아티스트 재구성 이아니 스미시. 최근에 발견된 이 초기 조각류 공룡은 백악기 중기인 약 9900만 년 전 지구 온난화 기간 동안 공룡 개체수의 급격한 변화를 초래한 종의 마지막 버팀목이 될 수 있습니다. 크레딧: Jorge Gonzalez
새로 발견된 공룡, 이아니 스미시그는 중기의 기후 격변기에 살았습니다.[{” 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.
백악기 중기는 공룡 개체수에 큰 영향을 미쳤던 큰 변화의 시기였습니다. 이 기간 동안 대기 중 이산화탄소 증가로 인해 지구의 온도가 상승하고 해수면이 상승하여 공룡이 점점 더 작은 육지 면적을 차지하게 되었습니다. 너무 따뜻해서 열대 우림이 기둥에서 번성했습니다. 꽃을 피우는 식물이 해안 지역을 점령하고 초식동물의 자연 식량원을 대체했습니다.
북미에서는 한 때 풍경의 거인이었던 거대한 초식 용각류가 알로사우루스 포식자와 함께 사라지고 있었습니다. 동시에 고대의 오리주둥이와 뿔이 달린 공룡과 같은 작은 초식 공룡과 티라노사우르스와 거대한 오비랍토로사우르스와 같은 깃털이 달린 수각류도 아시아에서 도착했습니다.
들어간다 이아니 스미시는 새로 발견되었다는 점뿐만 아니라 북미 화석 기록에서 희귀하고 공룡 역사에서 차지하는 위치 때문에 독특합니다.
“발견 나 행운의 연속이었습니다. 고립된 이빨이 여기저기서 수집되었기 때문에 우리는 이 생태계에 살았던 것과 같은 것을 알고 있었지만 특히 지구 역사상 이 시기부터 이렇게 아름다운 골격을 우연히 발견할 것이라고는 예상하지 못했습니다. 거의 완전한 두개골을 갖는 것은 이야기를 연결하는 데 매우 중요했습니다.”라고 Lindsey Zano 부교수는 말합니다.[{” 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.
