Seeking maple tree ID help
We've got a maple tree in our front yard, part of a sort of hedge that has grown from windblown and bird-dropped seeds. It's a bit odd, and I'm not having any luck identifying the variety. The leaves are opposite, moderately indented, longer than they are wide, and relatively small compared with other maple leaves I've seen: about 7 cm long (a bit less than 3"). The seeds have pink wings and in almost all cases appear in groups of 3, instead of the pairs that are usual for most maples.
Can anyone please tell me what kind of maple we've got?
Thanks!