Giant Dinosaurs With Sickle-Like Claws Lived In Patagonia, First Record Of Theropods From Region Reveals

Researchers have focused on theropods as part of the study. The theropod fossils identified date from 66 to 75 million years ago. They found that non-avian theropod dinosaurs included top predators.

Pic shows Ornithurine birds, flying and walking on the ground, Stegouros, an armoured dinosaur, Orretherium, a mammal, Yaminuechelys, a turtle, a megaraptorid, which is a large carnivore, unenlagiines, a pair of carnivores, and enantiornithine birds in the foreground.

Source : Mauricio Alvarez and Gabriel Diaz/The University of Texas at Austin

A team of researchers led by The University of Texas at Austin have discovered fossils which represent the first record of theropods from the Chilean portion of prehistoric Patagonia. Theropods were dinosaurs that included both modern birds and their closest non-avian dinosaur relatives, were flesh-eating, and mostly had feet resembling those of birds. 

The new study provides a glimpse into dinosaur and bird diversity at Patagonia during the Late Cretaceous, which ranged from 100.5 to 66 million years ago, and was the period just before the extinction of non-avian dinosaurs. The study was recently published in the Journal of South American Earth Sciences.

What were megaraptors?

Among the species identified as part of the study are giant megaraptors with huge sickle-like claws and birds from the group that also includes present-day modern birds. Megaraptors were large theropods of the Cretaceous Period that existed 84 to 65 million years ago, and were distinguished from other dinosaurs due to the 35-centimetre sickle-like claw on the thumb of both their hands. Megaraptors used to sheath their claws into a horny, keratinous material, making the claws bigger, longer and sharper. 

In a statement released by The University of Texas at Austin, Sarah Davis, the lead author on the paper, said the fauna of Patagonia leading up to the mass extinction was "really diverse". This means that the fauna from prehistoric Patagonia identified by the researchers included a wide array of dinosaurs. She explained that the fauna of Patagonia from the Late Cretaceous included large theropod carnivores, smaller carnivores and bird groups co-existing alongside other reptiles and small mammals. 

Davis works with Professor Julia Clarke at the University of Texas Jackson School of Geosciences Department of Geological Sciences. Members of the Clarke Lab have joined scientific collaborators from Chile in Patagonia since 2017, to collect fossils and map the ancient life from that region. Researchers have found evidence of plant and animal fossils from before the dinosaur-killing asteroid struck Earth. 

What theropod dinosaurs were identified?

In the new study, the researchers have focused on theropods. The theropod fossils identified date from 66 to 75 million years ago. 

The study found that non-avian theropod dinosaurs included the top predators in the food chain. These predators from prehistoric Patagonia included dinosaurs called megaraptors and unenlagiines. 

What are unenlagiines?

Megaraptors were among the larger theropod dinosaurs in South America during the Late Cretaceous, and reached over 25 feet long. The unenlagiines were a group of dinosaurs with members that ranged in size from chicken-sized to over 10 feet tall, and probably covered with feathers, similar to velociraptors, their close relatives. The unenlagiinae fossils identified as part of the study are the southernmost known instance of the unenlagiinae group. 

What are enantiornithines and ornithurines?

The researchers discovered bird fossils from two groups, namely enantiornithines and ornithurines. Enantiornithines, now extinct, were the most diverse and abundant birds millions of years ago. Enantiornithines resembled sparrows, but with beaks lined with teeth. The ornithurinae group includes all modern birds living today, and the ornithurines living in ancient Patagonia may have resembled a goose or duck. 

What did different fossil fragments reveal?

The researchers discovered small fossil fragments, teeth and toes, and small bone pieces. The authors identified theropods, dinosaurs and birds from the small fossil fragments, teeth and toes, and small bone pieces respectively. They spotted the fossils with the help of enamel glinting on the dinosaur teeth among the rocky terrain. 

The Southern Hemisphere faced less extreme or more gradual climatic changes than the Northern Hemisphere after the asteroid strike, researchers have suggested. As a result, Patagonia and other places in the Southern Hemisphere could have become a refuge for birds and mammals and other life that survived the extinction.

Marcelo Leppe, one of the co-authors on the paper, said researchers still need to know how life made its way in the apocalyptic scenario and gave rise to the southern environments in South America, New Zealand and Australia. He added that in Patagonia, 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.

Other dinosaurs which existed in Patagonia during the Late Cretaceous included Stegouros, an armoured dinosaur, Orretherium, a mammal, and Yaminuechelys, a turtle.