Brief
Newly Discovered Kayrasaurus Changliensis Sets Record for Largest Therizinosaur
A nearly complete fossil of Kayrasaurus changliensis, unearthed in China’s Yixian Formation, shows the dinosaur had the largest claws and most teeth of any therizinosaur, scientists say.
By Felo News Desk · Published
A nearly complete fossil of Kayrasaurus changliensis, found in the Lower Cretaceous Yixian Formation of northeastern China, has been described as the largest therizinosaur ever discovered. The specimen, which was still growing when it died, was estimated to have weighed between 250 and 600 pounds and measured almost 12 feet in length, making it 1.6 times larger than the next‑largest therizinosaur, Beipiaosaurus inexpectus.
Therizinosaurs were a group of feathered, plant‑eating theropods that lived from about 100 million to 65 million years ago. Kayrasaurus is notable not only for its size but also for its dental arrangement: the lower jaw held 45 teeth while the upper jaw had 32, a configuration not seen in other large therizinosaurs. The dinosaur also had a triangular opening on the lower jaw and a large opening near the snout of the upper jaw.
According to the study published in The Journal of Systematic Paleontology, the specimen’s massive claws, which could reach over three feet, are the longest known for any dinosaur. The authors, Chun‑Chi Liao, William J. Freimuth, Lindsay E. Zanno and Xing Xu, suggest that an adult Kayrasaurus would have been even larger than the juvenile specimen recovered.
The discovery adds to the growing body of evidence that therizinosaurs were diverse and that some species may have been among the last dinosaurs to survive before the mass extinction 65 million years ago.
Key facts
- Kayrasaurus changliensis weighed between 250 and 600 pounds (popsci.com)
- It measured almost 12 feet long (popsci.com)
- It had 45 teeth in the lower jaw and 32 in the upper jaw (popsci.com)
- Its claws could reach over three feet (popsci.com)
- It is 1.6 times larger than Beipiaosaurus inexpectus (popsci.com)
Background
The Yixian Formation in northeastern China is a renowned fossil site that has yielded numerous feathered dinosaur species, including other therizinosaurs. Previous discoveries in the area have helped scientists understand the diversity and evolution of this unusual group of theropods.
Why it matters
The find provides new insight into the size range and dental adaptations of therizinosaurs, contributing to knowledge of dinosaur diversity before the Cretaceous–Paleogene extinction.
What happens next
The research team plans to conduct further analysis of the fossil’s growth patterns and to compare its morphology with other therizinosaurs to refine evolutionary relationships.
Sources
- [1] popsci.com — originally reported as “Giant, feathered dinosaur with massive claws and tons of teeth found in China”
