It looks like a smilax to me.

I think the photos show veining that runs parallel to the leaf edges. So that makes me more inclined to favor the smilax ID.

I don't think it is Crossvine, the leaves are too thick and leathery.

FWIW I did follow down to the bottom of the vine and found what may be a prickle?

Smilax smallii likely

I looked up S. smallii. which is described as "mostly unarmed" attractive foliage apparently collected for the florist trade. One problem - I didn't mention my pix were taken @ Marshy Hope Swamp in Maryland and S. smallii doesn't range that far north.

One evergreen Smilax that does come into Maryland is S. laurifolia. Foote & Jones describes it as "The leathery leaves tend to stand erect, they are dark green above with a prominent midvein beneath".

Also according to Flora of Virginia about S. laurifolia "prickles sometimes lacking".

So I have settled on Smilax laurifolia unless someone can convince me otherwise.

Sounds good Sam! I'm certainly not a Smilax expert! But there aren't many evergreen vines in our region with spines/prickles.