Paleontological Research, vol. 9, no. 3, pp. 243–253, September 30, 2005 6 by the Palaeontological Society of Japan A revision of Tetraconodon (Mammalia, Artiodactyla, Suidae) from the Miocene of Myanmar and description of a new species THAUNG-HTIKE1, TAKEHISA TSUBAMOTO1, MASANARU TAKAI1, MASAHITO NATORI2, NAOKO EGI3,MAUNG-MAUNG4, AND CHIT-SEIN5 1Primate Research Institute, Kyoto University, Inuyama, Aichi 484-8506, Japan (e-mail: [email protected]) 2Department of Biosphere-Geosphere System Science, Graduate School of Informatics, Okayama University of Science, Okayama 700-0005, Japan 3Laboratory of Physical Anthropology, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan 4Department of Geology, University of Mandalay, Mandalay, Myanmar 5Department of Geology, University of Yangon, Yangon, Myanmar Received October 28, 2004; Revised manuscript accepted July 19, 2005 Abstract. We describe five new dento-gnathic specimens of Tetraconodon, a genus of Miocene tetraco- nodontine suid (Mammalia, Artiodactyla), discovered in Myanmar (FBurma). In Myanmar, we recognized three distinct species of Tetraconodon (T. minor, T. intermedius and T. malensis sp. nov.) and one specifi- cally 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 sin- diensis, 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. Key words: Mammalia, Miocene, Myanmar, new species, Suidae, Tetraconodon Introduction The precise geologic ages of these localities have been unclear, but the occurrence of Tetraconodon suggests Tetraconodon Falconer, 1868 is one of the tetraco- a middle to late Miocene correlation for them (Made, nodontine suid (pig) genera that existed in the Mio- 1999; Pickford, 1988). cene of Indo-Pakistan and Myanmar (¼ Burma) (Pilgrim, 1910a, 1926, 1927; Colbert, 1935b; Pickford, Abbreviations 1988; Made, 1999). Among the tetraconodontine suids, Tetraconodon is characterized by its extremely en- 3a4 larged P /3a4 (Pilgrim, 1926; Made, 1999). In Myan- NMM ¼ National Museum, Yangon, Myanmar; mar, only one species, Tetraconodon minor,waspre- NMMP-KU-IR ¼ National Museum, Myanmar, viously reported from the basal part of the Irrawaddy Paleontology–Kyoto University–Irrawaddy (stored in Beds (Pilgrim, 1910a, 1927). the National Museum, Yangon); GSI ¼ Geological In this paper, we describe five new dento-gnathic Survey of India, Kolkata, India; GSP ¼ Geology specimens of Tetraconodon collected from several lo- Survey of Pakistan; AMNH ¼ American Museum calities in Myanmar, and establish a new species for of Natural History, BMNH ¼ British Museum of part of the collection. Four of the five specimens are Natural History, TF ¼ Thai Fossil; Kpg ¼ Gyatpyegyi housed in the National Museum of Myanmar, and one (¼ Kyatpyegyi) fossil locality (southwest of Male vil- was discovered by our recent paleontology expedition. lage, Sagaing Division, central Myanmar). 244 Thaung-Htike et al. Figure 1. Map of central Myanmar. Materials and methods yield Tetraconodon, to compare dental measurement ratios. All new fossil materials were collected in central Myanmar (Figure 1). They are now stored in the Na- Systematic paleontology tional Museum of Myanmar. Dental terminology and method of measurement Family Suidae Gray, 1821 are shown in Figure 2. We mainly follow Made (1996), Subfamily Tetraconodontinae Lydekker, 1876 Hu¨ nermann (1968), Wilkinson (1976) and Pickford (1986) for dental terminology, and Made (1996) for Diagnosis.—Small to gigantic Suidae with enlarged 3a4 1a2 dental measurement method. All measurements we P /3a4 and reduced P /1a2. Detail diagnosis was taking using digital calipers. Dental measurements of described in Pickford (1988). the new Tetraconodon specimens and other correlated tetraconodont specimens are shown in Table 1, 2 and Genus Tetraconodon Falconer, 1868 3. We choose the length of lower M1 for the diagnoses Type species.—Tetraconodon magnum Falconer, of Tetraconodon species because M1 have been con- 1868 (including Tetraconodon mirabilis Pilgrim, 1926). sidered to express less size variation from individual to Other included species.—Tetraconodon minor Pil- individual than other teeth, and mandibular fragments grim, 1910a; Tetraconodon intermedius Made, 1999; with lower cheek teeth are more recovered than max- Tetraconodon malensis sp. nov. illary fragments with upper cheek teeth in general. Diagnosis.—Differs from the other tetracono- 3a4 We used the mean dental measurements of Propo- dontine genera in having extremely enlarged P /3a4, 3 tamochoerus wui (Made and Han, 1994) (Lufeng, simple and relatively small M /3, and thick and highly 3a4 China), which is recovered from the upper Miocene wrinkled enamel in P /3a4, and less wrinkled enamel 1a3 deposits of the same East Asian regions that in M /1a3. Tetraconodon from Myanmar 245 Figure 2. Dental terminology and measuring method of tetraconodontine teeth. All are occlusal views of right cheek teeth. Abbre- viations: BL ¼ base line; L ¼ mesiodistal length; W ¼ buccolingual width; W1 ¼ first lobe width; W2 ¼ second lobe width; W3 ¼ third 3 lobe width of M /3. Table 1. Upperdentalmeasurements(mm)ofTetraconodon cf. intermedius (NMMP-KU-IR 0225) and T. intermedius (GSI B 675) and mean measurements of Propotamochoerus wui (Made and Han, 1994). Abbreviations: L ¼ mesiodistal length; W ¼ buccolingual width; W1 ¼ first lobe width; W2 ¼ second lobe width; W3 ¼ third lobe width of M3;*¼ estimate. P3 P4 M1 M2 M3 Taxa Specimen L W L W L W1 W2 L W1 W2 L W1 W2 W3 T. cf. intermedius NMMP-KU-IR 0225 33.4 34.1 24.4 37.2 26.7 27.7 25.2 30.6 32.6 29.1 33.3 26.8 22.9 12.1 T. intermedius GSI B 675 46.5 41.4 37.4 49.4 26* 27.5 31.1 35.8* 43* 32* P. wui Made & Han (1994) mean 7–28 spec. 10.8 10.1 9.7 12.1 13.6 12.1 12.3 17.2 15.9 15.6 24.1 17.4 14.9 8 Tetraconodon minor Pilgrim, 1910a Type locality.—Yenangyaung, central Myanmar Figure 3 (Pilgrim, 1910a). Tetraconodon minor Pilgrim, 1910a, p. 67; Pilgrim, 1910b, p. 202; Type horizon and age.—LowermostpartoftheIr- Pilgrim, 1926 (in part), p. 17–19, pl. 2, fig. 12; Pilgrim, 1927, rawaddy Formation (¼ Irrawaddy Beds) (Aung-Khin p. 160–163, pl. 14, fig. 1; Matthew, 1929, p. 459; Colbert, 1935b, and Kyaw-Win, 1969), Nagri Formation (Siwalik p. 230; Colbert, 1938, p. 408. Group) equivalent, early late Miocene (Pilgrim, Sivachoerus giganteus, Falconer and Cautley. Pilgrim, 1926, p. 21, 1910a; Colbert, 1938; Made, 1999). pl. 3, fig. 2. New material.—NMM AN-1, a right mandibular Lectotype.—GSI B677, a left mandibular fragment fragment with P4-M2 (the meaning of ‘‘AN’’ is un- with P3a4. known); NMMP-KU-IR 0107, a left P3. 246 Thaung-Htike et al. Table 2. P4 and M1 measurements (mm) of the Tetraconodon and Asian Conohyus which are used in Figure 8 A. Tooth measurements for the Indian and Thai specimens are taken from Colbert (1935), Pickford (1988), Ducrocq et al. (1997) and Pickford and Gupta (2001). Ab- breviations: L ¼ mesiodistal length; W ¼ greatest buccolingual width. P4 M1 Taxa Specimen L W L W C. indicus GSI B 710 16.6 11.8 16.6 12.6 C. indicus Pickford & Gupta (2001) 17.2 15.7 17.3 13.0 C. thailandicus TF 2577 19.5 15.8 14.5 13.3 C. sindiense GSP 12587 17.0 16.0 15.0 13.5 C. sindiense GSI B 773 16.0 13.0 15.3 12.0 C. sindiense GSI B 537 14.4 14.4 13.4 11.5 C. sindiense AMNH 19386 16.0 15.0 14.0 12.5 C. sindiense BMNH M 12757 14.4 14.9 13.6 11.5 T. magnus GSI B 71 53.4 56.4 31.1 28.7 T. intermedius NMM 839/80 37.7 37.4 26.5 25.8 T. minor GSI B 771 34.6 31.1 24.0 20.4 T. minor NMM AN-1 30.8 29.3 23.3 22.0 T. malensis NMM KPG-1 18.2 16.5 13.9 12.2 Table 3. Lower dental measurements (mm) of the new Tetraconodon specimens and mean measurements of Propotamochoerus wui (Made and Han, 1994). Abbreviations: L ¼ mesiodistal length; W1 ¼ first lobe width; W2 ¼ second lobe width; W3 ¼ third lobe width of M3; * ¼ estimate. P3 P4 M1 M2 M3 Taxa Specimen L W1 W2 L W1 W2 L W1 W2 L W1 W2 L W1 W2 W3 T. intermedius NMM 839/80 37.7 29.2 37.4 26.5 25.8 25.1 31.6 30.4 28.8 43.8 28.0 24.7 18.7 T. minor NMMP-KU-IR 0107 37.3 25.0* 27.0* T. minor NMM AN-1 30.8 24.8 29.3 23.3 22.0 20.1 26.3 24.4 22.3 T. malensis NMM Kpg-1 18.2 14.9 16.5 13.9 12.2 12.0 16.7 14.2 12.7 20.1 12.5 10.3 8.5 P. wui mean 13–28 spec. 13.1 5.9 6.5 12.6 7.9 8.7 13.3 9.3 9.8 17.1 12.6 13.2 25.9 14.0 12.9 9.7 (Made & Han, 1994) Figure 3. Tetraconodon minor Pilgrim. A–B, NMM AN-1, a right mandibular fragment with P4-M2: A, occlusal view; B, lingual view.