page_title: Timeline of pachycephalosaur research
section_title: 21st century
hierarchical_section_title: Timeline of pachycephalosaur research / 21st century
caption_attribution_description: Computed tomography images from TMP 79.14.853, Hansseusia sternbergi. Scale bar equals 5 cm. Sagittal section (A, B) of frontoparietal with arrow annotating low-density region immediately ventral to dorsal lesion (C); Coronal section (D, E) of frontoparietal dome illustrating low-density region immediately ventral to dorsal lesion (F).
context_page_description: 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.
caption: Hanssuesia
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