An extinct tortoise known from the uppermost Pleistocene of the Ryukyu Islands is described as the new species, Manouria oyamai (: 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.

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千葉県袖ケ浦市吉野田の下総層群清川層からイシガメ科に属する2種類の淡水生カメ類, ハナガメ属の化石種Ocadia sp.と小型のヤベイシガメMauremys yabei が確認された. ハナガメ属はほぼ完全な骨格が発見され, またヤベイシガメは2個の保存良好な甲羅が知られている. いずれも日本固有の化石種と考えられ, 第四紀におけるイシガメ類の多様性の大きさを示唆している. 特にハナガメ属の発見は, 当時の古気候の推定に関して再考察をうながすものとして注目される.

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Extant side-necked turtles consist of three families: Chelidae, Pelomedusidae, and Podocnemididae. The lasttwo families (the subject of this study) include five genera, three of which are endemic to Africa (Pelomedusa andPelusios) and Madagascar (Erymnochelys), while the other two (Podocnemis and Peltocephalus) are restrictedto South America. This study was undertaken to determine the molecular relationships of side-necked turtlesbased on the primary and tertiary structures of α^A, α^D, and β globin chains as deduced by cDNA sequencing and amachine-learning algorithm for protein structure prediction, AlphaFold2. Analyses of the globin primary structures of four species from different genera provide three major insights. (1) The genera Pelomedusa and Pelusiosmight be endemic taxa that diversified in Africa after the Gondwana separation. (2) Although the extant species ofErymnochelys and Podocnemis are restricted to Africa and South America, respectively, they are closely related toeach other, and thus, these genera apparently diversified during the breakup of Gondwana. Thus, the colonizationof the ancestral population of Podocnemis unifilis in South America might have coincided with continental drift.(3) The divergence times of the four species based on globin genealogy were estimated to have begun 120–11million years ago (mya), which generally coincides with the break-up of Gondwana 135–65 mya. In addition,tertiary structures predicted by AlphaFold2 were compared using a PyMOL overlaying technique. An in-depth examination of the four α^A globin chains revealed considerable consistency among species, and a similar pattern wasobserved for α^D and β globin chains. Additionally, species-specific differences were recognized among the primarystructures, and their higher-order structures (i.e., tertiary structures) were consistent, offering new information onthe molecular phylogeny of side-necked turtles.

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The bone-bearing beds of the Lower Cretaceous Kuwajima Formation (Tetori Group) are described. Three facies of bone-bearing beds (Facies I: carbonaceous sandstones; Facies II: dark grey fine-grained silty sandstones; Facies III: dark greenish-grey mudstones) are present in inter-channel deposits that originated on a floodplain. The grain size of the sediments, and plant and molluscan fossils occurring in each bone-bearing bed, indicate that Facies I was deposited in a peat marsh, Facies II in a shallow lake, and Facies III in a vegetated swamp.

Isolated small bones and teeth are the most abundant vertebrate fossils. Common elements in Facies II are aquatic vertebrates such as fishes and turtles. Facies III is characterized by the occurrence of terrestrial lizards, tritylodontid synapsids and mammals. Vertebrate fossil assemblages in Facies II and III are not mixed with each other even though they both represent parautochthonous assemblages. In contrast, Facies I is allochthonous, and is composed mostly of reworked sediments from Facies II.

Depositional environments of the bone-bearing beds are strongly correlated with the composition of their fossil assemblages, indicating that different facies preserve the original faunal differences that existed between the shallow lake and vegetated swamp environments.

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Monophyly of the batagurid subfamily Geoemydinae was evaluated, and phylogenetic relationships within the subfamily were inferred on the basis of 35 morphological characters. Two approaches, parsimony analysis using the branch and bound algorithm, and neighbor joining clustering of an absolute distance matrix, were used. The results of these analyses yielded phylograms that were almost identical in branching topology, and poorly supported the monophyly of Geoemydinae. This subfamily thus seems to be a metataxon, most likely consisting of the sister group of Batagurinae (Geoemyda group) and a more primitive stock of Bataguridae (Mauremys group). The latter accommodates Mauremys and Sacalia and its monophyly is not well supported. The former consists of the remaining ten geoemydine genera united by two synapomorphies-absence or reduction of the quadratojugal, and posteriorly short-sided anterior neurals. Relationships revealed by our analyses necessitate some changes in the generic classification of Geoemydinae. First of all, Cistoclemmys Gray, 1863 (type species: Ci. flavomarginata, often synonymized to Cuora Gray, 1855 (type species: Cu. amboinensis), is shown to be a valid genus closely related to Pyxidea and Geoemyda rather than to Cuora (sensu stricto). Rhinoclemmys Fitzinger, 1835 (type species: R. punctularia) is shown to be polyphyletic, and Chelopus Cope, 1870 (type species: C. rubida), is resurrected to accommodate R. rubida and R. annulata. The plastral hinge seems to have evolved three times in the Bataguridae-in the Cyclemys-Notochelys clade, Cuora (sensu stricto), and the Cistoclemmys-Pyxidea clade.

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Sea turtles have well developed lacrimal glands for their electrolyte homeostasis. In turtles, stapedial artery and palatine artery send branches to supply orbital region, but supply artery for lacrimal glands was not identified. Micro-CT scans showed dorsoventrally large lacrimal glands of sea turtle are supplied by both stapedial artery and palatine artery. The circulatory pattern in cranial region was reconstructed based on the micro-CT scans, showing that sea turtle has basically similar pattern with the common snapping turtle: stapedial artery supplies orbital region and mandibular artery is ramified from stapedial artery. We also investigate the foramen stapedio-temporalis in turtles using osteological specimens. The foramen stapedio-temporalis, where the stapedial artery passes through, has different size among four families of turtles. We compared the sum of cross sections of left and right foramen stapedio-temporalis since homeostasis of one individual is maintained by a pair of lacrimal glands. The size difference may reflect primarily the share of stapedial artery against palatine artery in cranial circulation pattern and blood supply of orbital regions. Our observations confirmed a significantly larger cross-section in the foramen stapedio-temporalis of sea turtles than other freshwater/terrestrial turtles. Since the circulatory pattern is shared, the size difference of foramen stapedio-temporalis reflects the amount of arterial blood supply to lacrimal glands. Therefore, the size of the foramen stapedio-temporalis may indicate marine adaptation of turtles and are applicable to both fossil and osteological specimens.

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We investigated the effect of incubation temperature on hatchling sex in the Japanese pond turtle, Mauremys japonica. Eggs obtained from females collected in the Tokai District of Japan invariably produced males when incubated at constant temperatures from 22.0 to 28.0 C, whereas they produced only females under a higher temperature of 30.0 C. Both males and females hatched from eggs incubated at 28.5, 29.0, and 29.5 C. These results indicate that M. japonica has a mechanism of temperature-dependent sex determination (TSD) with higher temperatures favoring females and lower temperatures males as in several other species of the family Geoemydidae, as well as of a few other testudine families so far studied. The pivotal temperature and the transitional range of temperature (TRT) in M. japonica obtained by the inverse estimation from logistic regression were 28.8 C and from 27.8–29.8 C, respectively. Possible effect of TSD on the sex ratio observed in some wild populations of this turtle is discussed.

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A partial skeleton of Mesodermochelys undulatus Hirayama and Chitoku, 1996 (: Chelonioidea: Dermochelyidae), with carapace estimated as 1.3m long, was collected from the Late Cretaceous (early Late Campanian) Izumi Group at Shionoe, Takamatsu City, Kagawa Prefecture, Western Japan. This occurrence supports the presence of highly localized sea turtle fauna dominated by Mesodermochelys in the sea adjacent to Japan during the Late Cretaceous.

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The first cytogenetics of the Malayan snail-eating turtle (Malayemys macrocephala) from the Chi river basin, Khon Kaen Province, Thailand, were studied. Blood samples were taken from two male and two female turtles. Standard T-lymphocyte cell culture at 26°C for 96 h was applied. The mitotic chromosomes were harvested by colchicine-hypotonic-fixation-air drying technique. Conventional staining and GTG-banding techniques were applied to stain the chromosomes with 20% Giemsa's solution. Results showed that the number of diploid chromosomes was 2n=50, while the fundamental number (NF) was 40 in both males and females. The types of macrochromosomes were 4 metacentric, 8 submetacentric, 6 acrocentric, 4 telocentric chromosomes, and 28 microchromosomes. The GTG-banding technique showed that each chromosome pairs could be clearly differentiated and the numbers of bands in the M. macrocephala was 99. There is no observation of strangely size chromosomes related to sex. The karyotype formula is as follows:
2n (50)=L₂^m+L₂^sm+M₂^a+S₂^m+S₆^sm+S₄^a+S₄^t+28 microchromosomes

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We describe morphological changes observed throughout the embryonic development of Mauremys japonica, a geoemydid species endemic to Japan. Eggs laid in captivity were incubated under two different temperature conditions, 26C and 30C. A total of 185 embryos and seven hatchlings were observed. We divided the whole embryonic development into 26 stages on the basis of morphological criteria previously proposed for Chelydra serpentina. Eggs of the turtle developed faster at 30C (taking 44-47 days for completion of the whole process) than at 26C (56-64 days). As has been reported previously, embryos of M. japonica developed to males after being incubated at 26C and to females at 30C, but without any visually recognizable differentiation in external morphology. Comparisons of embryos between M. japonica and three other testudinoid turtles revealed that the carapace of M. japonica started pigmentation at stage 18, i.e., earlier than the other three species by two stages.

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Partial skeletal remains of Mauremys reevesii, consisting of the right second and third costals of an individual, were discovered from late medieval deposit of an archaeological site in Hiroshima Prefecture, Japan. Because the site was a local port town with relatively frequent commercial exchanges then, the turtle may have possibly been brought there through direct or indirect foreign trade in the 15th Century. Current Japanese populations of M. reevesii have generally been considered as descendants of artificially transported individuals from outside Japan in no earlier than the late Edo period (late 18th Century). However, the present finding suggests that the species was actually introduced to Japan in the late medieval period or even earlier.

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Sex-determining systems are highly divergent between different lineages of reptiles. Birds and snakes have genotypic sex determination (GSD), whereas all crocodilians and tuataras exhibit temperature-dependent sex determination (TSD). Sex-determining mechanisms in turtles and squamates include GSD with male heterogamety, GSD with female heterogamety, and TSD. Comparing different sex determination systems with molecular cytogenetics and comparative genomics thus provides unparalleled opportunities to capture the evolution of sex chromosomes and determination systems in action. The direct or indirect comparison of linkage homologies of sex chromosomes among various GSD species highlighted that the evolutionary process of sex determination systems in reptiles is highly complex and includes transitions between sex determination systems in closely related species and cryptic transitions (ZW system to new ZW system, XY system to new XY system). This approach also revealed the convergent evolution of sex chromosomes, in which ancestral autosomes suitable for the role of sex determination evolved into new sex chromosomes multiple times during reptile evolution. We discuss the mechanisms and rules underlying the evolution of the sex chromosomes and sex determination systems, such as the association of simple short repeat amplification with the heterochromatinization of sex-specific chromosomes and temperature-induced transition from GSD to TSD.

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Sea turtles can detect airborne and waterborne odors, but whether they recognize scents from the same species and if so, how they affect their behavior remains unknown. The present study evaluated the behavioral effects of odorants on juvenile green sea turtles (Chelonia mydas). The odorants were derived from Rathke glands (external scent glands) of mature male green sea turtles, and from two types of food. The activity of the juveniles increased when exposed to food scents, and significantly decreased compared with controls when exposed to scents from Rathke glands. These findings indicated that scents from the same species affect behavior, and that chemical communication via olfaction has important outcomes for sea turtles.

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In order to clarify whether the populations of Pelodiscus from the main islands of Japan are indigenous or artificially introduced, we constructed a mitochondrial phylogeny among samples from Japan and adjacent regions. The results strongly suggested the presence in Japan of various mitochondrial haplotypes that largely formed two divergent groups, one supposedly corresponding to P. sinensis (Wiegmann, 1834) sensu stricto and the other to P. maackii (Brandt, 1857). Haplotypes putatively associated with P maackii were unique to, and broadly prevailing in Japan. This may reflect indigenous nature of P. maackii in Japan, which would be more appropriately referred to as P. japonicus (Temminck and Schlegel, 1835). The others, putatively associated with P. sinensis, were fewer in Japan, and included those shared with individuals sold in a fish market of the continental China, suggesting the current Japanese P. sinensis to be exotic.

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Turtle fossils discovered from the putative Upper Pleistocene fissure-filling deposit on Tokunoshima Island of the Amami Group is described as a new species, Geoemyda amamiensis (Chelonii: Geoemydidae). These fossils include a carapace exclusive of peripherals and a few other elements, fragments of a neural, a costal, eight peripherals, an anterior half of the plastron, two epiplastra, and an incomplete right humerus. Geoemyda amamiensis most resembles G. japonica, an extant species endemic to three islands of the Okinawa Group, but is distinguished from the latter by the presence in dorsal view of a short anterior projection in the entoplastron. These two species seem to have split from each other through vicariance within the central Ryukyus.

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Skeletal remains of the geoemydid turtle, Mauremys mutica, were recovered from the lower layer of the Tugurubama archeological site on Yonagunijima Island, which corresponds to the period from the late middle to early late Holocene (ca., 4,000 yBP). These represent the first concrete evidence for the prehistoric occurrence of this turtle in the Yaeyama Islands and offer strong support for the indigenous nature of the current Yaeyama populations of M. mutica.

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An adult female Aldabra giant tortoise (Geochelone gigantea) was found dead with a 2 month-history of decreased appetite. At necropsy, multiple ulcers were seen in the mucosa of stomach and colon. Histopathologically, the ulcers were characterized by extensive necrosis, hemorrhage, and marked edema, along with numerous chlamidospores and aseptate fungal hyphae. Fungal structures infiltrated into the lamina propria, submucosa and muscle layer; their invasion into blood vessels formed thrombosis. Immunohistochemically, the fungal structures were strongly positive with an antibody against Candida spp. This case is the first report on gastrointestinal candidiasis in an Aldabra giant tortoise.

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