The investigations reveal that "larger domed pachycephalosaurs such as Pachycephalosaurus may have been head-butting like Dall sheep or head-shoving like bison, while smaller, high-domed taxa such as Stegoceras may have been flank-butting like mountain goats," Peterson said.
"Based on all of the evidence, I think it is likely that pachycephalosaurs butted their heads against 'something'-probably each other.
But, for the thick-headed pachycephalosaurs, there is little doubt in my mind that they were ramming their skulls," he said.
BONE HEAD Pachycephalosaurs, in Greek, means thick-headed lizards.
A variety of evidence undermines the notion of head-butting pachycephalosaurs, says Goodwin.
Microscopic analyses of fossils from pachycephalosaurs of various ages also counter the notion of head butting.
Goodwin and his colleague Jack Horner of Montana State University in Bozeman found that the distinctive fibers appeared in the skulls of young pachycephalosaurs. In adults, which might be expected to head butt regularly in mate and territory disputes, the fibers had disappeared, Goodwin and Homer reported in the spring 2004 Paleobiology.
"Pachycephalosaur domes are weird structures not exactly like anything in modern animals.
"Finding out brings us closer to their social lives: were pachycephalosaurs more likely just showing off their domes like peacocks with their tails, or were they also cracking their heads together like musk oxen?" he added.