Study: New Utah fossil improves understanding of mid-Cretaceous
(CN) — Every unearthed scrap of knowledge is valuable in understanding the mid-Cretaceous period, even if it is in the form of one mostly preserved fossil.
Earth between the Early and Late Cretaceous period experienced climate change, according to a study published Wednesday in PLOS ONE. Increased atmospheric carbon dioxide warmed the planet so much that rainforests thrived at the poles, elevated sea levels, forced dinosaurs onto increasingly smaller landmasses, and flowering plant life supplanted herbivores' usual coastal food sources, according to the study.
However, researchers involved in the study say that while the ecological shift for marine habitats in the western North American fossil record is well-documented, the same cannot be said for mid-Cretaceous terrestrial life, making the discovery of Iani smithi so valuable.
The researchers who recently unearthed the dinosaur that lived around 100 million years ago in Utah’s Cedar Mountain Formation named it after Ianus or Janus, the two-faced Roman god of transitions and change. The scientists say that the fossil consists of its spine, limbs and a well-preserved skull that featured a powerful jaw, possessing teeth designed to chew through tough plant material.
The researchers uncovered two important facts: First, Iani is a member of an early branch of the ornithopod dinosaurs, or mostly bipedal herbivores that boast members such as Iguanodon and Tenontosaurus. Second, Iani is the first early-diverging ornithopod known from North America’s Late Cretaceous which were among the predators that became extinct during that time, according to study author Lindsay Zanno via email.
“The lineage that Iani belongs to was once extremely common across North American landscapes, but ultimately, these animals, along with many other dinosaur groups, including top predators of the time and long-neck sauropods, went extinct here. Horned and duckbill dinosaurs, and the tyrannosaurs that hunted them, ultimately took their place. Iani and other types of North American dinosaurs were casualties of climate change during the Cretaceous and we want to understand why,” said Zanno, associate research professor at North Carolina State University and head of paleontology at the North Carolina Museum of Natural Sciences.
Researchers do not know what Iani and its closest cousins did or how long they lived, but Zanno believes that studying their ancient coastal habitats, or those of a similar age, are beneficial to future research despite the difficulty that may pose.
“These are places that typically don’t preserve great dinosaur skeletons, so one reason we may not have found dinosaurs like this in younger rocks may be habitat-related,” wrote Zanno. “This is why we suggest that renewed attention on the often-scrappy fossils that stem from these habitats will aid us in understanding if dinosaurs like Iani survived longer through this transition period than we currently understand, or if Iani was the last of its kind here in North America.”
While details of the mid-Cretaceous’ effect on terrestrial life remain scarce, Zanno reveals that Iani lived, however long that was, in conditions that bear a resemblance to the current climate.
“During the mid-Cretaceous, Earth experienced a temperature spike known as the Cretaceous Thermal Maximum. Greenhouse gas concentrations were three to four times higher than today, and sea levels rose between 500 to 1000 feet above today’s levels," Zanno said. "Earth’s poles were blanketed with temperate rain forests. Back then, climate change was caused by volcanic gases. Today of course, we are the cause, but the impact will be the same. Estimates indicate that without efforts to curb our current levels of greenhouse gas emissions, we will experience a Cretaceous climate in the next 100 to 300 years."