Hollow structures in radiolarian skeletons

Spines are the major element of radiolarian skeletons; they are usually solid or, rarely, hollow. Subcylindrical hollow spines and other hollow structures of radiolarian skeletons appeared in the Middle Cambrian. Later, hollow skeletal structures repeatedly developed in the evolution of all radiolarian classes of the subphylum Polycystina throughout the Phanerozoic to the Recent. The analysis of appearance and distribuion in the Phanerozoic of morphotypes with hollow spines has shown that the formation of hollow skeletal structures allowed better adaptation for the planktonic mode of life and could become a key adaptation in struggle for life under stressful conditions.     

Morphological characteristics of boreal radiolarians from the Triassic and Late Cretaceous: Comparative analysis

When comparing boreal radiolarian assemblages of the Triassic and Late Cretaceous, significant differences in their morphotypic composition are recognized. In particular, Triassic assemblages are dominated by spherical morphotypes, including pylomate forms of the genus Glomeropyle, while Late Cretaceous assemblages are dominated by prunoid morphotypes without polar spines (genera Prunobrachium and Amphibrachium). It is concluded that, in the course of evolution, high-latitude radiolarian assemblages considerably changed both taxonomically and morphologically. Therefore, it is impossible to determine the uniform morphological and taxonomic characters describing boreal assemblages of the entire Mesozoic. Features of boreal radiolarian assemblages are unique to each geological epoch.     

Tetrentactinia barysphaera Foreman, 1963: skeletal structure and age of a biostratigraphically important Famennian (Upper Devonian) radiolarian from the Ohio Shale, USA

Tetrentactinia barysphaera Foreman, 1963 is a very characteristic Famennian (Upper Devonian) radiolarian species from the Huron Member of the Ohio Shale of North America. Its skeletal structure shows a massive, double-layered shell with main spines constructed from radial beams and concentric bars over a primary ray as the core. The species is common in limestone concretions at the type locality Milan, Ohio, associated with a diverse radiolarian fauna of predominantly spherical spumellarian forms, but has also been recorded from the Russian platform. It may be highly useful as an index species for the mid-Famennian time interval as it is one of the few spumellarians that is easily recognized and differentiated in the fauna.     

The pre-cephalic development of the skeleton of Amphimelissa setosa (Actinopoda: Nassellarida)

The ontogeny of the skeleton of the nassellarian radiolarian Amphimelissa setosa begins with the formation of three radial bars of silica; these correspond to the medial bar and spines L₁ and L₂ in the adult. By a precise sequence of the addition of various siliceous arcs and spines, this basic structure develops into the eucephalus. A new growth mechanism, in which existing skeletal elements serve as templates for the formation of new skeletal members, is hypothesized to explain the observed developmental patterns. The early ontogeny of nassellarian skeletons can be used to determine which skeletal features develop earliest. Among the structural characteristics used by radiolarian systematists, these conservative features are most suitable for use in interpretation of the taxonomic relationships and phylogeny of the group.     

新疆库鲁克塔格地区中奥陶统黑土凹组的放射虫新属种

新疆库鲁克塔格地区的奥陶系黑土凹组黑色硅质岩中发现丰富的放射虫动物群,以泡沫虫类球形放射虫最多,不具外刺和具外刺的Inaniguttidae科占优势,及一些分类位置待定的特殊放射虫族群。本文描述该动物群中4个新属 Quasibeothuka , Batoballa , Protosegmentum Tetrasphaera , 10个新种 （ Quasibeothuka fusiforma , Q. ovata ,Q. ellipsoidala ,Q. longi f usi forma ,Q. bithornya ,Batoballa communis ,B. longiovata , Protosegmentum xinjiangensis, Tetrasphaera kuruktagensis ,Beothuka longispini forrna ）。黑土凹组的放射虫动物群拟建立Tetrasphnern kuruktagensis带,下分二个亚带,下部的Protosegmentum xinjiangensis亚带和上部的Quasibeothuka fusiform。亚带。该组的黑色页岩中产Exigraptusclavus带笔石化石,时代为中奥陶世大坪期。该组很可能是一个很好的牛油层。     

Taxonomic study of the tetrahedral, pentagonal and hexagonal spongy spumellarian Radiolaria from the middle Carnian (Late Triassic) of the Köseyahya nappe (Elbistan, SE Turkey) and other Triassic localities

This article is a taxonomic study of all spongy radiolarian taxa with five to six coplanar and four tetrahedrally disposed spines or spongy arms occurring in the middle Carnian from the Köseyahya section, near the town of Elbistan, SE Turkey. This fauna is characteristic of the Tetraporobrachia haeckeli radiolarian Zone, and comes from an 8 m thick succession of clayey–cherty limestones occurring at the lower part of the section. In addition, a few species from the Middle and Upper Triassic from other areas have been also included in this study to improve some generic diagnoses and to better understand the diversity and evolutionary trends of some genera, subfamilies and families. The taxonomy at the generic and suprageneric levels is based primarily on the types of microsphere. This new approach allowed new taxonomic arrangements of genera and suprageneric units, and suggested new and unexpected phylogenetic relationships among these radiolarians and between them and younger radiolarians. The authors discuss and describe 42 species, of which 36 are new, and 12 genera of which three are new (Charlottalum, Pentaspongodisculus, and Trimiducaella). The genera Pseudohagiastrum Pessagno, Natraglia Pessagno, Cantalum Pessagno and others are reinterpreted. All the genera studied, except Charlottalum, are assigned to three subfamilies, of which two (Pseudohagiastrinae and Trimiducinae) are new, and to two families (Angulobracchiidae and Relindellidae). The genus Charlottalum is described to replace the genus Cantalum, which has been erroneously used until present for Late Triassic pantanelliids with four tetrahedrally disposed three-bladed spines.     

Early Tithonian Saturnalidae (Radiolaria) from the Solnhofen area (Southern Franconian Alb, southern Germany)

In order to complete the study of the very rich early Tithonian (Hybonoticeras hybonotum Zone) radiolarian fauna from the Mühlheim Member of the Mörnsheim Formation outcropping in the Solnhofen area, the taxa of the family Saturnalidae are described. Although rather rare, the Saturnalidae of this member contain 14 species, ten of which are new. These species belong to four genera, one of which is new (Moebicircus n. gen.), and two subfamilies (Hexasaturnalinae and Saturnalinae). The taxonomy at generic level of these late Jurassic radiolarians is founded on the basis of the position of the blades along the ring and number and morphology of the spines. Type of spines (simple or forked) has either species level value or none, depending on species. Special attention was given to anomalies, which sometimes are rather frequent, since they can give Information of paleobiological and paleoecological Orders. Among them frequent cases of open ring and additional spines withDicerosaturnalis and Siamese twins skeletons withSpongosaturninus andDicerosaturnalis are to be noted. The authors hope that this new taxonomy will give a better image of the evolution and radiation of the Saturnalidae during the Tithonian.     

New radiolaria of the family Prunobrachidae from the uppermost Cretaceous of the eastern Polar Urals

New radiolarian genera and species from Upper Cretaceous siliceous clays of borehole 22 (Polar Urals) are described. The family Prunobrachidae Pessagno, 1975 is reviewed. The new genus Pseudobrachium gen. nov. has a dumbbell skeleton without a patagium and Spinibrachium gen. nov. has apophysis-like spines and a patagium in the central part of the skeleton. Five new species, Spinibrachium amoni, Prunobrachium kozlovae, P. boreale, Pseudobrachium gracile, and P. trilobatum, are described; they are of great importance for paleogeography and stratigraphic correlation of Campanian deposits.     

Taxonomic study of spongy spumellarian Radiolaria with three and four coplanar spines or arms from the middle Carnian (Late Triassic) of the Köseyahya nappe (Elbistan, SE Turkey) and other Triassic localities

The present article is a taxonomic study of all spongy spumellarian radiolarian taxa with three and four coplanar spines or spongy arms occurring in the middle Carnian from the Köseyahya section, near the town of Elbistan, SE Turkey. This fauna is characteristic of the Tetraporobrachia haeckeli radiolarian Zone, and comes from an 8 m thick succession of clayey-cherty limestones occurring at the lower part of the section. In addition, a few species from the Middle and Upper Triassic from other areas have been also included in this study to improve some generic diagnoses, and to better comprehend the diversity and evolutionary trends of some genera, subfamilies and families. The taxonomy at the generic and suprageneric levels is based primarily on the types of microsphere. This new approach allowed new taxonomic arrangements of genera and suprageneric units, and suggested new phylogenetic relationships among these radiolarians and between them and younger radiolarians. The authors discuss and describe 69 species, of which 37 are new, and 14 genera, of which three are new (Paraparonaella, Pseudangulobracchia, and Ropanaella). The genus Triassoastrum and others are reinterpreted. All genera studied are assigned to five subfamilies, of which two are new (Tetrapaurinellinae and Triassocrucellinae), and two families (Tritrabidae and Veghicycliidae). Nine species in open nomenclature are also illustrated.     

西藏丁青蛇绿岩带中一个晚三叠世放射虫动物群

西藏丁青地区晚三叠世Carnian期放射虫动物群共描述19属35种（7个未定种）,归于16科（亚科）中,以Capnuchosphaera,Palaeosaturnalis,Perispongidium,Spongostylus,Annulotriassocampe,Poulpus,Xenorum,Veghicyclia,Tetraporobrachia,Canoptum,Xiphotheca等属为主的这个动物群被命名为Capnuchosphaera triassica组合带,由于Capnuchosphaera属在全世界广泛分布,无论在特提斯生物大区还是环太平洋生物大区,以这个属为主的放射虫动物群已成为国际间Carnian期至Norian早中期放射虫地层学对比的重要依据。     

Provenance analysis of Cenozoic conglomerates: Insights from Lower Cretaceous radiolarians in chert clasts from the Xigaze area,southern Tibet

Conglomerates, exposed on either side of the Yarlung Tsangpo suture zone (YTSZ) in southern Tibet, have attracted wide attention in elucidating uplift and erosion histories of the Himalayan-Tibetan orogen. However, the provenance of these conglomerates remains controversial. Although radiolarian-bearing chert clasts within these conglomerates have received little focus, identification of the radiolarian assemblages they contain could shed light on the provenance of these sedimentary units. We present the first report of Upper Jurassic to Lower Cretaceous (upper Kimmeridgian–lower Barremian) radiolarian assemblages recovered from chert clasts within the Liuqu and Gangrinboche conglomerates in the Xigaze area. To extract radiolarian fossils from independent clasts in the conglomerates, a detailed and efficient experimental process is illustrated. The assemblages are well correlated to those in the YTSZ and Tethyan Himalaya, showing typical Tethyan characteristics. The lithology of chert clasts and ages of constituent radiolarian faunas suggest that the chert clasts in Liuqu and Gangrinboche conglomerates were derived from the Bainang terrane. This interpretation implies that Early Cretaceous accretionary complexes in the YTSZ had been exposed and eroded before deposited as clasts in the Cenozoic Liuqu and Gangrinboche conglomerates.     

Ladinian radiolarian fauna from West Sichuan, China

A poorly preserved, but diversified radiolarian fauna was recovered from thin-bedded cherts occurring in the southeast of Daofu, Sichuan Province, southwestern China. Twenty-two radiolarian species belonging to 10 genera are identified and three new species (Paroertlispongus daofuensis n. sp., Falcispongus heinzi n. sp., Falcispongus pauliani n. sp.) are described. Falcispongus heinzi represents a transitional species between genera Oertlispongus inaequispinosus Dumitrica, Kozur and Mostler and Falcispongus Dumitrica. The fauna is divided into two assemblages, namely Muelleritortis cochleata and Oertlispongus inaequispinosus assemblages, which can be well correlated with the Ladinian radiolarian zones from Europe. The fauna indicates that basaltic rocks occurring in the Xianshuihe Belt were formed mainly during the Middle Triassic. Our results thus extend the previously known geological age of the Xianshuihe Belt to the Middle and Late Triassic interval.     

The Radiolarian biotic response during OAE2. A high-resolution study across the Bonarelli level at Bottaccione (Gubbio, Italy)

In order to improve our understanding of the radiolarian biotic response and the palaeoceanographic changes associated with the Late Cenomanian oceanic anoxic event (OAE2), a high-resolution radiolarian study was carried out across the Bonarelli level at its typical locality (Bottaccione section, central Italy). Our results confirm that a drastic radiolarian faunal change took place during the OAE2. The radiolarian turnover took place within the median part of the Bonarelli level, associated with an interval of high organic matter preservation, but relatively low values of silica. Therefore, this part constitutes a critical period in the evolutionary history of Radiolaria. A synthesis of all data available in the Umbria-Marche basin suggests that the lower part of the Bonarelli level (and underlying limestones) records mainly radiolarian extinctions (ca. 41%), while its upper part (and overlying limestones) records mainly first occurrences (ca. 35%). Our results improve understanding of the paleoecology of the family Saturnalidae, which would seem to prefer oligotrophic environments.     

Oceanography of the Gulf of Tehuantepec, Mexico, indicated by Radiolaria remains

The morphology of the Gulf of Tehuantepec, Mexico, is redefined through a bathymetric analysis and this redifinition is considered to explain the distribution patterns of non-carbonate sediments, particularly the radiolarian remains. Although the distribution patterns of pelagic sediments are influenced by the Gulf of Tehuantepec bathymetrical morphology and the terrigenous input, these “reflect” clearly the regional oceanography. Northern strong winds, called the “Tehuanos”, blowing across the sea surface of this Gulf when the Intertropical Convergence is at its southernmost position, define the main sedimentologic dynamics of this region. This wind field gives rise to an oceanic front at the southwestern part of the Gulf, as well as upwelling processes at its central-eastern part. In the mixing at the front there is some contribution of California Current waters, while in the upwelling area there is a large contribution of the tropical-subtropical water which is carried by the Costa Rica Coastal Current. This oceanographic framework controlls the makeup of radiolarian assemblages. Consequently, at the seabottom, under the oceanic front, the presence of the radiolarian species Lithomelissa thoracites and Cycladophora davisiana is observed, while under the upwelling region, Acrosphaera murrayana is conspicuous.     

藏南泽当雅鲁藏布缝合带中的三叠纪放射虫

西藏南部泽当西金鲁村附近发现的一套硅质岩含有两个放射虫化石组合：Capnuchosphaera triassica组合和Pseudostylosphaera nazaroui组合。这些放射虫化石可以同中三叠世拉丁期至晚三叠世卡尼期放射虫动物群对比,这套硅质岩为一外为岩体,包括在由高劈理化泥岩组成的混杂岩基质中,这是雅鲁藏布江缝合带三叠纪放射虫的首次报道。     

中国东北部那丹哈达地体T-J界线地层中的放射虫生物组合

本研究系统描述了中国东北那丹哈达地体中三叠系顶部和侏罗系下部的放射虫动物群及其系统分类,包括5个放射虫生物群,建立了一个新属,10个新种,并报道了121个种级分类单元。通过与加拿大和日本的相关动物群进行比较研究,我们确定了所描述的放射虫生物群的年代归属分别为:晚三叠世诺利(Norian)晚期至瑞替(Rhaetian)早期,辛涅缪尔(Sinemurian)早、中期。     

The Early Ordovician<Emphasis Type="Italic">Beothuka terranova</Emphasis> (Radiolaria) faunal assemblage in western Newfoundland

TheBeothuka terranova radiolarian assemblage from theIsograptus victoriae lunatus Biozone of western Newfoundland is described and compared with the slightly older assemblage from theDidymograptellus bifidus Biozone of Spitsbergen. Specimens ofBeothuka terranova are described for the first time from material preserved in silica with little diagenetic changes. In the Spitsbergen specimens the skeleton is replaced by pyrite, destroying most of the original details and thickening distinctly fine bars and spines. The Newfoundland assemblage lacks specimens ofSphaeroentactinia, while possible specimens ofSvalbardospiculum andProtoentactinia sp. are represented by juveniles.Nyfrieslandia specimens are common in the sample. Faunal differences may relate to preservational factors and, in part indicate biostratigraphic differences. Several new species are described, some in open nomenclature:Antygopora irregularia n. sp.,Labyrinthia robusta n. sp.     

Facies characterization of mid-mesozoic deep-water sediments by quantitative analysis of siliceous microfaunas

Summary Quantitative approaches to the analysis of Late Mesozoic radiolarian faunas are rare and often poorly defined. In order to overcome preservational and taxonomic biases, general information indices were tested for their paleoecologic potential. 300 samples from different Tethyan localities and Antarctica were used for this study. The general information indices defined here are: absolute radiolarian abundance, nassellarian/spumellarian ratio, percentage of sponge spicules, morphological diversity and degree of recrystallization and fragmentation. Indices like radiolarian, nassellarian and sponge spicule abundance are suitable for a simple characterization of samples and sections even in poorly preserved material. The spicule abundance in basinal sediments indicates turbiditic influences and provides a proxy for shelf distance and water depth. The relative nassellarian content is useful for a bathymetrical interpretation in Tethyan sediments. Although there is a great loss of information in using only general information indices, the method has the advantage of being appropriate for sedimentologists unfamilar with radiolarian taxonomy, thus providing a fast and powerful tool for paleoecological analysis, which is applicable to different geological periods.     

Structure, development, and plasticity of dendritic spines.

Dendritic spines are distinguished by their shapes, subcellular composition, and synaptic receptor subtypes. Recent studies show that actin-dependent movements take place in spine heads, that spines emerge from stubby and shaft synapses after dendritic filopodia disappear, and that spines can form without synaptic activation, are maintained by optimal activation, and are lost with excessive activation or during degeneration.     

苏皖地区早志留世坟头组腹足类

记述苏皖地区坟头组腹足类１１属１２种,其中Ｕｍｂｏｎｅｌｌｉｎａ ｃｆ．ｇｌｏｂｕｌｏｓａ Ｙｕ,Ｒａｐｈｉｓｔｏｍｉｎａ ｒｈｏｍｂｉｓｔｏｍａ Ｙｕ,Ｔｒｏｃｈｏｎｅｍａ ｃｆ．ｆｒａｇｉｌｅ Ｕｌｒｉｃｈ ｅｔ Ｓｃｏｆｉｅｌｄ常见于西南地区早志留世秀山组、上翁项群及石牛栏组。坟头组上段所产的三叶虫Ｃｏｒｏｎｃｅｐｈａｌｕｓ,Ｋａｉｌｉａ;头足类Ｓｉｃｈｕａｎｏｃｅｒａｓ;腕足类Ｓａｌｏｐｉ