Early Cambrian – Early Triassic
Bellerophontida is an extinct order of slow-moving low-level epifaunal detritivores.
Characteristics of the Order
- Closely coiled and rarely slightly asymmetrical
- Usually contain selenizone generated by median labral sinus or slit
- Variable shell wall thickness
Treatise on Invertebrate Paleontology, Part I, Mollusca 1 (1960):
- Shell most commonly isostrophic, rarely slightly asymmetrical; mostly closely coiled, but in some genera cyrtiform; predominantly with median labral sinus or slit, or tremata, probably exhalant in function and usually generating a selenizone; shell wall of variable thickness, no evidence of nacre; operculum unknown; presence of paired and equal ctenidia and osphradia, also of single pair of retractor muscles, inferred (latter from muscle scars); nothing known of other soft parts.