The New Encyclopedia of the Dog. They look rather remarkably like black field-bred Labrador Retrievers, but they are indeed exceptionally different when it comes to behavior.
The breed is Spanish in origin, coming from the Balearic Islands. It is a herding and guardian breed, and was bred for function rather than looks. The ancestry is of unknown dogs from the European mainland. They are black in color, but do quite well in hot climates. They are bold, tenacious, independent dogs and are described as "uncomplicated, unsophisticated, and utilitarian." Their popularity has been spreading to other parts of the world, including South America where it is used as a guardian dog. There is also some effort to used it to protect sheep ranches from coyotes in North America.
It is accepted by the FCI and UKC, though the FCI standard is currently unavailable in English. According to the UKC, the breed is characterized as follows:
Height: 22-24 inches
Weight: 77-88 pounds
Overall, the standard appears to be a very loose.
Here's a video of one of these dogs herding. I can't get over how much they look like my Ebon.
Image is copyright free from Wikimedia Commons.