It is outlined how seemingly fundamental differences between high-level groups such as phyla and classes may have been introduced in fairly simple and rapid ways. Examples of such ways are development of endosymbiosis, heterochrony involving change of adult mode of feeding with associated changes of basic life habits and body plan, development of asymmetry, and turning upside-down. The latter modification has resulted in fundamental misinterpretations of so-called deuterostomes (or notoneuralians). The basal deuterostomes, the hemichordates, are much more similar to protostomes than textbook authors have been willing to admit. In fact, it is difficult to understand why they are at all considered as deuterostomes. For instance, protostome characteristics found in hemichordates include a main nerve cord on the ventral side, a circum-oesophageal nerve ring, a larva surprisingly similar to a protostome trochophora, blood circulation in the same direction as in protostomes, and (in all pterobranchians and many enteropneusts) schizocoelic formation of the coelom. New consideration of morphologies and life postures indicates that deuterostomes (notoneuralians) are not upside-down compared with protostomes (gastroneuralians). Instead, it is vertebrates that are upside-down compared with all other animals, including other deuterostomes. Fossils very poorly reveal the changes in body plans, but at least indicate that in general these changes are of (at least) Cambrian age. The oldest known group with vertebratetype orientation is the conodonts.

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The trace fossil Zoophycos was newly discovered in the lower part of the Hikoroichi Formation (Lower Carboniferous) distributed in the southern Kitakami Mountains, Northeast Japan. It consists of a helically coiled spreite, in which black-colored, chevron-shaped lamellae occur in cross section as an internal structure. Apart from the absence of distinct pellets and axial shaft, morphological features of the Hikoroichi Zoophycos are similar to those of Zoophycos known from Tertiary deep-sea sediments. X-ray diffractional analysis and microscopic observation in thin section revealed that the black material of the lamellae in the spreite appears to be derived from a higher level as a result of downward conveyor activity by tracemakers. This inference and morphological similarity to Tertiary specimens imply that the black material in the spreite of the Hikoroichi Zoophycos is probably of fecal origin, although there is no compelling evidence such as pellets. According to this interpretation, the producing animals of the Hikoroichi Zoophycos fed in surface and/or subsurface sediments and deposited fecal matter deep in sediment, as did Zoophycos from Pliocene deep-sea sediments of the Boso Peninsula, Central Japan. Such feeding and excretory styles in the Zoophycos producer may have already been achieved by at least the Early Carboniferous and have remained unchanged over a long peroid.

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Polyptychoceras, a Cretaceous heteromorph ammonite genus, is characterized by a trombone-like shell called a "hamitoid" shell. In order to clarify the shell-forming mechanism, a large sample, which consists of more than 320 specimens of P. pseudogaultinum (Yokoyama) obtained from the Upper Santonian of Hokkaido, was biometrically analyzed. Besides the shell coiling, cyclic changes of growth pattern are recognized by the analyses of the shell ornamentation, the relative growth rate of shell height, and the distance between septa. Intermittent shell growth, which was also deduced from the ontogenetic stage distribution in the population samples, is probably the cause of such peculiar shell coiling. Also, we carried out some computer simulations to reconstruct hydrostatically the ontogenetic change of the living attitude of P. pseudogaultinum. It is suggested that the rate of absolute shell growth possibly depends on the living attitude of this ammonite in the water column; the shell grows slowly when the shell aperture faces upward, and grows rapidly when the aperture faces in other directions. It is likely that every individual of this ammonite spent most of its life time with an upward-facing aperture.

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The non-ammonoid cephalopod fauna described here was collected from the upper Gzhelianlower Asselian (Upper Carboniferous to Lower Permian) hydrozoan-algal buildups in the Taishaku Limestone Group, Southwest Japan. The fauna consists of four orthocerids : Michelinoceras? sp., Bogoslovskya miharanoroensis sp. nov., Geisonocerina? sp., Lopingoceras hayasakai sp. nov.; two nautilids : Parachouteauoceras bingoense gen. et sp. nov., Parachouteauoceras? sp.; and a bactritid : Bactrites sp. Parachouteauoceras is most similar to Chouteauoceras, but unlike the latter has a lobated aperture. The occurrence of Bogoslovskya miharanoroensis represents one of the latest records of the genus in the world. This fauna is important because it adds some new data to a poorly known Late Carboniferous-Early Permian non-ammonoid cephalopod fauna.

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Permian nautiloids and ammonoids are described from the middle part of the Ochiai Formation distributed in the Kurosawa district of northern Kesennuma City, Southern Kitakami Massif, Northeast Japan. The nautiloids are Tainoceras, Pleuronautilus and Stearoceras. One new species, Tainoceras carinatum, is proposed. The ammonoids are Jilingites, Stacheoceras, Timorites, Pseudagathiceras, Propinacoceras and Eumedlicottia. Jilingites kesennumensis, Timorites takaizumii and Pseudagathiceras ornatum are newly proposed species. Based on the stratigraphic distribution of Timorites, Jilingites and Pseudagathiceras, and the stratigraphic relationship between the cephalopod horizon and Lepidolinabearing limestones, the cephalopod-bearing formation of Kurosawa is considered to be correlatable with the upper Capitanian.

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A new species of a small allosoricine shrew from Late Pliocene cave deposits in Yinan County is described under the name Paenelimnoecus chinensis, and its systematic position is discussed. Detailed description of the species reveals morphological characters that distinguish it from the known species of Paenelimnoecus. Comparisons with the known species indicate close relationships between this new species and P. pannonicus from the Pliocene of Europe. Owing to lack of reliable Pliocene records in the literature, P. chinensis first demonstrates the Pliocene distribution of Paenelimnoecus in East Asia, although this genus was very recently described from the Late Miocene of Inner Mongolia. It is inferred that Paenelimnoecus was widely distributed from Europe to north China across the northern part of Eurasia in the Late Pliocene.

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