Sculpture is a feature of many of the shells of mollusks. It is

three-dimensional In geometry, a three-dimensional space (3D space, 3-space or, rarely, tri-dimensional space) is a mathematical space in which three values (''coordinates'') are required to determine the position (geometry), position of a point (geometry), poi ...

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

gastropod Gastropods (), commonly known as slugs and snails, belong to a large Taxonomy (biology), taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and fro ...

bivalve Bivalvia () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class (biology), class of aquatic animal, aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed b ...

s, and

scaphopod Scaphopoda (plural scaphopods , from Ancient Greek σκᾰ́φης ''skáphē'' "boat" and πούς ''poús'' "foot"), whose members are also known as tusk shells or tooth shells, are a class (biology), class of shelled Marine life, marine inve ...

s. The word "sculpture" is also applied to surface features of the aptychus of

ammonite Ammonoids are extinct, (typically) coiled-shelled cephalopods comprising the subclass Ammonoidea. They are more closely related to living octopuses, squid, and cuttlefish (which comprise the clade Coleoidea) than they are to nautiluses (family N ...

s, and to the outer surface of some calcareous opercula of marine gastropods such as some species in the family

Trochidae The Trochidae, common name top-snails or top-shells, are a family of various sized sea snails, marine gastropod molluscs in the subclass Vetigastropoda. This family is commonly known as the top-snails because in many species the shell resembles ...

. 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 calcareous 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''; : 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 name and ...

, 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. These are markings which extend from the summit of the whorls toward the umbilicus. The axial sculpture may be: ** Vertical, when the markings are in general parallelism with the axis of the shell. ** Protractive, when the markings slant forward from the preceding suture ** Retractive, when the markings slant backward from the suture *Bead - A small hemispherical protuberance resembling a bead, similar to but smaller than a nodule. *Beaded - resembling rows or strings of beads. *Cyrtoconoid spire - approaching a cone in shape, but with convex sides. *Growth line - A fine transverse line marking the growth of the shell. *

Lira Lira is the name of several currency units. It is the current Turkish lira, currency of Turkey and also the local name of the Lebanese pound, currencies of Lebanon and of Syrian pound, Syria. It is also the name of several former currencies, ...

, 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. *Prosocline - with the growth lines leaning forward (adapically) with respect to the direction of the cone. *Pustule - A very fine knob-like protrusion, smaller than a tubercle. *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

List of terms

See also

References