Portuguese Sheepdogs are very like Pyrenean Sheepdogs, which rather suggests that they are actually a subdivision of that breed, crossed with the Briard to improve it.
About the Portuguese Sheepdog
This medium-sized breed is exceptionally intelligent and very lively. These very dogs are devoted to their owners and will steadfastly work to protect whatever livestock or property they are given. As such, Portuguese Sheepdogs can be distrustful of strangers.
They are reminiscent of monkeys in attitude and appearance, which has earned them the nickname "monkey dog" in their native country. They are popular for the way they keep livestock in the fields and bring back any animals that stray too far.
Source: key facts and characteristics sourced from Fédération Cynologique Internationale (FCI)