A restudy of Rhinocerotini fossils from the Miocene Jiulongkou Fauna of China

分类： 生物学 >> 生物进化论 提交时间： 2024-03-15

LI Shi-Jie DENG Tao

摘要： All the extant rhino species belong to Rhinocerotini and either have one horn (a nasal horn) or two horns (a nasal horn and frontal horn). So far, the earliest Rhinocerotini to have been identified in China is the “Dicerorhinus” cixianensis, which was based on a juvenile skull with an associated mandible from the Middle Miocene locality of Jiulongkou in Cixian County, HebeiProvince of northern China. Our analyses suggest that there are similarities between this specimenand the modern genus, Dicerorhinus, but it differs in several cranial traits and therefore cannotbe assigned to the modern genus. Instead, it is closer to the Middle Miocene Lartetotheriumfrom Europe, especially the specimen from La Retama in Spain and should be assigned to thatgenus, indicating the presence of intracontinental dispersal at this time. The Jiulongkou faunais the only Middle Miocene fauna with Rhinocerotini in China, and, together with the faunalcomposition, this implies a more humid and closed environment, in contrast to those found inwestern China. We suggest that the position of the posterior border of the nasal notch is a goodindication of the specimen’s evolutionary level in Rhinocerotini. The anterior position of the nasalnotch as seen in modern Dicerorhinus, together with its certain similarities to L. cixianensis aswell as its differences with more specialized species of the Dihoplus-Pliorhinus-Stephanorhinus-Coelodonta lineage, supports the conclusion that Dicerorhinus experienced little change during anearly 10 Myr evolutionary history, possibly due to the low selection pressure seen in the tropical/subtropical forests in southeastern Asia.

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