Mouse-like hamsters
The mouse-like hamsters are not real hamsters, although they look like hamsters.  They were once thought to be hamsters based on the shape of their teeth, but they do not have the cheek pouches, and short tail of the true hamsters. All animals in this genus were part of the same species before, Calomyscus bailwardi, but they are now separate species because they have big differences in chromosome number, skull length and weight, and other differences.