A specimen referable to an Early Jurassic ammonite, Cleviceras cf. chrysanthemum (Yokoyama, 1904), was discovered from a limestone conglomerate layer of the Kuzu Complex in the Ashio Belt, central Japan. Cleviceras chrysanthemum, a species comparable to the present specimen, is a diagnostic ammonite of early Toarcian age in the Circum-Pacific. The limestone conglomerate layer in question is a part of a sequence composed of, from top to bottom, siliceous shale, limestone conglomerate itself, calcareous sandstone, and again siliceous shale. The siliceous shale above and below the ammonite-bearing conglomerate bed carries radiolarian fossils which indicate the Unuma echinatus Assemblage Zone or Tricolocapsa plicarum Zone of Middle Jurassic age. The whole sequence is judged to be normally superposed by frequently observable normal graded bedding. Thus, the age indicated by the fossil ammonite for the limestone conglomerate is in contradiction with the age of the overlying and underlying beds. These facts suggest that the ammonitebearing pebble of Early Jurassic age is a fragment transported from elsewhere and redeposited in its present position during a Middle Jurassic time. The description of the ammonite is given.

An extinct tortoise known from the uppermost Pleistocene of the Ryukyu Islands is described as the new species, Manouria oyamai (Testudines: Testudinidae) based on the skull, lower jaw and some postcranial elements. The specimens of M. oyamai were newly collected from the latest Pleistocene fissure deposits on Okinawa and Tokunoshima Islands, Ryukyu Islands, Japan. This is the first fossil record of Manouria sensu stricto. Phylogenetic analysis shows that Manouria sensu stricto, comprising M. emys, M. impressa and M. oyamai, is monophyletic. Manouria oyamai flourished in the Central and South Ryukyus until the Late Pleistocene and became extinct there, along with other endemic terrestrial vertebrates, in the latest Pleistocene.

We reevaluate some fossil specimens of ungulate mammals from the uppermost middle Eocene Pondaung Formation (central Myanmar), describing some new materials. The taxa studied in this paper are Hsanotherium parvum (Ungulata), Asiohomacodon myanmarensis gen. et sp. nov. (Artiodactyla; Dichobunidae; Homacodontinae), Indomeryx (Artiodactyla; Ruminantia), Indolophus guptai (Perissodactyla; Tapiromorpha; Indolophidae), and Ceratomorpha fam., gen. et sp. indet. (Perissodactyla). (1) The lower molars of Hsanotherium show a similarity to those of Gobiohyus pressidens (Artiodactyla; Helohyidae), and its mesiodistally elongated and trilobed dP₄ morphology recalls that of artiodactyls and macroscelideans. However, the unique molar and P₄ morphologies of Hsanotherium indicate that Hsanotherium cannot confidently be classified into any present ungulate order, although it can be identified as belonging to the Ungulata because of its large, elongated, and posteriorly projecting hypoconulid on M₃. (2) The molar size and morphology of Asiohomacodon recall primitive protoreodontine agriochoerids (Oreodontoidea) such as Protoreodon parvus and derived and agriochoerid-like homacodontine dichobunids such as Pentacemylus, both of which occur in Eocene North America. Asiohomacodon is classified not into the Protoreodontinae but into the Homacodontinae because of the lack of molar metastylid. The lower molar morphology of Asiohomacodon also resembles that of an unusual and agriochoerid-like anthracotheriid, Atopotherium, from Eocene Thailand, although the affinity between these two genera cannot be tested because of the lack of the P₄ material of Asiohomacodon. (3) The Pondaung Indomeryx consists of large and small species, I. cotteri (including I. pilgrimi) and I. arenae (including I. minus). Dental morphology in each species of the Pondaung Indomeryx indicates relatively high variation, and the two species are not separable based on their dental morphology. Indomeryx shows many primitive characteristics among ruminants and lacks any critical derived features referable to any ruminant family. (4) Indolophus is referable to primitive tapiromorphs in having a somewhat lophodont dentition and in lacking lingual and buccal cingula and molar metaconule, paraconule, and metastylid. It differs from other tapiromorphs in having a smaller parastyle on the upper dentition and a unique P^2–4 morphology with large protocone, high and acute preprotocristid, and no postprotocristid. (5) Although the material of the indeterminate ceratomorph is poorly preserved, its preserved tooth is not identical to any other ceratomorph from the Pondaung Formation, indicating an occurrence of an additional ceratomorph species in the Pondaung fauna.

We introduce a new biometric method to reconstruct ontogenetic shell development of Baculites species. In order to estimate original total shaft length from fragmentary specimens and to clarify their shell growth patterns, a large number of samples of Baculites tanakae Matsumoto and Obata, collected from the Upper Cretaceous deposits in Hokkaido, Japan, were examined. Biometric analysis revealed a characteristic allometric shell growth pattern of B. tanakae expressed by the formula L = 3.03H^1.50, where L and H are original total shaft length and whorl height, respectively. The analysis gives a quantitative diagnosis of the morphology of this species and enables us to estimate L including the missing apical part. Reconstruction of the total shaft length reveals that the shell ornament of B. tanakae shifts ontogenetically from a smooth phase to a tuberculate phase via a ribbed phase. It also demonstrates wide intraspecific variation on switching timing of the shell ornament phases. The ontogenetic change and the intraspecific variation can be clearly discriminated from each other by our method.

The correlation between the depth-areal distribution of the ostracod fauna in surface sediments and water mass properties in the open sea area of the southwestern-northeastern Japan Sea is presented. This is the first report of the temperature and salinity ranges for the ostracod fauna in this sea giving specific values for summer and winter. The fauna on the shelf and continental slope was divided into four assemblage types based on species composition. The depth distribution of these assemblages is stratified and differs between the northern and southern areas. The four assemblages are distributed according to the four different water masses; Tsushima Warm Current Surface Water (TWS), Tsushima Warm Current Core Water (TWC), Japan Sea Intermediate-Proper Water (JSI-P) and Japan Sea Central Water (JSC). Each assemblage is characterized by the following species and temperature-salinity range; (1) TWSA: Aurila spinifera, Schizocythere kishinouyei, 15–25°C and 33–34.5‰, (2) TWCA: Bradleya spp., Acanthocythereis munechikai, 7–20°C and 34–34.5‰, (3) JSI-PA: Krithe sawanensis, Acanthocythereis dunelmensis, 0–10°C and around 34‰, and (4) JSCA: Laperousecythere robusta, 5–15°C and around 34‰. The JSCA consists of a part of the species in the cryophilic Omma-Manganji ostracod fauna, which flourished during glacial periods in the Japan Sea. These species inhabit the characteristic and intercalated water mass between the shallowest-warmest current water (TWS) and deepest-coldest water (JSI-P). Their southern distributional areas have decreased since the Pleistocene due to the warm current flowing during interglacial periods. These species live in the restricted water mass environment, changing their depth distributions between the south and north of the Tsugaru Strait. They are interpreted to be the survivors of the cyclic environmental fluctuations in the Japan Sea during the glacial-interglacial periods since the Pleistocene. The results may indicate a water mass temperature of 5–15°C during glacial periods in the shallow-open areas in the Japan Sea.