Beefalo
In 1965, Jim Burnett of Montana produced a hybrid bull that was fertile. Soon after, Cory Skowronek of California formed the World Beefalo Association and began marketing the hybrids as a new breed. The new name, Beefalo, was meant to separate this hybrid from the problems associated with the old cattalo hybrids.  The breed was eventually set at being genetically at least five-eighths Bos taurus and at most three-eighths Bison bison.