Sinomastodon ("Chinese mastodont") is an extinct gomphothere genus (of order Proboscidea) known from the Late Miocene to Early Pleistocene of Asia, including China, Japan, Thailand, Myanmar, Indonesia and probably Kashmir.

Description

Sinomastodon, in comparison to earlier gomphotheres, had a shortened (brevirostrine) lower jaw that lacked permanent tusks/incisors. The skull was proportionally relatively short. The upper tusks, which are circular in cross-section, are upward curving and lack enamel bands. The molar teeth were triolophodont and bunodont. One individual of S. hanjiangensis, suggested to about 30-years-old, is estimated to have been about 2.07 m tall and weighed 2.1 t.

Taxonomy and evolution

The taxonomic position of Sinomastodon is disputed. Some authors suggest that Sinomastodon originated from North American gomphotheres that migrated into Asia. Position according to Mothé et al. 2016 supporting this hypothesis, showing Sinomastodon nested amongst North American gomphotheres: However, the teeth of the earliest Sinomastodon species from the Late Miocene are zygodont, a morphology unknown in North American gomphotheres. Therefore is it is alternatively suggested that it derived from an Asian species of Gomphotherium, such as G. subtapiroideum or G. wimani. The earliest members of the genus appear during the Late Miocene, while the youngest members are known from the end of the Early Pleistocene, around 800,000 years ago.

Diet

Specimens of Sinomastodon from the Early Pleistocene of South China (S. jiangnanensis, S. yangziensis) are suggested to have had browsing diet based on dental microwear analysis, while Sinomastodon bumiajuensis from the Early Pleistocene of Java is suggested based on stable carbon isotope analysis to have been a variable feeder, with the majority of specimens found to have a predominantly grazing diet.