Abstract:The essentials of the taxonomy and cytology of Radiolaria at the order level are summarized from approximately 110 papers. Living Radiolaria comprise representatives of the following orders: Acantharia, Collodaria, Spumellaria, cyrtid Nassellaria, spyrid Nassellaria and Taxopodia (ϭSticholonche). This analysis is based on the most recent molecular biological and fossil data. Phaeodaria, which used to belong to the Radiolaria, belong to the Cercozoa now. Heliozoa are closer to the Cercozoa than to the Alveolata or Radiolaria. A molecular phylogenetic analysis indicates that Polycystina (including Collodaria, Spumellaria and Nassellaria) should not be treated as a monophyletic group."Polycystine" Radiolaria are characterized by the presence of axopodia, a capsular wall, and a fusule. The endoplasm consists of the Golgi bodies, mitochondria, and other organelles, whereas the ectoplasm is an alveolated reticulum with food, digestive, and perialgal vacuoles, suggesting zonal specialization. The Acantharia are characterized by the presence of a periplasmic cortex with myoneme, acting as a motile contractile plasmalemma, rather than a capsular wall. Taxopodia have thick axopodia and a thick nuclear wall instead of a capsular wall. Characteristic protoplasmic structures such as an intracapsular axopodial system and nucleus are found in "polycystine" Radiolaria, but these structures do not seem to reflect phylogenetic relationships.

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Triassic radiolarians are reported from two horizons in Waipapa Terrane at Arrow Rocks, Whangaroa area, Northland. This relatively undisturbed succession represents an ocean-floor sequence, consisting (in ascending order) of basalt with limestone layers, bedded chert, black shale, and red, maroon and green siliceous mudstone.

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This paper contains extended abstracts of the seven papers presented at the symposium 'Radiolarians and Orogenic Belts' held at the seventh meeting of the International Association of Radiolarian Paleontologists (INTERRAD). Important results of the symposium include the following: (1) Upper Paleozoic and Mesozoic cherts are widely distributed within accretionary complexes in the circum-Pacific orogenic belt. Radiolarian dating reveals that long durations of chert sedimentation in a pelagic environment are recorded on both sides of Pacific-rim accretionary complexes (e.g. New Zealand, Japan, Russian Far East, Canadian Cordillera). (2) Triassic radiolarian faunas from New Zealand and the Omolon Massif, northeast Siberia are similar in composition and are characterized by the absence of typical Tethyan elements. This suggests that radiolarian faunal provincialism may have been established as early as the Triassic. High-latitude radiolarian taxa exhibit a bi-polar distribution pattern.(3) The Lower Triassic interval in chert dominant pelagic sequences is mechanically weaker than other levels and acted as a dkcollement in accretionary events. This lithologic. contrast in physical property is considered to reflect radiolarian evolution, such as the end-Permian mass extinction.