Back home, five million years ago, the warm, wet climate of the Miocene sloped downwards into the cooler, drier Pliocene before descending even further into the more so Pleistocene. The slope was so gradual that to my knowledge, no extinction events happened.
But not in this alternate Earth. Five million years ago, the Miocene skipped the Pliocene and took a sharp drop to the Pleistocene. This drop in temperature happened so dramatically and so quickly that half of all plant and animal species became extinct, and the once-widespread rainforests had been cut down to their equatorial margins. (Like the refugia of back home.)
But considering that rainforest species have always been resilient against ice ages, one must ask, in this ice age mass extinction, which latitude would actually be hit harder--the lower tropics or the middle temperate?