The Bellerophontidae were an Ordovician to Triassic family of coiled molluscs. They were superficially similar to small nautiloids with a deep sinus or slit at the aperture on the outer side of the coil. The umbilicus was narrow or absent, and the shell was ornamented by prominent growth lines (Knight et al. 1960). Most authors have considered the bellerophontids as basal (probably stem-)gastropods, though there is some debate on whether they underwent torsion like modern gastropods.
Knight, J. B., L. R. Cox, A. M. Keen, R. L. Batten, E. L. Yochelson & R. Robertson. 1960. Gastropoda—Systematic description. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt I. Mollusca 1. Mollusca—General Features. Scaphopoda. Amphineura. Monoplacophora. Gastropoda—General Features. Archaeogastropoda and some (mainly Paleozoic) Caenogastropoda and Opisthobranchia pp. I169-I310. Geological Society of America, Inc. and University of Kansas Press.
Christopher 10:27, 4 February 2011 (UTC)