The inventory of Late Cretaceous radiolarian fauna, rarely done on alpine series so far, shows similar result to those obtained in Central American and California.     

Une nouvelle sous-famille,les Poulpinae, et quatre nouvelles espèces de Saitoum radiolaires mésozoiques téthysiens

Studies of skeleton elements of several jurassic species of Saitoum allow to compare them with Poulpus from Trias. The sub-family Poulpinae is introduced, caracterised by three cephalic arcs and the collar position of the cephalic structure. Among the jurassic forms, 4 species are newly described: S. corniculum, S. elegans, S. levium and S. trichylum.     

The biostratigraphic and palaeoenvironmental significance of Lower Cambrian (Botomian) trilobites from the Ak-Kaya section of the Altai Mountains (southern Siberia,Russia)

The presence of one of the oldest records of polycystine Radiolaria in the Lower Cambrian sedimentary sequence of the Ak-Kaya section (Gorny Altai) requires a biostratigraphic dating. The trilobites found recently a few tens of meters below the radiolarian-bearing level belong to Calodiscus resimus Repina, Serrodiscus fossuliferus Repina and Alacephalus aff. contortus Repina; they suggest that this part of the Shashkunar Formation can be correlated with the lower part of the Botomian stage. The absence of eyes in the two former species suggests a mode of life buried in the fine pelagic sediments. Indications of the presence of a strongly developed musculature on the third species point to a palaeoenvironment characterized by a relatively high hydrodynamic regime.     

New radiolarian species from the Upper Cretaceous-Lower Paleogene of the eastern slope of the northern Ural Mountains

Five new radiolarian species, Dictyophimus? orbiculiporosus sp. nov., Spongomelissa imperceptusa sp. nov., Theocoronium puncticulatum sp. nov., Pterocyrtidium porrectum sp. nov., and Tripodiscinus corona sp. nov., from the Campanian-Danian diatomites of the Leplinskaya Formation of the northern Ural Mountains are described. They are useful for stratification and correlation of the Upper Cretaceous and Lower Paleogene beds of the Ural Region of Western Siberia.     

Late Norian (Triassic) Radiolaria from the Kotel’nyi Island (New Siberian Islands,Arctic, Russia)

Two radiolarian assemblages were recovered from upper Norian strata of the Kotel’nyi Island (Russia); the first assemblage, from the Monotis zabaikalica Subzone (lower part of Upper Norian), is represented by Betraccium inornatum Blome, Dumitricaella (?) parva Sugiyama, Ferresium titulense Blome and 24 other species; the second assemblage, from the Monotis subcircularis Subzone (upper part of Upper Norian), is represented by Crucella sp. cf. C. angulosa Carter, Kahlerosphaera acris Bragin, K. sp. cf. K. parvispinosa Kozur & Mostler, Pseudohagiastrum crassum (Carter) and 11 other species. Both assemblages have common taxa with Upper Norian and Rhaetian radiolarian assemblages of British Columbia and they display clear Boreal features: low taxonomic diversity, abundance of taxa known from high-latitude regions, absence or rare presence of taxa known from low-latitude areas. The presence of early representatives of nassellarian genera Droltus and Parahsuum is very distinctive. Six new species are described: Pseudohagiastrum spinosum nov. sp., Cantalum boreale nov. sp., Plafkerium carteri nov. sp., Droltus guttaeformis nov. sp., Laxtorum blomei nov. sp., L. glacialis nov. sp.     

Lower Cambrian (Botomian) polycystine Radiolaria from the Altai Mountains (southern Siberia, Russia)

Relatively well-preserved polycystine Radiolaria are here described from Lower Cambrian (Botomian) strata of the Shashkunar Formation, Altai Mountains in southern Siberia (Russia). These radiolarians display a test formed of a disorderly and three-dimensionally interwoven meshwork of numerous straight and curved bars branching from a five-rayed point-centered spicule located within the inner shell surface. The shell structure allows their assignment to the family Archeoentactiniidae, thus extending the known age range of the family down to the Lower Cambrian. The Botomian age is based essentially on trilobites (Parapagetia-Serrodiscus zone), but also on archaeocyathids identified in earlier publications. The study of the radiolarian-bearing sedimentary sequence confirms the presence of polycystine radiolaria in the external platform environments of Lower Cambrian ecosystems.     

西藏南部放射虫微体古生物研究进展

西藏南部的雅鲁藏布蛇绿岩带以及该带之南的沉积地层带（特提期沉积区,北喜马拉雅亚区）中广泛发育着大量含放射虫地层,放射虫研究在确定该区蛇绿岩的形成时代,解释造山带复杂的地层层序以及揭示印度板块与欧亚板块在古近纪碰撞老祖宗前的古海洋盆地的演化历史等方面发挥了重要作用。根据已发表的文献以及我们正在进行中的初步成果显示,藏南地区的含放射虫地层的时代分布之中三叠世（安尼期）至晚白垩（土仑期）。这些地层的岩性包括硅质岩,硅质泥岩,凝灰质细碎屑岩和泥晶灰岩等,尽管藏南的放射虫研究已取得一些成果,但系统的放射虫研究与地层研究仍然有待于进一步深入开展。     

Permian and Triassic Radiolaria from Northwest Thailand: paleogeographical implications

Well-preserved radiolarians were recovered from seven sections in the Mae Hong Son-Mae Sariang area, northwestern Thailand. 51 species assigned to 34 genera are identified, including 1 new species (Triassospongosphaera erici Feng sp. nov.) and 19 unidentified species. They are divided into the Late Permian, late Ladinian and middle Carnian radiolarian assemblages. Newly identified radiolarian assemblages, together with the published radiolarian biostratigraphic data from this region, indicate that there was a pelagic basin during the Late Paleozoic and Triassic. This basin was joined to the Chiang Dao and Changning-Menglian oceanic basins, and they represent the main oceanic basin of the Paleotethyan Archipelago Ocean. This main oceanic basin was situated in the traditional “Shan-Thai Block”. Therefore, “the Shan-Thai Block” was not a single block during that stage, but composed of the Paleotethyan Ocean and two continental terranes that were affiliated with the Gondwana and Cathaysian domains, respectively.