You're a spineless chicken! Er, perhaps it's a good insult, but it isn't very factual. If someone does call you a spineless chicken, you can wow them with your knowledge of the animal kingdom with a witty response like...
"First of all, people are mammals -- not birds. Secondly, neither birds nor mammals are spineless!"
Mammals are vertebrates, which means that they all have backbones (spines). Believe it or not, most animals don't have backbones -- mammals are one of the few groups that do.
All mammals, except some sea cows and sloths have seven bones in their necks. This includes giraffes who have VERY long spines! Their necks can be 6 1/2 feet long, but they're still made up of just seven bones.