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(biology) species, genera, families, and other groups of animals that arose and developed on other territories and settled on a given territory considerably later. Immigrants are usually named after their place of origin (Siberian immigrants in Europe; South American immigrants in North America) and according to the time of their immigration. In some cases, the time of immigration and its direction are determined by direct observation or from historical information (the process of migration of species, especially in recent decades, is proceeding intensively). However, in most cases these problems are solved on the basis of geological and paleontological data, analysis of kinship relations (taxonomic position), and the nature of the area of distribution. For example, the family Equidae of Eurasia are Upper Tertiary immigrants from America (where they became extinct).