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  • Belemnites
    • Morphology
      • Eye
        • For sight
      • Phragmacone
        • Chambered part in the centre of the guard which during life would have been filled with gas for buoyancy
      • Pro-ostracum
        • Extension of the guard, possibly for protection from damage. Covered the head and tentacles
      • Tentacles
        • Part of the soft tissue used to propel the organism backwards
      • Protoconch
        • First chamber of the Phragmacone
      • Siphuncles
        • Tube linking chambers which controlled the amount of gas in each chamber, and so controlled the position of the organism in the water column
      • Guard
        • solid internal skeleton
    • Mode of life
      • Nektonic
      • Vertical movement controlled by gas chambers
      • Horizontal movement controlled by tentacles
      • alignment of the guard in sediment can be used to determine the palaeocurrent direction
    • Mollusca, Cephelopoda
    • Devonian to cretaceous
      • Extinct


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