Paleontologists have identified a new species of iguanodontian dinosaur from a partial skeleton found in the Cedar Mountain Formation, Utah, the United States.
Life reconstruction of Iani smithi. Image credit: Jorge Gonzalez.
The new dinosaur lived in what is now the United States during the mid-Cretaceous period, approximately 99 million years ago.
Named Iani smithi, the species was an early-diverging ornithopod, a group of mostly bipedal herbivores that also includes famous examples like Iguanodon and Tenontosaurus.
“We recovered Iani smithi as an early rhabdodontomorph, a lineage of ornithopods known almost exclusively from Europe,” said Dr. Lindsay Zanno, a paleontologist at North Carolina State University and head of paleontology at the North Carolina Museum of Natural Sciences.
“Recently, paleontologists proposed that another North American dinosaur, Tenontosaurus — which was as common as cattle in the Early Cretaceous — belongs to this group, as well as some Australian critters.”
“If Iani smithi holds up as a rhabdodontomorph, it raises a lot of cool questions.”
“Iani smithi may be the last surviving member of a lineage of dinosaurs that once thrived here in North America but were eventually supplanted by duckbill dinosaurs.”
“Iani smithi was alive during this transition — so this dinosaur really does symbolize a changing planet.”
The most striking feature of Iani smithi is its powerful jaw, with teeth designed for chewing through tough plant material.
“The mid-Cretaceous was a time of big changes, which had big effects on dinosaur populations,” Dr. Zanno and colleagues said.
“Increased atmospheric carbon dioxide during this time caused the Earth to warm and sea levels to rise, corralling dinosaurs on smaller and smaller landmasses.”
“It was so warm that rainforests thrived at the poles. Flowering plant life took over coastal areas and supplanted normal food sources for herbivores.”
“In North America, giant plant-eating sauropods — once titans of the landscape — were disappearing, along with their allosaurian predators.”
“At the same time, smaller plant eaters, like early duckbills and horned dinosaurs, and feathered theropods like tyrannosaurs and enormous oviraptorosaurs, were arriving from Asia.”
Iani smithi is known from a single fossil specimen including a well-preserved skull and parts of the spine and limbs.
The specimen was found in the Cedar Mountain Formation in Utah, the United States.
“Finding Iani smithi was a streak of luck,” Dr. Zanno said.
“We knew something like it lived in this ecosystem because isolated teeth had been collected here and there, but we weren’t expecting to stumble upon such a beautiful skeleton, especially from this time in Earth’s history.”
“Having a nearly complete skull was invaluable for piecing the story together.”
The discovery is reported in a paper in the journal PLoS ONE.
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L.E. Zanno et al. 2023. An early-diverging iguanodontian (Dinosauria: Rhabdodontomorpha) from the Late Cretaceous of North America. PLoS ONE 18 (6): e0286042; doi: 10.1371/journal.pone.0286042
