A bizarre new therizinosaur fossil has been discovered in Mongolia’s Gobi Desert, shedding light on the evolution of these strange creatures. The fossil, named Duonychus tsogtbaatari, is a 90-million-year-old dinosaur that stood over 13 feet tall and weighed over five tons. Unlike its relatives, which had three fingers with large claws at the end of each, Duonychus only has two fingers on each hand.
The discovery was made by paleontologists from Hokkaido University, who uncovered parts of the spine, ribs, hips, and shoulders in 2012. The fossils were initially recognized as those of a therizinosaur, but it took time to fully uncover its status as a new dinosaur.
Lead study author Yoshitsugu Kobayashi was surprised by the discovery, stating that one of the fingers had a preserved keratinous sheath. This unique feature is thought to have played a key role in Duonychus’s ability to grasp branches and other vegetation.
The two-fingered trait is not uncommon among theropod dinosaurs, which include carnivores like T. rex and herbivores like the therizinosaurs. Some species, such as Gualicho and Limusaurus, also had reduced numbers of fingers or toes over time.
Experts believe that Duonychus’s loss of a finger may have been an evolutionary happenstance that did not have a particular cost to it. The dinosaur’s flexible wrists and preserved keratinous sheath suggest that its claws were used for grasping plants rather than capturing prey.
The discovery of Duonychus highlights the diversity of theropod dinosaurs, which walked on two legs and had varying adaptations for feeding and defense. While Duonychus resembles a giant potbellied sloth due to its herbivorous diet, it was likely an formidable hunter in its own right.
Source: https://www.nationalgeographic.com/science/article/weird-new-dinosaur-therizinosaur-claws-sloth