Bellerophontoidea, common name "bellerophonts",[2] is a superfamily of extinct planospirally-coiled globose molluscs. This superfamily is generally included within the Gastropoda, but may instead be a group of monoplacophorans. The taxon first appeared late in the Cambrian and continued until late in the Triassic.
Unlike normal gastropods, the shells of Bellerophonts are characterised by a completely planispiral pattern of coiling, such as one finds in shelled cephalopods. Experts disagree whether Bellerophontids should be classified as torted gastropods, or as untorted Tergomya, or whether the group Bellerophontida is perhaps an artificial construct, consisting of a number of distinct groups of Palaeozoic molluscs which evolved the same type of spiral shell independently.[3]
J.B. Knight, et al.[4] (1960) regarded the bellerophontids as torted gastropods even though they have essentially symmetrical, planispiral shells.
The narrower apex was probably held to the rear while the wider aperture was oriented to the front where the animal could easily emerge or retreat.
The taxonomy of the Bellerophontoidea (renamed from the original Bellerophontacea) has gone through a number of revisions since M'Coy established the Bellerophontaceae in 1851 for planospiral archeogastropods. The naming followed the convention for superfamilies that prevailed until at least 1992 with Wahlman
The Bellerophontacea were placed in the order Bellerophontida established by Ulrich and Scofield in 1897[5] and included the families Bellerophontidae, Bucaniidae, Cyrtolitidae, and Protowarthiidae.