Planispira

A Planispira is a coiled shell, typically of a mollusk, where the whorls lie in a single plane. This type of shell coiling results in a flat or disc-shaped appearance, distinguishing it from shells with more conical or spiraling forms. The term is primarily descriptive, referring to the geometry of the shell rather than a specific taxonomic group. Many different species of snails, both terrestrial and aquatic, exhibit planispira coiling. While not a formal taxonomic term itself, "planispiral" is used as an adjective to describe this type of shell morphology in various gastropod families and genera. The coiling can be tightly wound or more loosely arranged, impacting the overall proportions of the shell. Characteristics such as the number of whorls, presence of ornamentation, and apertural shape are used to further differentiate species with planispira shells.