Morphology of the Jaws and Radula in Ammonoids

  • Marion Nixon
Part of the Topics in Geobiology book series (TGBI, volume 13)


Some ammonoids have been found with structures still in the living chamber that are now recognized as jaws (beaks or mandibles) because small teeth, characteristic of those of the radula of extant Cephalopoda, lie between upper and lower jaws. The radulae so far found in ammonoids have the same number of teeth in each transverse row as do those of living Coleoidea, and the teeth are of similar shape and form. The first discovery was of just a few teeth in Eoasianites (Closs and Gordon, 1966), a member of the taxon Goniatitina. A year later, eight specimens of the same species, in which the radula and jaws were preserved together, were reported (Gloss, 1967). The jaws and radulae of two adult microconchs of Eleganticeras elegantulum, a Liassic ammonite, were found by Lehmann (1967); other descriptions have followed, mostly of jaws but also of radulae (for reviews see Lehmann, 1971a, 1981a,b, 1988, 1990; Dagys et al.,1989).


Lateral Tooth Body Chamber Shell Diameter Marginal Tooth Outer Plate 
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Copyright information

© Springer Science+Business Media New York 1996

Authors and Affiliations

  • Marion Nixon
    • 1
  1. 1.Research School of Geological and Geophysical SciencesBirkbeck College and University College LondonLondonEngland

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