The Mid-Cretaceous period is one period in the geologic past that stands out as distinctly warmer than today, particularly at high latitudes. During the mid-Cretaceous Period, 120-90 million years ago, fossil remains of plants and animals believed to inhabit warm environments, were found at much higher latitudes.he Mid-Cretaceous period is one period in the geologic past that stands out as distinctly warmer than today, particularly at high latitudes. During the mid-Cretaceous Period, 120-90 million years ago, fossil remains of plants and animals believed to inhabit warm environments, were found at much higher latitudes.