Iguanodont

Iguanodont Temporal range: Late Jurassic–Late Cretaceous,
Heads of different iguanodonts
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Clade:	†Ornithischia
Clade:	†Neornithischia
Clade:	†Ornithopoda
Clade:	†Iguanodontia Dollo, 1888
Subgroups
Dryomorpha Rhabdodontidae Tenontosaurus And see text.

Iguanodonts (members of the group Iguanodontia) were herbivorous dinosaurs that lived from the mid-Jurassic to Late Cretaceous. Some members include Camptosaurus, Callovosaurus, Iguanodon, Ouranosaurus, and the hadrosaurids or "duck-billed dinosaurs". Iguanodonts 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. Iguanodontians were generally large animals, and some (such as Shantungosaurus, which measured up to 50 ft (15 m) in length and weighed up to 8 tons) equaled the largest carnivorous dinosaurs in size.

Classification

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, iguanodonts 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 is usually defined as the most inclusive group containing Parasaurolophus walkeri but not Hypsilophodon foxii or Thescelosaurus neglectus, or other combinations of species that would ultimately result in the same group in most modern analyses. The group was first defined as a clade in 2008 by Paul Sereno.

Many iguanodonts have not yet been included in a large phylogenetic analyses, or are too fragmentary to place confidently. These include Barilium, Bolong, Bihariosaurus, Dakotadon, Dollodon, Draconyx, Kukufeldia, Hypselospinus, Macrogryphosaurus, Owenodon, Proplanicoxa, Sellacoxa and Xuwulong. The simplified cladogram below follows an analysis by Andrew McDonald and colleagues, published in November 2010 with information from McDonald, 2011.

Iguanodontia	Rhabdodontidae Tenontosaurus Dryomorpha Dryosauridae Ankylopollexia Camptosaurus Styracosterna Cumnoria Uteodon Hippodraco Theiophytalia Cedrorestes Dakotadon Iguanacolossus Lanzhousaurus Hadrosauriformes Iguanodon Mantellisaurus Ouranosaurus Hadrosauroidea

Cladogram after Butler et al, 2011.

Iguanodontia	Talenkauen Anabisetia Rhabdodontidae Tenontosaurus T. tilletti T. dossi Dryosauridae Ankylopollexia