Bilateria

• A 3rd germ layer on top of [[Eumetazoa]], the [[mesoderm]]
• Bilaterally symmetric
• The [[Urbilaterian]]:
  • MRCA of the Bilaterians
  • Must have been extremely unspecialized to give rise to both [[deuterostomes]] and [[protostomes]]
• Anterior to Posterior positioning controlled by [[Hox Genes]]
  • In this case, they're called Hox cluster genes