Urbilaterian

Gave rise to the protostomia and deuterostomia
- Had to be simple based on this
Based on Hox genes common to most descendants:
- The Urbilaterian most likely had 6 segments
- It most likely had 2 eyes
- It most likely had a heart
- Had to be complex based on this
Due to lack of fossil evidence, we don't know much for certain about it