THE PACHYCEPHALOSAURIAN DINOSAURS

Homalocephale

Hom-AL-oh-KEF-al-ee

Level head

Ornithischia: Pachycephalosauria

Late Cretaceous

Mongolia

Homalocephale was a medium-sized pachycephalosaur with a flat head. The top of its skull was very thick and the surface was rough. It was covered with pits and bony knobs. The most important feature of Homalocephale is that the skeleton is well known. Many pachycephalosaurs are only known from thickned skull roofs. The hip bones of Homalocephale are very wide and are loosely attached to the backbone. It has been suggested that Homalocephale may have given birth to live young, rather than lying eggs.

Pachycephalosaurus

PAK-ee-CEF-al-oh-SAW-rus

Thick-headed reptile

Ornithischia: Pachycephalosauria

Late Cretaceous

Western North America

Pachycephalosaurus was a very large bone-headed dinosaur. It was probably far bigger than its relatives – up to 15ft. (4.5m) long – although its skeleton is not known. The skull had a very thic top, just behind and above the eyes, and it was detailed with knobs and spines. It seems that Pachycephalosaurus used its head as a helmet while fighting with other members of its own species. Today, male deer and goats batter each other head-on in fighting for mates.

Stegoceras

Steg-O-ser-as

Covered horn

Ornithischia: Pachycephalosauria

Late Cratecous

Western North America

Stegoceras was a medium-sized plant-eater about 8ft. (2.5m) long with a very curious thick skull. It had a heavy skull covered with horny lumps and knobs. The top of the skull was very thick and it formed a high crest. This crest grew higher as Stegoceras grew older.