A Griffin is a magical creature with the body of a lion and the head and wings of an eagle. I believe that the evolution of this magnificent creature would have come about partially through interbreeding between species and partially between natural selection. It is said that they lay eggs which one would assume puts them firmly amongst the birds in their category however, a lion is a mammal. I would therefore like to put it as a dinosaur. I think it would be well placed in the same category as a winged horse such as a granian. It has been around for a very long time considering it was spoken about in early mythology by the ancient greeks and romans. It is different from its ancestors because it is an animal that is known for its pride, they are powerful and majestic all the same time. The combination of both is wonderful. All different cultures know of this animal and it allows us to be open minded.
Ziz was a griffin-like bird in jewish mythology that was said to be large enough to be able to block out the sun with its wingspan, one of three biblical angels/beasts. These are not just animals known to the magical community but to Muggles as well. This means that they have been around for a very very long time.
Such as dragons we must place our faith in the history of the dinosaurs, and winged horses. That they are descended. Fed on raw meat, they are fierce creatures and rated XXXX by the Ministry.