Today I just randomly thought of Yoshi, and then suddenly have a feeling that the red thingy on the back of Yoshi looks like a shell. A simple Google search did result in some random links of people arguing whether that is a shell or a saddle.
However, Google search didn't get anything conclusive. Are there any strong evidences or canonical answers (e.g. from Nintendo) which perhaps unluckily didn't show up in Google search?
Here is an image on the Yoshi page on Wikipedia which I think that red thingy on his back really seems to resemble a shell:
(source: wikimedia.org)
2 Answers
The answer appears to be a shell used as a saddle.
"Yoshi was originally supposed to be a type of Koopa. That saddle you see on his back was actually his shell." —Super Mario World Director Takashi Tezuka, Super Mario History
Cite Source from Takashi Tezuka according to MarioWiki
It's a shell because ... Yoshi wears the same shoes as koopa, has the same back scales as koopa, has the same look as koopa, so the only missing thing is the shell!
