What is "trigonocerataceae"

The Trigonocerataceae is a superfamily within the Nautilida that ranged from the Devonian to the Triassic that is thought to have contained the source for the Nautilaceae in which Nautilus is found.

Trigonocerataceae are characterized by open-spiraled, gyroconic, to closed, nautiliconic shells in which the whorl section is quadrate in primitive forms; the venter typically narrow to acute, the dorsum broad. In some advanced forms the venter may become concave or broad and rounded and In some the surfaces may be strongly lirate.