Sculpture (mollusc)

Source: Wikipedia, the free encyclopedia.
The shell of the sea snail Epitonium scalare has a sculpture of sharp vertical ribs known as "costae"
The shell of the freshwater snail Bulinus forskalii has strong transverse ribs which form an angle at the shoulder

Sculpture is a feature of many of the

ammonites, and to the outer surface of some calcareous opercula of marine gastropods such as some species in the family Trochidae.[1]

Sculpture can be

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
, 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.[2]

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.
  • 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.

See also

  • Sculpturing
    — arthropod equivalent

References