Enrichment and stability in the Pliocene mammalian fauna of North China

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Abstract
The Late Neogene vertebrate fossil record from Yushe Basin presents multiple, superposed assemblages from a single area, spanning roughly the interval of 6–2 Ma. Both large and small mammals show peak species richness in the middle Pliocene but indicate relative faunal stability throughout the Pliocene. Large mammals show turnover, especially extinction, around 5 and 2.5 Ma. Small mammals indicate change (over half of the species and several genera), as well as turnover at the species level, between 4 and 3.4 Ma. The loosely controlled dating of these events does not disprove hypothetical correlation with events in North America and with global climatic shifts. Elements that lack Yushe antecedents, some being long-distance dispersers, appear throughout the section, but with little effect on the resident assemblage. First records of well-documented immigrants (from North America, Europe, Africa, southern Asia, or high latitudes) generally do not coincide with ecomorph extinctions. Early Pliocene exchange between Asia and North America appears to have been balanced in both directions and involved a small proportion of the fauna. Immigration probably was opportunistic and contributed to faunal enrichment. We interpret the Yushe Pliocene mammalian assemblages as representing a fauna that was stable from ca. 5 to 2.5 Ma and changed mainly by additions and congeneric species substitutions.