Definition of lancelet in US English:



  • A small elongated marine invertebrate that resembles a fish but lacks jaws and obvious sense organs. Lancelets possess a notochord and are among the most primitive chordates.

    Subphylum Cephalochordata, phylum Chordata: several species, including amphioxus

    • ‘Unlike lancelets, however, Haikouella possessed a small number of pharyngeal bars that may have been composed of mucocartilage, as in modern lampreys.’
    • ‘To tease out the details of the transition, other researchers recently turned to lancelets, vertebrates' closest spineless relatives.’
    • ‘As examples, she worked on lampreys in the early sixties, molluscs and lancelet in the early seventies, and teleosts in the early eighties.’
    • ‘In lancelets, the trunk somites extend and fuse ventrally to give the unsegmented periviscelar coelom.’
    • ‘Biologists could examine the many living animals (such as lancelets and sea squirts) that represented stages in the transition from the invertebrates to the earliest jawless fishes.’


Mid 19th century: from the noun lance (because of its long narrow form) + -let.