Complex sentence: It is thought this breed of dog is the true descendant of the original Celtic Hound, although there is no known history of the Austrian Black and Tan Hound until after the middle of the 19th century.
Split into simpler sentences: It is thought this breed of dog is the true descendant of the original Celtic Hound. There is no known history of the Austrian Black and Tan Hound until after the middle of the 19th century.