Complex sentence: The Teddy Roosevelt Terrier is an American hunting terrier that is a small to medium sized, low-set, muscular, short legged with a heavier bone density than its cousin the American Rat Terrier.
Split into simpler sentences: The Teddy Roosevelt Terrier is an American hunting terrier that is a small to medium sized terrier. Lower-set with shorter leg, more muscular, and heavier bone density than its cousin the American Rat Terrier.