OK, it just has an extremely black head then! I've found some baby Sonora and they just looked like smaller version of the adults. This was in southeast NM, so maybe it's just a locale thing...?
:Oh, it's not tantilla, it's got a cream colored belly, and the black on the head is fading. The larger sonorans I have all have dusky heads, like they had black heads as neonates. there was a debate some long time ago in this forum about whether it was Tantilla or Sonora, and finally the debate concluded that it was Sonora Semiannulata. Other than size and coloration they are absolutely identical, down to the size and placement of scales, facial scales, etc. And the "tantilla lookalike" does not have an orange belly.