Sculpture is a feature of many of the shells of mollusks. It is three-dimensional ornamentation on the outer surface of the shell, as distinct from either the basic shape of the shell itself or the pattern of colouration, if any. Sculpture is a feature found in the shells of gastropods,

bivalve Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, biv ...

s, and scaphopods. The word "sculpture" is also applied to surface features of the aptychus of ammonites, and to the outer surface of some

calcareous Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines. In zoology ''Calcareous'' is used as an a ...

opercula of marine gastropods such as some species in the family Trochidae. Sculpture can be concave or convex, incised into the surface or raised from it. Sometimes the sculpture has microscopic detailing. The term "sculpture" refers only to the

outer layer of shell, and does not include the proteinaceous periostracum, which is in some cases textured even when the underlying shell surface is smooth. In many

taxa In biology, a taxon ( back-formation from '' taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular n ...

, there is no sculpture on the shell surface at all, apart from the presence of fine growth lines. The sculpture has a protective function because it increases the diameter of the shell, distributing mechanical stress (such as the force of a predator's jaws) across a larger surface area.

List of terms

*Axial sculpture - Sculpture running parallel to the axis of coiling, an imaginary line through the apex of a shell about which the whorls are coiled. *Bead - A small hemispherical protuberance resembling a bead, similar to but smaller than a nodule. *Beaded - resembling rows or strings of beads. *Growth line - A fine transverse line marking the growth of the shell. * Lira, lirate - ornamented with fine thread-like lines or grooves. *Longitudinal sculpture - Sculpture following the direction of the axis of the shell. *Nodule - A rounded protuberance on the shell sculpture; larger than a bead. *Nodose, Nodulose, Nodular - Bearing small rounded protuberances or tubercules. *Ornament - Can refer to surface sculpture standing out in relief on shell surface; or simply to sculpture as a whole. * Plait - Folds on the

columella Lucius Junius Moderatus Columella (; Arabic: , 4 – ) was a prominent writer on agriculture in the Roman Empire. His ' in twelve volumes has been completely preserved and forms an important source on Roman agriculture, together with the ...

. *Pustule - A very fine knob-like protrusion, smaller than a tubercule. *Reticulate - Sculpture consisting of a criss-crossing network of riblets, threads, or grooves. *Rib - A strong ridge on the surface of the shell. *Riblet - Smaller than a rib, but coarser than a thread. *Spiral sculpture - Sculpture following the spiral growth of the shell. *Stria (plural ''striae'') - A shallow incised groove. *Striate - Ornamented with striae. *Thread - A very fine riblet. *Transverse sculpture - Sculpture parallel to the edge of the outer lip of the aperture. *Tubercle - Elevated knob-like projections or protrusions; larger than a pustule. *Varicose - Bearing one or more varices.

References

{{DEFAULTSORT:Sculpture (Mollusc) Mollusc shells