Onychochilidae

Onychochilidae Temporal range: U Camb - L Dev
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Gastropoda(?)
Order:	Archaeogastropoda
Superfamily:	Clisospiracea
Family:	Onychochilidae Koken, 1925

Onychochilidae is an extinct family of small, upper Cambrian to lower Devonian, hyperstrophically coiled molluscs, generally with smooth whorls and elongate apertures, commonly regarded as gastropods.

The Onychochilidae is included in the Macluritacea in the Treatise, Part I, 1960, ^[1] as part of the Archaeogastropoda where it is divided into two subfamilies, the Onychochilina for those with high basal spires, and the Scaevogyranae for those with low basal spires. Robert M. Linsely and William M. Kier, 1984 ^[2] reassigned the Onychochilidea to the Paragastropoda, a new class of molluscs proposed for gastropod-like forms which they interpreted as being untorted - that is viscerally untwisted. The Onychochilidae was at that time placed in the Onychochilacea, a superfamily included in a new order, the Hyperstophina, named for paragastropods with hyperstrophic to depressed-orthstrophic shells.

Bouchet and Rocroi,, 2005 ^[3] tentatively retained the Onychochilidae in the Gastropoda, including them along with the Clisospiridae in the superfamily Clisospiroidea and added a third subfamily, the Hyperstropheminae, named for Hyperstrophema Horney, 1964, its sole known genus.

References

1. ^ Treatise on Invertebrate Paleontology, Part I, Mollusca 1. R.C. Moore (ed) Geol. Soc. of America and Univ. Kansas Press, 1960
2. ^ Linsely, R. M. & W.M Kier, 1984. The Paragastropoda: a proposal for a new class of Paleozoic Mollusca. Malacologia, v.25, no1, pp 241-254
3. ^ Bouchet, P. & Rocroi, J., 2005. Classification and Nomenclator of Gastropod Families Malacologia v.47. no 1-2.