•backbone⪢⪢
Though introduced 30 years after helicopters were a part of the U.S. air fleet, the CH-47 Chinook became the backbone of numerous major operations carried out by the military.
http://qindex.info/i.php?x=26416
○○○vertebrate⪢⪢
Snakes are also vertebrates which means that they have a backbone. Actually snakes are almost ALL backbone! A snake's skeleton is most made of its skull, the vertebrate (or bones of the spine) and ribs.
http://qindex.info/i.php?x=16217
○○○ vertebrate ⪢⪢
○○○ vertebrate ⪢⪢
