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The Paleo-Tokyo Bay (Kanto Plateau) that persisted during the transgression periods in the Middle-Late Pleistocene is known for its rich marine fauna that accommodated both the warm and cold water taxa brought by the Kuroshio and Oyashio Currents, respectively. However, little is known on the paleoichthyofauna in this area and the processes shaping the marine ichthyofauna of modern southern Kanto. We used fossil fish otoliths and teeth discovered in the Sha’ana Tuffaceous Sand Member belonging to the Chibanian Miyata Formation, exposed at Sha’ana-dai, Miura City, Kanagawa Prefecture, Japan, to reconstruct the paleoichthyofauna and its associated paleoenvironment and explore the content of fish assemblages during this period. The Sha’ana Tuffaceous Sand Member was composed of upper sandy mud and lower muddy sand horizons at the exposure. A total of 1,675 fish remains were collected from this site, of which 1,389 were assigned to 62 distinct taxa (20 orders, 31 families). The taxonomic composition revealed taxa from various environments, including shallow continental shelf, epi- to meso-pelagic settings, and the majority were from a generally temperate climatic zone. Paleoenvironmental analyses suggested that the fish assemblages were from the continental shelf (approximate depth of 100–200 m) in a temperate sea where both warm Kuroshio and cold Oyashio Currents had an influence on the biota. The analysis also showed that two boreal fishes, namely Clupea pallasii and Theragra chalcogramma, once had a wider distribution that extended to the southwestern areas of the Paleo-Tokyo Bay. This study provides a more complete view of the related paleobiogeography of marine fishes during the Chibanian and is essential for reconstructing the evolutionary processes of the rich ichthyofauna in the southern Kanto.

In several primates and carnivores, pronation/supination angles of the forearm skeleton were examined, and it is thought that a larger angle is useful to acquire dexterous behaviors in feeding and/or life style, including climbing. In this study, the pronation/supination angles in Asiatic black, brown and polar bears were nondestructively examined. These specimens were classified as adult or non-adult. Three or four carcasses of each group of Asiatic black and brown bears were used for CT analysis, whereas only one adult polar bear was used. The forearms were positioned within the gantry of a CT scanner in both maximally supinated and pronated states. Extracted cross-sectional CT images of two positions were superimposed by overlapping the outlines of each ulna. The centroids of the radii were detected, and then the centroid of each radius and the midpoint of a line which connects between both ends of the surface of each radius facing the ulna, were connected by lines to measure the angle of rotation as an index of pronation/supination. In adult brown and polar bears, the angles were smaller as compared with the other groups (Asiatic black and non-adult brown bears). Asiatic black and non-adult brown bears can climb trees, whereas adult brown bears and polar bears cannot. This suggests that the pronation/supination angle is related to arboreal activity in Ursidae.

A serologic investigation of Brucella infection was performed in 7 species of cetaceans inhabiting along the coast of Japan. A total of 32 serum samples were examined by enzyme-linked immunosorbent assay (ELISA) using Brucella abortus and B. canis antigens. One serum sample from five melon-headed whales (Peponocephala electra) was positive for B. abortus. No serum sample showed positive for B. canis. The ELISA-positive melon-headed whale serum demonstrated a strong band appearance only against B. abortus antigens in Western blot analysis. Many detected bands were discrete, while some of them had a smeared appearance. The present results indicate that Brucella infection occurred in melon-headed whale population and the bacterial antigenicity is more similar to that of B. abortus than B. canis.

In several primates and carnivores, pronation/supination angles of the forearm skeleton were examined, and it is thought that a larger angle is useful to acquire dexterous behaviors in feeding and/or life style, including climbing. In this study, the pronation/supination angles in Asiatic black, brown and polar bears were nondestructively examined. These specimens were classified as adult or non-adult. Three or four carcasses of each group of Asiatic black and brown bears were used for CT analysis, whereas only one adult polar bear was used. The forearms were positioned within the gantry of a CT scanner in both maximally supinated and pronated states. Extracted cross-sectional CT images of two positions were superimposed by overlapping the outlines of each ulna. The centroids of the radii were detected, and then the centroid of each radius and the midpoint of a line which connects between both ends of the surface of each radius facing the ulna, were connected by lines to measure the angle of rotation as an index of pronation/supination. In adult brown and polar bears, the angles were smaller as compared with the other groups (Asiatic black and non-adult brown bears). Asiatic black and non-adult brown bears can climb trees, whereas adult brown bears and polar bears cannot. This suggests that the pronation/supination angle is related to arboreal activity in Ursidae.

1 College of Bioresource Sciences, Nihon University, Fujisawa, Kanagawa 252-0880, Japan 2 Kanagawa Prefectural Museum of Natural History, Odawara, Kanagawa 250-0031, Japan 3 Yokohama Hakkeijima Sea Paradise, Yokohama, Kanagawa 236-0006, Japan 4 National Research Institute of Fisheries Science, Fisheries Research Agency, Yokohama, Kanagawa 236-8648, Japan 5 Japan Driftological Society, Hata, Kochi 789-1911, Japan

The cervical and thoracic regions including vertebrae, spinal nerves, and brachial plexus were examined by macroscopic and three-dimensional computed tomography observational scans in the two-toed sloth (Choloepus didactylus). This species possesses seven cervical vertebrae unlike closely related sloths, which possess varying number of cervical vertebrae ranging from five to ten. The large axis and the partially vestigial third cervical vertebra are morphologically characteristic of C. didactylus. In addition, the spinal nerve branches of C5, C6, C7, C8, and T1 contributed to the brachial plexus, whereas C4 and T2 did not supply nerves to the plexus. Histological data showed that the branches of C5, C6, C7, and C8 were obviously thicker than that of C4 and T1. The most notable observation was that only the two-toed sloth unlike other sloth species is conservative in these morphological characteristics regarding the cervical vertebrae spinal nerves. By comparing the morphological patterns of the cervical and thoracic spine and the brachial plexus of the two-toed sloth with ancestral morphological patterns and related species, which have derived a repatterned and variable morphology of these structures, it is possible to elucidate the morphological evolution of the cervical and thoracic regions in the evolutionary history of these mammals.

With 12 figures and 3 tables Summary The coxa of palaeognaths including extinct aepyornithid species was compared by means of osteology, computed tomography (CT) imaging and macroscopic anatomy. The pre-acetabular area of the ilium was proportionally much larger in width and height in aepyornithid species than in other extant palaeognaths. The post-acetabular area of the ilium, ischium and pubis was relatively short and bilaterally extended in aepyornithid species. Although the Aepyornis species might have produced egg with a major axis exceeding 300 mm in major axis, the short post-acetabular coxa and widely opened ischium and pubis would not have been able to stably hold the eggs in the posterior space of the pelvic cavity unlike the situation in the ostrich. As aepyornithid species resembled the kiwi in measurement ratios of length and width in the pre-acetabular area, a functional–morphological model of the coxa in the aepyornithid species can be proposed based on that of the kiwi. From our data, we suggest that the extinct species of Aepyornis and Mullerornis species effectively used the anterior space of the pelvic cavity to support their extraordinary large egg.

The armor-like folded skin of the Indian rhinoceros (Rhinoceros unicornis) was examined by CT image analyses and microscopic observation. The three-dimensional reconstructed images demonstrate that the folded skin has the subcutaneous tissues including cutaneous muscles and connective tissues inserted to the deepest holes and grooves of 2-3 mm thickness in each fold. The cutaneous muscles are well-developed in subcutaneous tissues, in which many small blood vessels are found. We conclude that the folded skin acts as a thermoregulator, since the thin blood vessels and capillaries and cutaneous muscles in the subcutaneous tissues transmit the thermal energy from the core region of the body to the skin folds. We suggest that the greater Indian rhinoceros, Rhinoceros unicornis, has evolved the extraordinary thermoregulation mechanism in the folded skin adapted to high temperature in the tropical and subtropical regions.

ZIN-MAUNG-MAUNG-THEIN1, HAJIME TARU2, MASANARU TAKAI1 AND AKIRA FUKUCHI3 1Primate Research Institute, Kyoto University, Inuyama, Aichi 484-8506, Japan (email: zinmaung@pri.kyoto-u.ac.jp; takai@pri.kyoto-u.ac.jp) 2Kanagawa Prefectural Museum of Natural History, Kanagawa 250-0031, Japan (email: taru@nh.kanagawa-museum.jp) 3Hanshin Consultants Co., Ltd., Satsumasendai, Kagoshima 895-0132, Japan (email: afkc@po5.synapse.ne.jp)

CT scanning and its related three-dimensional image techniques were applied for a carcass head of a newborn Indian rhinoceros (Rhinoceros unicornis) to clarify if the guttural pouch is well-developed or not in the early growth stages of this species. Observations from the sections of the CT three-dimensional reconstructed image reveal that the guttural pouch is not present around the stylohyoid bone in a new born Indian rhinoceros. Since the absence of the guttural pouch has been confirmed also in adult rhinoceros, we can point out that the guttural pouch does not disappear during the growth stages, but is originally absent in the newborn. Although the well-developed guttural pouch in the horse and ass has attracted anatomists, we can conclude that the guttural pouch is not commonly observed in the perissodactyls, but in a few species of Equus, and that the guttural pouch is adapted only to restricted roles in the smaller taxa within perissodactyls.

A total of 79 ostracode species were recognized from the embayment sediments deposited during the Late Pleistocene Shimosueyoshi transgression in central Japan. The most dominant species was Neomonoceratina delicata , now abundant in tropical inner bays of the Ryukyu Islands, the South China Sea and southeastern Asia. Bicornucythere bisanensis , widely dominant species in enclosed middle muddy bays of temperate climatic zones in Japan and northern China, was also abundant in the middle and upper sequences. Most of the other main species were assigned to the “Japonic elements” and are presently common in tropical or subtropical and temperate shallow seas near the Japanese Islands. Four ostracode biofacies were identified using the Q-mode cluster analysis. A change in water depth was clearly revealed in the study sequence, based on the vertical changes in the biofacies and the relative abundances of fossil ostracode species. The single most dominant species, N. delicata , does not currently exist in the Japanese Islands north of the Tokara Strait (Watase's line: one of zoological lines of demarcation), in southern Japan. Based on a compilation of fossil and recent distribution records, it is believed that N. delicata migrated from the south of the Tokara Strait by the marine oxygen isotope stage (MIS) 11 (∼ 430 ka), dominated other species in enclosed muddy bays and then spread to the northernmost areas during the MIS 5. However, almost all populations of this species probably disappeared north of the Tokara Strait during the Last Glacial Maximum due to a decrease in water temperature. This species could not survive colder water temperature and could not migrate north through the Tokara Strait during the postglacial transgression because the strait has been deep and wide since the Early Pleistocene. We conclude that this species lived commonly during the glacial stages of MIS 10, 8 and 6 north of the Tokara Strait because of the favorable water temperature for reproduction.

千葉県袖ケ浦市吉野田に分布する下総層群清川層から, 長鼻類の右下顎臼歯および左大腿骨遠位部の化石が産出した. 臼歯は板状歯であり, 咬板幅, 咬板数, エナメル環の形態的特徴などからナウマンゾウPalaeoloxodon naumanni の右下顎第3大臼歯であることが明らかになった.同地点からはニホンジカCervus (Sika) nippon, イヌ科Canidae, ヤベイシガメMauremys yabei , ハナガメ属の一種Ocadia sp. などの脊椎動物化石が共産した. これらと堆積環境, 植物化石から推定される古環境を考慮すると, 本地域は森林を控えた草原域や疎林域と考えられる. また, 植物化石と動物化石などの考察から, 当時の気候は現在より寒暖の格差が大きかったと推定されており, ナウマンゾウの生息環境を考える上で貴重な発見といえる.

The hindlimbs of the Malayan sun bear (Helarctos malayanus), the polar bear (Ursus maritimus), the brown bear (Ursus arctos) and the giant panda (Ailuropoda melanoleuca) have been anatomically and osteometrically studied. The Musculus tibialis cranialis of the Malayan sun bear and the giant panda possessed a well-developed rich fleshy portion until the distal end of the tibia. In the polar bear and the brown bear, however, the fleshy portion of the M. tibialis cranialis was not developed until the distal end of the tibia. The tendon of the M. tibialis cranialis inserting on the proximal end of the Ossa metatarsalia was shorter in the Malayan sun bear and the giant panda than in the polar bear and the brown bear. In the Malayan sun bear and the giant panda, moreover, the M. popliteus was attached more distally to the tibia than in the polar bear and the brown bear. The stable dorsiflexion and supination of the foot and the efficient pronation of the crus are important for skillful tree climbing. The present study suggests that the Malayan sun bear and the giant panda have hindlimbs especially adapted to tree climbing by the well-developed fleshy portion of the M. tibialis cranialis reaching the distal end of the tibia, its short tendon, and the M. popliteus inserting near the distal end of the tibia.

調査地点は千葉県袖ヶ浦市吉野田で,中部更新統下総層群清川層の露頭である.最近,調査地点において,シカ,カメ,ナウマンゾウなど多数の陸生脊椎動物化石や淡水生貝類化石および植物化石などが発見された.これらの化石を含む地層は河川の氾濫原堆積相(厚さ約1m)で,大きく分けて下位よりA,B,Cの3つの堆積ユニットが認められる.ユニットAは植物片を多く含む塊状粗粒シルト層からなる.ユニットBは淘汰の悪い泥質砂層からなり,木片や陸生脊椎動物の骨片・歯が密集する.この泥質砂層には砂層がレンズ状に複数挾まれ,平行層理や級化層理,粗粒デューンなどが認められる.ユニットCの下部は塊状シルト層で,上部はシルト層と極細粒～細粒砂層との砂泥互層からなる.このユニット中には,原地性を示すカメ化石や淡水生貝類化石などがみられる.これらの堆積相と化石群から,ユニットA～Bは河川の増水時に氾濫原に侵入してきた洪水堆積物で,自然堤防や堤防決壊堆積(クレバススプレイ)などを形成していたと考えられる.ユニットCは,その後,氾濫原に形成された湖沼の泥底とそこに氾濫時に流入した砂層の堆積物より構成される.

The morphological differences in the muscles of mastication between the giant panda (Ailuropoda melanoleuca) and the Asiatic black bear (Ursus thibetanus) were sought to confirm the adaptational strategy of these muscles in the giant panda. We measured some skull characteristics and weighed the muscles of mastication, and macroscopically observed the muscles of mastication in the two species. The noticeable differences between the two species are classified as follows: (1) The size ratio of the zygomatic width was much larger in the giant panda than in the Asiatic black bear. (2) The weight ratio of the two pterygoid muscles was also much larger in the giant panda than in the Asiatic black bear. (3) The lateral slips of the temporal muscles are thicker and stronger in the Asiatic black bear than in the giant panda. (4) The deep layer of the masseter muscle was rostrocaudally divided, and a complicated running of tendons is observed in the giant panda. (5) The two pterygoid muscles were much larger and well-developed in the giant panda than in the Asiatic black bear. The points (1) and (4) may be related to the generation of the force necessary to chew the bamboo in the giant panda. We thought that the large mass of the masseter and temporal muscles are needed in this species. In the points of (2) and (5), the two pterygoid muscles were obviously different in form and weight ratio between the two species. We suggest that the two pterygoid muscles may act as an additional force generator to dorsoventrally press and crush bamboo stems.

Morbillivirus infection is a severe threat to marine mammals. Mass die-offs caused by this infection have repeatedly occurred in bottlenose dolphins (Turiops truncatus) and striped dolphins (Stenella coeruleoalba), both of which belong to the family Delphinidae, but not in other cetaceans. However, it is unknown whether sensitivity to the virus varies among cetacean species. The signaling lymphocyte activation molecule (SLAM) is a receptor on host cells that allows morbillivirus invasion and propagation. Its immunoguloblin variable domain-like (V) region provides an interface for the virus hemagglutinin (H) protein. In this study, variations in the amino acid residues of the V region of 26 cetacean species, covering almost all cetacean genera, were examined. Three-dimensional (3D) models of them were generated in a homology model using the crystal structure of the marmoset SLAM and measles virus H protein complex as a template. The 3D models showed 32 amino acid residues on the interface that possibly bind the morbillivirus. Among the cetacean species studied, variations were found at six of the residues. Bottlenose and striped dolphins have substitutions at five positions (E68G, I74V, R90H, V126I, and Q130H) compared with those of baleen whales. Three residues (at positions 68, 90 and 130) were found to alternate electric charges, possibly causing changes in affinity for the virus. This study shows a new approach based on receptor structure for assessing potential vulnerability to viral infection. This method may be useful for assessing the risk of morbillivirus infection in wildlife.

Morbillivirus infection is a severe threat to marine mammals. Mass die-offs caused by this infection have repeatedly occurred in bottlenose dolphins (Turiops truncatus) and striped dolphins (Stenella coeruleoalba), both of which belong to the family Delphinidae, but not in other cetaceans. However, it is unknown whether sensitivity to the virus varies among cetacean species. The signaling lymphocyte activation molecule (SLAM) is a receptor on host cells that allows morbillivirus invasion and propagation. Its immunoguloblin variable domain-like (V) region provides an interface for the virus hemagglutinin (H) protein. In this study, variations in the amino acid residues of the V region of 26 cetacean species, covering almost all cetacean genera, were examined. Three-dimensional (3D) models of them were generated in a homology model using the crystal structure of the marmoset SLAM and measles virus H protein complex as a template. The 3D models showed 32 amino acid residues on the interface that possibly bind the morbillivirus. Among the cetacean species studied, variations were found at six of the residues. Bottlenose and striped dolphins have substitutions at five positions (E68G, I74V, R90H, V126I, and Q130H) compared with those of baleen whales. Three residues (at positions 68, 90 and 130) were found to alternate electric charges, possibly causing changes in affinity for the virus. This study shows a new approach based on receptor structure for assessing potential vulnerability to viral infection. This method may be useful for assessing the risk of morbillivirus infection in wildlife.

Upon studying the well preserved skulls referred to Paleoparadoxia tabatai from Japan, the short and low skull of the Yanagawa specimen requires an explanation. Six cranial and dental characters lead us to suggest that the Yanagawa individual is a female while the Izumi, Ohnohara, and Itsukaichi skulls are male. The important characters in the Yanagawa skull are its shortness and shallow depth, less pronounced sagittal and nuchal crests, smaller zygoma, and the small dentition with especially poorly erupted canines, most of which are indicative of weak masticatory musculature.

The determination of area and shape of articular surfaces on the limb bones of extinct archosaurs is difficult because of postmortem decomposition of the fibrous tissue and articular cartilages that provide the complex three-dimensional joint surfaces in vivo. This study aims at describing the shape of the articular cartilages in the elbow joints of six crocodilian specimens; comparing its structure with that of four birds, three testudines, and five squamates; and comparing the shapes of the surfaces of the calcified and the articular cartilages in the elbow joints of an Alligator specimen. The shapes of the articular cartilages of crocodilian elbow joint are shown to resemble those of birds. The humerus possesses an olecranon fossa positioned approximately at the midportion of the distal epiphysis and bordering the margin of the extensor side of the articular surface. The ulna possesses a prominent intercotylar process at approximately the middle of its articular surface, and splits the surface into the radial and ulnar cotylae. This divides the articular cartilage into an articular surface on the flexor portion, and the olecranon on the extensor portion. The intercotylar process fits into the olecranon fossa to restrict elbow joint extension. Dinosaurs and pterosaurs, phylogenetically bracketed by Crocodylia and Aves (birds), may have possessed a similar olecranon fossa and intercotylar process on their articular cartilages. Although these shapes are rarely recognizable on the bones, their impressions on the surfaces of the calcified cartilages provide an important indication of the extensor margin of the articular surfaces. This, in turn, helps to determine the maximum angle of extension of the elbow joint in archosaurs. J. Morphol., 2010. © 2010 Wiley-Liss, Inc.

The gross anatomical study was undertaken in the musculoskeletal system of the neck of the polar bear, and the findings were compared with those of the Malayan bear. The Musculus splenius and the M. trapezius were well-developed in the polar bear. The long neck of the polar bear consisted mainly of the M. splenius with the M. biventer cervicis and the M. complexus lying tightly underneath. The cervical vertebrae possessed huge ventral tubercle in the ventral part of the transverse process in the polar bear. These morphological characteristics suggest that the polar bear may rotate and bend the skull and the long cervical vertebrae. We postulate that the polar bear has evolved the high-mobility long neck to adapt for swimming. Unlike the polar bear, the Malayan bear has not specialized in the neck structure.

We examined the head of the gray wolf (Canis lupus) using MRI methods. Although the arising surface of the M. temporalis was not so enlarged in the frontal bone, the small frontal bone did not disturb the M. temporalis from occupying the lateral space of the frontal area in the gray wolf as in the domesticated dog. In the gray wolf, it is suggested that the M. temporalis may not be well-developed in terms of size of arising area, but in the thickness of running bundles. We suggest that the dog has changed the three-dimensional plan of the M. temporalis during the domestication and that the M. temporalis has developed a large arising surface in the frontal bone and lost the thickness of belly in the frontal area in accordance with the enlargement of the frontal bone and the increase in brain size.

茨城県つくば市東部を流れる花室川の中流域から,Palaeoloxodon naumanni (Makiyama)の臼歯が発見された.産出層準は,最上部更新統である桜川段丘堆積物に相当する緩斜面堆積物で,約2.7万年前より新しい年代を示す.歯種は左上顎第3大臼歯であり,歯冠長は331mm,咬板数は1/2・22・1/2と,これまでに報告された臼歯の中でも大型であり,特に咬板数は最大であることがわかった.この標本の産出は,P.naumanniの時代的な形態変異を明らかにする上で重要である.