Yes. Marsupial fossils would represent mammals that gave live birth, but aren’t placental mammals either.

Multituberculates are a lineage of mammal that is completely extinct today, but they were closer to therians (placentals+marsupials) than monotremes. Some of them had incredibly narrow pelvic openings too, hinting that they may also have been live-birthers (of tiny, underdeveloped offspring like the marsupials.)

https://tetzoo.com/blog/2020/5/29/did-mesozoic-mammals-give-birth-to-live-babies-or-did-they-lay-eggs