nan Thaung-Htike

A revision of Tetraconodon (Mammalia, Artiodactyla, Suidae) from the Miocene of Myanmar and description of a new species

ABSTRACT We describe five new dentognathic specimens of Tetraconodon, a genus of Miocene tetraconodontine suid (Mammalia, Artiodactyla), discovered in Myanmar (= Burma). In Myanmar, we recognized three distinct species of Tetraconodon (T. minor, T. intermedius and T. malensis sp. nov.) and one specifically undetermined specimen, which is here named Tetraconodon sp. cf. T. intermedius. The new species, T. malensis, has characteristics of Tetraconodon, such as extremely enlarged P4 and simple and relatively small M3. It is distinct from the other Tetraconodon species in being much smaller, suggesting that it is the most primitive known Tetraconodon species. The dental size and characteristics of T. malensis suggest that Tetraconodon was derived during the late middle Miocene from the early middle Miocene Conohyus sindiensis, which was discovered in the Siwalik Group of Indo-Pakistan and Nepal and has also been found in the middle Miocene deposits of Thailand, or a close relative. The discovery of the most primitive form in Myanmar suggests that Tetraconodon may have originated in Myanmar.

New Data on the Neogene Anthracotheres (Mammalia, Artiodactyla) from Central Myanmar

ABSTRACT Gnatho-dental specimens of the anthracotheres (Mammalia; Artiodactyla) from the four Neogene localities of central Myanmar are described. Four species of anthracotheres are recognized in the Neogene of central Myanmar: Microbunodon silistrensis and a small bothriodontine from the middle Miocene; and Microbunodon milaensis and Merycopotamus dissimilis from the latest Miocene to Pliocene. This discovery extends the temporal range of Microbunodon up to the Pliocene. The co-occurrence of forest-dwelling Microbunodon and grass-eating and semi-aquatic Me. dissimilis reinforces that central Myanmar was less arid and had a wider range of habitats than the northern Indian Subcontinent during the Pliocene. This implies the possibility that Pliocene Southeast Asia might have been a refugium for some late Miocene forest-dwelling ungulates.

New Hystrix (Mammalia, Rodentia) from the late Miocene/early Pliocene of Myanmar

YUICHIRO NISHIOKA,*,1 ZIN-MAUNG-MAUNG-THEIN,2 NAOKO EGI,1 TAKEHISA TSUBAMOTO,3 TAKESHI NISHIMURA,1 TSUYOSHI ITO,1 THAUNG-HTIKE,4 and MASANARU TAKAI1; 1Primate Research Institute, Kyoto University, Inuyama 484-8506, Japan, nishioka@pri.kyoto-u.ac.jp; 2Mandalay University, 73rd Road, Mandalay, Myanmar; 3Center for Paleobiological Research, Hayashibara Biochemical Laboratories, Inc, Okayama 700-0907, Japan; 4Shwebo Degree College, Shwebo, Myanmar

A New Genus and Species of Bunodont Artiodactyl from the Eocene Pondaung Formation, Myanmar

Abstract A new genus and species of small bunodont artiodactyl (Mammalia), Myanmarius chitseini, is established on the basis of molar specimens from the upper middle Eocene Pondaung Formation, Myanmar. The specimens consist of upper molars and one m3. The m3 is provisionally referred to this species. Myanmarius is characterized by a low crown, bunodont cusps, a wide crushing trigon basin, a large metaconule, a reduced paraconule, a protocone distinctly larger than the other main cusps, an obtuse angled and inverted V-shaped centrocrista, a mesiodistally oriented postprotocrista and premetacristule, a buccally shifted and almost mesiodistally oriented cristid obliqua, no hypocone, no styles, and no lingual separation into two (mesial and distal) lobes of the upper molars. Our cladistic analysis supports the raoellid affinity of Myanmarius, which is nested with Khirtharia. However, if the m3 is excluded from the hypodigm of Myanmarius, the cladistic analysis rather supports the suoid affinity of Myanmarius. Therefore, the phyletic position of Myanmarius is still unclear.

New species of large Tetraconodon (Mammalia, Artiodactyla, Suidae) from the late Miocene of Myanmar

ABSTRACT We describe two new species of Tetraconodon, T. irramagnus sp. nov. and T. irramedius sp. nov., from the late Miocene of Myanmar recognized when reevaluating large Tetraconodon specimens. Tetraconodon had also been recovered from the late Miocene Siwalik sediments of India/Pakistan. However, in the Siwalik specimens, the dimensions of the last two premolars and the third molar with respect to those of the first molar are distinctly greater than those of the Myanmar specimens. In Myanmar species, the relative dental sizes are similar, and the most obvious interspecies distinctions are their dental size differences. Considering the variation in the relative sizes of the last two premolars and third molar with respect to the first molar among the Siwalik and Myanmar Tetraconodon, the enlargement of the last two premolars and the third molar could be regarded as a characteristic of the interspecies distinction.

Late Pliocene Semnopithecus fossils from central Myanmar: rethinking of the evolutionary history of cercopithecid monkeys in Southeast Asia

We here describe a new fossil species of Asian colobine monkey, Semnopithecus gwebinensissp. nov. from the Late Pliocene Irrawaddy sediments of the Gwebin area in central Myanmar. Extant Semnopithecus (Hanuman langur) is a relatively large, terrestrial colobine monkey known as one of the most adaptable non-human primates. It is widely distributed, mainly in the Indian subcontinent, from Pakistan in the west to Bangladesh in the east. However, in Myanmar Semnopithecus is not distributed but Trachypihtecus is, which is the closest relative to Semnopithecus. It is presumed that extant Trachypithecus pileatus, which is considered to be a hybrid of Semnopithecus and Trachypithecus from molecular biological studies, appeared in the Early Pleistocene as the result of hybridisation between the two genera. On the other hand, no fossil specimens of other cercopithecid monkeys, such as Macaca, Trachypithecus or Rhinopithecus, all of which are commonly discovered from the Pleistocene cave sediments of South China, have been found from the Pliocene sediments in central Myanmar to date. The dissimilarity in the primate fauna between central Myanmar and South China suggests little faunal interchange between the two regions probably because of geographical barriers such as large rivers and high mountain ranges in the area.

First discovery of colobine fossils from the Late Miocene/Early Pliocene in central Myanmar.

Here we report two kinds of colobine fossils discovered from the latest Miocene/Early Pliocene Irrawaddy sediments of the Chaingzauk area, central Myanmar. A left mandibular corpus fragment preserving M1-3 is named as a new genus and species, Myanmarcolobus yawensis. Isolated upper (M(1)?) and lower (M2) molars are tentatively identified as Colobinae gen. et sp. indet. Although both forms are medium-sized colobines, they are quite different from each other in M2 morphology. The isolated teeth of the latter show typical colobine-type features, so it is difficult to identify their taxonomic position, whereas lower molars of Myanmarcolobus have unique features, such as a trapezoid-shaped long median lingual notch, a deeply concave median buccal cleft, a strongly developed mesiobuccal notch, and rather obliquely running transverse lophids. Compared with fossil and living Eurasian colobine genera, Myanmarcolobus is most similar in lower molar morphology to the Pliocene Dolichopithecus of Europe rather than to any Asian forms. In Dolichopithecus, however, the tooth size is much larger and the median lingual notch is mesiodistally much shorter than that of Myanmarcolobus. The discovery of Myanmarcolobus in central Myanmar is the oldest fossil record in Southeast Asia not only of colobine but also of cercopithecid monkeys and raises many questions regarding the evolutionary history of Asian colobine monkeys.

Chapter 9 Review of the investigation of primate fossils in Myanmar

Since the discovery of fossil primates in the early twentieth century, the later Eocene Pondaung Formation in central Myanmar has attracted the attention from many palaeoprimatologists (Fig. 9.1). There were two large-bodied primates, Pondaungia cotteri and Amphipithecus mogaungensis (Fig. 9.2), known from two localities (Pangan and Mogaung) in the Pondaung area (Fig. 9.3), and many researchers have argued over the phylogenetic position of these two monkeys, that is, whether or not the Pondaung primates are anthropoids, higher primates which includes the clades of New and Old World monkeys, apes and humans. However, due to the scarcity of the fossil specimens, the controversy concerning the phylogenetic position of the Pondaung primates was not resolved until the 1970s. Some authorities believed they are primitive anthropoids, while others regarded them as adapiforms or non-primate, such as condylarthrans (Pilgrim 1927; Colbert 1937; von Koenigswald 1965; Szalay 1970; Simons 1971; Szalay & Delson 1979). Another problem confusing the taxonomy of the Pondaung primates is whether these two animals belong to the same taxonomic group or not. For example, Szalay & Delson (1979) discussed the Pondaung primates, allocating Amphipithecus to the adapiforms and Pondaungia to the early catarrhines. At that time, only a mandibular fragment preserving P3–M1 for Amphipithecus (Fig. 9.2d) had been found, while a mandibular but also a maxillary fragment preserving M1–2 had been discovered for Pondaungia (Fig. 9.2a). The upper molars of Pondaungia likely retained the ‘true hypocone’ which has been considered the definitive feature of anthropoid primates, but there was no information on the upper molars for Amphipithecus . Fig. 9.1. Geological map of central Myanmar showing primate fossil localities. Pondaung Formation: BHN, Bahin; MGN, Mogaung. Irrawaddy Sediments: YSK, Yinseik; GBN, Gwebin; CHZ, Chaingzauk (including Myokhinthar). (Modified after Geological Map of Myanmar, Myanmar …

Body mass estimation from the talus in primates and its application to the Pondaung fossil amphipithecid primates

The relationship between talar size and body mass in extant primates is examined to provide the regression equations for estimating the body mass of extinct primate species based on the talar size. The results indicate that, among the linear talar dimensions, the whole talar size and the tibial trochlear size are good body mass estimators for primates. As an example, the regression equations presented here were applied to the body mass estimates of the fossil tali (NMMP-39 and NMMP-82) of the amphipithecid primates from the middle Eocene Pondaung Formation of Myanmar. Based on the estimated body masses determined by this study, NMMP-39 (estimated body mass: ca. 2.7 kg) should likely be assigned to Ganlea megacanina or Myanmarpithecus yarshensis, while NMMP-82 (estimated body mass: ca. 4.9 kg) should likely be assigned to ‘Amphipithecus’ mogaungensis or Pondaungia cotteri.