Horses.
The Ungulate order has been variously divided by zoologists, and is still said to be composed of two main sections, even-toed and odd-toed Ungulates, with the addition of a good many “outsiders” if one may use the term.
These sections form two sub-orders, and the division suits my purpose here very well. I take the odd-toed sub-order of the Ungulata Vera first.