There are are 8 Magnolia species listed in our Native Plant Database , but Saucer Magnolia is not among them because it is a Hybrid.
These two links will tell you more about your plant.
about.com
missouribotanicalgarden.org
Painting the cuts on trees with pruning paint used to be highly recommended. Today, the tendency is to leave them unpainted. To learn more about pruning, check out these three links:
purdue.edu
ces.ncsu.edu
washington.umd.edu