Unique Anatomy of a New Large Herbivorous Dinosaur Upends Chinese Paleontologists’ Benchmarks

Researchers in China reveal the fossil of a large herbivorous theropod dating back 120 million years. This animal shifts our understanding of the earliest therizinosaurs. Indeed, its distinctive morphology helps to better delineate the adaptation of these vanished giants.

An almost complete skeleton unearthed in China reveals the distinctive appearance of the new Kayrasaurus changliensis

Four specialists publish their work in the Journal of Systematic Palaeontology. They describe an almost intact fossil unearthed in the Yixian Formation, located in China. Consequently, this major discovery enriches our knowledge of the early Cretaceous period.

Chun-Chi Liao, William J. Freimuth, Lindsay E. Zanno and Xing Xu name this species Kayrasaurus changliensis. This large animal walked upright on two sturdy legs. Yet, this giant mostly fed on vegetation in its forest habitat.

The creature boasted a broad, prominent belly covered in feathers. Additionally, its elongated neck preceded limbs bearing very long, curved claws. Thus, this peculiar silhouette echoes present-day birds, albeit with a much heavier build.

This therizinosaur far exceeds in heft all other fossil specimens from the Jehol biota

This new dinosaur measured more than 3.6 meters in length. Its weight ranged between 117 and 274 kilograms according to scientific estimates. Hence, it becomes the largest therizinosaur recorded in the famous Jehol biota.

It is at least 1.6 times larger than its cousin Beipiaosaurus inexpectus. The researchers fill a morphological gap between several already listed groups. Finally, this remarkable stature demonstrates the rapid evolution of these herbivores during the Cretaceous.

A very dense dentition and a singular claw distinctly distinguish this large plant-eating dinosaur

The upper jaw housed more than 32 teeth particularly small and very tightly packed. On the lower jaw, more than 45 teeth were present. This unusual dental profusion likely facilitated the continuous grinding of very tough foliage.

Its cervical vertebrae exceeded the length of its dorsal bones. Thus, this elongated neck offered great mobility to reach the canopy. Yet, this bone structure imposed a relatively heavy posture during locomotion.

Scientists also note a curious raised ridge on one of its large claws. Yet, no other member of this family possesses such a feature. This curved weapon likely helped the animal sweep aside branches before each bite.

The overall shape of the skull and jaws reveals varied feeding strategies in the Early Cretaceous

The skull features a distinctive nasal opening and a triangular gap on the jaw. These traits confirm the existence of distinct ecological niches among these bipedal herbivores. Indeed, some individuals favored a powerful bite, while others leaned on agility.

Species such as Jianchangosaurus and Lingyuanosaurus ran faster to locate their food. However, researchers remain cautious about the behavior of this large fossil. Indeed, the absence of hind limbs and a very flattened skull limit conclusions.