Fossils highlight dinosaur diversity in prehistoric Patagonia

A new study led by the University of Texas at Austin (UT) has provided a first glimpse into dinosaur and bird diversity in Patagonia during the Late Cretaceous, before the asteroid strike that wiped-out all the non-avian dinosaurs. The fossils the experts discovered and analyzed represent the first record of theropods – a group of dinosaurs including both modern birds and their non-avian dinosaur relatives – from the Chilean areas of Patagonia. The findings include both giant megaraptors and birds from the group that nowadays includes most modern avian species.

“The fauna of Patagonia leading up to the mass extinction was really diverse,” said study lead author Sarah Davis, who completed this research as part of her doctoral studies in Geosciences at UT. “You’ve got your large theropod carnivores and smaller carnivores as well as these bird groups coexisting alongside other reptiles and small mammals.”

The scientists focused specifically on theropods, with fossils dating from 75 to 66 million years ago. The analysis revealed that in prehistoric Patagonia, two groups of predatory theropods – megaraptors and unenlagiines – were found. While megaraptors reached over 25 feet in length and were among the largest animals in that region, the unelagiines ranged from chicken-size to over ten feet tall and were likely covered in feathers like their close relatives, the velociraptors.

The bird fossils the scientists discovered were also from two different groups – enantiornithines and ornithurines. The former (resembling sparrows but with beaks with teeth) had once been the most abundant birds on Earth, but are now extinct. By contrast, the latter include all modern birds living today.

Some previous studies suggested that the Southern Hemisphere may have faced less extreme or more gradual climatic changes after the asteroid struck 66 million years ago, thus making Patagonia and other regions a refuge for animals that survived the extinction. The new findings could help in investigating this theory by constructing a record of prehistoric life before and after the mass extinction event.

“We still need to know how life made its way in that apocalyptic scenario and gave rise to our southern environments in South America, New Zealand, and Australia,” said co-author Marcelo Leppe, the director of the Chilean Antarctic Institute. “Here theropods are still present — no longer as dinosaurs as imposing as megaraptorids — but as the diverse array of birds found in the forests, swamps, and marshes of Patagonia, and in Antarctica and Australia.” 

The study is published in the Journal of South American Earth Sciences.

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By Andrei Ionescu, Earth.com Staff Writer

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