pachycephalosaurus - Science Definition[păkˌĭ-sĕfˌə-lə-sôrˈəs]
The American Heritage® Science Dictionary
A large herbivorous dinosaur of the genus Pachycephalosaurus of the late Cretaceous Period. It grew to about 7.6 m (25 ft) long and had a domed skull up to 25.4 cm (10 inches) thick that was lined with small bumps and spikes. The thick skull may have been used for head-butting during mating displays.
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