A new amynodontid from the Eocene of South China and phylogeny of Amynodontidae (Perissodactyla: Rhinocerotoidea)

<i>Cadurcodon maomingensis</i> sp. nov. is described based on a partial skull and associated vertebrae from the middle–upper Eocene Youganwo Formation in the Maoming Basin, Guangdong Province, China. The taxonomy of <i>Cadurcodon</i> Kretzoi, 1942 ( = <i>Sianodon</i> Xu, 1965, syn. nov.; = <i>Paracadurcodon</i> Xu, 1966, syn. nov.) is revised, and a new diagnosis of the genus is provided. It includes six species: <i>C. ardynensis</i> (Osborn, 1923), <i>C. kazakademius</i> Biryukov, 1961, <i>C. bahoensis</i> (Xu, 1965) comb. nov., <i>C. suhaituensis</i> (Xu, 1966) comb. nov., <i>C. houldjinensis</i> B.-Y. Wang, Qiu, Zhang, Wu, &amp; Ning, 2009 and <i>C. maomingensis</i> sp. nov. A new phylogenetic hypothesis of Amynodontidae is based on the cladistic analysis of the distribution of 48 characters in 16 amynodontid taxa. The family is divided into two sister taxa, Metamynodontini (<i>Paramynodon</i>, <i>Megalamynodon</i> and <i>Metamynodon</i>) and Cadurcodontini (<i>Procadurcodon</i>, <i>Zaisanamynodon</i>, <i>Cadurcodon</i> and <i>Cadurcotherium</i>). The remaining amynodontid genera are considered <i>incertae sedis</i>. The evolution of amynodontids was confined mainly to Central and East Asia, with four dispersal events to North America (<i>Amynodon</i>, <i>Amynodontopsis</i>, Metamynodontini and <i>Procadurcodon</i>), and one to Europe and South Asia (<i>Cadurcotherium</i>). The holotype of <i>C. maomingensis</i> sp. nov. is an adult male with body mass estimated as 1.4 tons. Amynodontids show considerable increase in size during evolution, with the largest species weighing over two tons (<i>C. kazakademius</i>, <i>Zaisanamynodon borisovi</i> and <i>Procadurcodon orientalis</i>). http://zoobank.org/urn:lsid:zoobank.org:pub:FD6EEE3E-AE06-4DA2-AFFD-39362724C1C2