The Deacon's Physiology

In looking at The Deacon's physiology, I'm having a hard time fully reconciling it's biological origins with the final result- especially it's skull. I can certainly see the human/Engineer influence (humanoid form) and the color of it's skin (Black Goo) but the shape of the cranium doesn't make sense. It has been speculated that Cuddles is shaped like a squid (initially) because these creatures are driven by some form of sexual architecture in both their behavior and physiology- a sperm cell, basically. So perhaps this has also influenced The Deacon's cranial development? The Deacon also looks a lot less mechanical than the traditional xeno- the original had what looked like pipes around the head and neck, protrusions in the back and of course the tail. It has the second jaw, but this also doesn't make sense- humans, Engineers don't have this, and Hammerpede didn't develop this- so the Black Goo's genetic influence is not entirely consistent. We could make the argument that if an Engineer got face-hugged while suited, this could account for the Xeno's greater mechanical characteristics (we are assuming the suit is not just a shell but becomes an extension of Engineer physiology). But the Engineers are unisex and so if they are not producing sperm, then how, again, would we explain the original Xeno's cranium and second set of jaws?