Urochord

from WordNet (r) 3.0 (2006)

urochord
    n 1: primitive marine animal having a saclike unsegmented body
         and a urochord that is conspicuous in the larva [syn:
         {tunicate}, {urochordate}, {urochord}]
    2: a notochord of a larval tunicate typically confined to the
       caudal region

from The Collaborative International Dictionary of English v.0.48

Urochord \U"ro*chord\, n. [2d uro- + chord.] (Zool.)
   The central axis or cord in the tail of larval ascidians and
   of certain adult tunicates. [Written also {urocord}.]
   [1913 Webster] Urochorda

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