Iguanodontia (the iguanodonts) is a clade of herbivorous dinosaurs that lived from the Middle Jurassic to Late Cretaceous. Some members include Camptosaurus, Dryosaurus, Iguanodon, Tenontosaurus, and the hadrosaurids or "duck-billed dinosaurs". Iguanodontians were one of the first groups of dinosaurs to be found. They are among the best known of the dinosaurs, and were among the most diverse and widespread herbivorous dinosaur groups of the Cretaceous period.[1]

Temporal range: Middle JurassicLate Cretaceous, 163–66 Ma
Display at the Sam Noble Oklahoma Museum of Natural History, Norman, Oklahoma (5977785055)
Tenontosaurus skeletal mounts at the Sam Noble Oklahoma Museum of Natural History
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Ornithischia
Suborder: Ornithopoda
Clade: Iguanodontia
Baur, 1891


Camptosaurus fruita
Skeletal mount of Camptosaurus at the Museum of Western Colorado’s Dinosaur Journey Museum

Iguanodontia is often listed as an infraorder within a suborder Ornithopoda, though Benton (2004) lists Ornithopoda as an infraorder and does not rank Iguanodontia. Traditionally, iguanodontians were grouped into the superfamily Iguanodontoidea and family Iguanodontidae. However, phylogenetic studies show that the traditional "iguanodontids" are a paraphyletic grade leading up to the hadrosaurs (duck-billed dinosaurs). Groups like Iguanodontoidea are sometimes still used as unranked clades in the scientific literature, though many traditional "iguanodontids" are now included in the more inclusive group Hadrosauroidea.

Iguanodontia was originally phylogenetically defined, by Paul Sereno, in 1998, as the most inclusive group containing Parasaurolophus walkeri but not Hypsilophodon foxii. Later, in 2005, he amended the definition to include Thescelosaurus neglectus as a secondary external specifier, alongside Hypsilophodon, accounting for the paraphyletic nature of Hypsilophodontidae.[2] A 2017 study which named and described Burianosaurus noted that the type species Iguanodon bernissartensis must be part of the definition, and that the 2005 definition would, in their analysis, include a far larger group than intended (including Marginocephalia). They proposed an entirely new, node-based definition: the last common ancestor of Iguanodon bernissartensis, Dryosaurus altus, Rhabdodon priscus, and Tenontosaurus tilletti.[3]

The cladogram below follows an analysis by Madzia et al. (2017):[3]
















  1. ^ McDonald, A.T.; Kirkland, J.I.; DeBlieux, D.D.; Madsen, S.K.; Cavin, J.; Milner, A.R.C.; Panzarin, L. (2010). Farke, Andrew Allen (ed.). "New Basal Iguanodontians from the Cedar Mountain Formation of Utah and the Evolution of Thumb-Spiked Dinosaurs". PLoS ONE. 5 (11): e14075. doi:10.1371/journal.pone.0014075. PMC 2989904. PMID 21124919.
  2. ^ Sereno, Paul (2005). "Iguanodontia". TaxonSearch. Retrieved July 5, 2018.
  3. ^ a b Madzia, Daniel; Boyd, Clint A.; Mazuch, Martin (2017). "A basal ornithopod dinosaur from the Cenomanian of the Czech Republic". Journal of Systematic Palaeontology. 16 (11): 967–979. doi:10.1080/14772019.2017.1371258.

External links


Anabisetia ( AH-nə-bee-SET-ee-ə) is a genus of iguanodont dinosaur from the Late Cretaceous Period of Patagonia, South America. It was a small bipedal herbivore, around 2 metres (6 ft 7 in) long.


Burianosaurus is a genus of ornithopod dinosaur that lived in what is now the Czech Republic (it was found in 2003 near the city of Kutná Hora), being the first validly named dinosaur from that country. It was named B. augustai in 2017; the genus name honours the Czech palaeoartist Zdeněk Burian, and the species name honours the Czech palaeontologist Josef Augusta. The holotype specimen is a femur discovered in 2003, which was described as possibly belonging to an iguanodont in 2005.


Darwinsaurus (meaning "Darwin's lizard") is a genus of herbivorous styracosternan ornithopod dinosaur.

In the early nineteenth century dinosaur remains were discovered in the Shornden Quarry at Shorden near Hastings in East Sussex. These were first reported by Richard Owen in 1842. In 1889 they were referred to Iguanodon fittoni by Richard Lydekker. They were then assigned to Hypselospinus fittoni by David Bruce Norman in 2010.

In 2012 Gregory S. Paul named them as a separate genus and species. The type species is Darwinsaurus evolutionis. The generic name honours Charles Darwin for his theory of evolution. The specific name refers to evolution in general and specifically to the strong evolutionary radiation that iguanodonts, according to Paul, are a prime example of. The holotype, as indicated by Paul, is an associated skeleton that includes material catalogued under the numbers NHMUK R1831, R1833, and R1835 (Paul mistakenly included NHMUK R1836 in the genus, unaware that it came from the younger Wessex Formation). Included by Lydekker and Norman was also specimen NHMUK R1832, lower arm elements.

Paul in 2012 provided a short diagnosis of Darwinsaurus. The dentary, the front bone of the lower jaw, is straight. An elongated diastema is present between the beak and the row of teeth. The dentary is shallow below the diastema and deeper below the teeth. The foremost dentary teeth are smaller. The arm is very robust. The olecranon of the ulna is well-developed. Some carpalia are very large. The metacarpals are rather elongated. The thumb spike, the claw of the first finger, is massive.Paul and Norman are in disagreement about the form of the diastema. According to Paul, an illustration in Lydekker (1889) shows that the fossil originally possessed a long and low gap between the tooth battery and the beak; subsequent damage would have removed three or four very small teeth in front of the main row. Norman, however, disputes this and thinks damage has considerably lowered the jaw, the front teeth originally having been large, resulting in a narrow diastema.Paul considered Darwinsaurus a basal member of the Iguanodontia.Norman (2013) considered Paul's description of Darwinsaurus to be inadequate, treating D. evolutionis as a junior synonym of Hypselospinus fittoni, and noting that NHMUK 1836, an associated partial skeleton from the late Barremian of the Isle of Wight, can referred to the species Mantellisaurus atherfieldensis. In a recent SVP abstract, Karen Poole considered Darwinsaurus a possible junior synonym of Huxleysaurus based on unpublished cladistic results.


Dysalotosaurus (meaning 'uncatchable lizard') is a genus of herbivorous iguanodontian dinosaur. It was a dryosaurid iguanodontian, and its fossils have been found in late Kimmeridgian age-rocks (Late Jurassic) of the Tendaguru Formation, Tanzania. The type and only species of the genus is D. lettowvorbecki. This species was named by Hans Virchow in 1919 in honour of the Imperial German Army Officer, Paul von Lettow-Vorbeck. For much of the 20th century the species was referred to related and approximately contemporary genus Dryosaurus, but newer studies reject this synonymy. In 2016, Gregory S. Paul estimated its length at 2.5 metres (8.2 ft), its weight at 80 kilograms (180 lb).


Eousdryosaurus ("eastern Dryosaurus") is a genus of basal iguanodontian dinosaur known from a partial skeleton discovered in Upper Jurassic rocks in western Portugal.


Hypsilophodontidae (or Hypsilophodontia) is a traditionally used family of ornithopod dinosaurs, generally considerd invalid today. It historically included taxa from across the world, and spanning from the Middle Jurassic until the Late Cretaceous. This inclusive status was supported by some phylogenetic analyses from the 1990s and mid 2000s, although there have also been many finding that the family is an unnatural grouping which should only include the type genus, Hypsilophodon, with the other genera being within clades like Thescelosauridae. A 2014 analysis by Norman recovered a grouping of Hypsilophodon, Rhabdodontidae and Tenontosaurus, which he referred to as Hypsilophodontia. All other analyses from around the same time have instead found these latter taxa to be within Iguanodontia.


Kukufeldia is a genus of iguanodont dinosaur that existed in what is now England during the Early Cretaceous period. Identified from a nearly complete right dentary (NHMUK 28660) found near Cuckfield and originally described in 1848 by Gideon Mantell, it was named by Andrew T. McDonald, Paul M. Barrett, and Sandra D. Chapman in 2010, and the type species is Kukufeldia tilgatensis. It was originally identified as Iguanodon anglicus, but the authors consider this a nomen dubium of which the type specimen BMNH 2392, some teeth found at the same location, is undiagnostic. The generic name refers to Kukufeld ("Cuckoo's Field"), the name of Cuckfield in the eleventh century, and the specific name refers to Tilgate Forest, the name then of the geological layer it was found in. Kukufeldia is within Iguanodontia a member of the Styracosterna.


Magnamanus is an extinct genus of herbivorous ornithischian dinosaur belonging to Iguanodontia, that lived during the Early Cretaceous in Spain.


Morrosaurus is an extinct genus of herbivorous ornithischian dinosaur member of the Euornithopoda, that lived in the late Cretaceous in the Antarctica. The only known species is the type Morrosaurus antarcticus.


Nanyangosaurus is a genus of herbivorous ornithischian dinosaur belonging to Hadrosauroidea that lived in the Late Cretaceous of present-day Henan Province, China.

In 1994 the remains of Nanyangosaurus were found near the village of Houzhuang, in Neixiang county in Henan. The type species, Nanyangosaurus zhugeii, was described by Xu Xing, Zhao Xijin, Lü Junchang, Huang Wanbo, Li Zhanyang and Dong Zhiming in 2000. The generic name is derived from the city of Nanyang. The specific name honours one of the most famous historic inhabitants of that city, the legendary strategist Zhuge Liang.The specimen, holotype IVPP V 11821, was excavated in the Xiaguan Formation dating to the Turonian-Campanian stages. It consists of a partial skeleton lacking the skull. Eight posterior dorsal vertebrae, a sacrum of six vertebrae and a tail of thirty-six vertebrae have been preserved, together with a partial ischium, a forelimb and a hindlimb. The describers considered Nanyangosaurus to be of Albian age because of its primitiveness, but the type horizon is now believed to be Turonian-Campanian in age based on plant and invertebrate fossils.Nanyangosaurus was a rather small euornithpod with an estimated length of four to five metres. The length of the femur is 517 millimetres. The forelimbs were relatively long with a long hand. The first digit of the hand was completely absent including the first metacarpal; according to the describers this was not an accident of preservation but the actual condition of the living animal. The species would then not have possessed the thumb spike typical of its relatives.

According to a cladistic analysis performed by the describers, Nanyangosaurus was a basal member of the Iguanodontia, more derived than Probactrosaurus and closely related to the Hadrosauroidea.


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.


Ornithopods () or members of the clade Ornithopoda ( or ) are a group of ornithischian dinosaurs that started out as small, bipedal running grazers, and grew in size and numbers until they became one of the most successful groups of herbivores in the Cretaceous world, and dominated the North American landscape. Their major evolutionary advantage was the progressive development of a chewing apparatus that became the most sophisticated ever developed by a non-avian dinosaur, rivaling that of modern mammals such as the domestic cow. They reached their apex in the duck-bills (hadrosaurs), before they were wiped out by the Cretaceous–Paleogene extinction event along with all other non-avian dinosaurs. Members are known from all seven continents, though they are generally rare in the Southern Hemisphere.


Parksosauridae is a clade or family of small ornithischians which have previously been generally allied to hypsilophodontids. Parksosauridae is often considered a synonym of Thescelosauridae, but the two groups cannot be synonyms because Parksosauridae is defined as a stem, while Thescelosauridae is defined as a node.


Penelopognathus ("wild duck jaw") is a genus of dinosaur which lived during the Early Cretaceous. It was an iguanodont ancestral to hadrosaurids. Fossils have been found in the Bayin-Gobi Formation in what is now China. The type species, Penelopognathus weishampeli, was described by Godefroit, Li, and Shang in 2005, based on fragmentary jaw fossils.


Ratchasimasaurus (meaning "Ratchasima lizard") is a genus of non-hadrosaurid iguanodontian ornithopod dinosaur from Early Cretaceous (Aptian stage) Khok Kruat Formation of Nakhon Ratchasima Province in northeastern Thailand. The type and only species is R. suranareae, named after Thao Suranari, a 19th-century war heroine. It was considered by one study to be a nomen dubium, diagnosed with characters widespread in Styracosterna.


Rhabdodon (meaning "fluted tooth") is a genus of ornithopod dinosaur that lived in Europe approximately 70–66 million years ago in the Late Cretaceous. It is similar in build to a very robust "hypsilophodont" (non-iguanodont ornithopod), though all modern phylogenetic analyses find this ("Hypsilophodontia/tidae") to be an unnatural grouping, and Rhabdodon to be a basal member of Iguanodontia.


Rhabdodontomorpha is a clade of basal iguanodont dinosaurs. This group was named in 2016 in the context of the description, based on Spanish findings, of an early member of the Rhabdodontidae. A cladistic analysis was conducted in which it was found that Muttaburrasaurus was the sister species of the Rhabdodontidae sensu Weishampel. Therefore, Paul-Emile Dieudonné, Thierry Tortosa, Fidel Torcida Fernández-Baldor, José Ignacio Canudo and Ignacio Díaz-Martínez defined Rhabdodontomorpha as a nodal clade: the group consisting of the last common ancestor of Rhabdodon priscus Matheron, 1869 and Muttaburrasaurus langdoni Bartholomai and Molnar, 1981; and all its descendants. Within the clade are included also Zalmoxes and Mochlodon.The group consists of small to large plant eaters from Europe and Gondwana. It must have split from other iguanodont groups during the Middle Jurassic.


Shuangmiaosaurus is a genus of herbivorous ornithischian dinosaur which lived during the late Albian age of the Early Cretaceous Period, about 100 million years ago. It was an iguanodont euornithopod which lived in China.

The type species, Shuangmiaosaurus gilmorei, was named and described by You Hailu, Ji Qiang Li Jinglu and Li Yinxian in 2003. The generic name refers to the village of Shuangmiao in Beipiao in Liaoning Province, the site of the discovery. The specific name honours the American paleontologist Charles Whitney Gilmore.The holotype, specimen LPM 0165, was found in the Sunjiawan Formation, originally seen as dating to the Late Cretaceous (Cenomanian to Turonian) but today considered to have been somewhat older. It consists of a partial left upper jaw and lower jaw, including the maxilla, part of the praemaxilla, elements of the lacrimal and the dentary.

Shuangmiaosaurus was a rather large euornithopod. In 2010 Gregory S. Paul estimated its length at 7.5 metres, its weight at 2.5 tonnes.Shuangmiaosaurus was originally considered a basal member of the Hadrosauroidea, one closely related to the Hadrosauridae. Subsequent authors, including David B. Norman of Cambridge University, consider it a more basal member of the Iguanodontia outside of the Hadrosauroidea.


Zalmoxes is an extinct genus of rhabdodontid ornithopod dinosaur from the Maastrichtian of Romania. The genus is known from specimens first named as the species Mochlodon robustum in 1899 by Franz Nopcsa before being reclassified as Rhabdodon robustum by him in 1915. In 1990 this name was corrected to Rhabdodon robustus by George Olshevsky, and in 2003 the species was once more reclassified, this time as the type species Zalmoxes robustus. Zalmoxes refers to the Dacian deity Zalmoxis, and robustus to the robustness of the remains. In 2003 another species was named, Zalmoxes shqiperorum, named for the Albanian name for Albanians.


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