News Release

New dinosaur species from Utah lived at a time of major transition

Iani smithi provides insights into how dinosaurs weather mid-Cretaceous ecological change

Peer-Reviewed Publication


An early-diverging iguanodontian (Dinosauria: Rhabdodontomorpha) from the Late Cretaceous of North America

image: Location of holotype locality for Iani smithi. (A) Global map showing location of Mussentuchit Member outcrop in central Utah, western North America, and a stratigraphic section at the quarry with dated ash horizons; and (B) graphical representation of preserved skeletal elements of the holotype specimen. Preserved elements are colored on the left facing skeletal whether they derive from the right or left side of the body. Exact positions of chevrons and ribs unknown due to poor preservation. view more 

Credit: Zanno et al., 2023, PLOS ONE, CC-BY 4.0 (

A new species of dinosaur from Utah sheds light on major North American ecological changes around 100 million years ago, according to a study published June 7, 2023 in the open-access journal PLOS ONE by Lindsay Zanno of the North Carolina Museum of Natural Sciences and colleagues.

The boundary between the Early and Late Cretaceous Period saw major reassembly of global ecosystems associated with a peak in global temperatures. In the fossil record of western North America, this ecological shift has been well-documented for marine habitats, but less study has been done regarding terrestrial life. In this study, Zanno and colleagues identify a new dinosaur from the early Late Cretaceous Cedar Mountain Formation of Utah.

The new dinosaur, named Iani smithi, lived around 100 million years ago and is known from a single fossil specimen including a well-preserved skull and parts of the spine and limbs. The name derives from Ianus, a Roman deity who presided over transitions, referencing the changing world of the mid-Cretaceous.

Iani is a member of an early branch of the ornithopod dinosaurs, a group of mostly bipedal herbivores that also includes famous examples like Iguanodon and Tenontosaurus. Iani is the first early-diverging ornithopod known from the Late Cretaceous of North America.

This discovery, along with other recent reports from the same geologic formation, indicates that several major groups of dinosaurs survived into the early Late Cretaceous despite the ecological changes of the time, but exactly what these survivors were doing and how long they lasted is still unclear. Since Iani and its closest cousins are typically found in ancient coastal habitats along the shores of the now-vanished Western Interior Seaway, the authors suggest that more investigation into coastal deposits of similar age might yield further evidence to address these lingering questions.

The authors add: “Early ornithopods were once a common part of North American ecosystems, but we did not know they survived into the Late Cretaceous. The discovery of Iani helps us link their extinction on the continent with a major interval of global warming, one with striking similarities to our current climate crisis.”


In your coverage please use this URL to provide access to the freely available article in PLOS ONE:

Citation: Zanno LE, Gates TA, Avrahami HM, Tucker RT, Makovicky PJ (2023) An early-diverging iguanodontian (Dinosauria: Rhabdodontomorpha) from the Late Cretaceous of North America. PLoS ONE 18(6): e0286042.

Author Countries: USA, South Africa

Funding: This research was supported by an award from the Canyonlands Natural History Association to LEZ and a National Science Foundation ( award 1925973 to LEZ and RTT. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.