No. 1 - - Stegosaurus of Colorado

[1] Colorado – Stegosaurus (1982)

shortly after this image was captured, the stegosaurus thagomized Kenny to death.

The coolest state dinosaur is definitively the Stegosaurus.

It looks cool, it’s a total classic and it’s covered in awesome and mysterious plates and spikes. Hailing in many instances from the Morrison Formation, some of which is in Colorado, around 80 samples of stegosaurus have emerged, giving paleontologists a lot of information to work with.

Stegosaurus’ weapon of choice is the Thagomizer, which is the actual name of its four-spiked tail. “Teeth,” “claws” and “horns” aren’t anywhere close to as cool as “thagomizer.”

Also, Colorado deserves wicked points for being a pioneer in naming an official state fossil by doing so in 1982, years before any of its contemporaries.

Stegosaurus is the largest of the stegosaurs, and adapted the awesome thagomizer and rows of plates by the mid-to-late Jurassic era, 150 million years ago, ages before ceratopsians became proficient in adapting horns and frills as deterrents from predators.

Hands down, the best official state dinosaur is stegosaurs.

References:

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

No 2 - - Triceratops of Wyoming

[2] Triceratops – Wyoming (1994) 
 

While not as awesome as stegosaurus, Wyoming has the second best official state dinosaur with the massive triceratops. At 12 tons and up to 9 metres in length, it was a badass monster with a massive skull (among the largest of all terrestrial animals) the largest of which is 2.5 metres in length, making the skull half the size of a stegosaurus - - and that’s just triceratops’ skull!)

Hailing from the Hell Creek formation, 38 skulls of this classic monster have helped make it one of the most famous and well-known dinosaurs of all. And believe it or not, back in the 1800s, the horns were initially believed to belong to a “large and unusual bison,” if you can believe it.

References:
http://en.wikipedia.org/wiki/Triceratops