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The origin of the Old World brevirostrine gomphotheriid taxon Sinomastodon has been debated intensively. The discovery of the oldest known Sinomastodon cranium, reported herein, supports its endemic origin and contradicts the prevalent theory of its North America origin. The new cranium was discovered from the Shuitangba locality, southwestern China, and is dated at about 6.5-6.0 Ma, corresponding to the latest Miocene. The new specimen shows distinct characters from the other species of Sinomastodon and was therefore named Sinomastodon praeintermedius, sp. nov. Newly discovered, isolated Sinomastodon-like teeth from the upper Miocene to the lower Pleistocene of southwestern China and Southeast Asia indicate a long evolution of Sinomastodon endemically. Remains of this species are frequently accompanied by those of stegodontid species. These two groups may have had a similar migration route, invading northern China and Japan during the latest Miocene, and retreating or becoming extinct from the Palearctic realm by the end of the Pliocene. The migrations of proboscideans may have been sparked by major paleoenviromental changes, i.e., the strengthened summer monsoon beginning in the late Miocene (~7-8 Ma) and global cooling due to the expansion of ice sheets from the middle Pliocene to the early Pleistocene. The new finding reveals a close relationship of the early Pliocene fauna of northern China and the latest Miocene fauna of southwestern China, and thus provides novel insight into the origin and components of Pliocene fauna in northern China. [ABSTRACT FROM AUTHOR]

We report a fossil specimen referable to Sinomastodontinae gen. et sp. indet. from the Neogene strata at Yanghecun locality, Xihe County, Gansu Province, China. The specimen is characterized by a brevirostrine mandible, complete pretrite trefoils, and relatively simple posttrite half lophids, showing typical features of Sinomastodon. It differs from the other known species of Sinomastodon by the following features: relatively short and wide m3 due to fewer lophid numbers, less inflated pretrite accessory central conules, poorly developed secondary trefoils and cementum, and relatively strong cingulid. All of these features indicate a bias towards pleisiomorphies of Sinomastodon, implying that this specimen is more ancestral than any known species of Sinomastodon. The symphysis of the new specimen is relatively long, which differs from the typical brevirostrine Sinomastodon, and thus we consider it a gen. et sp. indet. in the Subfamily Sinomastodontinae. In addition, the horizon in which the present specimen was found probably represents the Upper Miocene because it is lower than Pliocene strata yielding Hipparion ( Proboscidipparon) pater. Generally, Sinomastodon is considered to have migrated from North America at about the time of the Miocene/Pliocene boundary, and to have been derived from a certain clade of American gomphotheres. However, the discovery of the Yanghecun specimen verifies that Sinomastodon lived in East Asia during the Late Miocene, and probably derived from Old World gomphotheres (e.g., G. wimani). The similarity between the members of the Subfamilies Sinomastodontinae and those of Cuvieroniinae is suggested to have been the result of parallel evolution. [ABSTRACT FROM AUTHOR]

The first Sinomastodon (Gomphotheriidae, Proboscidea) skull of the Early Pleistocene, collected from the Renzidong Cave deposits in Anhui Province, Eastern China, is described here as S. jiangnanensis sp. nov. As the only brevirostrine trilophodont gomphotheriid known from the Old World, Sinomastodon was mainly indigenous to China from the Early Pliocene to the Pleistocene. Compared with a few single Pleistocene teeth previously found in China, S. jiangnanensis sp. nov. is represented by a relatively complete skull, mandible and dentition, which is the first discovery of a Quaternary Sinomastodon skull from China. With a brevirostrine, elephant-like skull, no lower tusks, and simple bunodont and trilophodont intermediate molars, the new species is morphologically distinct from other gomphotheres and should belong to the genus Sinomastodon. The new species is more progressive than S. hanjiangensis and the Pliocene type species S. intermedius in its skull and mandible morphology, but is evidently more primitive than the Pleistocene S. yangziensis in its molar morphology. The faunal analysis suggests that the emergence of S. jiangnanensis sp. nov. in Jiangnan area and its southward migration may have been related to a cooling event at the beginning of the Quaternary in Eastern China. [ABSTRACT FROM AUTHOR]