This resulted in drier and more open habitats dominating the early Oligocene, and the loss of the dense forests that characterised the Eocene epoch. This environmental change, coupled with the arrival of new and better-adapted mammalian groups from Asia, triggered a decline in endemic European mammal groups such as Palaeotheriidae and Anoplotheriidae.
The transition to drier and more open habitats during the early Oligocene, accompanied by the loss of dense forests typical of the Eocene epoch, had a profound impact. The introduction of new and better-suited mammalian species from Asia further accelerated this decline among European endemic mammal groups like Palaeotheriidae and Anoplotheriidae.