This could be an example of juvenile to adult transformation. The difference between juvenile and adult forms are usually much more subtle; it's rather uncommon to see such a huge differentiation. If the "two" are truly the same stem, let me apologize to you, Tom, for everyone's insistence that we can see better in a photograph than what you can see first hand.
I don't have a clue as to what the plant actually is, though.
Here is an example of seedlings I grew that are transforming form the juvenile to the adult stage.
--- the yellow arrow shows the cotyledons
--- the red arrow shows the juvenile foliage
--- the blue arrow shows the adult foliage
