Artist reconstruction Ianni Smithy. This recently discovered early ornithopod dinosaur may represent the species’ last stand during the period of global warming in the middle of the Cretaceous period, roughly 99 million years ago, which led to drastic changes in dinosaur populations. Credit: Jorge Gonzalez
newly discovered dinosaur, Ianni SmithyHe lived during the climatic upheavals of the middle[{” attribute=””>Cretaceous era and might be the last of its lineage, replaced by duckbill dinosaurs. This dinosaur, found in Utah, represents a critical transitional period in dinosaur history, affected by rising CO2 levels, global warming, and shifting dinosaur populations.
A newly discovered plant-eating dinosaur may have been a species’ “last gasp” during a period when Earth’s warming climate forced massive changes to global dinosaur populations.
The specimen, named Iani smithi after Janus, the two-faced Roman god of change, was an early ornithopod, a group of dinosaurs that ultimately gave rise to the more commonly known duckbill dinosaurs such as Parasaurolophus and Edmontosaurus. Researchers recovered most of the juvenile dinosaur’s skeleton – including skull, vertebrae and limbs – from Utah’s Cedar Mountain Formation.
Iani smithi lived in what is now Utah during the mid-Cretaceous, approximately 99 million years ago. The dinosaur’s most striking feature is its powerful jaw, with teeth designed for chewing through tough plant material.
The middle of the Cretaceous period was a time of great changes, which had major impacts on dinosaur populations. Increased carbon dioxide in the atmosphere during this time caused the Earth’s temperature to rise and sea levels to rise, causing the dinosaurs to occupy smaller and smaller land areas. It was so warm that rainforests flourished at the poles. Flowering plant life took over coastal areas and replaced natural food sources for herbivores.
In North America, the giant plant-eating sauropods–once titans of the landscape–were disappearing, along with their allosaurus predators. At the same time, smaller plant-eaters, such as ancient duck-billed and horned dinosaurs, and feathered theropods such as tyrannosaurs and huge oviraptorosaurs, were also arriving from Asia.
Enters Ianni Smithyis unique not only because it is newly discovered, but also because of its rarity in the North American fossil record and its place in dinosaur history.
“Finding me It was a streak of luck. We’ve known something like it lived in this ecosystem because isolated teeth were collected here and there, but we didn’t expect to stumble upon such a beautiful skeleton, especially from this time in Earth’s history. Having a near-complete skull was invaluable in piecing the story together,” says Lindsey Zano, associate research professor at[{” attribute=””>North Carolina State University, head of paleontology at the North Carolina Museum of Natural Sciences, and corresponding author of the work.
The lower jaw and teeth of new dinosaur Iani smithi. Credit: National Geographic, Mark Thiessen and Becky Hale
Zanno and her team used the well-preserved skeleton to analyze the evolutionary relationships of Iani and were surprised – and a bit skeptical – of the results.
“We recovered Iani as an early rhabdodontomorph, a lineage of ornithopods known almost exclusively from Europe,” Zanno says. “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 holds up as a rhabdodontomorph, it raises a lot of cool questions.”
Key among these is, could Iani be a last gasp, a witness to the end of a once successful lineage? Zanno thinks that studying this fossil in the context of environmental and biodiversity changes during the mid-Cretaceous will give us more insight into the history of our planet.
Iani smithi is named for Janus, the two-faced god who symbolized transitions – an apt name, given its position in history.
“Iani 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,” Zanno says. “Iani was alive during this transition – so this dinosaur really does symbolize a changing planet.
“This dinosaur stood on the precipice,” she says, “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. I think we can all relate to that.”
Reference: “An early-diverging iguanodontian (Dinosauria: Rhabdodontomorpha) from the Late Cretaceous of North America” by Lindsay E. Zanno, Terry A. Gates, Haviv M. Avrahami, Ryan T. Tucker and Peter J. Makovicky, 7 June 2023, PLOS ONE.
DOI: 10.1371/journal.pone.0286042
The work appears in PLOS ONE and was supported by the National Science Foundation. Zanno is lead author as well as corresponding. Terry Gates and Haviv Avrahami, both of NC State and the North Carolina Museum of Natural Sciences, along with Ryan Tucker of Stellenbosch University and Peter Makovicky of the University of Minnesota, also contributed to the work.
