Complex sentence: The Galician pony is a breed of pony developed in Galicia (Spain) that has had an influence on the Galiceno breed in Mexico and, allegedly, on the mustang.
Split into simpler sentences: The Galician pony ("Cabalo Galego " or"Potro Galaico" in Galician), is a breed of pony developed in Galicia (Spain). It has had an influence on the Galiceno breed in Mexico and, allegedly, on the mustang.