1979 Edition

Aptychus, anaptychus

  • U. Lehmann
Reference work entry

The term aptychus is from the Greek meaning a body apparently folded into two parts. Aptychi are symmetrical pairs of calcareous plates which in vivo were in contact along their hinge-like straight line of symmetry. They are often found close to or inside the shells of ammonoid cephalopods, and sometimes even closing the aperture of the shell.

Superficially, aptychi resemble bivalve shells, in that their concave surface is smooth and the convex surface is ornamented in various ways: granulated, ribbed, furrowed, or punctate ( Fig. 1). Between the outer and inner layers, a middle layer with a cellular or tubular structure may be found. If aptychi are completely preserved, a thin dark layer of horny or chitinous material covers the innermost calcareous layer. In section, aptychi consist of an outer calcareous layer; a middle layer with cellular or tubular structure; an inner calcareous layer; and, if completely preserved, a thin dark innermost layer of horny or chitinous material.
This is a preview of subscription content, log in to check access.


  1. Kaiser, P., and Lehmann, U., 1971. Vergleichende Studien zur Evolution des Kieferapparates rezenter und fossiler Cephalopoden, Paläont. Zeitschr., 45, 18–32.Google Scholar
  2. Lehmann, U., 1970. Lias-Anaptychen als Kieferelemente (Ammonoidea), Paläont. Zeitschr., 44, 25–31.Google Scholar
  3. Lehmann, U., 1971. New aspects in ammonite biology, Proc. N. Amer. Paleontological Conv., pt. I, 1251–1269.Google Scholar
  4. Lehmann, U., 1972. Aptychen als Kieferelemente der Ammoniten, Paläont. Zeitschr., 46, 34–48.Google Scholar
  5. Schindewolf, O. H., 1958. Über Aptychen (Ammonoidea), Palaeontographica, A, 111, 1–46.Google Scholar
  6. Trauth, F., 1927-1936. Aptychenstudien, I-VIII, Ann. Naturhist. Mus. Wien, 41–47.Google Scholar


Copyright information

© Dowden, Hutchinson & Ross, Inc. 1979

Authors and Affiliations

  • U. Lehmann

There are no affiliations available