Definition of orthocone in English:



  • 1The straight shell typical of early nautiloid cephalopods.

    • ‘Long straight slender smooth orthocones, similar internally to the Ellesmeroceratidae, developing broader cross section and a thin marginal siphuncle which may be somewhat separated from the ventral wall.’
    • ‘An orthocone is a usually long straight shell of a nautiloid cephalopod.’
    1. 1.1A fossil cephalopod with an orthocone shell.
      • ‘These latter orthocone ammonites do not modify the terminal body chamber, which cannot function as a floating egg-case.’
      • ‘This single specimen is unlike all the other embryologic orthocones, but we do not believe at this time that this single individual is sufficient to erect a new species.’
      • ‘The group continued right until the end of the Permian or - depending on the identification of the Triassic orthocones - the end of the Triassic.’