Size and Weight:
Its name notwithstanding, Pachyrhinosaurus (Greek for "thick-nosed lizard") was an entirely different creature from a rhinoceros, though these two plant-eaters do have a few things in common. Paleontologists believe Pachyrhinosaurus males used their thick noses to butt one another for dominance in the herd and the right to mate with females, much like modern-day rhinos, and both species were approximately the same length and weight (though Pachyrhinosaurus may have outweighed its modern counterpart by a ton or two).
That's where the similarities end, though. Pachyrhinosaurus was a ceratopsian, the family of horned, frilled dinosaurs (the most famous examples of which were Triceratops and Pentaceratops) that populated North America during the late Cretaceous period, only a few million years before the dinosaurs went extinct. Oddly enough, unlike most other ceratopsians, the two horns of Pachyrhinosaurus were set on top of its frill, not on its snout. (By the way, Pachyrhinosaurus may well have been the same dinosaur as a contemporary ceratopsian, Achelousaurus.)
Thanks to its numerous fossil specimens (including over a dozen partial skulls from Canada's Alberta province), Pachyrhinosaurus is quickly climbing the "most popular dinosaur" rankings, though the odds are slim that it will ever overtake Triceratops. This dinosaur should get a huge boost thanks to its starring role in Walking with Dinosaurs : The 3D Movie, slated for release in December 2013, and it has already featured prominently in the Disney movie Dinosaur and the History Channel TV series Jurassic Fight Club.