Vol.2 No.3 (September 2012)
Protanancus tobieni from the Anwan Section, Qinan County, Gansu Province
We report a specimen of Protanancus tobieni discovered in 1976 from the Anwan Section, Qinan County, Gansu Province, including a complete mandible with lower incisors and a complete left upper incisor. The material can be referred to the same species as P. tobieni from the middle Miocene Dingjiaergou locality, Ningxia Hui Autonomous Region, because they show almost identical characters. The mandibular symphysis is extremely elongated; the upper incisor is robust with a broad enamel band; the lower incisor is flattened with a biconcave, concentrated-laminated cross-section; and the m3 shows posttrite ornamentation and pseudo-anancody. The above features indicate that the specimen is referable to Protanancus rather than Amebelodon, as it has been previously assigned. Furthermore, P. tobieni shows relatively poor posttrite ornamentation and pseudo-anancody; the lower incisor has a biconcave cross-section —an autapomorphy. These features distinguish it from other known species of Protanancus, and thus support the validity of P. tobieni as a distinct species. Based on the field survey, we infer that the Anwan Section records continuously from the lower to the upper Miocene. The lithology is primarily composed of brownish-red sandy-mudstones and mudstones. The middle and lower members of the section are intercalated with glutenite, sandstone, and grayish-green marl lenses, which represent channel deposits developed on the flood plain; this reflects a fairly humid environment with a large aquatic environmental component, which existed during the early period of the Neogene. The upper member of the section contains numerous layers of calcareous muddy granules, demonstrating a multi-acidification process of environmental evolution that occurred after the middle Neogene.
王世骐 , 王多庆 , 史勤勤 (2012) 甘肃秦安安湾的托氏原互棱齿象(Protanancus tobieni)化石及其剖面。 地球科学前沿， 2， 150-158. doi: 10.12677/AG.2012.23022
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