A middle caudal vertebra of a diplodocid, presumably Tornieria africana , on display at the Museum fur Naturkunde Berlin, in left lateral view. Quick backstory: this post at Adam Mastroianni's Experimental History led me to this post at Nothing Human, and poking around there led me to another good'un: "Shallow feedback hollows you out". That post really hit for me, and it made me think about SV-POW!
Matt Wedel (Thu,) studied this question.