Please all travel from this topic to the current 'Something New At Meridiani on Sol 389 Discussion' and reply image #15 of Horton, as there is a classic 'fossil' appearance of a spinal section with external texturing and a small shiney white ovoid about the size of a chickens egg at the end of the assembly. Don't ever presume to have the answers in advance, if you expect to be correct all the time!
NASA image: 1P162717822ESF4700P2564L257R12c.jpg
or similar- it has been through a few hands to here- check the original as well.
Happy hunting.