<P> Horses only returned to the Americas with Christopher Columbus in 1493 . These were Iberian horses first brought to Hispaniola and later to Panama, Mexico, Brazil, Peru, Argentina, and, in 1538, Florida . The first horses to return to the main continent were 16 specifically identified horses brought by Hernán Cortés . Subsequent explorers, such as Coronado and De Soto, brought ever - larger numbers, some from Spain and others from breeding establishments set up by the Spanish in the Caribbean . Later, as Spanish missions were founded on the mainland, horses would eventually be lost or stolen, and proliferated into large herds of feral horses that became known as mustangs . </P> <P> The indigenous peoples of the Americas did not have a specific word for horses, and came to refer to them in various languages as a type of dog or deer (in one case, "elk - dog", in other cases "big dog" or "seven dogs", referring to the weight each animal could pull). </P> <P> The ancestors of the horse came to walk only on the end of the third toe and both side toes . Skeletal remnants show obvious wear on the back of both sides of metacarpal and metatarsal bones, commonly called the "splint bones". They are the remnants of the second and the fourth toe . Modern horses retain the splint bones; they are often believed to be useless attachments, but they in fact play an important role in supporting the carpal joints (front knees) and even the tarsal joints (hocks). </P> <P> Throughout the phylogenetic development, the teeth of the horse underwent significant changes . The type of the original omnivorous teeth with short, "bumpy" molars, with which the prime members of the evolutionary line distinguished themselves, gradually changed into the teeth common to herbivorous mammals . They became long (as much as 100 mm), roughly cubical molars equipped with flat grinding surfaces . In conjunction with the teeth, during the horse's evolution, the elongation of the facial part of the skull is apparent, and can also be observed in the backward - set eyeholes . In addition, the relatively short neck of the equine ancestors became longer, with equal elongation of the legs . Finally, the size of the body grew as well . </P>

What term describes a species that has fewer members today than in the past