Yoshiaki Aita

Triassic radiolarians from the ocean‐floor sequence of the Waipapa Terrane at Arrow Rocks, Northland, New Zealand

Abstract 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. The age of the lower part of the section is Middle‐Late Permian. The radiolarian assemblages reported here indicate Early or Middle Triassic and Middle Triassic (Anisian) ages for maroon siliceous mudstones in the upper part of the section. Between strata of known Permian and Triassic age there is a thin potential Permian/Triassic boundary interval consisting of alternating black shale and grey chert. Radiolarian paleogeography indicates that the Arrow Rocks sequence experienced long distance plate tectonic displacement from a position of relatively low latitude in the Middle Permian and to a high latitude in mid‐Triassic time.

The Ehrenberg type species of flat-shaped radiolarian genera (Spongodiscidae and Stylodictyidae, Spumellaria, Polycystina)

Synopsis Original material for almost all of the polycystine radiolarian species described by Christian Gottfried Ehrenberg (∼8o genera, ∼530 species) are housed in the Museum für Naturkunde, Berlin. Eleven type specimens of 10 spongodiscid and stylodictyid radiolarian genera were found in Ehrenbergs original mica strips. These micas are from six different sample locations and range in geological age from (approximately) late Eocene to Holocene. Ten specimens are confirmed as those sketched by Ehrenberg and are designated as lectotypes. Consequently, Dictyocoryne profunda is the senior valid synonym of Euchitonia für cata and Rhopalodictyum abyssorum. The Ehrenberg collection contains several specimens identified as F. concentrica, the type species of the genus Flustrella. After careful examination, the best preserved specimen was defined as the lectotype and, as a result, Flustrella (type species: F. concentrica) is confirmed as a valid name, while Porodiscus (Trematodiscus orbiculatus) and Trematodiscus (T. orbiculatus) are junior synonyms of Flustrella. The type species of Spongodiscus (S. resurgens), Spongaster (S. tetras) and Dictyocoryne (D. profunda) possess concentric internal structures, suggesting close phylogenetic relationships with Flustrella. Lectotypes of Stylodictya (S. gracile), Perichlamydium (Flustrella praetexta), and Stephanastrum (S. rhombus) are designated.

New radiolarian age information for the Chrystalls Beach Complex, southwest of Dunedin, New Zealand

Abstract On the basis of lithology, structural style, and fossil evidence, northern and southern units are recognised within the Chrystalls Beach Complex exposed on the coast south of Akatore Creek, southwest of Dunedin, South Island, New Zealand. Radiolarians including Spongopallium sp. cf. S. contortum Dumitrica, Kozur & Mostler, Eptingium(?) sp., Norispongus(?) sp., and Pseudostylosphaera(?) sp. have been discovered in phosphatic nodules in metamorphosed argillite of the northern unit of the complex. They are regarded as characteristic species of the Middle Triassic (Anisian‐Ladinian). It has previously been known that the more weakly metamorphosed southern unit of the Chrystalls Beach Complex contains moderately well preserved Middle Triassic (Early Ladinian) radiolarian faunas. Together with forms of Tethyan affinity, the faunas in the southern unit contain non‐Tethyan forms including Glomeropyle spp. Aita & Bragin, possibly of Southern Hemisphere high‐latitude origin. These non‐Tethyan forms are also known from the Mahinepua section of the Waipapa Terrane in Northland. Distinctive non‐Tethyan forms such as Glomeropyle Aita & Bragin have not yet been found in the northern unit, the fauna of which includes species that are known from the European Tethys area and which also occur in the southern unit.

A probable shark dorsal fin spine fragment from the Early Triassic of the Arrow Rocks sequence, Whangaroa, northern New Zealand

The ornament on a small external cast in pink chert shows considerable similarity with that of various Middle Palaeozoic and Triassic fish genera. It comes from the Permian–Triassic Oruatemanu Formation of Arrow Rocks, Whangaroa area, eastern Northland. Conodont faunas from a few metres above and below the sample allow correlation with the Neospathodus pakistanensis zone of the Early Triassic, which is assigned to the late Dienerian (late Induan), with adjacent conodont zone faunas in their correct stratigraphic association. The cast is assumed to be that of a small fragment of fin spine, most likely from the junction area of the crown and root on the right-hand side of a dorsal fin spine, possibly anterior, of a marine ctenacanthoid shark, a basal shark order not previously recorded from New Zealand.

Mesozoic phosphatic and calcareous nodules containing well-preserved radiolarian fauna from the North Island, New Zealand

ニュージーランドには日本とよく似たチャート・砕屑岩を含む中・古生代の地質体が広く分布するが, 放散虫化石による生層序学的研究はようやく端緒に着いたばかりある. 我々は1995, 96年の2年にわたり, 国際学術研究 (代表: 酒井豊三郎)による, ニュージーランドの中生界を中心とした含放散虫岩の調査を行った. その結果のうち, ワイパパ, ムリヒク両テレーンの, 中生代南半球の極めて保存のよい放散虫化ヨを産するノジュールの産状を紹介する.