''Avilionella'' is a Middle Ordovician tarphyceroid

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

consisting of closely coiled, compressed shells with a small perforation in the center, shallow dorsal impression, and subventral tubular

siphuncle The siphuncle is a strand of biological tissue, tissue passing longitudinally through the mollusc shell, shell of a cephalopod mollusc. Only cephalopods with chambered shells have siphuncles, such as the extinct ammonites and belemnites, and the li ...

with thin connecting rings. Chambers are very short, separated by closely spaced, dish-shaped septa. Coiling becomes loose in the mature, adoral, part of the shell. The subventral, tubular siphuncle along with the looser coiling in the mature portion of the shell and perforation at the center put ''Avilionella'' in the Plectoceratidae (Flower, 1984) rather than in the Barrandeoceratidae (Sweet 1964) where it had been placed earlier. It has been found the New York and Ontario.

References

*Rousseau H. Flower, 1984. ''Bodeiceras''; a New Mohawkian Oxycone, with Revision of the Older Barrandeocerida and Discussion of the Status of the Order. Journal of Paleontology v. 58, no.6, pp 1372–1379, Nov. 1984. *Walter C Sweet, 1964 Nautiloidea-Barrandeocerida;

Treatise on Invertebrate Paleontology The ''Treatise on Invertebrate Paleontology,'' published from 1953–2007 by the Geological Society of America and the University of Kansas, then 2009–present by the University of Kansas Paleontological Institute, is a definitive multi-authore ...

, Part K Mollusca 3. Geological Society of America and University of Kansas Press. {{Taxonbar, from=Q4828847 Prehistoric nautiloid genera Ordovician cephalopods of North America