Definition of cephalon in US English:



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

    • ‘Members of the Agnostina have only two segments between the cephalon and pygidium, and never have cephalic sutures.’
    • ‘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.’
    • ‘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.’
    • ‘This problem is reflected in the ongoing uncertainty about the number of biramous appendages in the trilobite cephalon.’
    • ‘This specimen cannot be specifically identified because it lacks the cephalon and first thoracic segment.’


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