Ashton Kutcher & Mila Kunis -- Baby Mystery Solved! (PHOTO)

Ashton Kutcher and Mila Kunis revealed their baby in a shroud of mystery Thursday night ... but TMZ has cracked the code and can say definitely, positively, absolutely which baby is theirs ... well, that's what we think.

In case you missed it, the couple posted six baby photos (plus a dog and a llama) ... revealing one was Wyatt ... the rest were just random babies (plus the dog and llama).

But our crack photo team figured it out ... only one of the babies was wearing the swaddle and cap that are uniquely provided by Cedars-Sinai Medical Center ... where Mila gave birth Tuesday morning.

The llama comes in second.