Ellesmerocerida

The Ellesmerocerida is one of four orders united in the nautiloid superorder Plectronoceratoidea. The others are the Plectronocerida, Protactinocerida, and Yanhecerida, which are restricted to the upper Cambrian. The Ellesmerocerida through the family Ellesmeroceratidae persisted into the Ordovician wherein it gave rise to other families, some which in turn gave rise to other orders.

Cambrian ellesmerocerid families are the Acaroceratidae, Huaiheceratidae, and Xiaoshanoceratidae. Those known from the Ordovician include the Baltoceratidae, Bassleroceratidae, and Protocycloceratidae. The Ellesmeroceratidae lived during both times.