Belongs within: Saphornithischia.
Contains: Stegosauria, Ankylosauria, Ornithopoda, Pachycephalosauria, Ceratopsia.
The Genasauria are a major clade of herbivorous dinosaurs that have been defined as uniting the Thyreophora (armoured dinosaurs), Ornithopoda and Marginocephalia (pachycephalosaurs and ceratopsians). All Ornithischia surviving after the early Jurassic are members of this clade.
Basal genasaurs include Lesothosaurus diagnosticus, a lightly built bipedal species about two metres in length from the early Jurassic of southern Africa. Scelidosaurus harrisonii, a quadrupedal thyreophoran from the early Jurassic of England, is one of the best-preserved early dinosaurs.
Synapomorphies (Butler et al. 2007): Metacarpals with proximal ends not block-like; manual phalanges/metacarpals with at least some extensor pits on dorsal surface of distal end absent or poorly developed; manual unguals not strongly recurved, without prominent flexor tubercle; brevis shelf and fossa with fossa facing ventrolaterally, visible in lateral view along entire length, creating deep postacetabular portion.
<==GenasauriaBSN07
|--Thyreophora [Ankylosauromorpha]NWW04b
| | i. s.: Bienosaurus Dong 2001NWW04b
| | `--B. lufengensis Dong 2001 (n. d.)NWW04b
| | Lusitanosaurus de Lappaarent & Zbyszewski 1957NWA04b, D07
| | `--L. liasicus Lapparent & Zbyszewski 1957 (n. d.)NWW04b
| |--+--Lesothosaurus Galton 1978FR24, NWW04a
| | | `--L. diagnosticus Galton 1978NWW04a [incl. Stormbergia dangershoekiFR24]
| | `--Laquintasaura venezuelaeFR24
| `--+--+--Emausaurus Haubold 1991FR24, NWW04b
| | | `--E. ernsti Haubold 1991NWW04b
| | `--Scutellosaurus Colbert 1981FR24, NWW04b
| | `--S. lawleri Colbert 1981NWW04b
| `--ThyreophoroideaFR24
| |--Scelidosaurus Owen 1860 [Scelidosauridae]NWW04b
| | `--S. harrisonii Owen 1861NWW04b
| `--+--Yuxisaurus kopchickiFR24
| `--+--Jakapil kaniukuraFR24
| `--EurypodaNWW04b
| |--StegosauriaNWW04b
| `--AnkylosauriaNWW04b
`--NeornithischiaBSN07
| i. s.: GongbusaurusNS04
| |--G. shiyii Dong, Zhou & Zhang 1983 (n. d.)NWW04a
| `--G. wucaiwanensis Dong 1989NS04
| Othnielosaurus celerBSN07
| Phyllodon henkeli Thulborn 1973 (n. d.)FR24, NS04
| Xiaosaurus Dong & Tang 1983FR24, D07
| `--X. dashanpensis Dong & Tang 1983 (n. d.)NWW04a
|--Agilisaurus Peng 1990BNB17, NS04
| |--A. louderbacki Peng 1990NS04
| `--A. multidens (He & Cai 1983) [=Yandusaurus multidens]NS04
`--+--Hexinlusaurus multidensBNB17
|--Sanxiasaurus modaoxiensisFR24
`--+--Minimocursor phunoiensisFR24
|--Yandusaurus He 1979FR24, NS04
| `--Y. hongheensis He 1979NS04
`--+--Nanosaurus Marsh 1877FR24, M96 (see below for synonymy)
| `--*N. agilis Marsh 1877M96 (see below for synonymy)
`--PyrodontiaFR24
| i. s.: ‘Laosaurus’ minimus Gilmore 1924 (n. d.)FR24, NS04
|--Thescelosauridae [Parksosauridae]FR24
| |--OrodrominaeFR24
| | | i. s.: Nevadadromeus schmittiFR24
| | |--+--Zephyrosaurus Sues 1980FR24, NS04
| | | | `--Z. schaffi Sues 1980NS04
| | | `--+--Oryctodromeus Varricchio, Martin & Katsura 2007FR24, D07
| | | | `--O. cubicularisD07
| | | `--Orodromeus Horner & Weishampel 1988FR24, NS04
| | | `--O. makelai Horner & Weishampel 1988NS04
| | `--+--Koreanosaurus boseongensisFR24
| | `--Albertadromeus syntarsusFR24
| `--Thescelosaurinae [Jeholosauridae]FR24
| |--Yueosaurus tiantaiensisFR24
| `--+--Changmiania liaoningensisFR24
| `--+--Haya grivaFR24
| `--+--+--Jeholosaurus Xu, Wang & You 2000FR24, NS04
| | | `--J. shangyuanensis Xu, Wang & You 2000NS04
| | `--Changchunsaurus parvusFR24
| `--+--Parksosaurus Sternberg 1937FR24, NS04
| | `--P. warreni (Parks 1926) [=Thescelosaurus warreni]NS04
| `--Thescelosaurus Gilmore 1913FR24, NS04 [incl. Bugenasaura Galton 1995FR24, NS04]
| |--T. assiniboiensisFR24
| |--T. garbanii Morris 1976FR24, NS04 [=Stygimoloch garbaniiS03]
| |--T. infernalis (Galton 1995)FR24, NS04 [=Bugenasaura infernalisFR24]
| `--T. neglectus Gilmore 1913 [incl. T. edmontonensis Sternberg 1940]NS04
`--+--Kulindadromeus zabaikalicusFR24
`--CerapodaFR24
| i. s.: Siluosaurus zhangqiani Dong 1997 (n. d.)FR24
|--OrnithopodaFR24
`--MarginocephaliaFR24
|--PachycephalosauriaZY09
`--CeratopsiaZY09
Nanosaurus Marsh 1877FR24, M96 [incl. Drinker Bakker, Galton et al. 1990NS04, Othnielia Galton 1977NS04; Nanosauridae]
*Nanosaurus agilis Marsh 1877M96 [incl. Laosaurus consors Marsh 1894NS04, Othnielosaurus consorsFR24, L. gracilis Marsh 1878NS04, Drinker nisti Bakker, Galton et al. 1990FR24, NS04; incl. Nanosaurus rex Marsh 1877NS04, Othnielia rexFR24]
*Type species of generic name indicated
References
[BNB17] Baron, M. G., D. B. Norman & P. M. Barrett. 2017. A new hypothesis of dinosaur relationships and early dinosaur evolution. Nature 543: 501–506.
[BSN07] Butler, R. J., R. M. H. Smith & D. B. Norman. 2007. A primitive ornithischian dinosaur from the Late Triassic of South Africa, and the early evolution and diversification of Ornithischia. Proceedings of the Royal Society of London Series B—Biological Sciences 274 (1621): 2041–2046.
[D07] Dixon, D. 2007. The Complete Illustrated Encyclopedia of Dinosaurs & Prehistoric Creatures. Hermes House: London.
[FR24] Fonseca, A. O., I. J. Reid, A. Venner, R. J. Duncan, M. S. Garcia & R. T. Müller. 2024. A comprehensive phylogenetic analysis on early ornithischian evolution. Journal of Systematic Palaeontology 22 (1): 2346577.
[M96] Marsh, O. C. 1896. The Dinosaurs of North America: Washington.
[NS04] Norman, D. B., H.-D. Sues, L. M. Witmer & R. A. Coria. 2004. Basal Ornithopoda. In: Weishampel, D. B., P. Dodson & H. Osmólska (eds) The Dinosauria 2nd ed. pp. 393–412. University of California Press: Berkeley.
[NWW04a] Norman, D. B., L. M. Witmer & D. B. Weishampel. 2004a. Basal Ornithischia. In: Weishampel, D. B., P. Dodson & H. Osmólska (eds) The Dinosauria 2nd ed. pp. 325–334. University of California Press: Berkeley.
[NWW04b] Norman, D. B., L. M. Witmer & D. B. Weishampel. 2004b. Basal Thyreophora. In: Weishampel, D. B., P. Dodson & H. Osmólska (eds) The Dinosauria 2nd ed. pp. 335–342. University of California Press: Berkeley.
[ZY09] Zheng, X.-T., H.-L. You, X. Xu & Z.-M. Dong. 2009. An Early Cretaceous heterodontosaurid dinosaur with filamentous integumentary structures. Nature 458: 333–336.