Reconstitution d’artiste Ianni Forgeron. Ce dinosaure ornithopode précoce récemment découvert peut représenter le dernier peuplement de l’espèce pendant la période de réchauffement climatique au milieu du Crétacé, il y a environ 99 millions d’années, ce qui a entraîné des changements drastiques dans les populations de dinosaures. 1 crédit
dinosaure nouvellement découvert, Ianni ForgeronIl a vécu pendant les bouleversements climatiques du milieu[{ » 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.
Le milieu du Crétacé a été une période de grands changements, qui ont eu des impacts majeurs sur les populations de dinosaures. L’augmentation du dioxyde de carbone dans l’atmosphère pendant cette période a provoqué une élévation de la température de la Terre et du niveau de la mer, obligeant les dinosaures à occuper des terres de plus en plus petites. Il faisait si chaud que les forêts tropicales fleurissaient aux pôles. La vie végétale à fleurs a envahi les zones côtières et a remplacé les sources de nourriture naturelles pour les herbivores.
En Amérique du Nord, les sauropodes géants herbivores – autrefois titans du paysage – disparaissaient, ainsi que leurs prédateurs allosaurus. Dans le même temps, de plus petits mangeurs de plantes, tels que les anciens dinosaures à bec de canard et à cornes, et des théropodes à plumes tels que les tyrannosaures et les énormes oviraptorosaures, arrivaient également d’Asie.
Entre dans Ianni Forgeronest unique non seulement parce qu’il vient d’être découvert, mais aussi en raison de sa rareté dans les archives fossiles nord-américaines et de sa place dans l’histoire des dinosaures.
« Trouvé moi C’était un coup de chance. Nous avons connu quelque chose comme ça qui vivait dans cet écosystème parce que des dents isolées ont été collectées ici et là, mais nous ne nous attendions pas à tomber sur un si beau squelette, surtout à cette époque de l’histoire de la Terre. Avoir un crâne presque complet a été inestimable pour reconstituer l’histoire », explique Lindsey Zano, professeur de recherche associé à[{ » 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.
