Yoshi definitely belongs to
a species of anthropomorphic dinosaur.
Super Mario World, where Mario and Luigi first meet Yoshi in his home, takes place in
Dinosaur Land. (And having Yoshi be a dinosaur is one of the few areas in which the
Super Mario Bros movie didn't radically depart from the source material!) The word dinosaur may literally mean "terrible lizard," but that's misleading as
there are significant differences between lizards and dinosaurs--they are two different categories of animal. (We didn't know better when we coined the term.) Then again, Yoshi does have characteristics of other species that I don't think any known dinosaur had--namely his frog like tongue!
Putting semantics aside though, the inclusion of Yoshi in
Super Mario World was perhaps an even bigger innovation to the
Super Mario franchise than taking it from 8-to-16 bits and adding to Mario's arsenal of mere power-ups! (One that was a long time coming no less, as Miyamoto wanted Mario to have a mountable dinosaur companion ever since the original
NES Super Mario Bros!) The only real comparison that comes to mind is the even longer-in-coming inclusion of a mountable steed in
The Legend of Zelda! And Yoshi easily surpasses that in terms of character and versatility! I'm hard pressed to think of another example, in video games at least, in which a mountable ride was given such a rich and versatile character that goes well beyond the usual "oh, now I can move faster and take another hit" etc.
