An Early Cretaceous radiolarian fauna is found from the Tagaung Taung area, central Myanmar. The fauna consists of the following species: Acanthocircus dicranacanthos (Squinabol), Stylosphaera squinaboli Tan Sin Hok, Hiscocapsa cf. subcrassitestata (Aita), Svinitzium cf. depressum (Baumgartner), Thanarla brouweri (Tan Sin Hok), Archaeodictyomitra mitra Dumitrica, Archaeodictyomitra apiarium (Rüst), Archaeodictyomitra vulgaris Pessagno, Hemicryptocapsa cf. pseudopilula Tan Sin Hok, Hemicryptocapsa capita Tan Sin Hok, Holocryptocapsa hindei Tan Sin Hok and Cryptamphorella challengeri Schaaf. These species indicate clearly an Early Cretaceous age (Hauterivian), and therefore this is the first report on Cretaceous radiolarians from Myanmar.

Polycystine radiolarian remains were collected during Expedition KS15-4 in a plankton tow sample from 0 to 3000 m water depth at station (Sta.) 1 (30°28.8537′N, 132°24.9532′E). Obtained data from this site provide precious information about radiolarian assemblages living at deep-water depths. Based on R-mode cluster analysis, the surface water is characterized by well known subtropical species such as the Tetrapyle circularis/ fruticosa group and Didymocyrtis tetrathalamus. The subsurface water depths (200–500 m) are characterized by species such as Siphonosphaera abyssi. The intermediate-water depths (500–1000 m) are characterized by relatively high abundances of Larcopyle weddellium and Actinomma boreale, while species such as Cycladophora davisiana inhabit mainly water depths below 2000 m and the Carpocanarium papillosum group inhabits the deep-water depths between 1000 and 2000 m.

The three-dimensional morphology of the flat-shaped spumellarian radiolarian Dictyocoryne was analysed using a microfocus X-ray CT with a special focus on whether it was capable of a planktonic lifestyle. Two types of 3D models, the shell model, which represents a realistic 3D shell, and the wrapped model, which mimics the whole body outline without pseudopodia, were reconstructed in order to estimate volume, surface area, and centres of gravity for the shell model and buoyancy for the wrapped model. The calculated values showed that the volume of shell with respect to the total volume was negatively allometric, regardless of the differences between threshold settings. Stepwise secretions of the patagium layer may result in a comparatively lightweight shell, thereby decreasing the total density during growth but not below the density of seawater. Estimated positions for the centres of gravity and buoyancy were too close to maintain an autonomous posture while floating. Instead, the ratio between surface area and volume was greater than that in an ideal sphere. Such a broad surface area could obtain the viscous resistance necessary for sinking retardation. Spumellarian radiolarians, including Dictyocoryne, have photosynthetic symbionts located primarily in the ectoplasmic layer, which is a habitable space that can be maximised within the larger surface area. Given that radiolarians float when extending their pseudopodia, it can be hypothesised that pseudopodia may play a role in the adjustment of life posture in a hydraulically unstable shell, which can be integrated into sinking retardation, enhancement of photosynthetic activity and manoeuvrability of life posture within a unique flat-shaped morphogenesis.

Studying marine paleobiogeographical conditions in the mid-latitudes of the Northwest Pacific around the Jurassic–Cretaceous boundary would be expected to contribute to a better understanding of the paleoclimatic and/or paleoenvironmental background of the evolution of the Late Mesozoic terrestrial ecosystem in East Asia. However, uncertainty about the paleogeography of the eastern margin of the Asian Continent has meant difficulties for paleobiogeographical discussion. In this paper, the strata containing Boreal faunal elements, Buchia, and cylindroteuthidid belemnites in East Asia (Far East Russia, Heilongjiang in northeastern China, and Japan) and their tectonic settings are reviewed.

The Uda and Torom (northern Sikhote-Alin), Suibin (Heilongjiang), and Tetori (northern Central Japan) regions were located from north to south in the eastern margin of the already amalgamated Asian Continent around the Jurassic–Cretaceous boundary and can be considered the “fixed points for paleobiogeographical reconstruction.” On the other hand, Buchia-bearing strata in the Komsomolsk (northern Sikhote-Alin) and Dong'an (Heilongjiang) regions can be considered to have been deposited in the fore-arc basin or trench slope basin on the accretionary complex along the East Asian continental margin. The strata around the Jurassic–Cretaceous boundary in the Partizansk Basin (southern Sikhote-Alin) contain both Buchia and Tethyan ammonoids and were deposited on the Paleozoic continental basement or block (Sergeevka Belt). The paleo-position of these three regions around the Jurassic–Cretaceous boundary is highly debated.

The Tethyan–Pacific ammonoids, Boreal belemnites, and Tetori bivalve fauna, showing some similarities with those in the Boreal Realm and Early Cretaceous strata in Heilongjiang, are present in the late Tithonian–Berriasian Mitarai Formation of the Tetori Group in the Tetori Region. This unit, deposited in the eastern margin of the North China Block, provides evidence that Boreal faunal elements reached the mid-latitudes of the Northwest Pacific. The position of the ecotone of the Boreal and Tethys realms in the Northwest Pacific can be discussed based on the comparison of the faunal elements among almost coeval strata in the Tetori Region (fixed point), the Sergeevka Belt, and the South Kitakami Belt (Pacific side of Northeast Japan), which is usually correlated with the Sergeevka Belt but contains only Tethyan faunal elements. Further studies of the records of Tethyan and Boreal taxa in the “fixed points” and other localities could provide clues to reveal the paleoclimatic and/or paleoenvironmental background of the evolution of the terrestrial and marine ecosystems in East Asia around the Jurassic–Cretaceous boundary.

Well preserved radiolarians of middle Permian age were extracted from a manganese carbonate nodule from the Nishiki Group of the Akiyoshi Belt in southwest Japan. These radiolarians consist of a middle Permian assemblage, including Parafollicucullus yanaharensis, P. lanceolatus, and Albaillella foremanae as well as two species newly described in this paper, P. babelis sp. nov. and P. grandis sp. nov. Because of their excellent state of preservation, we were able to study the structures of several species of Parafollicucullus in detail. Some have been previously recognized, including multilayered shells, a boundary structure (“pre-pseudoabdominal junction”) between the pre-pseudoabdomen and pseudoabdomen, a hole structure at the base of the wing, a “lingula” structure at the foot, and a “pleat” or folded structure resembling a skirt on the wing. These features should provide new criteria to distinguish species of Parafollicucullus.

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.