Pachycephalosaurus, the "Thick-
Headed Lizard," is a wildly popular
dinosaur due to the theory that it
used its iconic dome-shaped head to
ram into each other like bighorn 
sheep. However, there is significant
debate in the scientific community
over head-butting's feasibility.
Some paleontologists believe that
the Pachycephalosuaurs' skeletons 
were too weak for it, but others
argue that the amount of infections
on their domes show that they did 
engage in this form of combat. But 
at four and a half meters long, one
and a half tall, with a twenty-five
centimeter thick skull, Pachycephal-
osaurus could still pack a punch no
matter how they fought. Males likely
had thicker skulls than females,
either for display or for battling
for mates.

Pachycephalosaurus' western United
States home was a mild to sub-
tropical coastal plain at the end of
the Cretaceous Period. Their small
teeth were probably used to nibble on
soft plant matter as they roamed the
countryside. They lived there 
alongside fan-favorite herbivores 
like Ankylosaurus and Triceratops 
and also with the fearsome killer 
Tyrannosaurus. The presence of two
smaller, less developed pachycepha-
losaurids, Dracorex and Stygimoloch, 
leads paleontologists to think that 
these species may actually represent 
growth stages of Pachycephalosaurus 
instead of separate taxa.
