That is clearly a seedling or a sucker from your tuliptree(what we call
it here in michigan). Tuliptree is a member of the magnolia family and
is not related to other poplars. Trees are variable just like people,
and leaf morphology can be slightly different from tree to tree.
Chances are this is a seedling, and if the tree is a named cultivated
variety, you may be seeing traits more similar to the parent tree.

Toad