New Dinosaur Species ‘Haolong dongi’ Reveals Unique Skin Details

A newly discovered dinosaur species from China is offering scientists an unprecedented look at the skin of iguanodontian dinosaurs, a group long thought to be covered solely in scales. The remarkably well-preserved fossil, nicknamed the “spiny dragon,” reveals a complex skin structure with unique spikes never before seen in dinosaurs.

The new species, named Haolong dongi, lived approximately 125 million years ago during the Early Cretaceous period in what is now northeastern China. This discovery is generating excitement within the scientific community, as it provides new insights into dinosaur skin evolution and potential defense mechanisms.

Part of the Iguanodontia Group

Haolong dongi belongs to the iguanodontia group, a significant branch of herbivorous dinosaurs within the ornithopoda clade. Iguanodontians represent an evolutionary transition between smaller, two-legged dinosaurs and the later-appearing hadrosaurs, or duck-billed dinosaurs, which developed highly specialized adaptations. Understanding the evolution of these dinosaurs is crucial for understanding the broader history of plant-eating dinosaurs.

“Iguanodontia were herbivorous dinosaurs that dominated almost all terrestrial ecosystems throughout the Cretaceous period,” said Dr. Pascal Godefroit from the Institute of Natural Sciences in Brussels, a lead researcher on the study. He added that the group reached its peak during the late Cretaceous, when duck-billed dinosaurs spread across nearly all continents.

The Mystery of Iguanodontian Skin

Scientists have a relatively good understanding of the skin structure of hadrosaurid dinosaurs, thanks to the discovery of “mummy” fossils in North America and Mongolia. These fossils demonstrate a complex arrangement of mosaic-like scales, with larger scales along the back. However, information about the skin of more primitive iguanodontians has been limited. Previously, only small fragments of scale impressions were found on dinosaurs like Tenontosaurus, Iguanodon and Mantellisaurus, which resembled the scale patterns of hadrosaurs.

The discovery of Haolong dongi is now filling a significant gap in that understanding.

A Juvenile Fossil with Perfectly Preserved Skin

The Haolong dongi fossil was found in the Yixian Formation, a globally important fossil location. The specimen represents a young individual approximately 2.45 meters (8 feet) in length. What makes this fossil exceptional is not only the quality of the bones, but also the nearly perfect preservation of the outer skin (integument). Researchers identified:

• Overlapping scales on the tail
• Tuberculated (bumpy) scales on the neck and chest
• Distinct scale patterns that differ from other iguanodontians previously discovered

However, the most surprising finding was the presence of skin spikes scattered among the scales.

Unique Spiked Skin Structure

Using advanced imaging technology and microscopic analysis, scientists discovered that these spikes have a highly complex structure. The spikes are cylindrical and hollow, with a heavily hardened outer layer (keratin), containing skin cells (keratinocytes) that still show visible nuclei, and a porous dermal pulp in the center. This structure distinguishes the spikes of Haolong dongi from both proto-feathers found in some other dinosaurs and the scaled spines of modern lizards, suggesting the spikes evolved independently through a completely different evolutionary pathway.

Based on their shape and location, researchers believe these skin spikes primarily functioned as a passive defense mechanism to deter predators. However, they also suggest the possibility that the structures played a role in thermoregulation or even sensory functions.

“This discovery provides unprecedented insight into the microanatomy of dinosaur skin in non-avian dinosaurs and demonstrates how complex the evolution of skin was in ornithischian dinosaurs,” the researchers concluded.

Opening a New Chapter in Dinosaur Evolution

The discovery of Haolong dongi not only adds to the list of dinosaur species, but also opens a new chapter in the study of dinosaur integument evolution. The fossil demonstrates that the variation in dinosaur skin structure was far more diverse than previously imagined. The findings, published in the prestigious scientific journal Nature Ecology & Evolution, are expected to serve as a key reference for dinosaur research in the future.