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This timeline of pachycephalosaur research is a chronological listing of events in the history of paleontology focused on the pachycephalosaurs, a group of dome-skulled herbivorous marginocephalian dinosaurs. One of the first major events related to the history of pachycephalosaur research actually regards the discovery of an unrelated dinosaur called ''Troodon'', reported from the western United States by Joseph Leidy in 1856.〔 The type specimen of ''Troodon'' was simply an unusual tooth, but the close resemblance between ''Troodon'' teeth and pachycephalosaur teeth would cause taxonomic confusion for over a century. This was resolved by Phil Currie in 1987, who realized that ''Troodon'' belonged to a group of bird-like carnivores then known as saurornithoidids, but since renamed Troodontidae after ''Troodon'' itself.〔 The first scientifically documented true pachycephalosaur remains were discovered in Early Cretaceous rocks from England and named ''Stenopelix'' not long after ''Troodon'' was named in America.〔 Other notable early finds include the well-known pachycephalosaur ''Stegoceras validum''.〔 In 1924, Charles Whitney Gilmore named the family Troodontidae after ''Troodon'', but most of its members would be recognizable today as pachycephalosaurs.〔 Seven years later, Gilmore named the new species "''Troodon''" ''wyomingensis'' which would be formally reclassified as ''Pachycephalosaurus'' in 1943. ''Pachycephalosaurus'' was so unusual that Sternberg named a new family for it, the Pachycephalosauridae.〔 From the time paleontologists identified the pachycephalosaurs as a distinct group of dinosaurs, the chief mystery surrounding their biology has been the function of their distinctive cranial domes. Edwin Colbert interpreted the structure as a biological battering ram in 1955, but never specified who or what may have been on its receiving end. The idea that it was used in head butting between members of the same pachycephalosaur species was first proposed by science fiction writer Sprague de Camp. From then it became a staple of both scientific and cultural reconstructions of these animals.〔 Nevertheless, this perennial hypothesis would come to be criticized by researchers like Hans-Dieter Sues as less likely than "flank butting" where pachycephalosaurs' domed heads would be aimed at rivals' bodies rather than in head-to-head combat. Others, like Goodwin and others have thought the dome purely for display because its high density of internal blood vasculature may have rendered it too fragile for combat.〔 Meanwhile, in 1998 Chapman and others found the biomechanics of pachycephalosaur domes consistent with the old head-butting hypothesis, suggesting that the idea retains scientific merit.〔 ==19th century== 1856 * Joseph Leidy described the new genus and species ''Troodon formosus'' based on an isolated tooth crown. It was one of the first dinosaurs from North America to be formally named.〔 1857 * Meyer described the new genus and species ''Stenopelix valdensis''.〔 This taxon was one of only two known Early Cretaceous pachycephalosaurs as of 2004. It is also one of only two pachycephalosaurs known from Europe.〔 1872 * Leidy described the new genus and species ''Tylosteus ornatus''.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Timeline of pachycephalosaur research」の詳細全文を読む スポンサード リンク
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