What was more: the older fossils were, the less likely they were to resemble living organisms.
The youngest fossils included relatively familiar forms, like the long-horned bison at the top.
Older fossils included less familiar beasts, such as the vaguely rhino-like titanothere in the center.
And if you went back far enough in time, you found only bizarre reptile-like animals with no living counterparts at all.