This appears to be Northern Tooth Fungus, but would need to look at it more closely for certain identification. This fungus causes a heart rot on maples and other trees. In most cases the tree has to be tested for the exten of the decay. Presense alone of the fruiting bodies is usually not reason for removal, however, it should be reviewed by a certified arborist for risk assessment.
Northern Tooth Fungus-Climacodon septentrionale, Department of Biology, University of Wisconsin
Indiana Certified Arborists, International Society of Arboriculture
Lindsey Purcell, Urban Forestry Specialist
Department of Forestry and Natural Resources, Purdue University