Iguanodontia

Calvarius is a genus of styracosternan ornithopod from the Late Cretaceous of Spain. The name alludes to its chronostratigraphic proximity to the extinction event that wiped out the non-avian dinosaurs at the end of the Cretaceous. The highly modified metatarsal that is known from shows an example of convergent evolution, as it is more similar to non-iguanodontian ornithopods than to other styracosternans. It is thought that this is due to fulfilling a niche in its island habitat, resulting in Calvarius becoming a small-bodied animal, capable of rapid locomotion.

Figure 1: Geographic distribution of Early Cretaceous iguanodontians in North America. Taxa found at each locality are as follows: (A) Dakotadon lakotaensis; (B) Osmakasaurus depressus; (C) Tenontosaurus tilletti, Tenontosaurus dossi; (D) Tenontosaurus tilletti; (E) Theiophytalia kerri; (F) Cedrorestes crichtoni, Planicoxa venenica; (G) Hippodraco scutodens; (H) Iguanacolossus fortis; (I) Tenontosaurus sp; (J) Tenontosaurus tilletti.

Figure 1: Geographic distribution of Early Cretaceous iguanodontians in North America. Taxa found at each locality are as follows: (A) Dakotadon lakotaensis; (B) Osmakasaurus depressus; (C) Tenontosaurus tilletti, Tenontosaurus dossi; (D) Tenontosaurus tilletti; (E) Theiophytalia kerri; (F) Cedrorestes crichtoni, Planicoxa venenica; (G) Hippodraco scutodens; (H) Iguanacolossus fortis; (I) Tenontosaurus sp; (J) Tenontosaurus tilletti.

Seven ornithopods (top to bottom): Ouranosaurus, Tenontosaurus (background) with Convolosaurus (foreground), Muttaburrasaurus, Edmontosaurus annectens, Dryosaurus altus, Corythosaurus casuarius

Seven ornithopods (top to bottom): Ouranosaurus, Tenontosaurus (background) with Convolosaurus (foreground), Muttaburrasaurus, Edmontosaurus annectens, Dryosaurus altus, Corythosaurus casuarius

Seven ornithopods (top to bottom): Ouranosaurus, Tenontosaurus (background) with Convolosaurus (foreground), Muttaburrasaurus, Edmontosaurus annectens, Dryosaurus altus, Corythosaurus casuarius

Seven ornithopods (top to bottom): Ouranosaurus, Tenontosaurus (background) with Convolosaurus (foreground), Muttaburrasaurus, Edmontosaurus annectens, Dryosaurus altus, Corythosaurus casuarius

Seven ornithopods (top to bottom): Ouranosaurus, Tenontosaurus (background) with Convolosaurus (foreground), Muttaburrasaurus, Edmontosaurus annectens, Dryosaurus altus, Corythosaurus casuarius

Seven ornithopods (top to bottom): Ouranosaurus, Tenontosaurus (background) with Convolosaurus (foreground), Muttaburrasaurus, Edmontosaurus annectens, Dryosaurus altus, Corythosaurus casuarius

skull of iguanodontian Altirhinus kurzanovi

Simplified cladogram of Iguanodontia, drawn by me, based on Norman 2004 ("Basal Iguanodontia" in The Dinosauria 2nd Edition).

The Maastrichtian, Transylvanian giant azhdarchid pterosaur Hatzegopteryx sp. preys on the rhabdodontid iguanodontian Zalmoxes. Because large predatory theropods are unknown on Late Cretaceous Haţeg Island, giant azhdarchids may have played a key role as terrestrial predators in this community.

Illustration of the iberian iguanodontian Delapparentia turolensis.