Artistieke reconstructie Ianni Smithy. Deze recent ontdekte vroege ornithopod-dinosaurus vertegenwoordigt mogelijk de laatste stand van de soort tijdens de periode van opwarming van de aarde in het midden van het Krijt, ongeveer 99 miljoen jaar geleden, wat leidde tot drastische veranderingen in dinosauruspopulaties. Krediet: Jorge Gonzalez
nieuw ontdekte dinosaurus, Ianni SmithyHij leefde tijdens de klimatologische omwentelingen van het midden[{” 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.
Het midden van het Krijt was een tijd van grote veranderingen, die grote gevolgen hadden voor de dinosauruspopulaties. Verhoogde koolstofdioxide in de atmosfeer gedurende deze tijd zorgde ervoor dat de temperatuur van de aarde steeg en de zeespiegel steeg, waardoor de dinosaurussen steeds kleinere landgebieden bezetten. Het was zo warm dat regenwouden bloeiden aan de polen. Het bloeiende plantenleven nam kustgebieden over en verving natuurlijke voedselbronnen voor herbivoren.
In Noord-Amerika waren de gigantische plantenetende sauropoden – ooit titanen van het landschap – aan het verdwijnen, samen met hun allosaurus-roofdieren. Tegelijkertijd arriveerden ook kleinere planteneters, zoals oude eendensnavel- en gehoornde dinosaurussen, en gevederde theropoden zoals tyrannosauriërs en enorme oviraptorosauriërs, uit Azië.
komt binnen Ianni Smithyis uniek, niet alleen omdat het nieuw is ontdekt, maar ook vanwege zijn zeldzaamheid in het Noord-Amerikaanse fossielenbestand en zijn plaats in de geschiedenis van dinosauriërs.
“Vinden mij Het was een gelukstreffer. We hebben geweten dat zoiets in dit ecosysteem leefde omdat hier en daar geïsoleerde tanden werden verzameld, maar we hadden niet verwacht zo’n mooi skelet tegen te komen, vooral niet uit deze tijd in de geschiedenis van de aarde. Het hebben van een bijna complete schedel was van onschatbare waarde bij het samenstellen van het verhaal”, zegt Lindsey Zano, universitair hoofddocent bij[{” 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.
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