Evolutionary History Of Spalacidae And Geometric Morphometric Study Of Spalacadae(Mammalia: Rodentia)

The Spalacidae, is a family of strictly subterranean rodents with a long evolutionary history. The earliest fossil record of this family was dated to the late Oligocene. The early split and rare species of Spalacidae are of interest to researchers. Through compiling the fossil records, determining the date of divergence for extant taxa and analyzing the geographical evolution based on molecular data, the present study explored the origin and evolutionary process of Spalacidae in detail. This research showed that the evolutionary history of Spalacidae is relatively stable. Distribution of these animals mainly confined to regions of Asia, southeast Europe and north Africa that showed lowest climate-change velocity in the history. The low species diversity and narrow distribution of Spalacidae were also evidenced by fossil records. It likely originated in the southeast Europe and the eastern Mediterranean in the Oligocene(23.03-33.90 Ma), and then split into two clades. The first clade includes Rhizomyinae, which spread into Asia in the late Oligocene. Then Rhizomyinae from Asia invaded north Africa two times during the formation of Afro-Eurasian land bridge in the Miocene. Rhizomyinae in Asia dispersed eastward after the late Miocene and reached northern China and divided into Myospalacinae, which stayed in eastern and central Asia and did not show large-scale migration in the evolutionary history. The second clade includes Spalacinae that have persisted in southeast Europe and around the Mediterranean region since the Late Oligocene. The evolution of this family was affected by the global environment changes, remarkably, the prominent range contraction of Rhizomyinae in eastern and central Asia.The environmental change is not to be the only cause for the radiation of Spalacidae, the morphological change is another factor for Spalacidae. The shape changes shape in the skull of Spalacidae can react different lifestyles and the adaptive shape deformation. In the morphological study, we apply the geometric morphometric approaches to explore the adaptive shape deformation in the skull of Spalacidae adopting different lifestyles. In addition, we also explore the controversial spacies of Myospalacinae and we can prove six zokors are species.