Spiralia

Spiralia is a group of protostome animals, it has many animals with a common ancestor like molluscs, annelids, platyhelminths and more groups. The term Spiralia comes from the fact that they have spiral cleavage, in their embryos. 

 Embryo growth 
Members of the molluscs, annelids, platyhelminths and nemerteans all have spiral cleavage in their embryos. Other groups like rotifers, brachiopods, phoronids, gastrotrichs, and bryozoans do not do it, but might have had it in the past.

 Family tree of Spiralians 
This is a version of the family tree of Spiralians.In 2019 this new version of the family tree was made.

In 2022 scientists found this family tree. 

 References