Cameroceras

Cameroceras ("chambered horn") is a genus of extinct, giant orthoconic cephalopod that lived during the Ordovician period, 470 to 460 million years ago.[

Size
The partial shell of one giant Cameroceras yielded a total length estimated at the time at nearly 30 feet (9 m). This estimate has since been revised downward quite a bit;[2] Frey (1995) gives a length of up to 6 m.[3] Regardless of this estimate's degree of accuracy, this gargantuan cephalopod is thought to be among the largest known Paleozoic molluscs.

Taxonomic usage
"Cameroceras" has become a "wastebasket taxon" in which large orthoconic endocerids such as Endoceras, Vaginoceras, and Meniscoceras have been inserted. This makes it extremely difficult to describe Cameroceras as a distinct genus. Although the type species Cameroceras trentonense was first described by Conrad in 1842, since then the generic term has had variable meaning.

Hall, who named and described Endoceras in 1847 recognized C. trentonense specifically, but used Endoceras for other specimens of large endocerids from the Trenton Limestone of western New York state. "Cameroceras" and "Endoceras" have even apply to different stages of the same species. Although Cameroceras takes precedence where the two refer to the same species, its vague application leaves Endoceras or other better-described genus the term of choice.