The Pastore Abruzzese is the original central Italian flock guardian. Dogs from the Abruzzo mountains was taken down to the lowland of Maremma, where they developed different breed characteristics than the mountain dogs. In the lowland the dogs were bred for other characteristics, and it is also possible that other breeds had some influsion on the development of the the Maremmano.
Todays Maremmano Abruzzese is a "constructed" breed, much the same way as the Tibetan Mastiff, -which is several Tibetan & Himalayan Molosser breeds that is united in the western created Tibetan Mastiff. The large, heavy and mastiff like Pastore Abruzzese, -which still can be found in the Abruzzo mountains, were united in 1951 with the smaller, lighter, and more lupoid Pastore Maremmano, -a breed that now is gone. The result of these two united breeds were the modern constructed dog breed Maremmano Abruzzese, with the standard basically drawn up from the lighter Maremmano type.
Modern dog breeding are breeding for a uniform size and type, and the danger in "tossing" several close related breeds together is that the local variants will eventually dissapear, if not any entusiasts still care enough for saving their local type, despite of the FCI's breed calssification.
In addition to the Pastore Abruzzese, Pastore Maremmano and the modern Maremmano Abruzzese, there are according to the Abruzzese expert Marco Petrella several other local sub-types of the Pastore Abruzzese; tipo Marsicano, tipo Aquilano, tipo di Pescocostanzo, tipo della Maiella, tipo Peligno, tipo a pelo raso, tipo Pezzato, tipo baffuto and tipo a naso rosa. You can find these sub-types described and pictured at one of Mr. Petrella's webpages, which you can go to by clicking HERE, or if you prefer the Italian version.

In the standard of the modern dog-show Maremmano Abruzzese the size of the male is given as 65-73 cm. (25,5-28,7 in) and 35-45 kg. (77-99 lb). The Pastore Abruzzese has however a larger dimension, with at least 40 kg. (88 lb) for the females and at least 55-60 kg. (121-132 lb) for the males. The normal weight of the female is 48 kg. (106 lb) and up, while the normal weight on the male is 65-70 kg. (143-154 lb) and up. The height of the Pastore Abruzzese is at least 66-68 cm. (26-27 in) for the females and 72-75 (28,3-29,5 in) for the males, at the withers of course.
As a much larger and heavier dog than the Maremmano Abruzzese, the weight of a full grown Pastore Abruzzese can even reach up to as much as 100 kg. (220 pounds). We can easily understand that the standard of the Maremmano Abruzzese is completly wrong for the Pastore Abruzzese, not only in size and weight, but also when it comes to type, which in the Pastore Abruzzese should be more molossoide than the modern show Maremmano Abruzzese.
I will ask you to use your common sence. Why take a heavy breed; the Pastore Abruzzese, and a lighter breed; the Pastore Maremmano, and try to create a breed inbetween these two, when on the other hand a breed as the Japanese Akita Inu have been split into to breeds; the heavier Great Japanese Dog and the lighter Akita Inu. It all completly looses its understanding when we know that there were greater differences between the Pastore Abruzzese and the Pastore Maremmano, and even between the Pastore Abruzzese still working in the mountains and the Maremmano Abruzzese usally seen at dogshows, than between the two types of Akita Inu.

"Puma".

The Pastore Abruzzese is a large white dog with clearly visable molossoide traits. It is much larger and heavier built than the standard of the Maremmano Abruzzese describe.
The Pastore Abruzzese are often born with declaws and even double dewclaws. However, at dogshows this original trait is penalized. Another evidence that the standard of the Maremmano Abruzzese is not suited for the Pastore Abruzzese.
In the Abruzzo mountains the Pastore Abruzzese is still used to protect the sheeps, even if the original and true type have become rare.