Neornithischia

Neornithischia ("new ornithischians") is a clade of the dinosaur order Ornithischia. They are the sister group of the Thyreophora within the clade Genasauria. Neornithischians are united by having a thicker layer of asymmetrical enamel on the inside of their lower teeth. The teeth wore unevenly with chewing and developed sharp ridges that allowed neornithischians to break down tougher plant food than other dinosaurs. Neornithischians include a variety of basal forms historically known as "hypsilophodonts", including the Parksosauridae; in addition, there are derived forms classified in the groups Marginocephalia and Ornithopoda. The former includes clades Pachycephalosauria and Ceratopsia, while the latter typically includes Hypsilophodon and the more derived Iguanodontia.

Neornithischians
Temporal range: Early Jurassic–Late Cretaceous, 199.6–66 Ma
Hypsilophodon skeletal mount at the Brussels Science Institute
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: †Ornithischia
Clade: †Genasauria
Clade: †Neornithischia
Cooper, 1985
Subgroups

Classification

Neornithischia was first named by Cooper in 1985 and defined as "all genasaurians more closely related to Parasaurolophus walkeri Parks, 1922, than to Ankylosaurus magniventris Brown, 1908 or Stegosaurus stenops Marsh, 1877a".[1]

A 2017 study by Matthew G. Baron, David B. Norman, and Paul M. Barrett recovered the Early Jurassic taxon Lesothosaurus diagnosticus from Southern Africa as the most basal known member of Neornithischia – a position previously held by Stormbergia dangershoeki (a taxon considered by the authors to be an adult form of Lesothosaurus and therefore a junior subjective synonym). However, Baron et al. go on to state that this result is only poorly supported and that future studies will be needed in order to better resolve the base of the ornithischian tree.[2]

The below cladogram follows an analysis by Clint A. Boyd published in 2015 on the relationships of neornithischians:[3]

Ornithischia
 

Pisanosaurus mertii

 
 
 

Heterodontosauridae

 
Genasauria
 

Thyreophora

 
Neornithischia
 

Stormbergia dangershoeki

 
 
 

Agilisaurus louderbacki

 
 
 

Hexinlusaurus multidens

 
 

Yandusaurus hongheensis

 
 

Leaellynasaura amicagraphica

 
 
Jeholosauridae
 

Yueosaurus tiantaiensis

 
 

Jeholosaurus shangyuanensis

 
 
 
 

Othnielosaurus consors

 
 
Cerapoda
 

Marginocephalia

 
 

Ornithopoda

 
 
Parksosauridae
Orodrominae
 
 

Oryctodromeus cubicularis

 
 

Koreanosaurus boseongensis

 
 
 
 

Zephyrosaurus schaffi

 
 
 

Kaiparowits ornithopod

 
 

Orodromeus makelai

 
 
 
 
Thescelosaurinae
 
 

Changchunsaurus parvus

 
 

Haya griva

 
 
 
 

Parksosaurus warreni

 
 
 
 

Thescelosaurus neglectus

 
 

Thescelosaurus assiniboiensis

 
 

Thescelosaurus garbanii

 
 
Elasmaria
 

Macrogryphosaurus gondwanicus

 
 

Notohypsilophodon comodorensis

 
 

Talenkauen santacrucensis

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

References
  1. Richard J. Butler; Paul Upchurch; David B. Norman (2008). "The phylogeny of the ornithischian dinosaurs". Journal of Systematic Palaeontology. 6 (1): 1–40. doi:10.1017/S1477201907002271.
  2. Matthew G. Baron; David B. Norman; Paul M. Barrett (2016). "Postcranial anatomy of Lesothosaurus diagnosticus (Dinosauria: Ornithischia) from the Lower Jurassic of southern Africa: implications for basal ornithischian taxonomy and systematics". Zoological Journal of the Linnean Society. doi:10.1111/zoj.12434.
  3. Clint. A Boy (2015). "The systematic relationships and biogeographic history of ornithischian dinosaurs". PeerJ. 3 (e1523). doi:10.7717/peerj.1523. PMC 4690359. PMID 26713260.


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