Complex sentence: Many of today's Spanish breeds of mastiffs, claim to be this breed; the Spanish mastiff, the Pyrenean mastiff or the old Spanish Alano, some Ca de Bestiar breeders believe that their dog was the breed that King James I brought over.
Split into simpler sentences: Many of today's Spanish breeds, of mastiffs, claim to be this breed; the Spanish mastiff, the Pyrenean mastiff or the old Spanish Alano. Some Ca de Bestiar breeders believe that their dog was the breed that King James I brought over.