In contrast, a few researchers have advanced an argument that mustangs should be legally classified as "wild" rather than "feral".
The mustang is a free-roaming horse of the American west that first descended from horses brought to the Americas by the Spanish.
Mustangs are often referred to as wild horses, but because they are descended from once-domesticated horses, they are properly defined as feral horses.
The facial profile may be straight or slightly convex. Height varies across the west, but most are small, generally 14 to 15 hands (56 to 60 inches, 142 to 152 cm), and not taller than 16 hands (64 inches, 163 cm), even in herds with draft or Thoroughbred ancestry.
Withers are moderate in height and the shoulder is to be "long and sloping." The standard considers a very short back, deep girth and muscular coupling over the loins as desirable. The mustang of the modern west has several different breeding populations today which are genetically isolated from one another and thus have distinct traits traceable to particular herds.
The croup is rounded, neither too flat nor goose-rumped. Genetic contributions to today's free-roaming mustang herds include assorted ranch horses that escaped to or were turned out on the public lands, and estray horses used by the United States Cavalry.