I have been going around in circles trying to figure out which of these is a pothos or a philodendron or if these are just something else entirely. All were in a jar of water that were given to me and I call them the mystery plants.
Pothos has a larger, waxier leaf. Philodendron has a dainty stem. My guess is that you have a heart shaped philodendron.
This is an ongoing debate and there are dozens of websites that talk about the differences.
This is just one of many and each one is more confusing than the next because there are adult leaves, juvenile leaves, under watered issues, over watered issues etc....see the article on the link:
I say send a photo to the experts at your local home extension and let them give the final blessing on what you have!!
The finder is easy to use if you are in the US. Post back what you learn: