This was creepy, he didn't like it one bit either as he made sure to keep himself facing the skeleton and hopefully drawing it's attention. Tsukishima would likely be able to feel the vibrations of the growl Skyfire lets out in frustration as he's trying to take the thing out without destroying the blade.

Once he's fairly sure the skeleton is focused on his claws as he tries to attack it, he whips his tail around fast and hard. It was an attempt to try and smash the end of his tail into it, aiming to send the thing flying into a cave wall... With the metal substructure underneath the false flesh in his tail, if it connected, it would be much like getting hit with a steel beam at high speed...