Help! Species identification.

[Bpswieringa]

I dug up a tree and put it in a training pot back in April and I don't know what it is! It seems very vigorous but I hope something can be done with it. If anyone knows what kind of tree this is that would be great.

 

[Michigan Tree Murderer]

Looks like a Buckthorn, not sure if they bonsai nice or not.

 

[Bpswieringa]

Looks like a Buckthorn, not sure if they bonsai nice or not.

Thanks that's what I was thinking.