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Changes in the palaeoenvironment and paleoclimate expedite the process of evolutionary divergence in animals. The evolutionary events of some small mammals distributed in Xinjiang Arid Region remain ambiguous. Thus, it is necessary to predict their evolutionary histories based on divergence estimates. Some museum specimens were involved in this analysis because of sampling limitation for threatened species in the arid region. A related problem is that some mutilated specimens without complete taxonomic data made it difficult to directly analyze species divergence. Here, sequences of cytochrome c oxydase I were used to identify museum specimens and combined with cytochrome b to estimate the recent divergence of extant small mammals constrained with eight fossil calibrations. The results showed that the massive species differentiation emerged during the Middle and Late Miocene periods. We inferred that differentiation of these small mammals might be associated with the retreat of the Tethys Sea from the Tarim Basin around the Eocene-Oligocene boundary and the global climate fluctuations during the Miocene period. Furthermore, the aridification and changes in the Taklimakan and Gurbantunggut Deserts might have driven the diversification of intraspecies and the emergence of cryptic species since the Late Pleistocene. [ABSTRACT FROM AUTHOR]

Przewalski's gazelle Procapra przewalskii is an endangered species endemic to China. A question remains about subspecific variation in this species. Skulls of Przewalski's gazelle collected from its current remnant ranges around the Qinghai Lake in combination with those collected prior to the 20th century were measured and analyzed using Hierarchical Cluster Analysis in order to clarify the question. Unexpectedly, P. p. diversicornis, extirpated from its historic range, has spread to the Qinghai Lake region where it has replaced nominotypical P. p. przewalskii and is now restricted to a few small isolated populations around the lake. We discuss the causes of this unexpected replacement. In this study, we discuss the possibility of a new form, possibly a new subspecies, in the Guide Basin, adjacent to Qinghai Lake; it is unclear whether the new form has long existed and was only discovered in recent years, or whether it evolved in recent times due to the geographical isolation and anthropogenic landscape features. The study sheds light on the processes of microevolution and subspeciation in Procapra przewalskii, and based on the findings, we propose measures for conservation strategies for Przewalski's gazelle. [ABSTRACT FROM AUTHOR]