leptictidium
An ancient shrew-looking creature that died out and left no descendants behind. Jumps like a kangaroo but is very small. Lived in southern Europe. Lived shortly after dinosaurs died out, as the forests returned and it became very hot. Europe was hot and humid then. The creatures were bipedal. Interesting due to their alien appearance, and the fact that they died out without any descendants.
Wow, leptictidiums are such alien creatures yet had they lived maybe there would be a kangaroo-seeming creature in one of the birthplaces of western civilization!