Late last fall I found a small bird nest with the skeletal remains of a baby bird in it. As I was looking at the bones under my microscope, I noticed that the tarsometatarsus was not fully fused together. My main question is this, based on the bones incomplete development, should I expect this baby bird, at the time of its death, to be still developing in the egg, or is this type of bone fusion continue out of the egg until the bird fledges? The bird bone pictured is 9mm long.

My second question; is this unfused stage of development a peek into this birds ancestral dinosaurian past??

paul

Post's pictures

DSCN0331.JPG, 3.87 mb, 4896 x 3672

The paper below implies that fusion occurs by the time the egg hatches (though this is not my area of expertise) so your assumption is probably correct. I don't know the answer to your second question.

http://onlinelibrary.wiley.com/doi/10.1002/ar.21179/pdf