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New fossils from the late Cretaceous period represent the first record of theropods–a group of dinosaurs that includes both modern birds and their closest non-avian relatives–from the Chilean part of Patagonia. The researchers’ findings include giant raptors with large sickle-shaped claws and birds from the group that also includes modern species.
“The fauna of Patagonia before the mass extinction was truly diverse,” lead author Sarah Davis, who completed this work as part of her doctoral studies with Professor Julia Clarke in the UCLA Department of Geosciences, said in a statement. UT Jackson School of Geosciences. “You have large, two-legged theropod carnivores and smaller carnivores, as well as groups of birds that coexist alongside other reptiles and small mammals.”
The study was published in the South American Journal of Geosciences.
Since 2017, members of Clark’s lab have joined scientific collaborators from Chile in Patagonia to collect fossils and create a record of ancient life in the region. Over the years, researchers found abundant plant and animal fossils before the asteroid impact that wiped out the dinosaurs.
The study focuses particularly on theropods, whose fossils date back between 66 and 75 million years.
Non-avian theropod dinosaurs were mostly carnivores and included the top predators in the food chain. This study shows that in prehistoric Patagonia, these predators included dinosaurs from two groups: the massive raptors and the unilagins.
more than seven metres
At over seven meters long, the massive birds of prey were among the largest theropod dinosaurs in South America during the late Cretaceous period. Unenlagiinos—a group that includes members the size of a chicken or over 3 meters tall—may have been covered in feathers, like their close relative Velociraptor. The unenlagiinae fossils described in the study are the known southern case of this group of dinosaurs.
Bird fossils also belong to two groups: enantiornithines and orniturines. Although already extinct, enantiornithines were the most diverse and abundant birds millions of years ago. They looked like sparrows, but their beaks were covered with teeth. The ornithurae group includes all modern birds living today. Those who lived in ancient Patagonia could have resembled a goose or a duck, though the fossils are too fragmentary to be certain.
Researchers have identified theropods from tiny fossil fragments. Dinosaurs, first of all, from teeth and fingers, and birds, from small pieces of bone. According to Davis, the sheen of the enamel on the dinosaur’s teeth helped locate it in the rocky terrain.
Some researchers have suggested that the Southern Hemisphere experienced less extreme or more gradual climate changes than the Northern Hemisphere after the asteroid impact. This would have made Patagonia and other places in the Southern Hemisphere a refuge for birds, mammals, and other organisms that escaped extinction. Davis says this study can help investigate this theory by creating a record of ancient life before and after the extinction.
Marcelo Lippi, co-author of the study and director of the Chilean Antarctic Institute, stated that these records from the past are key to understanding life as it exists today.
“We still need to know how life made its way into this doomsday scenario and gave rise to our southern environments in South America, New Zealand and Australia,” he said. “Here theropods still exist—no longer majestic dinosaurs like megaraptors—but like a variety of birds found in the forests, swamps and swamps of Patagonia, and in Antarctica and Australia.”
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