This diagram shows a history of horse hind feet. It has been scaled so that all the animals seem to be the same size.
Since 1879, there have been books and museum exhibits showing a "horse series". They show about four to six species. They may also show the front feet, the teeth, and the skulls. They show the size increasing, from about the size of a small dog, on up to the modern horse size. And, they show the shape (which gets horsier).