We describe fossil dental specimens of a chalicothere (Perissodactyla, Mammalia) and Dorcabune (Tragulidae, Artiodactyla, Mammalia) discovered from the upper part (lower Pleistocene) of the Irrawaddy Formation at Gwebin area, central Myanmar. The specimens described here consist of three molar fossils: a left upper molar and a left M, or M 2 of a chalicothere (cf. Nestoritherium sp.); and a right M3 of Dorcabune sp. Although fragmentally, this is the first discovery of the Chalicotheriidae and Dorcabune from the upper part of the Irrawaddy Formation

Chit-Sein,

Egi, Naoko

Maung-Maung,

Takai, Masanaru

Thaung-Htike

Tsubamoto, Takehisa

Zin-Maung-Maung-Thein

Kyoto University Research Information Repository

Title Discovery of chalicothere and Dorcabune from the upper part(lower Pleistocene) of the Irrawaddy Formation, MyanmarAuthor(s)Tsubamoto, Takehisa; Zin-Maung-Maung-Thein; Thaung-Htike; Egi, Naoko; Chit-Sein,; Maung-Maung,; Takai,MasanaruCitationAsian paleoprimatology (2006), 4: 137-142Issue Date2006URL http://hdl.handle.net/2433/199766RightType Departmental Bulletin PaperTextversionpublisherKyoto University                                             Asian  Paleoprimatology, vol. 4:137-142 (2006)                                                     Kyoto University Primate Research Institute   Discovery of chalicothere and Dorcabune from the upper part     (lower Pleistocene) of the Irrawaddy Formation, Myanmar         Takehisa  Tsubamotol, Zin-Maung-Maung-Thein2, Thaung-Htike2, Naoko Egi2,                    Chit-Sein3, Maung-Maung4, and Masanaru Takai2       'Center for Paleobiological Research, Hayashibara Biochemical Laboratories, Inc.,        Shimoishii, Okayama 700-0907, Japan  'Primate Research Institute, Kyoto University, Inuyama, Aichi 484-8506, Japan       3Department of Geology, University of Yangon, Yangon, Myanmar       4Department of Geology, University of Mandalay, Mandalay, Myanmar                            Abstract          We describe fossil dental specimensof a chalicothere (Perissodactyla, Mammalia)      and Dorcabune (Tragulidae, Artiodactyla, Mammalia) discovered from the upper part      (lower Pleistocene) of the Irrawaddy Formation at Gwebin area, central Myanmar.The      specimens described here consist of three molar fossils: a left upper molar and a left  M, or      M 2 of a chalicothere (cf. Nestoritherium sp.); and a right  M3 of Dorcabune sp. Although      fragmentally, this is the first discovery of the Chalicotheriidae nd Dorcabune from the      upper part of the Irrawaddy Formation.                            Introduction    The upper Miocene to lower Pleistocene Irrawaddy Formation (= Irrawaddy Group = Irrawaddy Series = Fossil Wood Group) is widely distributed in central Myanmar (Theobald, 1869; Noetling, 1895; Stamp, 1922; Bender, 1983), yielding many mammalian fossils (Colbert, 1938, 1943; Moe Nyunt, 1987). We, the Kyoto University field parties with Myanmar researchers, carried out a fossil expedition at the Gwebin area of central Myanmar, where the upper part of the Irrawaddy Formation is exposed (Bender, 1983; Moe Nyunt, 1987) during the field season of 2002 November. At the Gwebin area, we found fossil dental remains of the Chalicotheriidae (Perissodactyla, Mammalia) and Dorcabune (Tragulidae, Artiodactyla, Mammalia).    In this short article, we describe these fossils. Although fragmentally, this is the first discovery of the Chalicotheriidae and Dorcabune from the upper part of the Irrawaddy Formation (Colbert, 1938, 1943; Moe Nyunt, 1987).                          137                                  Tsubamoto et al.  2  1'  1  5'  N  I  Myitche             rn                                             7t,  Eagan                                                           4-  Gonkor                                                          Nakyo-Aing                                      A                Kyundaw  2  I  COO'N Gwebin 2 N—                     CCHINA              INDIA  Gbnl • Lanywa  Milaungbya        k                   (c3   ,SinQu                r  _FMandalay                                  Seikpyu                                               Chauk          MYANMAR  Yangon                                  Ta-Nyaung                           THAILAND                                      Sale                Andaman Seel       0 500    kmci2                                                    rrl              1  20'45' N             Fossil locality  • City/Town/Village Main road Main river  Figure 1. Map of the central part of Myanmar, showing the fossil ocality (Gbnl) of the upper part of the   Irrawaddy Formation.                          Abbreviations    NMMP-KU-IR, National Museum - Myanmar - Paleontology - Kyoto University  -Irrawaddy (stored in the National Museum, Yangon, Myanmar, and in the Department of Geology, University of Yangon, Yangon, Myanmar).                          Fossil locality   The Gbnl locality (an approximate GPS =  20°58'31"N; 94°41'27"E), which is located at the west side of the main road of Gwebin village, Seikpyu Township, Magway Division, central Myanmar (Figure 1).                       Stratigraphic position    The upper part of the Irrawaddy Formation, geologically located in the Central Irrawaddy Lowland (Ba Than Haq, 1981; Bender, 1983). The upper part of the Irrawaddy                           138                      Chalicothere and Dorcabune from Myanmar  .protoconid  mela   metastylid  cristid  obliqua  hypoconid  entoconid  1 IA                                                                        ectoloph                      --,1:---.--_, ,v4f;.„:,                                      - .               , . .. .k.     14;11.4,tiL ' -                                                             ,                c . - • , 247 --SA, tr.'                   ... eNi ,:i* -. 10C. ''' • ' -.. ' ' f.;:: t -AK 3k . - ' '‘i`. - '              .        ,',1i:.'1.' .,$'S  V4 B 10 mm in                                                                                  Np_                                                         paraconeprotocone  Figure 2. Cf. Nestoritherium sp. A: NMMP-KU-IR 0051, afragmentary leftM1  or  2,  occlusal view (stereo pair).   B: NMMP-KU-IR 0053, afragmentary leftupper molar,  occlusal view (stereo pair). Formation at Gwebin area consists mainly of fluvial deposits, yielding many mammalian fossils such as bovids, suids, hippos, anthracotheres, rhinos, and elephants (Moe Nyunt, 1987).                          Geologic age    Early Pleistocene, according to the mammalian fauna of the upper part of the Irrawaddy Formation at Gwebin area (Colbert, 1943; Moe Nyunt, 1987).                          Systematic paleontology                       Order PerissodactylaOwen, 1848                      Family Chalicotheriidae Gill, 1872                    Subfamily Chalicotheriinae Gill, 1872                      Genus cf. Nestoritherium Kaup, 1859                             Cf. Nestoritherium sp.                               Figure 2  Material.  —NMMP-KU-IR 0051, a fragmentary left  M1 or  2; NMMP-KU-IR 0053, a fragmentary left upper molar.    Dental  measurements.  —M1  or  M  2 (NMMP-KU-IR 0051): length (estimate) = 30.8  mm; trigonid width = 20.8 mm; talonid width (estimate) = 20.2 mm.                          139                                  Tsubamoto et al.  —  premetacristid • -__.,.         4o'  preprotocristid  meiaconid  protocon  id entoconid     t:' hypoconid  10  mm  hypoconulid                    A                              B                                                                                                                       •                    Ae   Figure 3. Dorcabunesp. (NMMP-KU-IR 0055, a right M3). A: occlusal view (stereo pair). B: buccal view. C:   lingual view.    Description and  comments.  —NMMP-KU-IR 0051 (Figure 2A) is referable to a fragmentary left lower molar of a chalicothere in having brachyodont crown, a metastylid, a cristid obliqua linking to the metastylid, and no hypoconulid. NMMP-KU-IR 0053 (Figure 2B) is referable to a fragmentary left upper molar of a chalicothere in having W-shaped ectoloph and in being relatively large. These materials are provisionally referred to Nestoritherium because the present materials are very poor and because Nestoritherium is the only recorded Pleistocene chalicotheriid in Asia. This is the first discovery of the Chalicotheriidae in the upper part of the Irrawaddy Formation, although a possible chalicotheriid femur have been found in the lower part of the Irrawaddy Formation (Noetling, 1897a, b; Hooijer, 1951).                        Order Artiodactyla Owen, 1848                       Suborder Ruminantia Scopoli, 1777                    Family Tragulidae Milne-Edwards,1864                       Genus Dorcabune Pilgrim, 1910                                   Dorcabune sp.                               Figure 3 Material.  —NMMP-KU-IR 0055, a right M3.    Dental  measurements.—M3 (NMMP-KU-IR 0055): length = 25.4 mm; trigonid width = 12.6 mm; talonid width = 11.9 mm.    Description and  comments.  —NMMP-KU-IR 0055 shows a typical morphology of tragulid M3 with Dorcatherium-fold  (= "sigma structure" in Qiu and Gu, 1991;  =  "M                          140                      Chalicothere and Dorcabune from Myanmar  structure" in  Mottl, 1954, 1961) and enlarged hypoconulid. The present M3 is low-crowned, rather bunodont than selenodont among the tragulids, and moderately worn. The metaconid is mesiodistally located nearly at the same position as the protoconid. The preprotocristid and premetacristid do not protrude mesially very much; and they are connected to one another, forming  mesially closed trigonid basin. The entoconid is  mesial to hypoconid. There seems to be no hypoconulid loop. There is no cristid linking the entoconid to the hypoconulid. Cingula are present at the mesial margin of the crown and at the lingual base of the hypoconulid. There are accessory cusps between the lingual base of the protoconid and hypoconid and between the lingual base of the hypoconid and hypoconulid. The dental size (M3 length = 25.4 mm) is rather similar to that of larger Dorcabune and Dorcatherium species rather than to that of smaller species (Colbert, 1935).    The present M3 is referable to Dorcabune rather than to Dorcatherium because: (1) the cusps of the present M3 seem to be more bunodont than those in Dorcatherium; (2) the preprotocristid and premetacristid of the present M3 are not so mesially protrudent as those in Dorcatherium; and (3) the present M3 has distinct lingual and buccal cingulids on the hypoconulid region (Pilgrim, 1915:  pls. 21-23; Colbert, 1935: p. 303, fig. 137, p. 308, fig. 140, p. 310, fig. 142, p. 312, fig. 144; Qiu and Gu, 1991). This is the first discovery of Dorcabune in Myanmar and is the first discovery of the Tragulidae from the Irrawaddy Formation.                         Acknowledgments    We are grateful to the personnel of the Ministry of Culture of Myanmar and the Myanmar Embassy in Japan for the permission of our fossil research. We are also grateful to the personnel of the Myanmar-Japan (Kyoto University) Joint Fossil Expedition Team and to the curators of the National Museum of Myanmar for their guidance and help in the field and museum. Thanks are also to Prof. Nobuo Shigehara (Kyoto University, Japan) for his financial support. Researchers from several Myanmar and Japanese universities have been helped us with paleontological and geological information on the Irrawaddy Formation, particularly Drs. Aye Ko Aung, Tin  Thein, Soe Thura Tun, Aung Naing Soe, Hisashi Suzuki, Hiroaki Ugai, and Takeshi Nishimura. Financial supports were provided by the MEXT Overseas Scientific Research Fund (09041161, 14405019, 16405018) and by the MEXT Grant-in-Aid for the COE Research (10CE2005), for the 21st Century COE Program  (A14 to Kyoto University), and for the JSPS Fellows (15004836, 15004748).                               References Ba Than Haq (1981)  Metallogenic provinces and prospects of mineral exploration in Burma.   Contributions toBurmese Geology 1:1-16, fig.1-5. Bender, F. (1983) Geology of Burma.  Gebriider Borntraeger: Berlin. viii+293pp. Colbert, E.H. (1935) Siwalik mammals in the American Museum of Natural History. Transactions of the   American Philosophical Society (new series) 26:1-401.                          141                                   Tsubamoto etal. Colbert, E.H. (1938) Fossil mammals from Burma in the American Museum of Natural History. Bulletin  of  the American Museum  of  Natural History 74:255-436. Colbert, E.H. 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Discovery of chalicothere and Dorcabune from the upper part (lower Pleistocene) of the Irrawaddy Formation, Myanmar

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Discovery of chalicothere and Dorcabune from the upper part (lower Pleistocene) of the Irrawaddy Formation, Myanmar

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