Preface to Class of Polyplacophora

Photos: David Tipton
Literal meaning: Many plate bearers

Common name: Sea cradles or chitons

chiton Shell: The shell is composed of eight overlapping plates or valves. These are joined to each other on the outer margin and undersides to the girdle, a thickened part of the mantle.
  • Scales, spines or bristles may be present on the girdle.
  • Since the plates allow flexibility, the animal is able to mold itself to uneven surfaces or roll up in a ball to protect its soft under parts.

  • Animal: The animal has an elongated, bilaterally symmetrical body.
  • No tentacles or cephalic eyes are present although some species have light-sensitive spots in the integument covering the plates.
  • The mouth is anterior with a radula.
  • The anus is posterior.
  • The muscular foot allows the animal to move easily and to clamp down tightly on the firm substrate.
  • Adults range in size from 5mm to 35cm.

    Habitat: All Polyplacophorans are marine.

  • Specimens may be found from the shallow intertidal to the deep ocean depths in temperate to warmer seas.

    Etc: Approximately 600 living species are known.

    Food: Most feed by scraping algae off hard surfaces with the radula.

  • Some species prey on small crustaceans.

    Reference: Class - Polyplacophora {Chitons} H. M. D. de Blainville, 1816

    Ref. Abbott & Dance, 1982 p 284
    Amer. Fish. Soc., 1988 p 8,148
    Emerson & Jacobson, 1976 p 461
    Kaas & Van Belle, 1980
    Keen, 1971 p 19,861
    Keen & Coan, 1974 p 147
    Lindner, 1977 p 16
    Simon & Schuster, 1979 p 467
    Wagner & Abbott, 1977
    Syn. Amphineura in part
    Crepipoda A. Goldfuss, 1820
    Loricata C. F. Schumacher, 1817
    Ref. Abbott, 1974 p 392 Blainville, 1816
    Vaught, 1989 p 2

    Some taxonomists refer to Class Amphineura with Polyplacophora being a subclass. This index recognizes Polyplacophora as a separate class. References for Amphineura are: Keen, 1971 p 19, 859 and Keen & Coan, 1974 p 148. Formerly named classes Crepipoda, Loricata and Placophora are generally recognized today as Polyplacophora.