But it looks like phylotypic animal body plans may have originated in cell aggregates before the development of the egg:

https://onlinelibrary.wiley.com/doi/epdf/10.1002/jez.b.21417

Therefore instead of Chicken of Theseus, I propose Chicken of Thesaurus.

Which itself is surely evolved from Chicken of Thesea.

And, consequently, canned tuna.