You mean that ssmall white blob only visible in the first frame? IMO the tail is not visible since the object, which could pass for a tail fin, in visible the successive frames. As far as I could see the only change looking strictly at the right hand side of the sequence is a white blob at the beginning.
The tail is the dark, flat-topped triangle,seen at the top of the right post, that is gone in the next frame.
The white blob is the dust and/or smoke from sliding along the ground.
Notice in the second frame, the dust now goes right up to the explosion, where previously it was green grass.