Dinosaurus yang baru ditemukan, Iani, mungkin merupakan spesies “terkesiap terakhir” di planet yang terus berubah

Rekonstruksi artis Ian Smith. Dinosaurus ornithopod awal yang baru ditemukan ini mungkin mewakili spesies terakhir bertahan selama periode pemanasan global di pertengahan periode Cretaceous, kira-kira 99 juta tahun yang lalu, yang menyebabkan perubahan drastis pada populasi dinosaurus. Kredit: Jorge Gonzales

dinosaurus yang baru ditemukan, Ian SmithDia hidup selama pergolakan iklim di tengah[{” 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.

Pertengahan periode Cretaceous adalah masa perubahan besar, yang berdampak besar pada populasi dinosaurus. Peningkatan karbon dioksida di atmosfer selama ini menyebabkan suhu bumi naik dan permukaan laut naik, menyebabkan dinosaurus menempati wilayah daratan yang semakin kecil. Itu sangat hangat sehingga hutan hujan tumbuh subur di kutub. Kehidupan tanaman berbunga mengambil alih daerah pesisir dan menggantikan sumber makanan alami bagi herbivora.

Di Amerika Utara, sauropoda pemakan tumbuhan raksasa—dulu raksasa lanskap—menghilang, bersama dengan predator allosaurus mereka. Pada saat yang sama, pemakan tumbuhan yang lebih kecil, seperti dinosaurus paruh bebek dan bertanduk purba, dan theropoda berbulu seperti tyrannosaurus dan oviraptorosaurus besar, juga berdatangan dari Asia.

Masuk Ian Smithunik bukan hanya karena baru ditemukan, tetapi juga karena kelangkaannya dalam catatan fosil Amerika Utara dan tempatnya dalam sejarah dinosaurus.

“Temuan Pidana Itu adalah keberuntungan. Kami telah mengetahui sesuatu seperti itu hidup di ekosistem ini karena gigi yang terisolasi dikumpulkan di sana-sini, tetapi kami tidak menyangka akan menemukan kerangka yang begitu indah, terutama sejak saat ini dalam sejarah Bumi. Memiliki tengkorak yang hampir lengkap sangat berharga dalam menyatukan cerita, ”kata Lindsey Zano, profesor riset asosiasi di[{” 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.