Radiolarian Genus Research Articles

Multiple short-lived marine incursions into the interior of Southwest Gondwana during the Aptian

The Lower Cretaceous sediments of the Sanfranciscana Basin, southeast Brazil, are considered to have been deposited under a Gondwanan continental context. However, different authors have occasionally observed marine elements in these same deposits. This study analyzes samples from five sections of the Sanfranciscana Basin, Quiricó and Três Barras formations, to characterize the paleoenvironment around these marine incursions. We recovered continental (non-marine ostracods and palynomorphs) and marine microfossils (e.g., foraminifera, radiolarians, and ascidian spicules). The alternance of quartz-rich biogenic chert and claystone might be indicative of the occurrence of radiolarites in the studied sessions. The presence of the radiolarian genus Turbocapsula sp., the radiolarian species Holocryptocapsa fallax, and the palynomorph Tucanopollis crisopolensis enabled us to date the interval as early Aptian. Based on the lithologies and microfossils recovered, we interpreted the studied interval as a continental setting that was episodically subjected to marine incursions. We propose three successive paleoenvironmental scenarios: (1) an initial lacustrine depositional setting with a non-marine biota; (2) a second stage, characterized by the presence of episodic marine influence in the sedimentary succession (as evidenced by radiolarians, foraminifera and ascidians), and (3) the return to continental settings dominated by aeolian dune fields. These environmental scenarios characterize the initial development of the Central Segment of the South Atlantic Ocean.

Pirumosphaera armandae nov. sp., a new Southern Ocean polycystine radiolarian genus and species

This paper describes a new monospecific polycystine radiolarian genus and its single species so far, Pirumosphaera armandae, found in the Southwest Pacific and Indian sectors of the Southern Ocean. The new spumellarian form is rarely found as a complete specimen, as only its first and second shells are commonly found. However, partially complete specimens suggest that the test of this species is made of four shells. The most diagnostic feature of the species is the peculiar shape of the first shell which protrudes through the second shell, a characteristic that does not conform to any other Quaternary spumellarian genus. Based on the distinct and unique relationship between the first and second shells, the species is assigned to the newly established Pirumosphaera genus.

Desmoinesian (middle Pennsylvanian) radiolarians from the Excello Shale of Kansas, USA

Desmoinesian (Middle Pennsylvanian) radiolarians are described from carbonate concretions found in the black phosphatic facies in strata of the Excello Shale Member of the Fort Scott Limestone (Marmaton Group) in southeastern Kansas (K69 section), USA. Ten new species of radiolarians are described: Albaillella kansaensis, Holdsworthella trifurca, Pseudoalbaillella deformata, Entactinia jayhawkensis, E. heckeli, E. boardmani, Apophysiacus martiali, Moskovistella insolita, Palacantholithus umbrelliformis, and Ormistonella perrara. The Kansas radiolarian assemblage is different from the assemblage described from the Excello Shale of Iowa in the preservation and taxonomic composition. The radiolarians are preserved as pyritized internal molds or regular tests replaced by pyrite, and unidentifiable organic material. The domination of entactinarians and albaillellarians in the Kansas assemblage and their poor to excellent preservation indicate the formation of early diagenetic calcareous concretions in anoxic conditions. The appearance of the spicular radiolarian genus Palacantholithus indicates an influx of relatively cold water connected with upwelling. The Kansas location was much farther offshore (450 km basinward) compared to the Iowa localities suggesting a difference in thermocline depth, affecting water temperature, oxygenation, and nutrients.

Micro-CT analysis of Katian radiolarians from the Malongulli Formation, New South Wales, Australia, and implications for skeletogenesis

AbstractA diverse and well-preserved radiolarian assemblage from the Malongulli Formation, New South Wales, Australia, contains 13 species representing 10 genera and six families. One new genus, Wiradjuri, is introduced to accommodate pre-Devonian single-shelled entactiniid taxa, and one new species, Secuicollacta malongulliensis, is recorded together with some previously described forms. The microstructures of the “rotasphaerid structure/primary unit” and the “ectopic spicule” are investigated to validate their roles as fundamental units in the Secuicollactidae, together with comprehensive documentation of the previously enigmatic Pseudorotasphaera internal skeleton.The results of this investigation suggest that, among all radiolarian genera that survived the Late Ordovician Mass Extinction event (LOME) and transitioned into the Silurian, Secuicollacta, Haplotaeniatum, and Palaeoephippium maintained stable body plans during the transition and were more successfully established. The selective advantages these lineages had during the LOME were most likely spontaneous outcomes of the mode of structural development involving sequential skeletogenesis and a tendency to evolve toward simpler body plans.UUID: http://zoobank.org/264c026f-35af-4025-a4f7-de8f9a91f8b9

A New Radiolarian Genus Alexialeks gen. nov. and New Species from the Early Permian of the South Urals, Russia

A New Radiolarian Genus Alexialeks gen. nov. and New Species from the Early Permian of the South Urals, Russia

Artificial intelligence applied to the classification of eight middle Eocene species of the genus Podocyrtis (polycystine radiolaria)

Abstract. This study evaluates the application of artificial intelligence (AI) to the automatic classification of radiolarians and uses as an example eight distinct morphospecies of the Eocene radiolarian genus Podocyrtis, which are part of three different evolutionary lineages and are useful in biostratigraphy. The samples used in this study were recovered from the equatorial Atlantic (ODP Leg 207) and were supplemented with some samples coming from the North Atlantic and Indian Oceans. To create an automatic classification tool, numerous images of the investigated species were needed to train a MobileNet convolutional neural network entirely coded in Python. Three different datasets were obtained. The first one consists of a mixture of broken and complete specimens, some of which sometimes appear blurry. The second and third datasets were leveled down into two further steps, which excludes broken and blurry specimens while increasing the quality. The convolutional neural network randomly selected 85 % of all specimens for training, while the remaining 15 % were used for validation. The MobileNet architecture had an overall accuracy of about 91 % for all datasets. Three predicational models were thereafter created, which had been trained on each dataset and worked well for classification of Podocyrtis coming from the Indian Ocean (Madingley Rise, ODP Leg 115, Hole 711A) and the western North Atlantic Ocean (New Jersey slope, DSDP Leg 95, Hole 612 and Blake Nose, ODP Leg 171B, Hole 1051A). These samples also provided clearer images since they were mounted with Canada balsam rather than Norland epoxy. In spite of some morphological differences encountered in different parts of the world's oceans and differences in image quality, most species could be correctly classified or at least classified with a neighboring species along a lineage. Classification improved slightly for some species by cropping and/or removing background particles of images which did not segment properly in the image processing. However, depending on cropping or background removal, the best result came from the predictive model trained on the normal stacked dataset consisting of a mixture of broken and complete specimens.

A New Radiolarian Genus Nestelliana gen. nov. and New Species from the Late Devonian of the Polar Urals and the Early Carboniferous of the Volga–Ural Basin of Russia

A New Radiolarian Genus Nestelliana gen. nov. and New Species from the Late Devonian of the Polar Urals and the Early Carboniferous of the Volga–Ural Basin of Russia

Catalogue of Cenozoic radiolarian genera (Class Polycystinea)

This catalogue provides the most complete and revised work of Cenozoic genera as of December 2019. It is the result of four exhausting years of collaborative work. The first radiolarian genus was described in 1834 by Meyen, so this revision covers 185 years of research on polycystine radiolarians. Additionally, it concludes a pharaonic research project on the taxonomy of all described genera of radiolarians that started fifteen years ago. The main objective was to provide radiolarian researchers with a modern and revised version of the Campbell's work accessible to everyone in an open access journal. This catalogue is organized as a series of plates displaying the images of the type species consisting of all available images of the name-bearing type for the generic names in the Cenozoic Era. This catalogue encompasses extensive information in a very limited space. There are a total of 1683 revised genera. All valid genera provided appear with a diagnosis and an additional support image which is included to ensure the identification of the genus. This catalogue is somewhat different from previous issues on this thematic series. For this reason, it is recommended that the reader refer to the “guide for the users” for a comprehensible reading of the catalogue and to understand the taxonomic acts adopted in this revision. At the end of the plates, the reader will find a set of synthetic figures that display the most important result of this revision project, a result of 409 valid genera. Since numerous taxa of Christian Gottfried Ehrenberg and Ernst Haeckel had no fixed holotype, 207 lectotypes and 7 paralectotype were chosen and designated here from the series of syntypes. 11 neotypes were also designated for taxa that did not have syntypes.

On the status of the radiolarian genus Spongoliva Haeckel, 1887 and the description of the genus Spongolivella n. gen

The author erects a new genus for the Quaternary artiscin radiolarian species Spongoliva ellipsoides Popofsky 1912. The genus Spongoliva Haeckel 1887 is a nomen dubium because none of its six species has been illustrated and, above all, its type species is Eocene in age, an epoch when the artiscins had not yet appeared.

Origami Reconstruction of the Cortical Shell Structures of Radiolarian genus Pantanellium from Planar Graphs

We describe paper models which represent the cortical shell structures of radiolarian genus Pantanellium using the unit origami method: the construction of a polyhedral frame using origami units. Each unit corresponds to the edge of a polyhedron. The models are constructed based on planar graphs representing the cortical shell structures of real specimens. The resulting models reproduce the cortical shell structures appropriately. This means that the origami model is useful for both naked-eye practical observation of shell structures and group educational/art activities.

Paleobiogeographic Distribution of the Early Cretaceous Radiolarian Turbocapsula costata and Its Correlation Potential

Abstract. Turbocapsula, having three (or four) segments with a characteristic oval shape and a hemi-closed segmental end, is a radiolarian genus with a high stratigraphic value due to its phyletic evolution in the mid-Cretaceous period. An overview of lithology, depositional setting, associated fossil records, and paleomagnetic data from each locality of Turbocapsula costata (Wu) is summarized. All these data lead to the conclusion that locations of known T. costata-bearing strata are restricted to the low- to mid-latitude Mediterranean and eastern Tethys of the Tethyan realm. The results emphasize that the phyletic evolution of the genus Turbocapsula is significant in correlations within the Tethys. The zonation established by the phyletic evolution of the genus Turbocapsula cannot be utilized for Early Cretaceous zonal correlations beyond the T. costata territory.

Taxonomic re-evaluation of the Permian radiolarian genus Longtanella Sheng and Wang (Follicucullidae, Albaillellaria)

This article re-evaluates the taxonomy of the radiolarian genus Longtanella Sheng and Wang, based on materials obtained from the Guadalupian (Permian) Gufeng Formation in Anhui, China. This leads to the improved description of two previously introduced species (L. zhengpanshanensis and L. turgida) and the documentation of two additional morphotypes left in open nomenclature (L. sp. A and L. sp. B). Based on the new observations and measurements of Longtanella specimens and co-occurring species of Parafollicucullus Holdsworth and Jones, Longtanella differs from Parafollicucullus by having a turriform, slightly bent test and lacking a clear wing or pseudothorax.

Geometrical Properties of Skeletal Structures of Radiolarian Genus Didymocyrtis

This paper discusses the geometrical properties of a radiolarian skeletal structure, namely, that of genus Didymocyrtis. We characterized the evolution of skeletal structures and analyzed the structures using geometry. We defined two ratios in order to quantify the geometrical properties of Didymocyrtis and verified that the two ratios changed with their phylogenic evolution. We also used the 3D skeletal data of a specimen of species D. tetrathalamus, which was obtained through micro X-ray CT. The cortical shell obtained in the 3D data was projected onto a spherical surface, and we determined the centers of the pores. Our analysis revealed that the number of pores is approximately 200 and their distribution is not regular. We also determined that the column-like parts of the skeleton, which connect the inner and upper parts of the specimen, do not lie on a plane and their intervals are not equal.

New Radiolarian Genus Ganjiangmoyea gen. nov. from the Lopingian (Upper Permian) in Guangxi, South China

A new radiolarian genus, Ganjiangmoyea gen. nov., was discovered from the Lopingian (upper Permian) of the Yutouling section, Xiaodong area, Guangxi Zhuang Autonomous Region, South China. Ganjiangmoyea includes one new species (G. conica gen. et sp. nov.) and one possible new species (G.? striata gen. et sp. nov.). This new genus is characterized by numerous, swordlike radial spines extending from a central test. Single spines, presumably detached from the central test, co-occur with the Ganjiangmoyea species. Owing to these characteristics, Ganjiangmoyea could be placed under the family Oertlispongidae Kozur and Mostler. Paroertlispongus Kozur and Mostler and Pararchaeospongoprunum Lahm, belonging to the Oertlispongidae, also occur in the Permian, but their spines are bipolar and are not easily detached from the central test. Some of the Oertlispongidae genera, which occur abundantly in the Middle Triassic, also possess easily detached spines. Ganjiangmoyea might belong to a lineage of the Oertlispongidae that differs from that of Paroertlispongus and Pararchaeospongoprunum.

First Report of Redeposited Cretaceous Radiolarians in the Eocene Sand-Shale Member of Zhepure Formation, Tüna, Yadong, Tibet

Cretaceous radiolarians were firstly reported from the Eocene Sand-Shale Member of Zhepure Formation in the Gulupu section, Tuna, Yadong, Tibet. In spite of poor preservation, 24 species of 14 radiolarian genera have still been identified, clearly indicating an age, ranging from early Aptian–Maastrichtian, and therefore should have occurred in the Eocene as a result of redeposition. The study of the stratigraphic origin of these radiolarians will shed light on the paleoenvironment and late evolutionary history of the Tibet-Tethys.

Family Pseudoaulophacidae (Radiolaria) from the Upper Cretaceous (Coniacian-Maastrichtian) of Cyprus

Well-preserved Late Cretaceous (Coniacian–Early Maastrichtian) radiolarians from the Perapedhi, Moni and Kannaviou formations (Cyprus) were investigated. Abundant and diverse members of the family Pseudoaulophacidae are recognized and studied. The description of the species Pseudoaulophacus lenticulatus and Pseudoaulophacus pargueraensis are emended. A new radiolarian genus Pseudoalievium with two new species (P. parekklisiense and P. inflatum), one new species of the genus Alievium (A. mangaleniense) and one new species of the genus Pseudoaulophacus (P. decoratus) are described. Geographical and stratigraphical ranges of the studied taxa of the family Pseudoaulophacidae are more exactly defined. Several rare species of this family are traced in the Tethyan Realm.

NEW EARLY TUVALIAN (CARNIAN, TRIASSIC) RADIOLARIANS FROM THE HUǦLU-PINDOS SUCCESSION IN THE SORGUN OPHIOLITIC MÉLANGE, SOUTHERN TURKEY

Three new radiolarian genera ( Paramonocapnuchosphaera , Monocoronella and Minicrampus ) and 8 new species are described herein from one of the most diverse and best preserved Carnian (Late Triassic) radiolarian faunas of the world, from the early Tuvalian sequence of the Sorgun Ophiolitic Melange, southern Turkey. The radiolarian fauna belongs to the Spongotortilispinus moixi Zone (equivalent to Paragondolella postinclinata - Paragondolella noah conodont Zone). The very similar late Julian-early Tuvalian radiolarian faunas from the Northern Calcareous, Alps through the Lagonegro Basin, Sicily, Rhodes Island, Greece and farther east in the Antalya nappes, in the Mersin Melange and in Elbistan, Turkey may confirm that the Pindos-type succession found in different units of early Mesozoic oceanic basins formed in a single oceanic basin.

Phyletic evolution of the mid-Cretaceous radiolarian genus Turbocapsula from southern Tibet and its applications in zonation

Abstract A radiolarian biostratigraphic study ranging from the latest Barremian to the Aptian of a pelagic sequence (section BB1) near Babazhadong in southern Tibet revealed phyletic relationships of species belonging to the genus Turbocapsula . Three species and two subspecies are included in this genus: Turbocapsula tetras LI & MATSUOKA, n. sp., T. fugitiva O'DOGHERTY, and T. costata ( T. costata (WU) multicostata LI & MATSUOKA, n. ssp. and T. costata (WU) costata ). Turbocapsula fugitiva appears to have arisen from T. tetras by losing the septa between the third and the fourth segments. Turbocapsula fugitiva seems to have given rise to T. costata multicostata following the development of thicker costae between its two to five rows of pores. With the decrease in the number of the costae and the development in the costae, T. costata multicostata evolved into T. costata costata . The phyletic evolution of the genus Turbocapsula has a high stratigraphic value. Based on the phyletic evolution of Aurisaturnalis and Turbocapsula , two radiolarian zones have been defined: the Aurisaturnalis carinatus Zone and the Turbocapsula costata Zone. These zones are defined by evolutionary first appearance bio-horizons (EFABs), which are more reliable than the first and the last occurrence bio-horizons over wide areas. The Turbocapsula costata Zone is subdivided into the Turbocapsula costata multicostata Subzone and the Turbocapsula costata costata Subzone. Based on comparisons with radiolarian biostratigraphic research conducted in other areas, in which age-diagnostic calcareous nannofossils and planktonic foraminifera occur alongside radiolarians, the Aurisaturnalis carinatus Zone and the Turbocapsula costata Zone are assigned to the Lower Hauterivian–Lower Aptian and the Lower Aptian–Lower Albian, respectively. This newly proposed zonation is useful for comparing the stratigraphic relationships of Turbocapsula -bearing horizons in other areas. A zonal scheme like this scheme can be used for identifying certain episodes such as mid-Cretaceous oceanic anoxic events (OAEs) in the pelagic realms. The Early Aptian OAE 1a is located between the first appearance bio-horizon of the genus Turbocapsula and the EFAB of T. costata multicostata .

Taxonomy of Permian radiolarian genus Pseudoalbeilella from Pos Blau, southwest Kelantan, Peninsular Malaysia

Taxonomy of Permian radiolarian genus Pseudoalbeilella from Pos Blau, southwest Kelantan, Peninsular Malaysia

Cretaceous (Albian to Turonian) radiolarians from chert blocks of the Moni Mélange (Southern Cyprus)

Well-preserved Cretaceous (Albian–Turonian) radiolarians were extracted from radiolarian-bearing chert olistoliths of the Monagroulli Member within the Moni Mélange (Campanian-Maastrichtian, Southern Cyprus). Four assemblages were distinguished: Middle Albian–Lower Cenomanian (Thanarla spoletoensis Zone), Upper Albian–Lower Cenomanian (Thanarla spoletoensis Zone, Dorypyle? anisa Subzone), lowermost Turonian (base of Alievium superbum Zone) and Lower Turonian (Alievium superbum Zone). The radiolarian assemblages are diverse and have taxonomic composition similar to coeval assemblages of Italy and Spain. The sediments of the Monagroulli Member differ from coeval rocks of the Mamonia Complex (western Cyprus) by the more common presence of radiolarian cherts and may have been formed in the distal part of a continental margin with less input of clastic material. A new spicular radiolarian genus Cyprothamnus with 2 new species (C. multifurcatus and C. moniensis) is described from the Lower Turonian strata.