Micropachycephalosaurus, a tiny thick headed lizard, is a genus of ornithischian dinosaur from the Upper Cretaceous. It was a herbivore, and lived in what is now Shandong, China. It was one of the smallest dinosaur ever discovered, just over a meter long, but with the longest name. Before it was discovered Compsognathus was the smallest known dinosaur.
Temporal range: Upper Cretaceous 70.6–68.5 mya
The lack of the skull roof means the fossil cannot be placed at family level. It might or might not be a pachycephalosaur. Butler and Zhao therefore classified it as an indeterminate member of the Cerapoda. In 2011, cladistic analysis showed that Micropachycephalosaurus is a basal member of the Ceratopsia. In this context, basal does not mean 'ancestral'; the fossil is far too late for that. It means simply 'unspecialized', or lacking derived traits.
- Butler R.J. and Zhao Q. 2009. The small-bodied ornithischian dinosaurs Micropachycephalosaurus hongtuyanensis and Wannanosaurus yansiensis from the Late Cretaceous of China. Cretaceous Research 30(1):63-77. doi:10.1016/j.cretres.2008.03.002
- Butler, Richard J. et al (2011). "The postcranial osteology and phylogenetic position of the small ornithischian dinosaur Changchunsaurus parvus from the Quantou Formation (Cretaceous: Aptian–Cenomanian) of Jilin Province, north-eastern China". Palaeontology 54 (3): 667–683. doi:10.1111/j.1475-4983.2011.01046.x.