Most gastropod shells are spirally coiled. The majority (over 90%) [2] of gastropod species have dextral (right-handed) shells, but a small minority of species and genera are virtually always sinistral (left-handed), and a very few species (for example Amphidromus perversus [3]) show a mixture of dextral and sinistral individuals.

Jan 5, 2023 · Most gastropod shells are coiled out of a single plane, which is termed conispiral coiling. In contrast, Nautilus, the modern cephalopod with a coiled shell, is coiled in the same plane, which is termed planispiral coiling.

Mar 10, 2025 · The typical snail has a calcareous shell coiled in a spiral pattern around a central axis called the columella. Generally, the coils, or whorls, added later in life are larger than those added when the snail is young. At the end of the last whorl is the aperture, or opening.

Sep 16, 2021 · The coiled gastropod shell is a conical tube wrapped in a spiral around a central, usually vertical, axis. The shell gets larger by adding material at the opening.

Sep 11, 2024 · These early forms primarily exhibited a coiled shell, the defining characteristic of gastropods. During the Ordovician Period, the first crown-group members of gastropods appeared, inhabiting various aquatic environments.

Jan 5, 2023 · Most gastropod (snail) shells are helically coiled around a central axis, and the aperture (opening) is to one side or the other of the axis of coiling. Helical coiling is distinctive for gastropod mollusks.

In studying the functional significance of the coiled shell, it is important to be able to analyze the types that do not occur in nature as well as those represented by actual species. Both digital and analog computers are useful in constructing accurate pictures of the types that do not occur.

Jan 5, 2023 · Gastropods have coiled shells. The shell is wrapped around a central axis, termed the columella, forming whorls. Each whorl is a complete revolution of the shell around the columella. Whorls are in contact with successive whorls along a groove or …

May 14, 2011 · The top of the coiled shell, where the diameter of the tube is at its smallest, is called the apex of the shell. Each complete turn of the shell tube, each coil, is known as a whorl.

Oct 15, 2020 · In typical gastropods the shell is an expanding spiral supported by a central rod called a columella. Shells can be coiled in either of two directions. These are referred to as ‘Dextral’ = right-handed, and ‘Sinistral’ = left-handed. Most snail shells are dextral, especially among marine species.