Bactroceras is a genus of orthoceratoid cephalopods that lived during the early Middle Ordovician, from about 472—464 mya, existing for approximately 8 million years.

For instance, the first shell chamber of Bactroceras resembles that of other Ordovician orthocerids, such as Archigeisonoceras and Hedstroemoceras: it is about 10 mm in diameter and is short, forming a spherical cap.

Moreover, there is a large stratigraphic gap of nearly 50 million years between Bactroceras and the next orthocones with a spherical apex and ventral siphuncle.

[4] Bactroceras differs from the later cephalopod Bactrites in that its shell was more circular in cross section and has deeper V-shaped ventral lobes.

Locations were varied and stretched from New South Wales, Australia to El Puente, Bolivia to Antelope Valley, Nevada.