Duangkrayom et al.—The first Neogene record of Zygolophodon in Thailand
(Chavasseau et al., 2009). Then, the Chiang Muan coal mine (12.4–12.2 Ma), Prayao Province, has produced Tetralophodon cf. xiaolongtanensis (Thasod, 2007; Chavasseau et al., 2009). The recognition of G. cf. browni in northern Thailand implies a degree of biogeographic affinity with Pakistan, whereas the presence of Tetralophodon cf. xiaolongtanensis in Chiang Muan is a clear link with the fauna of South China. The most widespread taxa in the middle Miocene of Pakistan are the mammutid Zygolophodon metachinjiensis, the amebelodont Protanancus chinjiensis, the choerolophodont Choerolophodon corrugatus and the
gomphothere Gomphotherium browni (Tassy, 1983a, 1983b, fig. 7). The first three taxa have apparently not been recorded from the middle Miocene of Thailand, which points to obvious faunal dissimilarities between Thailand and Pakistan (Chavasseau et al., 2009). The middle Miocene localities of North China have yielded a very different fauna dominated by Zygolophodon, the amebelodont Platybelodon, and supposedly endemic Gomphotherium species (Tobien et al., 1986; Tobien et al., 1988, fig. 7). Thus, the new Zygolophodon specimens in Tha Chang sand pit might indicate a dispersal link between South and East Asian middle and late Miocene proboscideans. The late Miocene paleoenvironmental record from the Tha
Chang sand pits indicates a transition from woodland- dominated to grassland-dominated landscapes (Sepulchre et al., 2010). These results can be correlated to a long-term climatic change that occurred between 8.5 and 6 Ma, leading to a major environmental change with C4 savannas replacing C3 forests and woodlands (Cerling et al., 1994; Sepulchre et al., 2010). However, the late late Miocene new rhino species, Aceratherium porpani, from the same sand pit as the Zygolophodon materials, is consistent in its chronological implications with the faunal sample from Tha Chang sand pit no. 8, which includes such taxa as Khoratpithecus piriyai and Merycopotamus thachangensis (Chaimanee et al., 2004, 2006; Hanta et al., 2005, 2008; Deng et al., 2013). The occipital surface of the Tha Chang rhino is slightly inclined posteriorly or nearly vertical and the cheek teeth are subhypsodont (Deng et al., 2013). Both features indicate a woodland habitat (Zeuner, 1934). The zygodont proboscidean discovered in Thailand
has significant implications for understanding the dispersal of Zygolophodon. The oldest zygodont proboscidean in Africa, Losodokodon losodokius, is dated to late Oligocene (Rasmussen and Gutierrez, 2009). The oldest Zygolophodon in Europe is in the late early Miocene, either MN3b or MN4 (approximately 17 Ma) (Drake in Tassy, 1990) while the Zygolophodon materials from Pakistan are in the lower Chinji Formation (approximately 14–13 Ma) (Osborn, 1929; Chavasseau et al., 2009). The North Chinese species are from the middle Miocene (Tobien et al., 1988) and might be older than the species from Pakistan. Finally, the South Chinese species are from the upper Miocene (Biasatti et al., 2012) (Fig. 6). Zygolophodon appears to have dispersed from Africa to Europe in the early Miocene, and become widespread in Asia (especially at middle and high latitudes) in the middle Miocene. Zygolophodon then shifted to low latitude areas such as Thailand in the late Miocene (Fig. 6).
Conclusion
The zygodont proboscidean teeth from the Tha Chang sand pits (no. 10) show the zygodont pattern. The adaxial conelets are small, more closely resembling Chinese specimens of Zygolophodon gobiensis and Pakistan species Z. metachinjiensis than the holotype species Z. turicensis. Despite deep wear, it is evident that the central conules are less inflated than those of the type specimen of Z. gobiensis and Miomastodon tongxinensis, but similar to Z. lufengensis and Z. chinjiensis from the upper Miocene of South China. However, the Tha Chang specimens are badly worn and the m3 is broken anteriorly, making it only to designate these specimens as Zygolophodon sp. This Zygolophodon is the first zygodont proboscidean recorded in Southeast Asia and is likely late Miocene in age.
Acknowledgments
This paper was completed with the help of several people. We would especially like to thank P. Vachajitpan for allowing us to study his collection.Wewish to thank to people of the Institute of Vertebrate Paleontology and Paleoanthropology including T. Haowen, who gave us generous suggestions about the proboscideans morphology; C. Sullivan, who advised us about English; and C. Jin, who generously provided us with a comfortable workspace as we studied the specimens in the institute’s collections room., We would like to thank to the staffs of the Research Institute of Petrified Wood and Mineral Resources and Nakhon Ratchasima Rajabhat University, especially W. Songtham, W. Rugmai, N. Boonchai, P.J. Grote, K. Jenjitpaiboon, P. Kachenchat, S. Sodok, S. Ruanjangreed, N. Kullaprutmetha, and P. Pipatwatchara for preparing samples and documents as well as making some valuable suggestions while we were studying samples in Thailand. We thank N. Chanon, who gave us a vehicle for comfortable transportation during our work in Thailand. We are grateful for financial support from the National Natural Science Foundation of China (41430102), the Institute of Vertebrate Paleontology and Paleoanthropology, the University of Chinese Academy of Sciences, and Nakhon Ratchasima Rajabhat University.
References
Biasatti, D., Wang, Y., Gao, F., Xu, Y., and Flynn, L., 2012, Paleoecologies and paleoclimates of late Cenozoic mammals from Southwest China: Evidence from stable carbon and oxygen isotopes: Journal of Asian Earth Sciences, v. 44, p. 48–61.
Blumenbach, J.F., 1799, Handbuch der Naturgeschichte, Sechste Auflage: Johann Christian Dieterich, Göttingen, (I)-XVI, (1)-708 p., 2 pls.
Bergh, G.D. van den, 1999, The Late Neogene elephantoid–bearing faunas of Indonesia: Scripta Geol, v. 117, 388 p.
Borissiak, R.L., 1936, Mastodon atavus n. sp., der primitivste Vertreter der Gruppe M. Angustidens: Trav. Inst. Paleozool. Acad. Sci. USSR, v. 5, p. 171–234.
Buffetaut, E., Helmcke–Ingavat, R., Jaeger, J–J., Jongkanjanasoontorn, Y., and Suteethorn, V., 1988, Mastodon remains from the Mae Teep Basin (northern Thailand) and their biostratigraphic significance: Comptes Rendus de l’Académie des Sciences de Paris, v. 306, p. 249–254.
Cerling, T.E., Quade, J., and Wang, Y., 1994, Expansion and emergence of C4 plants: Nature, v. 371, p. 112–112.
Cerling, T.E., Harris, J.M., and Leakey, M.G., 1999, Browsing and grazing in elephants: the isotope record of modern and fossil proboscideans: Oecologia, v. 120, p. 364–374.
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