Systematic Paleontology
Class Cephalopoda
Subclass Bactritoidea
Order Bactritida
Family Bactritidae
The Bactritidae are Bactritida with narrow, elongate, straight or exogastrically curved shells and siphuncles in contact with the ventral (lower) wall of the shell, septal necks straight, orthocoanitic.
The Bactritidae includes Bactrites which ranges from the middle Silurian, if not before, to the upper Permian, Pseudobactrites, mostly from the upper lower Devonian, Kokenia from the upper middle Devonian and the sequence of Lobobactrites and Cyrtobactrites stemming from an early Bactritites that leads to the ammonoids. Lobobactrites which precedes Cyrtobactrities in the lower Devonian ranges throughout most of the Devonian almost to the Mississippian. Cyrtobactrites, which appears slightly later, is restricted to the lower Devonian.
Referennces
H. K. Erben 1964. Bactritoidea. Treatise on Invertebrate Paleontology, Part K. Bactritidae pp K501 & K502