3-foot claws, tons of teeth: ‘Anatomically bizarre’ giant dinosaur found by scientists

Paleontologists in China have described a newly identified dinosaur so unusual that researchers called it “anatomically bizarre,” even by the standards of its already strange family. The species, named Kayrasaurus changliensis, belongs to Therizinosauria, a rare group of theropod dinosaurs known for combining fearsome claws with a mostly plant-based diet.

The discovery appears in a new study published in the Journal of Systematic Palaeontology, authored by Chun-Chi Liao, William J. Freimuth, Lindsay E. Zanno and Xing Xu.

A bizarre family portrait

Therizinosaurs share a distinctive look across the group. They walked upright on two legs, carried long necks and small heads, and sported a soft, feathered potbelly that made them resemble an unlikely cross between an ostrich and a grizzly bear. Their signature feature, though, was their claws, some of which stretched more than 3 feet (0.9 meters) long, among the longest of any creature known to science.

Researchers uncovered the new species from a nearly complete skeleton in the Lower Cretaceous Yixian Formation, a fossil-rich stretch of northeastern China roughly 125 million years old and already famous among paleontologists for its wealth of feathered dinosaur remains.

Bigger than its cousins

Even though the specimen was still young and growing when it died, K. changliensis was already substantial, likely weighing between 250 and more than 600 pounds (113 to 272 kilograms), comparable to an adult male grizzly bear, and stretching close to 12 feet (3.7 meters) long, roughly the length of a small moving truck. That makes it about 1.6 times larger than Beipiaosaurus inexpectus, the next-largest therizinosaur previously known from China.

Unusual teeth and jaws

K. changliensis also stood out for its dental arrangement, packing a severe underbite along with small, tightly clustered teeth, 45 along the lower jaw and 32 along the upper. No other large therizinosaur discovered so far carries more than 40 teeth in either jaw. Its lower jaw also featured a triangular opening on the side, while the upper jaw had a large opening near the snout, structures researchers have not yet fully explained.

Built to bite, not run

Unlike smaller, more agile therizinosaurs built for running, K. changliensis appears to have been a heavier, sturdier animal built around its bite rather than speed. Despite that intimidating build, and the dinosaur’s admittedly terrifying claws, researchers say its jaw and teeth closely resemble those of known herbivorous dinosaurs, suggesting K. changliensis spent most of its time eating plants rather than hunting prey.

That’s a notably calmer reputation than the therizinosaur depicted in a tense scene from the 2022 film “Jurassic World Dominion,” where the creature appears anything but vegetarian-minded.

Source: https://interestingengineering.com/science/kayrasaurus-changliensis-giant-therizinosaur-china-dinosaur-discovery