Definition of bilaterian
: an animal having bilateral symmetry Scientists refer to animals, including humans, with this two-sided symmetry as bilaterians. — Carl Zimmer, New York Times, 21 June 2005 Comb jellies and cnidarians branched off before bilaterians diversified into the variety of animal groups known today, and they are considered relatively “simple” organisms. — Elizabeth Pennisi, Science, 6 July 2007
bilaterianadjective bilaterian animals … it is possible that bilaterian life emerged early in the Ediacaran, but at present, no fossils or trace fossils from this time have been reported. — Ernesto Pecoits et al., Science, 29 June 2012
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First Known Use of bilaterian
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