Clematis terniflora - sweet autumn clematis - is known for producing young foliage with a pronounced white center vein. And since it reseeds very freely in many areas - to the point of being considered invasive - it is quite likely that is a seedling of SAC. Interesting that it should pick the same location as an already existing clematis variety :-))

It is coming from a branch of Romantkia. I will see if I can get a pictute

I cut Romantkia back and this new growth has the strange leaves

Well, ya got me!! I've grown an awful lot of different clematis in my day and the ONLY one that has foliage that looks like this is SAC. Did your Romantika bloom as normal this season? It really looks like two different plants, IMO.

I think what happened was that a bird did plant the clematis with the strange leaves and Romantika cover the vine until I trimmed. I dug up the wild clematis because I love Romantika and don't want any other vine in the mix