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|-Wannanosaurus yansiensis
|-?Yaverlandia bitholus
      |-Goyocephale lattimorei
      |-Micropachycephalosaurus hongtuyanensis
            |-Homalocephale calathocercos
                  |-Stegoceras validum
                  |-Stegoceras browni
                        |-Prenocephalini (non official clade)
                        |  |-Gravitholus albertae
                        |  |-Prenocephale prenens
                        |  |-?Prenocephale brevis
                        |  |-?Prenocephale edmontonensis
                        |  |-Tylocephale gilmorei
                        |  |-Tylocephale bexelli
                           |-Pachycephalosaurus wyomingensis
                           |-Stygimoloch spinifer

Pachycephalosaurids are unformally known as the "bone heads", because their skull roof was extra thick, and often hightened
into a dome, that could easily take great impacts, indicating the same behaviour as goats, and bulls, knocking their head together
with mighty power.
They were bipedal, and could run into each other with a hard crash.
It's an interesting speculation to put them in rocky environments, such as mountain goats.

They probably fed on low plants and bushes, and ranged from 2-5 metres. Due to the big skull Pachycephalosaurus used to be estimated to 8 metres of lenght. But Pachycephalosaurids
had pretty big skulls compared to body size, so the correct lenght would be closer to 5 metres.

Stygimoloch may actually be a "extra-spiky" Pachycephalosaurus, and that they are the
same species, but only differed by sexual dimorphism.

Pachycephalosaurids had teeth that resembled those of troodontids (the name Troödon validum was orriginally
classified as a pachycephalosaur), and it's highly possible that they were omnivorous, and could have
eaten flesh, if they found a corpse or easy prey.




Copyright 2001 © Øyvind M. Padron, all rights reserved