What is "gigantoproductus"

Gigantoproductus is a genus of extinct brachiopod in the order Productida and the family Monticuliferidae. The species were the largest of the carboniferous brachiopods, with the largest known species ranging in size from 9 to 12 centimeters (3.5 to 4.7 inches). Productids date back to approximately 407 million years ago. As fossils, their shells occur within a limestone matrix.