The newly discovered Ianni dinosaur may have been the “last gasp” of the species on a changing planet

The copy, named Ian Smith since Janus, the two-faced Roman god of change, was an early ornithopod, a group of dinosaurs that eventually gave rise to the better-known duck-billed dinosaurs such as Parasaurolophus and Edmontosaurus. Researchers recovered most of the young dinosaur’s skeleton — including skull, vertebrae and limbs — from Utah’s Cedar Mountain Formation.

Ian Smith lived in present-day Utah during the mid-Cretaceous, approximately 99 million years ago. The dinosaur’s most impressive feature was its powerful jaw with teeth designed for chewing tough plant material.

The mid-Cretaceous was a time of major changes that had a major effect on dinosaur populations. Increased atmospheric carbon dioxide during this time caused the Earth to warm and sea levels to rise, drawing the dinosaurs to smaller and smaller land masses. It was so warm that rainforests flourished at the poles. Flowering plant life has taken over riparian areas and displaced normal food sources for herbivores.

In North America, the giant plant-eating sauropods—once titans of the landscape—were disappearing along with their allosaur predators. At the same time, smaller herbivores, such as early ducks and horned dinosaurs, and feathered theropods such as tyrannosaurs and huge oviraptorosaurs arrived from Asia.

Enter Ian Smithunique 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 Gianni it was a streak of luck. We knew something like this lived in this ecosystem because isolated teeth were collected here and there, but we didn’t expect to come across such a beautiful skeleton, especially from this period of Earth’s history. Having an almost complete skull was invaluable in piecing together the story,” says Lindsay Zano, associate professor at

Zano and her team used the well-preserved skeleton to analyze the evolutionary relationships of Gianni and were surprised – and a little skeptical – by the results.

“We recovered Gianni as an early rhabdodontomorph, an ornithopod lineage known almost exclusively from Europe,” Zano says. “Recently, paleontologists have proposed another North American dinosaur, Tenontosaurus – which was as common as cattle in the early Cretaceous – belongs to this group, as do some Australian creatures. If Gianni behaves like a rhabdodontomorph raises a lot of cool questions.

Key among them is, can Gianni to be the last gasp witnessing the end of a once successful line? Zano believes 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.

Ian Smith is named after Janus, the two-faced god who symbolizes transitions – a fitting name given his place in history.

“Gianni may be the last surviving member of a lineage of dinosaurs that once thrived here in North America but were eventually displaced by duck-billed dinosaurs,” Zano says. “Gianni was alive during this transition – so this dinosaur really does symbolize a changing planet.

“This dinosaur was standing on the precipice,” she says, “able to look back at the way North America’s 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 Iguanodont (Dinosauria: Rhabdodontomorpha) from the Late Cretaceous of North America” ​​by Lindsey E. Zano, Terry A. Gates, Haviv M. Avrahami, Ryan T. Tucker, and Peter J. Makoviki, June 7, 2023 , PLUS ONE.
DOI: 10.1371/journal.pone.0286042

The work appears in PLUS ONE and was supported by the National Science Foundation. Zanno is the lead author as well as correspondence. 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 Makowicki of the University of Minnesota, also contributed to the work.