Lassaux's Sphinx Caterpillar

I found this caterpillar last year on Oxypetalum caeruleum. The native plant it usually feeds on is the vine Cynanchum racemosum or Talayote. I lost the photo of the full caterpillar. It is a Sphinx moth, but this one did not have the horn on it's rear. I was told that they lose it after one of the instars.