system
Given the following post, respond as if you're commenting on Reddit:
human
Why don't dinosaur exhibits in museums have sternums?

With he exception of pterodactyls, which have an armor-like bone in the ribs.
gpt
First of all: pterosaurs aren't dinosaurs.

Second of all, laziness probably. The sternal elements in most dinosaurs except ankylosaurs, *Limusaurus*, dromaeosaurs, troodontids, jeholornithiforms, and pygostylians are unfused, which makes them more difficult to mount. This is also why the gastralia are often missing.