Two small, spiky dinosaurs previously identified as separate species Dracorex and Stygimoloch have been suggested to actually be juvenile Pachycephalosaurus individuals.
Notes on verification
Confirmed by peer-reviewed primary source (Horner & Goodwin 2009, PLoS ONE) and corroborated by independent science journalism (Science News) and secondary paleontology sources. Hypothesis is widely accepted though still debated by some researchers.
Sources
- Dome-headed dinosaurs are rare. Scientists just found the most ... (nationalgeographic.com)
- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2762616/ (ncbi.nlm.nih.gov)
- https://www.sciencenews.org/article/three-dino-types-may-be-just-three-dino-ages (sciencenews.org)
- https://dino.fandom.com/wiki/Stygimoloch (dino.fandom.com)