Definition of cephalon in US English:



  • (in some arthropods, especially trilobites) the region of the head, composed of fused segments.

    • ‘This specimen cannot be specifically identified because it lacks the cephalon and first thoracic segment.’
    • ‘Members of the Agnostina have only two segments between the cephalon and pygidium, and never have cephalic sutures.’
    • ‘This problem is reflected in the ongoing uncertainty about the number of biramous appendages in the trilobite cephalon.’
    • ‘I assume that, as in Phacops and older trilobites, the cephalon bore one pair of antennae and three pairs of biramous limbs, and each thoracic segment a pair of limbs.’
    • ‘The anteriormost region was the cephalon and was constructed from segments that were commonly demarcated by lateral furrows in the glabella (the stomach capsule), but which were fused together.’


Late 19th century: from Greek kephalē ‘head’.