The mode of life of the Japanese Miocene bizarre pectinid Nanaochlamys notoensis (Yokoyama, 1929) is postulated on the basis of functional morphologic and biometric examinations of a large sample from the Middle Miocene Moniwa Formation in northern Japan. This species exhibits a remarkable ontogenetic change of shell morphology; i.e., the weight of valves becomes negatively allometric to the cube of shell size, indicating relative thinning of the shell with growth. Following this allometric change, the umbonal angle increases, the auricles become symmetrical, and the ctenolium disappears. Comparison of shell morphology with Recent pectinids strongly suggests that the present species changed its life style from byssally attached to free-living during ontogeny. This pectinid probably could swim in the later growth stage, but its swimming ability appears to have been poor in view of the high convexity of the left valve. Secondary flaring of the shell and splitting of the first-order plicae are apomorphic features in N. notoensis, suggesting that this species is not a direct ancestor of the extant North Pacific pectinid Swiftopecten swiftii, with seemingly similar overall shell morphology.

Ontogenetic shell development of the Turonian desmoceratine ammonoid Tragodesmoceroides subcostatus is examined based on more than 200 specimens collected by detailed biostratigraphic survey in the Tappu and Saku areas, Hokkaido, Japan. After the ammonitella stage, the mode of ribbing on the shell surface becomes coarser with growth. The shell surface ornament changes from stage 1 (almost smooth) to stage 3 (coarse ribbing) via stage 2 (weak ribbing). Stage 1 is subdivided into an earlier substage 1a with desmoceratid-type constrictions and a subsequent substage 1b without constrictions. Appearance order of these four ornament stages and substages seems to be ontogenetically fixed in the present species. Other characters, such as ammonitella and early shell shape and whorl geometry are also stable.

On the other hand, the shifting-timing from stages 1 to 2 and from stages 2 to 3 changes chronologically, i.e., it becomes ontogenetically earlier in upward sequence. In the Lower and Middle Turonian, the adult or subadult shells still remain stage 1 or 2. In contrast the strongly ribbed holotype and paratypes showing stage 3 are regarded as the Upper Turonian peramorphic endmembers of the single biospecies T. subcostatus. Taking these features into consideration, T. subcostatus should be taxonomically revised.

Chelonian eggshell fossils from the Lower Cretaceous Kuwajima Formation of the Tetori Group are described. The eggs were originally spherical or ellipsoidal in shape. The eggshells consist of a single layer of spherulitic shell units composed of needle-like crystallites originating from a nucleation center. This corresponds to modern rigid-shelled chelonian eggs. The eggshell fragments are commonly found buried together and are known from deposits of subaerial environments, such as vegetated swamps. In contrast, the vast majority of turtle remains are known primarily from nearby shallow lake deposits, indicating that they are aquatic; no terrestrial turtles are known from this formation. These taphonomic settings suggest that the eggs were laid on land by lacustrine turtles in a process still apparent today.

The Middle Permian Izuru and Nabeyama Formations in the Kuzu area, Tochigi Prefecture are composed of thick basaltic rocks and fossiliferous partly dolomitized limestone. Fusulinoidean biostratigraphy is first established in these two formations, and the stratigraphic distribution of the 30 species of fusulinoideans distinguished from 70 localities is shown. The Izuru and Nabeyama Formations are biostratigraphically subdivided into the lower Parafusulina nakamigawai, the middle Parafusulina yabei, and the upper Parafusulina tochigiensis zones. The first zone is correlated to the Parafusulina nakamigawai Zone of the basal part of the Akasaka Limestone. The middle part of the third zone corresponds to the upper part of the Neoschwagerina craticulifera Zone to the lower part of the Neoschwagerina margaritae Zone of the Akasaka Limestone based on the occurrence of Gifuella amicula. More precise correlation of the Parafusulina yabei and Parafusulina tochigiensis zones will be possible when biostratigraphic zonation by schwagerinids is made clear in relation to the stratigraphic range of neoschwagerinids in Middle Permian limestones of the Jurassic terrane of Japan. Seven species of Parafusulina including two new species, P. shimotsukensis and P. tochigiensis, and Pseudodoliolina ozawai and Gifuella gifuensis are described and discussed herein.

Middle Permian Izuru and Nabeyama Formations in the Kuzu area, central Japan are divisible into three zones based on the stratigraphic distribution of larger fusulinoideans: the lower Parafusulina nakamigawai Zone, the middle Parafusulina yabei Zone, and the upper Parafusulina tochigiensis Zone. Although schubertellid and ozawainellid fusulinoideans and non-fusulinoidean foraminifers are accessary in comparison with dominant schwagerinid fusulinoideans, 56 species assignable to 25 genera and a few more indeterminate genera are distinguished in these three zones. Their taxonomic diversity is very low in the lower zone, and becomes higher in the middle zone and highest in the upper zone. The difference of their variety well agrees with lithologic change of limestone in these three zones. There are no remarkable differences in the faunal composition of schubertellid and ozawainellid fusulinoideans and non-fusulinoidean foraminifers between the Izuru and Nabeyama Formations and other contemporaneous limestones of Japan. The similar faunal composition of these groups shows a striking contrast to the provinciality of the schwagerinids and neoschwagerinids of the Izuru and Nabeyama Formations. Six species of schubertellid fusulinoideans newly proposed herein are systematically described and discussed. They are Schuberetella? karasawensis, Schubertella? minutisphaera, Codonofusiella ashioensis, Codonofusiella elongata, Codonofusiella nabeyamensis, and Dunbarula oviformis.

To gain basic insights into the marine pelagic diatom species Neodenticula seminae, and particularly the relationships between morphology, evolution and environment, we conducted a scanning electron microscopic image analysis using modern specimens collected in the subarctic North Pacific and Bering Sea during the summers of 1955 and 1996–2003. We recognized an apparent intraspecific variability between two biogeographic provinces in terms of morphology: (1) the Oyashio Region (in the northwestern margin of the Pacific Ocean) and (2) other oceanic regions. This variability may reflect spatial variation in the availability of nutrients such as silicate. Specimens from the Oyashio morphological province had thinly silicified valves, whereas those from the other oceanic provinces were extraordinarily rich in heavily silicified valves.

A numerical procedure for calculating the buoyancy, apertural orientation and rotational stability of ammonoids can accommodate noncircular apertures and allometries. The hydrostatic properties of the Triassic oxyconic ammonite Intornites nevadanus were estimated from measured coiling parameters, body chamber length and digitized whorl section. The calculations indicate close to neutral buoyancy. The orientation of the aperture is 33 degrees from the horizontal, and the stability index relatively high at 0.054. Unlike for many other ammonites, these values are comparable to those of Nautilus, suggesting a similar nektobenthic lifestyle. An apertural interior shell callus does not contribute to stability in this genus, and its function remains unknown. In Amaltheus margaritatus, hydrostatic properties and body chamber length vary significantly as a result of intraspecific variation in shell shape. Covariation between septal spacing and whorl shape can be given a functional explanation in terms of hydrostatic properties. Buckman's second law of covariation between ribbing and sutural complexity can possibly be thought of in terms of heterochrony.