A few days ago, my friend Michael Sims came to me with a paleontological quandary. The question centered on a cute little dinosaur. Michael’s young son is currently enamored with a rattle and pacifier modeled after a horned dinosaur, but, Michael wanted to know, which dinosaur? What’s the exact genus of the Wubbanub?

The answer is simple enough. The “Okey Dokey Dino” has a frill and three horns – one over each eye, and one on the nose. That’s classic Triceratops. And, appropriately enough, the plush dinosaur seems to be a juvenile Triceratops.

In 2006, paleontologists Jack Horner and Mark Goodwin published a landmark paper on how dramatically the appearance of Triceratops changed as the dinosaur grew up. Indeed,