the world > animals > mammals > group Ungulata (hoofed) > family Equidae (general equines) > [noun] > hybrid horse and ass > mule > used for specific purpose
sumpter mule1579
bât-mule1787
pack mule1834
post-mule1835
pole mule1862
lead-mule1877
1877 R. W. RaymondStatistics Mines & Mining 345 Give me the lead-mule, and the rest of us will go on to camp.