urbilaterian

== English == === Etymology === From ur- (“original”) +‎ bilaterian. === Noun === urbilaterian (plural urbilaterians) (biology) The hypothetical last common ancestor to all bilaterians. 2008, Philosophical Transactions: Biological Sciences, Volume 363, Issues 1493-1496, page 1523, This way, different aspects of the molecular architecture of the urbilaterian nervous system are reconstructed and yield insight into the degree of centralization that was in place in the bilaterian ancestors.