thaung htike

We present a model for the petrogenesis of magma with adakitic affinity in an old subduction zone, which does not involve slab melting and is constrained by new geochronological and geochemical data for Mt. Popa, the largest of three Quaternary volcanoes in central Myanmar (Popa, Monywa and Singu). The edifice is composed of Popa Plateau (0.8–0.6 Ma) with high-K rocks and a stratovolcano ( 40). The distinct K contents indicate that the adakitic magmas cannot be derived from Popa high-K rocks, but they share trace-element signatures and Sr–Nd isotope ratios with medium-K basalts from Monywa volcano. Our estimation of water contents in Popa magma reveals that primary magma for medium-K basalts was generated by partial melting of wedge mantle with normal potential temperature (TP 1330–1340 °C) under wet conditions (H2O 0.25–0.54 wt%). Its melting was probably induced by asthenospheric upwelling that is recognized by tomographic images. Mafic adakitic magma (Mg# ~ 63, Sr/Y ~ 64) was der...

FIGURE 4. SEM images of ostracodes and benthic foraminifer from sample 69-1. The arrows point anteriorly. A–I, Bicornucythere concentrica Yamaguchi sp. nov. (A–D), UMUT-CA31128, holotype, carapace, left external view (A), right external view (B), dorsal view (C), and anterior view (D). E–H, UMUT-CA31129, paratype, right valve, external view (E), internal view (F), dorsal view (G), and hingement (H). I, UMUT-CA31131, paratype, carapace, left external view. J, Trachyleberididae gen. et sp. indet.1, right external view of carapace. K, Buntoninae gen. et sp. indet., left external view of carapace. L, Cytheromorpha? sp., right valve, external view. M–O, Ammonia subgranulosa (Jacob and Sastri, 1950), spiral view (K), umbilical view (L), and apertural view (M). Scale bars =100 µm.

FIGURE 5. Measurements of Bicornucythere bisanensis and Bicornucythere concentrica sp. nov. A, SEM images of B. bisanensis in the A, A-1, and A-2 stages. Scale bars = 100 µm. B, Measurements used in the study: valve length (L), valve height (H), and width of marginal infold (WM). Scale bar = 100 µm. C, The 95% confidence intervals of L, H, and WM/L of B. bisanensis and B. concentrica sp. nov. The bars in the A and A-1 stages indicate 95% confidence intervals of the measurements, while the bars in the A-2 stage indicate ranges of the measurements. The open diamonds indicate mean values. The horizontal dotted lines indicate the WM/L ratios of B. concentrica sp. nov. "n" indicates the number of measurements. The measurements and detailed information about B. bisanensis specimens are given in the Appendix.

In this work, the dental morphology the Neogene fossil Suidae of central Myanmar are analyzed, and the paleoecological evolution of the Neogene fossil suids are discussed. Morphological evolution of the third molar in suids has been considered an adaptation to more abrasive diet, i.e. from a browsing to grazing diets. In Myanmar, three distinct types of diet, predominant frugivore (Middle to Late Miocene) , frugivore to hyperbrowser or folivore (Late Miocene to Early Pliocene) and predominant folivore (Middle Pliocene to Early Pleistocene), have been distinguished in the dental characteristics of suid fossils. The pattern of faunal transition in Neogene suids strongly suggests a critical floral change at the Late Miocene in Myanmar. The coexisted appearance of Propotamochoerus with Sivachoerus suggesting that the C3-C4 floral transition accompanying the last faunal turnover may have occurred to bring wide spreading of C4 plants in the Early Pliocene of Myanmar, later than that in La...

We redescribe an extinct river shark, Glyphis pagoda (Noetling), on the basis of 20 teeth newly collected from three different Miocene localities in Myanmar. One locality is a nearshore marine deposit (Obogon Formation) whereas the other two localities represent terrestrial freshwater deposits (Irrawaddy sediments), suggesting that G. pagoda from the Irrawaddy sediments was capable of tolerating low salinity like the extant Glyphis. Glyphis pagoda likely reached up to at least 185 cm in total body length and was probably piscivorous. The fossil species occurs in rocks of Myanmar and eastern and western India and stratigraphically ranges at least from the Lower Miocene (Aquitanian) to the lower Upper Miocene (mid-Tortonian). It has been classified under at least eight other genera to date, along with numerous taxonomic synonyms largely stemming from the lack of understanding of the heterodonty in extant Glyphis in the original description. Our literature review suggests that known Miocene shark faunas, particularly those in India, are manifested with unreliable taxonomic identifications and outdated classifications that warrant the need for a comprehensive taxonomic review in order to evaluate the evolutionary history and diversity pattern of Miocene shark faunas. The genus Glyphis has a roughly 23-million-year-long history, and its success may be related to the evolution of its low salinity tolerance. While extant Glyphis spp. are considered to be particularly vulnerable to habitat degradation and overfishing, the fossil record of G. pagoda provides renewed perspective on the natural history of the genus that can be taken into further consideration for conservation biology of the extant forms.

Cenozoic sediments of Japanese Islands are yielding diversified terrestrial turtles from the Early Eocene to Late Pleistocene. Middle Miocene of Southwestern Japan, Pliocene Tsubusagawa Formation of Oita Prefecture, Pleistocene of Ryukyu Islands, and Pleistocene fissure deposits of Honshu Island are especially important localities. They are all cryptodires, including Geoemydidae, Testudinidae, Trionychidae, and Platysternidae. Ocadia nipponicais a large geoemydid (33 cm long shell), based on a nearly complete skeleton from the Middle Pleistocene Kiyokawa Formation of Chiba Prefecture. Same taxon has been found from the Pleistocene deposits of Nagasaki, Hyogo, Osaka, Shiga, Shizuoka, and Kanagawa Prefectures. Smaller geoemydids are represented by Mauremys yabei and Cuora miyatai from the Pleistocene fissure deposits of Tochigi Prefecture. Additional materials of M. yabei have been collected from the Pleistocene of Chiba, Kanagawa, Shizuoka, Nagasaki Prefectures, and the Miyako Group ...

In this study, we report the additional dental specimens of Tetraconodon malensis (Artiodactyla, Suidae) discovered near Nwegwe Village, Chaung-U Township, Sagaing Division, central Myanmar. The well preserved maxillary and mandibular fragments of T. malensis, firstly recorded from the basal part of the Khabo Formation (Middle Miocene) provide new dental characteristics of this species: large P3 with salient buccal and lingual walls; longer and wider P3 relative to P4; extremely large P and P; longer but not wider P relative to P; minute M with indistinct talon; well developed buccal cingulum in upper molars. The additional dental characteristics of T. malensis elucidates the taxonomic status of this species among tetraconodont suids, suggesting that T. malensis may have originated in Myanmar and was derived from Conohyus sindiensis of Indian Subcontinent during the Early Miocene.

In this study, anthracotheres from the Middle Miocene of Sagaing Region, Upper Myanmar are re-investigated and newly discovered dental specimens are described. In Myanmar, two Middle Miocene localities are well known for anthracotheres, Male and Thanbinkan localities, Sagaing Region. Four species of anthracotheres (Microbunodon silistrensis, two definite bothriodont anthracotheres and cf. Anthracotherium ingens) are recognized. Most of these are forestdwelling brachyodont and bunodont species suggesting that their habitats were not open land (savanna) but forest environment with relatively humid, thick forests and large rivers, located not so far from the sea shore.

Background. The genus Megalochelys is the largest known testudinid (family Testudnidae) found from the upper Miocene to lower Pleistocene of India to Indonesian Islands. The maximum length of the shell in this genus has been estimated as up to about 2 m long based on a specimen from the lower Pleistocene of Java Island, Indonesia. Recently, joint paleontological expeditions of Japan and Myanmar led by M. Takai have unearthed abundant fossils of this genus from the Neogene since 2003. These materials shed new light on this unique gigantic tortoise. Methods. All materials of Megalochelys were found from the Lower Irrawaddy Beds in poor preservation except for one nearly complete shell. The shell lengths from the fragmentary materials were estimated by using those of medium to large–sized testudinids. Results. Postcranial materials, including twenty-five epiplastra, one cervical vertebra, appendicular skeletons, and one nearly complete shell (about 180 cm long) have been discovered fro...

1 Department of Geology, University of Mandalay, Mandalay, Myanmar 2 Department of Biosphere-Geosphere System Science, Graduate School of Informatics, Okayama University of Science, Okayama, Japan 3 Primate Research institute, Kyoto University, Inuyama, ...