52 species assignable to 39 genera of Middle Permian (Midian in the Tethyan standard scale) foraminifers are distinguished in the limestone blocks exposed in Kaize, southern part of the Saku Basin, Nagano prefecture, central Japan. Faunal composition and biostratigraphic distribution of these taxa are described and discussed, in addition to systematic description of eleven species including Yabeina kaizensis based on the topotype materials. The ozawainellid genus, Primoriina is concluded to be probably a junior synonym of Sichotenella. The Kaize fauna is represented by (1) abundant occurrence of Yabeina kaizensis and Yabeina higoensis, (2) complete absence of genera assignable to Verbeekinidae and Staffellidae, (3) variable non-fusulinacean foraminifers consisting of 39 species assignable to 31 genera, and (4) occurrence of Robutoides, Dagmarita, and Postendothyra, characteristic of the Tethyan Upper Permian. These foraminifers are important paleogeographically in relation to the faunal composition and taxonomic diversity of the Tethyan and Circum-Pacific regions in the late Middle Permian time.

抄録全体を表示

Ashicaulis macromedullosus sp. nov. (Osmundaceae) is described on the basis of one silicified rhizome, collected from the Middle Jurassic Tiaojishan Formation in Hebei, China. This specimen consists of a small, upright stem surrounded by frond bases, and adventitious roots. The stem consists of pith, xylem cylinder, a two-layered cortex and petiole bases. In cross section, the stem has a dictyoxylic xylem cylinder composed of 24-32 xylem strands separated by many leaf gaps with some incomplete leaf gaps. This species is characterized by continuous cylindrical phloem, absence of medullary traces in the pith, no sclerenchyma in leaf trace concavity, homogeneous cortical sclerenchyma, and one mass of sclerenchyma in each stipular wing. This is the third structurally preserved rhizome of Ashicaulis from the Mesozoic in northern China and adds to the knowledge of fern diversity in China. Northern Hemisphere species from the Jurassic have a tendency to larger stele diameter than comparable Mesozoic species in the Southern Hemisphere.

抄録全体を表示

Black shale exposed north of Satun, southern peninsular Thailand, lies upon Upper Ordovician limestone and includes abundant graptolites. This fauna contains Normalograptus pseudovenustus pseudovenustus (Legrand, 1986) and Normalograptus sp. N. pseudovenustus is a reliable index species of an interval containing the Ordovician-Silurian boundary. Based on the range of this species, the graptolite-bearing black shale is inferred to be of latest Ordovician age, with the study section including the O/S boundary. The taxonomy of these two graptolite species is discussed in this study.

抄録全体を表示

Lower and Middle Ordovician conodonts from the Thung Song Group, in the Thung Song and Thung Wa areas of southern peninsular Thailand, are described and illustrated here for the first time. These conodonts are divided into faunas A, B, and C, which are middle to late Arenigian, middle Arenigian to Darriwilian or Caradocian, and late Arenigian to early Caradocian, respectively. Fauna A resembles faunas in Australia, South China, the Argentine Precordillera, and North America. Fifteen species belonging to twelve genera were studied systematically.

抄録全体を表示

Cerithiform gastropods possess high-spired shells with small apertures, anterior canals or sinuses, and usually one or more spiral rows of tubercles, spines or nodes. This shell morphology occurs mostly within the superfamily Cerithioidea. Several morphologic characters of cerithiform shells are adaptive within five broad functional areas: (1) defence from shell-peeling predators (external sculpture, preadult internal barriers, preadult varices, adult aperture) (2) burrowing and infaunal life (burrowing sculptures, bent and elongated inhalant adult siphon, plough-like adult outer lip, flattened dorsal region of last whorl), (3) clamping of the aperture onto a solid substrate (broad tangential adult aperture), (4) stabilisation of the shell when epifaunal (broad adult outer lip and at least three types of swellings located on the left ventrolateral side of the last whorl in the adult stage), and (5) righting after accidental overturning (projecting dorsal tubercles or varix on the last or penultimate whorl, in one instance accompanied by hollow ventral tubercles that are removed by abrasion against the substrate in the adult stage). Most of these characters are made feasible by determinate growth and a countdown ontogenetic programme. These varied adaptations often have evolved independently among different taxonomic groups of cerithiforms, and multiple times within the same group.

抄録全体を表示