reconstrucción artística de Iani Smithi. Este dinosaurio ornitópodo recién descubierto puede representar la posición final de una especie durante un período de calentamiento climático global a mediados del Cretácico, hace aproximadamente 99 millones de años, que obligó a cambios drásticos en las poblaciones de dinosaurios. Crédito: Jorge González

El dinosaurio recién descubierto, Iani Smithivivió durante las convulsiones climáticas de mediados de[{» 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.

El Cretácico medio fue una época de cambios importantes, que tuvieron efectos importantes en las poblaciones de dinosaurios. El aumento del dióxido de carbono atmosférico durante este período hizo que la Tierra se calentara y aumentara el nivel del mar, atrapando a los dinosaurios en masas de tierra cada vez más pequeñas. Hacía tanto calor que las selvas tropicales prosperaban en los polos. La vida vegetal floreciente se apoderó de las áreas costeras y suplantó las fuentes normales de alimento para los herbívoros.

En América del Norte, los saurópodos herbívoros gigantes, que alguna vez fueron titanes del paisaje, estaban desapareciendo, junto con sus depredadores alosaurios. Al mismo tiempo, llegaron de Asia herbívoros más pequeños, como los primeros picos de pato y los dinosaurios con cuernos, y terópodos emplumados, como los tiranosaurios y los enormes oviraptorosaurios.

Digitar Iani Smithiúnico no solo por su reciente descubrimiento, sino también por su rareza en el registro fósil de América del Norte y su posición en la historia de los dinosaurios.

«Encontrarse Iani fue un golpe de suerte. Sabíamos que algo similar vivía en este ecosistema porque se recolectaron dientes aislados aquí y allá, pero no esperábamos tropezar con un esqueleto tan hermoso, especialmente de este momento en la historia de la Tierra. Tener un cráneo casi completo fue invaluable para unir las piezas de la historia”, dice Lindsay Zanno, profesora asociada de investigación en[{» 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.