There is only one breed of Yorkie, the Yorkshire Terrier. So-called "teacup" Yorkies are not a separate breed. They are simply unhealthy runts passed off at high prices.
Pitbulls were originally bred by selecting bulldogs with fox terriers. This generated the bull terrier. From there they were mixed with other breeds to finally arrive to pitbull types
There are about 27 differend breeds of foxes but there is argument that there are only 10 'true' foxes. This may be due to the fact that foxes have been cross-bred over the years for their fur (an...