then again, it would be neither definitively. It could have been born a turkey but through natural adaption it varied enough from turkey to create its own niche as a chicken which could have happened at any arbitrary point during its beginning.
what predates dinosaurs? the basic building blocks life started off as single cell organisms like algae. Before that, closest thing to life was a group of nucleic acids, proteins, lipids and carbohydrates which resembled neither an egg or animal.