The messel pit between Frankfurt and darmstadt is the richest site in the world for understanding the living environment of the Eocene it provides unique information about the early stages of the evolution of mammals and details of exceptionally well-presrved fossils from fully articulated skeletons to hair feathers wing membranes and stomach contents many different species of plants and animals are found including crocodiles bats birds reptiles fish turtles insects and even a herd of primitive horses.