Latest Oligocene–Early Miocene in Europe: Dark Period for booid snakes

The diversity of booid snakes strongly decreased during the Latest Oligocene (zones MP 29-30) and Early Miocene (zones MN 1-2, and perhaps MN 3) in Europe. Moreover, the few remaining taxa were all small and displayed fossorial trends. This crisis is referred to as the Dark Period of booid snakes. The outset of this event probably resulted from cooling and aridization that were prevailing during the Late Oligocene. The period ended when a warm and humid climate was restored; aside from direct effect, the latter change caused the arrival of immigrants that probably contributed to the elimination of the booids of the Dark Period.