Cyptendoceras is an extinct nautiloid cephalopod included in the family Ellesmeroceratidae

Ellesmeroceratidae

The Ellesmeroceratidae constitute a family within the cephalopod order Ellesmerocerida. They lived from the Upper Cambrian to the Lower Ordovician...

 that lived in what would be North and South America during the latter part of the Early Ordovician (late Arenig) from about 475 - 472 mya, existing for approximately .

Taxonomy

Cyptendoceras was named by Ulrich and Foerste (1936). Teichert (1964, in the Treatise

Treatise on Invertebrate Paleontology

The Treatise on Invertebrate Paleontology published by the Geological Society of America and the University of Kansas Press, is a definitive multi-authored work of some 50 volumes, written by more than 300 paleontologists, and covering every phylum, class, order, family, and genus of fossil and...

, included it in the endocerid family
Proterocameroceratidae

Proterocameroceratidae

The Proterocameroceratidae were the first of the Endocerida. They began early in the Ordovician with Proendoceras or similar genus which had developed endocones, replacing the diaphragms of the ellesmerocerid ancestor....

. Flower (1964) in Memoir 12 assigned it to the Baltoceratidae

Baltoceratidae

Baltoceratidae is an extinct family of orthoconic cephalopods belonging to the subclass Nautiloidea endemic to what would be Asia, Australia, Europe, North America, and South America during the Ordovician living from about 480–460 mya, existing for approximately .-Taxonomy:Baltoceratidae was...

, at that time included in the Ellesmeroceratida

Ellesmerocerida

The Ellesmerocerida is a order of primitive cephalopods belonging to the subclass Nautiloidea with a widespread distribution that lived during the Late Cambrian and Ordovician.-Morphology:...

. Kroger et al (2007) reassigned it to the Ellesmeroceratidae on the basis of the ellesmeroceratid type siphuncle, removing it from the Baltoceratidae which had been reassigned to the Orthocerida

Orthocerida

Orthocerida is an order of extinct nautiloid cephalopods also known as the Michelinocerda that lived from the Early Ordovician possibly to the Late Triassic . A fossil found in the Caucasus suggests they may even have survived until the Early Cretaceous...

.