Dinosaur named "Iani smithi" lived during a time of major transition

Scientists have uncovered a newly discovered plant-eating dinosaur, Iani smithi, that appears to be a species’ “last gasp.” This dramatic event took place during a period when Earth’s warming climate was forcing profound shifts in global dinosaur populations.

Unearthed from Utah’s Cedar Mountain Formation, the majority of the juvenile dinosaur’s skeleton – encompassing its skull, vertebrae, and limbs – was successfully retrieved. 

The specimen is named after Janus, the two-faced Roman god of change. It serves as a tribute to its place as an early ornithopod, a group of dinosaurs that would eventually pave the way for well-known duckbill dinosaurs like Parasaurolophus and Edmontosaurus.

Iani smithi lived during a transformative time on Earth

The striking feature of Iani smithi is its powerful jaw, specially equipped with teeth perfect for chomping through robust plant material. This creature roamed the region now known as Utah approximately 99 million years ago during the mid-Cretaceous period.

This era was one of significant transformation, affecting dinosaur populations considerably. Enhanced levels of atmospheric carbon dioxide caused the Earth’s temperature to rise and sea levels to swell, leaving dinosaurs confined to increasingly smaller landmasses. 

So intense was the warmth that rainforests flourished at the poles while flowering plant life began to dominate coastal regions, replacing the traditional food sources for herbivores.

Most dinosaur species were vanishing when Iani smithi arrived

As the mid-Cretaceous period unfolded, giant plant-eating sauropods, once the reigning titans of North American landscapes, were vanishing along with their allosaurian predators. Concurrently, smaller plant eaters like early duckbills and horned dinosaurs were arriving from Asia, accompanied by feathered theropods such as tyrannosaurs and enormous oviraptorosaurs.

The discovery of Iani smithi is momentous, not just for its novelty but also due to its infrequent appearance in the North American fossil record and its unique place in dinosaur history.

“We had a stroke of luck finding Iani,” says Lindsay Zanno, head of paleontology at the North Carolina Museum of Natural Sciences and associate research professor at North Carolina State University. 

“We knew something like it inhabited this ecosystem because we had come across isolated teeth, but we didn’t anticipate finding such an impressive skeleton, particularly from this era. Having a nearly complete skull was crucial for piecing together the story.”

Zanno and her team, employing the well-preserved skeleton, have been examining the evolutionary relationships of Iani, expressing surprise and slight doubt at their findings.

“Upon analysis, we identified Iani as an early rhabdodontomorph, an ornithopod lineage primarily known from Europe,” explained Professor Zanno. “Lately, paleontologists have suggested that Tenontosaurus, a North American dinosaur as prevalent as cattle in the Early Cretaceous, along with some Australian dinosaurs, belong to this group. If Iani is indeed a rhabdodontomorph, it poses several fascinating questions.”

Iani smithi may have been the last in a successful dinosaur lineage

One of the central questions raised is whether Iani smithi could represent the final gasp, a final witness to the demise of a once successful lineage. Zanno believes that examining this fossil in light of environmental and biodiversity shifts during the mid-Cretaceous will yield further insights into our planet’s history.

“Iani might 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 was alive during this transition – so this dinosaur really does symbolize a changing planet,” said Professor Zanno.

“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. I think we can all relate to that.”

As this dinosaur signifies a significant transition, it is fittingly named after Janus, the two-faced god symbolizing transitions.

Glimpse into a critical period in Earth’s history

The discovery of Iani smithi and the ensuing research offers a unique glimpse into a critical period in Earth’s history, when rapid climatic changes transformed landscapes, ecosystems, and the organisms that lived in them. 

Studying these ancient creatures provides scientists with a powerful tool for understanding how life on Earth has evolved in response to such changes, and perhaps how it may continue to do so in the face of modern-day climate change.

This landmark research has been published in PLOS ONE and received support from the National Science Foundation.

As scientists continue to unearth and examine fossils like Iani smithi, we are gifted with a deeper understanding of our planet’s history. In the face of today’s environmental challenges, this knowledge proves invaluable. 

More about the mid-Cretaceous period 

The mid-Cretaceous period, dating from around 125 to 90 million years ago, was a time of significant change for life on Earth.

This era, part of the larger Cretaceous period that spanned from about 145 to 66 million years ago, saw significant shifts in global climates, landmasses, and ecosystems, resulting in the evolution of new species and the extinction of others. It’s best known for being the last era in which dinosaurs roamed the Earth, culminating in a mass extinction event at the end of the period.

Much warmer climate

From an environmental perspective, the mid-Cretaceous period was marked by a significantly warmer climate than we have today. This climate change was due in large part to high levels of atmospheric carbon dioxide, likely resulting from increased volcanic activity. 

During this time, there was no polar ice, and even the polar regions enjoyed a tropical or subtropical climate. This warmth led to higher sea levels, with shallow seas covering parts of the continents.

Plants began to flourish

The mid-Cretaceous was also a time of flourishing plant life. It witnessed the rise of the angiosperms, or flowering plants, which rapidly diversified and spread across the globe, significantly altering ecosystems and providing new food sources for various herbivorous dinosaurs. 

The first bees appeared during this period too, likely evolving alongside these flowering plants in a mutual relationship of pollination.

New types of dinosaurs emerged

As for animal life, the mid-Cretaceous was a time of significant shifts. While dinosaur groups like the large, long-necked sauropods were beginning to decline, new kinds of dinosaurs were on the rise. 

This period saw the emergence of new types of theropods like tyrannosaurs, which would later give rise to the iconic Tyrannosaurus rex near the end of the Cretaceous. Meanwhile, feathered dinosaurs and early birds continued to evolve and diversify.

In the oceans, the mid-Cretaceous period saw the rise of large marine reptiles like mosasaurs and pliosaurs, along with an increased diversity of ammonites and mollusks. At the same time, the first true birds began to appear, and mammals, although still small and largely nocturnal, started to diversify into a wider array of forms.

Overall, the mid-Cretaceous was a time of considerable global change, with fluctuating climates, shifting landmasses, and evolving ecosystems setting the stage for the world we know today. It provides a fascinating lens through which to study how life on Earth responds to large-scale environmental changes over time.

Image Credit: Jorge Gonzalez

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