Allocotoceras is an endocerid from the Lower Ordovician (upper Canadian) of Australia (Tasmania

Tasmania

Tasmania is an Australian island and state. It is south of the continent, separated by Bass Strait. The state includes the island of Tasmania—the 26th largest island in the world—and the surrounding islands. The state has a population of 507,626 , of whom almost half reside in the greater Hobart...

), included in the Endoceratidae

Endoceratidae

The Endoceratidae is a family of large to very large straight shelled nautiloid cephalopods belonging to the order Endocerida that lived during the Middle and Late Ordovician...

, based on small, straight or gently curved siphuncles.

Septal necks, according the Teichert, 1964, are holochoantic, reaching to the previous septum. Endocones are described as having a dorsal wedge, or process, making the internal opening, or endosiphocone, simicircular in cross section. In this sense Allocotoceras seems to resemble the genus Najaceras

Najaceras

Najaceras is a genus of straight, slender endocerid known only from the Whiterockian age Oil Creek Limestone of Oklahoma, introduced and named by Rousseau Flower in 1971 and further described by him in 1976....

.

References

• Teichert, C. 1964. Endoceratoidea. Treatise on Invertebrate Paleontology, Part K. Endoceratoidea, Actinoceratoidea, Nautiloidea. Geological Soc. of America and Univ. Kansas Press.
• Allocotoceras -Paleodb