What class of Chordates are the donkey and the horse? What are the characteristic features of this class?

What class of Chordates are the donkey and the horse? What are the characteristic features of this class? What is the difference between the liver cells of these animals?

1) to the class Mammals;
2) the presence of mammary glands and feeding of cubs with milk, intrauterine development and viviparity (with the exception of the first animals), the presence of a diaphragm, differentiated teeth, as well as wool, sweat glands and subcutaneous tissue that provide warm blood;
3) the structure of the liver cells of a donkey and a horse are the same, since both animals belong to mammals, differ in the number of chromosomes (species characteristic).