During a time when global dinosaur populations were drastically altered by Earth’s warming climate, a newly discovered plant-eating dinosaur may have served as a species’ “last gasp.”
The specimen, which was given the name Iani Smithi in honor of Janus, the Roman god of change with two faces, was an early ornithopod—a group of dinosaurs that eventually led to the more well-known duckbill dinosaurs like Edmontosaurus and Parasaurolophus. In Utah’s Cedar Mountain Formation, researchers found the majority of the juvenile dinosaur’s skeleton, including its skull, vertebrae, and limbs. PLoS ONE is where the research was published.
Approximately 99 million years ago, during the middle of the Cretaceous, Iani Smith lived in Utah. The strongest feature of the dinosaur is its powerful jaw, which has teeth made to chew through tough plant material.
“Finding Iani was a stroke of good fortune. We knew something like it existed in this habitat since isolated teeth had been found here and there, but we weren’t expecting to come across such a gorgeous skeleton, especially from this period in Earth’s history. “Having a nearly complete skull was extremely helpful in piecing together the story.”
Lindsay Zanno, associate research professor at North Carolina State University,
During the middle Cretaceous, there were significant shifts that had a significant impact on dinosaur populations. Expanded climatic carbon dioxide during this time made the Earth warm and ocean levels rise, corralling dinosaurs on increasingly small bodies of land. It was warm to such an extent that rainforests flourished at the posts. Flowering plants took over coastal areas and became herbivores’ primary source of food.
3D reproduction of the skull of Iani Smithi. Credit: Haviv Avrahami, CC-BY 4.0 (creativecommons.org/licenses/by/4.0/)
In North America, the allosaurian predators of giant plant-eating sauropods are also disappearing. Smaller plant-eating animals like early duckbills and horned dinosaurs, as well as feathered theropods like tyrannosaurs and massive oviraptorosaurs, were also arriving from Asia at the same time.
Iani smithi is an exception not only due to its recent discovery but also due to its rarity in the North American fossil record and position in the history of dinosaurs.
“Iani’s discovery was a stroke of luck. We were surprised to find such a beautiful skeleton, especially from this time in Earth’s history, even though isolated teeth had shown that something similar existed in this ecosystem. Lindsay Zanno, associate research professor at North Carolina State University, head of paleontology at the North Carolina Museum of Natural Sciences, and corresponding author of the work, says, “Having a nearly complete skull was invaluable for piecing the story together.”
Area of holotype territory for Iani smithi. (A) A worldwide guide showing the area of the Mussentuchit Part outcrop in focal Utah, western North America, and a stratigraphic segment at the quarry with dated debris skylines; and (B) a graphical representation of the holotype specimen’s preserved skeletal components. Whether they come from the right or left side of the body, preserved elements are colored on the left-facing skeletal structure. Due to poor preservation, the precise positions of the ribs and chevrons are unknown. Credit: Zanno et al., 2023, PLOS ONE, CC-BY 4.0 (creativecommons.org/licenses/by/4.0/)
Zanno and her team used the well-preserved skeleton to examine Iani’s evolutionary relationships. They were surprised and a little bit skeptical by the findings.
According to Zanno, “We recovered Iani as an early rhabdodontomorph, a lineage of ornithopods almost exclusively known from Europe.” Paleontologists have recently proposed that this group also includes some Australian animals and another North American dinosaur, Tenontosaurus, which was as common as cattle in the Early Cretaceous. There are a lot of interesting questions that could be asked if Iani proves to be a rhabdodontomorph.
Key among these is: might Iani at any point be a last heave, an observer to the furthest limit of a once fruitful heredity? Zanno is of the opinion that if we examine this fossil in the context of changes in biodiversity and the environment in the middle Cretaceous, we will gain a deeper understanding of our planet’s past.
Given its position in history, Iani Smithi is named after Janus, the two-faced god of transitions.
According to Zanno, “Iani may be the last surviving member of a lineage of dinosaurs that once thrived in North America but were eventually replaced by duckbill dinosaurs.” Iani was alive during this progress, so this dinosaur truly represents an evolving planet.
She says, “This dinosaur stood on the precipice, able to look back at the way North American ecosystems were in the past but close enough to see the future coming like a bullet train,” and she refers to the dinosaur as “standing on the precipice.” I figure we can all connect with that.”
More information: An early-diverging iguanodontian (Dinosauria: Rhabdodontomorpha) from the Late Cretaceous of North America, PLoS ONE (2023). DOI: 10.1371/journal.pone.0286042
