[Conan the Librarian]

It’s not a Stegosaurus.

There is no Thangomizer attached to the tail.

http://en.wikipedia.org/wiki/Thagomizer

[Alex Murphy]

It’s not a Stegosaurus. There is no Thangomizer attached to the tail.

ROTFL!

[Disambiguator]

The explanation is funny:

“The arrangement of spikes originally had no distinct name; the term Thagomizer was coined in 1982 by cartoonist Gary Larson in his The Far Side comic strip, and thereafter became gradually adopted as an informal term within scientific circles, research, and education.”

[bkopto]

From the picture, it seems to me that one could argue that the tail is not completely drawn, especially the part where the thagomizer would be located.