Pterosaur Finger Bone?

[GPayton]

I've been doing a lot of exploration in the Grayson Formation (Lower Cretaceous) exposures south of Waco lately, and so last week I was doing some hunting on a nice marly slope in the South Bosque River. I picked up lots of pyritized heteromorph ammonites and some turritella, but what really caught my eye was this tiny piece of fossilized bone. I know that vertebrate material can be found in the Grayson - I've even found some nice Cretolamna and Ptychodus teeth myself - but this doesn't seem to be fish or shark. The walls of the inner cavity are extremely thin when you look at the cross section where it is broken which is what's leading me in the pterosaur direction. Maybe a metatarsal? Or a fragment of a larger bone from a much smaller species? Any help would be appreciated. 

[Rockwood]

Pterosaur bone seems quite possible. A clearer look at the cortical bone in cross section would be helpful though.