A newly discovered dinosaur may have been a last gasp for the species during a period when Earth’s warming climate forced big changes to global dinosaur populations, a study suggests.
The plant-eating animal, named Iani smithi after Janus, the two-faced Roman god of change, was an early ornithopod.
This group of dinosaurs ultimately gave rise to the more commonly known duckbill dinosaurs such as Parasaurolophus and Edmontosaurus.
Most of the young dinosaur’s skeleton – including skull, vertebrae and limbs – was recovered from Utah’s Cedar Mountain Formation in America.
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— Dr Lindsay Zanno, North Carolina State University
Corresponding author Lindsay Zanno, associate research professor at North Carolina State University and head of palaeontology at the North Carolina Museum of Natural Sciences, said: “Finding Iani was a stroke of luck.
“We knew something like it lived in this ecosystem because isolated teeth had been collected here and there, but we weren’t expecting to stumble upon such a beautiful skeleton, especially from this time in Earth’s history. Having a nearly complete skull was invaluable for piecing the story together.”
She added: “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.
“Iani was alive during this transition – so this dinosaur really does symbolise a changing planet.
“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.”
Iani smithi lived some 99 million years ago (the mid-Cretaceous), and researchers say its most striking feature is its powerful jaw, with teeth designed for chewing through tough plant material.
The researchers say the mid-Cretaceous was a time of big changes that had a massive effect on dinosaur populations.
Greater carbon dioxide in the environment during this time caused the planet to warm and sea levels to rise, corralling dinosaurs on smaller and smaller landmasses.
If Iani holds up as a rhabdodontomorph, it raises a lot of cool questions— Dr Lindsay Zanno, North Carolina State University
It was so warm that rainforests thrived at the poles, and flowering plant life took over coastal areas and supplanted normal food sources for herbivores.
The experts suggest that giant plant-eating sauropods – once titans of the landscape – were disappearing across North America, along with their allosaurian predators.
At the same time, smaller plant eaters, such as early duckbills and horned dinosaurs, and feathered theropods like tyrannosaurs and enormous oviraptorosaurs, were arriving from Asia.
According to the study published in Plos One, Iani smithi is unique not just because it is newly discovered, but also because of its rarity in the North American fossil record and its position in dinosaur history.
Dr Zanno added: “We recovered Iani as an early rhabdodontomorph, a lineage of ornithopods known almost exclusively from Europe.
“Recently, palaeontologists 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.”
One of these questions is whether Iani was a last gasp, a witness to the end of a once successful lineage.
Dr Zanno thinks that studying this fossil in the context of environmental and biodiversity changes during the mid-Cretaceous will shed more light on the history of Earth.
