[Latest Discovery] A Third Type of Skin, Neither Scales Nor Feathers? Meet “Haolong dongi,” a New Dinosaur Species Covered Entirely in Spikes

When you think of dinosaur skin, many people imagine the hard scales of a crocodile or the bird-like feathers that have been increasingly discovered in recent years.
However, a dinosaur with a “completely new skin structure” that fits neither of these categories and shakes the very foundations of paleontology has been discovered in China.

A new species of herbivorous dinosaur found in strata from the Early Cretaceous period (about 125 million years ago) was covered all over its body with “hollow spikes,” much like a modern porcupine.
We will explain in detail the true nature and possible roles of these unique spikes on this astonishing new species, “Haolong dongi,” which was announced in the academic journal “Nature Ecology & Evolution” in February 2026.

Miraculous Preservation! A Fossil Discovery Where Even Cell Nuclei Are Visible

This historic fossil was excavated from the “Jehol Group (Yixian Formation)” in Liaoning Province, northeastern China, a site world-famous for yielding many extremely well-preserved fossils, including feathered dinosaurs.

As a result of analysis using the latest technology by an international research team, it was revealed that this fossil is a new species of dinosaur belonging to the “iguanodontian” group, and it was named Haolong dongi (meaning “spiny dragon”).
The iguanodontians are an important group of herbivorous dinosaurs that thrived worldwide throughout the Cretaceous period, but this is the first time in the 200-year history of dinosaur research that such skin traces have been found.

Microscopic Internal Structure of the Skin Revealed

Not only did the excavated juvenile specimen retain a nearly complete skeleton, but surprisingly, it was preserved in extremely good condition—to the point where “even the nuclei of the skin cells can be identified under a microscope.”
It is a major discovery of incredibly high documentary value, succeeding in identifying the skin structure of a dinosaur at the cellular level, something that could only be imagined until now.

A “Third Skin Tissue” That is Neither Scale Nor Feather

A detailed examination of the skin fossil of Haolong dongi revealed facts that overturn the common sense of dinosaur science.

Countless “spine-like projections” grew pointing backward over a wide area covering the neck, back, torso, base of the limbs, and tail.
Most are about 2 to 3 mm long, but there were also large spikes exceeding 44 mm among the largest.

“Hollow Skin Tissue,” Not Bone

Even more surprisingly, these spikes were not bones but “tissues originating from the skin,” and their internal structure was a “tube-like structure with a hollow center (hollow cylindrical shape).”
The outside consisted of a stratum corneum (horny layer), and epidermal tissue was preserved inside.

Until now, it was thought that the body surface of dinosaurs was either “reptilian-like scales” or “feathers like those seen in the ancestors of birds.”
However, the research team concluded that Haolong’s spikes are neither pointed scales nor modified feathers, but a “third tissue” with its own unique multi-layered structure.
They had evolved their skin through a unique route entirely unrelated to the evolution of feathers.

Why Covered in Spikes? A Survival Strategy to Become a “Troublesome Prey”

So, exactly why was Haolong dongi clad in these bizarre hollow spikes all over its body?
The research team considered several possibilities and derived the most plausible hypothesis.

Thermoregulation Theory (Questioned)

The possibility that it helped regulate body temperature by increasing surface area was considered, but it is thought that a high heat-retaining effect could not be expected because the density of the spikes is low.

Display / Sensory Organ Theory (Questioned)

This is questioned because there are no traces of pigment cells, and the structure is too large to have functioned as a sensory organ.

The Most Plausible is the “Defense Function Theory”

Currently, the most widely supported theory is that it was a “defensive organ” to keep predators at bay, much like a modern porcupine.
As a juvenile of a gentle herbivorous dinosaur, Haolong was a prime target for the many small carnivorous dinosaurs that inhabited the same area.

While these spikes were not fatal weapons capable of stabbing an enemy to death, they must have been sufficiently effective to make it a “prey that is hard to bite and hard to swallow.”
It is thought that they played a role in reducing the probability of being eaten by making predators hesitate to attack and forcing them to spend extra time and effort.
By turning its whole body into a spiky, “troublesome prey,” it likely tried to survive the harsh struggle for existence.

The Endless Wonders of Evolution

It should be noted that because the Haolong dongi specimen discovered this time is a “juvenile” about 2.45 meters long, it is not known at this time whether these spikes were maintained into adulthood or shed during the growth process.

However, with the discovery of Haolong dongi, a completely new third skin structure—the “hollow spike”—has been added to the history of dinosaurs.
The body surfaces of dinosaurs were not so simple as to be explained by a binary of scales or feathers; they were far more diverse and complex than we ever imagined.
Deep underground, unknown clues that will overturn the next set of common sense are waiting for their moment of discovery even right now.